Glosser Biology 8 PreComp Study Guide 2023 KEY PDF

Glosser Biology 8 PreComp Study Guide 2023 Answer all questions legibly in complete sentences 1.1 Observation, Inference, Hypothesis DATA PRACTICE 1. Individually, list 3 types of quantitative data and 3 types of qualitative data that you can get from a giraffe. Quantitative: Height,...

Glosser Biology 8 PreComp Study Guide 2023 Answer all questions legibly in complete sentences 1.1 Observation, Inference, Hypothesis DATA PRACTICE 1. Individually, list 3 types of quantitative data and 3 types of qualitative data that you can get from a giraffe. Quantitative: Height, Weight, Number of spots Qualitative: Color, shape, texture 2. Come up with your own example of an observation and an inference you could make from it. You observe a plant wilting in the corner of a room. You infer that the plant may need water to become healthy HYPOTHESES PRACTICE 3. Assume you observe two trees of the same size and species in your back yard that are wilted and have not grown since they were planted four months ago. Based on your previous experience, what are some explanations for this phenomenon? Perhaps the trees are not getting enough water. Perhaps they are not getting enough light. Perhaps that species of tree does not grow well in the climate. 4. Assume you did some research and discovered that the region in which you live is experiencing a drought and that the two trees in your back yard are not drought-resistant trees. Which of these would be a more focused and testable hypothesis? Discuss each possible hypothesis with your neighbor. Point out the strengths and weaknesses of each. Trees are not happy when there is not enough water. This is not testable Trees need adequate water in order to grow. Probably the best hypothesis, but could be written in a more proper format (If trees get adequate water, they will grow more healthy) Trees need water and fertilizer and reasonable temperatures in order to grow. This is not focused enough – water, fertilizer, and temperature are listed as three separate independent variables 5. Design a valid hypothesis for the following 3 experimental questions (remember hypotheses do not have to correct, but they should be valid in their construction) Experimental question 1: How does the temperature affect the height at which the ball will bounce? If a ball is bounced in a room with high temperature, the ball will bounce higher than in a room with lower temperature. Experimental question 2: How does the surface that the ball is bounced on affect how high the tennis ball will bounce?  The harder the surface becomes, the higher the ball will bounce. Experimental question 3: How does the height at which the tennis ball is dropped affect how high the tennis ball will bounce? The higher the ball is dropped from, the higher it will bounce. Biology 8 Activity 1.2 – Variables Independent Variable Practice 6. Imagine that a group of researchers wants to find out how the amount of sunlight a plant receives affects the growth of the plant. What is a hypothesis for this experiment? the more sunlight a plant receives in a given time frame, the taller the plant will grow How could the researchers conduct this experiment? Place one group of plants in full light, one group in partial light, and one group in no light. Allow the plants to grow for 7 days, giving each the same amount of water and nutrients. Measure the height of the plants after 7 days 7. Using this data, what is the independent variable? How many levels of independent variable are there? the IV is the level of light. There are 3 levels to the IV (Full light, partial light, no light) Experimental Design Practice 8. An investigation was done to determine how the type of exercise affects heart rate. People were divided into five groups. The heart rates of people in each group was measured before exercising and after. Group 1 walked for 30 minutes. Group 2 ran for 30 minutes. Group 3 lifted weights for 30 minutes. Group 4 did not exercise for 30 minutes. Group 5 did yoga for 30 minutes. 9. What are the independent and dependent variables? Give an example of a variable we would want to control. (More questions on back page)  The independent variable is the type of exercise. The age of each group would be one example of a control variable. 10. Which group is the control group? group 4 11. Why is this control group needed? Group 4 is needed because we can use their heart rate as a “normal” result, and compare the experimental results to this baseline. Accuracy, Reliability, Sample size Practice 12. The percentage chance of a coin flips landing on heads or tails is known to be 50%. Pretend you flip a coin once and it lands on heads. Using only this data, what percentage of coin flips landed on heads? What about tails? 100% of flips landed on heads. 0% landed on tails You flip the coin a second time, and again it lands on heads. Using only these first two flips as data, what percentage of flips landed on heads? What about tails? Still 2/2 or 100% of flips land on heads, 0/2 or 0% land on tails A third flip is done and this time lands on tails. What percentage of coin flips landed on heads? What about tails? Now 2/3 have landed on heads (66%) where 1/3 have landed on tails (33%) A fourth flip is done and again lands on tails. Same question as previous three. Now, 2/4 (50%) have landed heads, and 2/4 (50%) have landed tails. 13. What does this exercise tell you about accuracy and sample size? The more coin flips (larger sample size) you have, the closer the results will resemble known probabilities. Thus, the higher the sample size, the more accurate your results will be. Mean, Median, Mode 14. EXAMPLE 2: Which number (mean, median or mode) best reflects the researcher’s data and why? (Use Table on next page) The median best represents the results. This is because there are outliers in the data that drag the mean higher, making the mean less reliable. The median is unaffected by the outliers in the data, making the median more useful.  Day Number of Birds Spotted Monday 15 Tuesday 16 Wednesday 9 Thursday 87 Friday 18 Saturday 14 Sunday 9 Mean 24 Median 15 Mode 9 GRAPHING PRACTICE 15. A student measures the heart rate of 5 of her classmates. The heart rates are 68, 75, 83, 78 and 80. What type of graph should she use to convey this data? The student should use a bar graph (5 separate classmates) 16. A student measures the heart rate every minute of a classmate as the classmate exercises for 5 minutes. The heart rates are 68, 79, 98, 110 and 121. What type of graph should she use to convey this data? The student should use a line graph (one continuous heart rate) 17. A student measures the length of a tree’s shadow at various times of the day. Her data is summarized below. What kind of graph should this be? Why? A line graph (one continuous shadow over time) 18. A student determines the pH of various fruits and vegetables. What kind of graph would best represent her data? Why? A bar graph (the pH of a banana has nothing to do with the pH of a lemon.) 19. A student is training for track and field. The student practices running every day and at the end of the week, she measures the amount of time it takes her to run 800 m. Her times are as follows (in min:sec): Week 1-4:05 Week 2-3:46 Week 3-3:20 Week 4-3:13  What type of graph should this be? Explain. Bar graph. the result for week 1 does not directly affect week 2, 3, or 4. What goes on the X and Y axis? Explain. The week number should be on the X axis, the time should be on the Y-Axis Lesson 2.1: Types of Cells Cell Review Practice 1) List the levels of organization of a multicellular organism Cells, Tissues, Organs, Organ systems, Organisms 2) List your own example of homeostasis (do not use the examples from the notes – think for yourself!) When you get cold, your muscles and blood vessels condense, allowing them to hold on to more heat to counteract the drop in temperature 3) List all three parts of cell theory 1. All cells come from pre-existing cells 2) Cells are the basic unit of life 3) All living things are made of one or more cells 4) Why do you think it is important for a physician to understand cell biology in order to make an accurate diagnosis for their patients? Because any illness a person is experiencing is due to irregularities at the cellular level. Treating the cells treats the person 5) What are three components of cells that all cells have in common? DNA, ribosomes, and a cell membrane Prokaryote Practice 6) Which of the three domains of life are classified as prokaryotic? Archaea and Bacteria 7) Which of the two major cell types are considered ‘compartmentalized’? Eukaryotes 8) Which of the two major cell types is considered less complex? Prokaryotes 9) Prokaryotes do not have membrane-bound organelles. What do we mean by “membrane bound”? Membrane bound means that the cellular structure is surrounded by a membrane that defines its boundaries 10) What does the term prokaryote mean? Why is this a fitting term for this type of cell? Prokaryote means before the nucleus which is fitting b/c prokaryotes lack nuclei in their cells 11) When a prokaryotic cells divides, do we consider this growth and development, or reproduction? Reproduction, b/c bacteria are unicellular, when one bacterial cell becomes two, there are now two bacteria 12) Why is that bacteria and archaea will never be found in multicellular form? B/c they are prokaryotes and prokaryotes can only take the unicellular form. They are not complex enough to be multicellular 13) Eukaryotes and Prokaryotes have many different features. What structure is shared by bacteria and plant cells, that animal cells do not have? Variations of the cell wall are found in plants, bacteria, some protists, and fungi, but not found in animals 14) Are there any eukaryotic cells that have a cell wall? What kingdoms can they be found in? Yes, plants, fungi, and most protists have cell walls. Lesson 2.2 Cell Organelles Basic Practice 15) Why is having a plasma membrane so important for all cells? The cell plasma membrane provides a barrier between the organized inner cell and the chaotic exterior environment. Thus, the membrane protects the delicate biochemical balance that maintains homeostasis in the cell. The membrane also allows for the regulated exchange of materials between cell and the environment. 16) What does “selectively permeable” mean? The membrane is selective about what can pass through it. An important property of the membrane. 17) Based off of what we know about prokaryotes, do you think they would have nucleolus? Why? No, nucleoli are found in nuclei, which prokaryotes do not have. 18) What’s the difference between the nucleus and the nucleolus? The nucleus is a membrane bound structure found in eukaryotes that stores DNA. The nucleolus is a section of the nucleus that creates ribosomes for the cell. 19) What two places can you find ribosomes in a eukaryotic cell? Bound to the rough ER or free-floating in the cytoplasm. 20) Can ribosomes be found in all cell types or are they only found in eukaryotic cells? Ribosomes are found in all cells 21) Briefly describe the function of each the organelles: Ribosome (non-membrane bound): Creates proteins for the cell to use or secrete Nucleus (membrane bound): Stores DNA, acts as a decision-making center for the cell Rough ER (membrane bound): Modifies proteins made by Rough ER bound ribosomes, sends them to Golgi Smooth ER (membrane bound): Stores calcium, detoxifies cellular substances, synthesizes lipids and carbs Golgi Apparatus (membrane bound): Sorts and modifies products from endoplasmic reticulum, send products to final destinations. Vesicles (membrane bound): Membrane bound sacks that serve as transport vehicles that the cell can use to send materials from one point to another Centrosome (non-membrane bound): The organizing center of the microtubule cytoskeleton. Plays major role in cell structure, movement, and division 22) A ribosome that is attached to the Rough ER synthesizes a protein. Describe the path the protein will take as it travels to its final destination a) Rough ER -> Vesicle -> Smooth ER -> Golgi -> Cytoplasm b) Rough ER -> Vesicle -> Golgi -> Vesicle -> Cell membrane c) Smooth ER -> Vesicle -> Rough ER -> Golgi -> Cell membrane d) Rough ER -> Vesicle -> Golgi -> Vesicle -> Cell Cytoplasm 23) Structure to function is a key principle in science, especially in biology. What does structure to function mean to you? The structure of a molecules, macromolecules, cells, tissues, organs, etc, determine their function. If the structure changes, the function changes. 24) Muscle cells are in need of a high quantity of energy in order to continue functioning. What organelle would you expect to find in high abundance in a muscle cell? This is a structure to function question. In order for muscles to perform this function, they must have many mitochondria to provide ATP which can be used to make muscles move. 25) Your neurons (nerve cells) produce a high quantity of proteins that are used as neurotransmitters, which are released from the cell to send signals to other neurons. What are at least two organelles you would you expect to find in high concentration in neurons? The neurotransmitters are being secreted from the cell. We learned that the endomembrane system is responsible for the secretion of proteins. Thus, the neurons would likely have extensive Rough ER and Golgi Apparatuses. 26) Your white blood cells (part of your immune system) have a lot of lysosomes. Why would this be useful in the immune system? Lysosomes are used to break down molecules or foreign invaders in the cell. Immune cells often track down infectious bacteria in the body and destroy them using lysosomes. 27) Leaves are the site of photosynthesis in plant cells. Therefore, they must have a large number of: Structure to function. In order to perform the function of photosynthesis, leaves must have high numbers chloroplasts in their cells Lesson 2.3 Endosymbiotic Theory 28) How long ago do scientists estimate the first prokaryotic cells emerged on Earth? Around 3 billion years ago 29) What does the endosymbiotic theory set out to explain about the evolution of life on Earth? The endosymbiotic theory explains the evolution of eukaryotic cells from prokaryotic cells 30) In your own words, describe the endosymbiotic theory. A small oxygen metabolizing bacteria was engulfed by a larger bacteria. Instead of the larger cell digesting the smaller cell, the two cells formed a mutualistic relationship. The small cell provided ATP for the larger cell, while the larger cell provided food and protection for the smaller cell. Over time, the smaller cell reproduced inside the larger cell, and the larger cell in turn reproduced, giving rise to new endosymbionts that could not survive without each other. After hundreds of millions of years, the smaller prokaryote developed into the eukaryotic organelle, the mitochondria. This endosymbiosis also occurred with a photosynthetic prokaryotic cell that later developed into chloroplasts. Thus, the endosymbiont theory states that mitochondria and chloroplasts are both the descendants of these ancient bacteria. 31) What kind of symbiotic relationship formed between the cells that are the subject of the endosymbiotic theory? Mutualistic 32) What does endosymbiont mean? An organism living inside of another organism. 33) Which two modern day organelles are believed to be the descendants of ancient prokaryotic cells? See explanation above: the mitochondria and chloroplasts 34) Describe three pieces of evidence in support of endosymbiotic theory. 1) Mitochondria and chloroplasts have very similar structures (anatomy) as bacteria cells. Specifically, mitochondria resemble bacteria called rickettsia and chloroplasts resemble cyanobacteria 2) Mitochondria and chloroplasts reproduce on their own, independent of the great cell, likely due to the fact that they are descendants of formerly free-living cells 3) Mitochondria and chloroplasts have their own DNA that is separate from the DNA in the nucleus of the cell. Genetic sequencing reveals that mitochondria genes are similar to those genes found in rickettsia while chloroplast genes are similar to genes found in cyanobacteria. 35) How old are the oldest fossils of eukaryotic cells? About 2 billion years old 36) According to molecular biologists, endosymbiosis has occurred at least three times in the history of life on Earth. Describe each of these three instances of endosymbiosis 1) The first act of endosymbiosis was when ancestors of mitochondria were engulfed by a larger prokaryotic cell, eventually forming the first mitochondrion, and forming the first organisms in the domain eukarya. 2) The second act of endosymbiosis was when a mitochondria containing cell engulfed an ancestor of the chloroplasts, forming the early ancestors of green algae, and later, the plant kingdom. 3) The third and most recent act was when a heterotrophic protist (eukaryote) engulfed a smaller photosynthetic red algae, forming the first brown algae cells. 3.1 Structure of Water Practice 1) Why is it important to understand the chemical properties of water if we want to understand the biochemistry of living cells? Because water is the biological medium for life on earth. Water makes up nearly 70% of an organism. Water has unique properties that no other known substances have. For example, most of the other biological molecules can interact together in cells because they dissolve well in water. Even molecules that don’t mix well with water, like lipids, take on useful structures when they are surrounded by water, like cell membranes. 2) Are electrons always shared evenly in a covalent bond? No, they are not. When an electronegative atom, like oxygen, is covalently bonded to a non-electronegative atom, like hydrogen, the electrons in the bond spend more time around oxygen than hydrogen. This is because electrons are attracted to more electronegative atoms. This gives the covalent bond a “dipole” – the oxygen gains a partial negative charge due to the increased presence of electrons. The hydrogen gains a partial positive charge, because the electrons are not spending as much time near the hydrogen nuclei. 3) Water is a polar molecule, meaning it is slightly negative on one side and slightly positive on the other side. 4) Draw 4 water molecules that are engaged in hydrogen bonds with one another. 5) Glucose is a polar molecule. Will it dissolve well in water? Why? Yes, polar molecules mix well with other polar molecules. Since water and glucose are both polar, they will mix well together. This is because water and glucose molecules can form hydrogen bonds with one another, allowing them to mix very well. 6) Lipids are nonpolar molecules. Will they dissolve well in water? Why? No, non-polar molecules do not mix well with polar molecules. This is because non-polar molecules cannot form hydrogen bonds, and therefore water molecules “push” lipids away in favor of forming more hydrogen bonds with other water molecules. 7) To summarize, polar molecules are hydrophilic and can form hydrogen bonds with water. Nonpolar molecules are hydrophobic and cannot form hydrogen bonds with water 3.1 Monomer, Polymer, Carbohydrate Practice 8) Describe the relationship between monomers and polymers Monomers are small molecular building blocks that, when covalently bonded together, form polymers. 9) What is a dehydration reaction? What is a hydrolysis reaction? How are these reaction related? The type of reaction that forms covalent bonds between monomers is called a dehydration reaction, which produces water as a product. Polymers can also be broken down into their monomeric subunits. The type of reaction that breaks down polymers to monomers is called a hydrolysis reaction, and water is used as a reactant to break the covalent bond. Look at the image below, showing the linkage of two amino acids (right to left = dehydration; left to right = hydrolysis): 10) Which of the four classes of macromolecules have monomeric and polymeric structure? Carbohydrates, nucleic acids, and proteins all have true monomers and polymers. Lipids do not have true monomers or polymers. 11) Is glucose a monosaccharide or a polysaccharide? Glucose is a monosaccharide. 12) Draw a monosaccharide. 13) What is the primary function of carbohydrates in cells? They are the primary fuel source for cells. They deliver energy to our cells, which our cells then convert to ATP, the cellular currency of energy. 14) What is the relationship between glucose and glycogen? Glycogen is a polysaccharide made up from glucose monosaccharides. When there is excess glucose that an organism does not immediately need, the organism can store the excess glucose as glycogen to save it for later use. 15) Do animals store excess glucose as glycogen or starch? What about plants? Animals store excess glucose as glycogen. Plants store excess glucose as starch. Starch and glycogen are nearly identical in their structure and function. 16) What is a secondary function of carbohydrates? Carbohydrates can also be used for building other molecules in the cell that are used for structural “biomass”. 17) What two polysaccharides are used for structural support by plants, fungi, and arthropods? Two examples of structural polysaccharides are cellulose, which is found in plant and algae cell walls, and chitin, which is found in arthropod exoskeletons and fungi cell walls. Lipid Practice 18) Explain the difference between carbohydrates and triglycerides in terms of how they are used by our cells for energy. Triglycerides can store nearly twice as much chemical energy as glucose however, triglycerides are more difficult for our cells to breakdown in order to make ATP. Therefore, our cells choose glucose as a primary source of energy, and only will use triglycerides if no glucose is available. Triglycerides are a secondary energy source. 19) Do lipids have a true monomer/polymer form? What are the parts of a triglyceride? No lipids do not have true monomers or polymers. They can still be broken down into parts though. A triglyceride is made from one glycerol group bonded to three fatty acid tails. A dehydration reaction takes place to bond the fatty acid tails to the glycerol group. 20) Draw a triglyceride 21) Are lipids generally hydrophilic or hydrophobic? What lipid is an amphipathic? All lipids have hydrophobic character to them. However, one type of lipid, the phospholipid, has both hydrophobic and hydrophilic chemical groups, making phospholipids amphipathic. Amphipathic means “containing both hydrophobic and hydrophilic chemical groups.” (Recall from bio7, “amphi” = “both”) 22) What is the structural difference between a triglyceride and a phospholipid? Triglycerides have three fatty acids connected to a glycerol. Phospholipids have two fatty acids connected to a glycerol, and then a phosphate group attached at the third position on the glycerol. 23) What lipid type is the primary component of the cell membrane? Phospholipids make up all cellular and organelle membranes. 24) What are the functions of steroids? Steroids are used as hormones for long term cell signaling and communication (estrogen, testosterone, cortisol, etc.). They also can help maintain the fluidity of cell membranes (cholesterol) Nucleic Acid Practice 25) What are two examples of a nucleic acid? DNA and RNA are the only two nucleic acids. 26) What is the relationship between nucleic acids and proteins? Nucleic acids store the information for how to build proteins. 27) What is the monomer of a nucleic acid called? How many types are there? Nucleic acid monomers are called nucleotides. There are 5 types found in cells. DNA has nucleotides called adenine, thymine, guanine, and cytosine. RNA has all the same nucleotides, except thymine is replaced by a different nucleotide called uracil. 28) Draw a nucleotide 29) What is the relationship between glucose and ATP? The chemical energy stored in glucose is used to be converted to a more usable type of chemical energy in the nucleotide derivative, ATP (adenosine triphosphate) (Notice adenosine is related to the nucleotide adenine) 3.3 Protein Practice 30) Would you consider proteins to be hydrophobic, hydrophilic, or amphipathic? (Remember, amphipathic means both hydrophobic and hydrophilic) Proteins could be considered amphipathic. Amino acids can be hydrophobic or hydrophilic, and most proteins have a combination of hydrophobic and hydrophilic amino acids. 31) What is the monomer of a protein called? The monomer of a protein is called an amino acid. 32) Draw an amino acid. 33) What is the distinction between polypeptides and proteins? Polypeptides are single, linear chains of amino acids. A protein is one or more polypeptides precisely folded, twisted, and coiled into a unique shape with a unique function. 34) True or false: Proteins are the most structurally complex of the macromolecules True. Proteins are the most structurally and complex machines (yes, machines) known to humankind. 35) Why are proteins so important for cells? Because proteins are the work horses for our cells. They carry out nearly all cellular functions. They are like the tools that our cells use to get work done. 36) Name at least three functions of protein (there are many to choose from!) Protein functions: Catalyze chemical reaction (enzymes), immune defense, cell-cell communication, structural support, cell movement, muscle movement, transport of cell materials, cell recognition, etc. 37) What part of the amino acid determines its identity? All amino acids have the same “backbone”. The R group, otherwise known as the sidechain, gives the amino acid its identity. 38) Why is it important to understand how a protein folds? Because STRUCTURE DETERMINES FUNCTION. The specific folding pattern of a protein will determine that protein’s precise function. By understanding protein structure, we can predict protein function – this is an incredibly powerful tool in studying cell biology, especially if you’re interested in pharmacy or medicine. 39) Imagine we have a protein that is 1,000 amino acids long. If we change the sequence of the first 200 amino acids, what would you predict to happen to the protein’s function? Removing the first 200 amino acids will have a dramatic effect on protein structure, and therefore will likely have a dramatic effect on protein function. Its hard to say exactly what could happen, but we can be sure that this protein will no longer function like it was coded to do by DNA. 40) What does it mean when a protein “denatures”? Denaturation refers to the act of a protein unfolding. Again, this is not good for cells because if proteins denature, then they lose their structure and therefore lose their function. This could end up killing the cell. 41) What are 3 variables that cause the denaturation of proteins? Changes in environmental conditions can cause denaturation. These factors include changes in pH (acidity level of the cell), temperature, or ion concentration. 42) How do these factors cause the protein to denature? These factors can cause denaturation by disrupting the thousands of interactions between amino acids in the polypeptide chain that stabilize the protein’s overall structure. If these amino acid interactions are disrupted, the protein will unfold. 3.4 Enzymes Practice 43) What is the difference between an endothermic and exothermic reaction? Endothermic reaction absorb energy from the environment. Exothermic reactions release energy to the environment. 44) What is activation energy when referring to chemical reactions? Activation energy is the energy that is required to start a chemical reaction. Both endothermic and exothermic reactions require an initial input of energy to begin, and this is the activation energy. 45) How do catalysts affect activation energy? What is the consequence of catalysts not being consumed in reactions? When a catalyst is added to a reaction, the catalyst will lower the required activation energy to make that reaction begin. This speeds up the rate of chemical reactions because there is not as much energy needed for the reaction to start. Notice in the picture below, the dotted line is the uncatalyzed reaction, the solid line is the catalyzed reaction. The catalyzed reaction has a much lower energy barrier. Because catalysts are not consumed by reactions, they catalyze hundreds of millions of the same reaction over and over again without being broken down. 46) What is an enzyme? An enzyme is a biological catalyst. Most enzymes are proteins. 47) Why have enzymes historically been compared to a lock and key? Because enzymes, like a key to a lock, are incredibly specific about what kind of reaction they will perform. Each enzyme only performs one type of reaction. Thus, there are tens of thousands of enzymes in our cells, each performing a different type of reactions. This allows for biochemical reactions to be highly regulated – an important characteristic for maintaining homeostasis. 48) What is the enzyme-substrate complex? Enzymes catalyze chemical reactions. Every reaction begins with reactants that get turned into products. When reactants bind to an enzyme, the two form an enzyme-substrate complex (the reactants are the “substrates”) The enzyme catalyzes the reaction and releases the substrates as products. 49) What is the special name for the pocket in an enzyme where specific reactions are catalyzed? The pocket of an enzyme where the enzyme catalyzes a reaction is called the active site. 50) How does an enzyme lower the activation energy of a reaction? Enzymes lower the activation energy of a reaction by providing the absolute perfect chemical environment in the active site for that specific reaction to take place. Providing the perfect chemical environment allows for the reaction to take place very easily and very quickly. 51) Do factors like temperature, ion concentration, or pH affect enzyme function? Why? Yes, because most enzymes are proteins, they can become denatured if temperature, pH, or ion concentrations in the cell change. Again, this is because the chemical interactions between amino acids that hold the shape of enzyme together could become disrupted, causing the denaturation of the enzyme 52) How does the rate of an enzyme-catalyzed reaction change with substrate concentration? As substrate concentration increases, the reaction rate increases until all of the enzyme active sites are filled. At this points the rate of the reaction levels off 4.1 Cell Membrane Structure 1. What cell structure provides a hydrophobic barrier between the inside and the outside of a cell, allowing the cell to protect the delicate biochemistry that sustains homeostasis? The cell membrane protects the cytoplasm, which is highly ordered, from the disorder outside of the cell, allowing for homeostasis to be maintained. It does this by being selectively permeable about what molecules/ions can enter the cell. 2. Draw a single phospholipid. Label hydrophilic & hydrophobic regions 3. Draw a phospholipid bilayer. Label the hydrophilic & hydrophobic regions 4. What types of molecules can be found in the membrane? a) lipids b) proteins c) glycoproteins d) glycolipids e) all can be found in the membrane 5. What does it mean to say the phospholipid bilayer forms spontaneously in water? Why does membrane form this structure? It means that the formation of the bilayer happens automatically when phospholipids are surrounded by water. This is the most physically stable state these molecules take on in the presence of water. The structure forms this way b/c the hydrophilic head groups can interact with water inside and outside of the cell while the hydrophobic tail groups bury themselves away from water in the center of the membrane. 6. Although phospholipids are amphipathic, we refer to phospholipid bilayers as hydrophobic barriers because the non- polar fatty acid phospholipid tails stop hydrophilic molecules from passing through 7. The membrane is often thought of as a fluid mosaic. Define the words fluid and mosaic and explain why this is an appropriate model of the cell membrane. Fluid – Molecules in the membrane are mobile, not static. The molecules move side-to-side with ease. Mosaic – There are an assortment of different molecules in the membrane, not just phospholipids. The model describes the structure and behavior of the cell membrane 8. As cells grow in size, what happens to the surface are to volume ratio of the cell? Why can this be dangerous for the cell? How do cells resolve this surface area to volume ratio problem? As cells grow larger, the surface area to volume ratio of the cell decreases. This can harm the cell because if the cell is too large, nutrients and wastes can not be transported efficiently, leading to cell death. To resolve this problem, cells maintain a high surface area to volume ratio by remaining small in size and having folded membranes. 9. Many cells have highly folded membranes. How does this affect the surface area of the cell? This allows for cells to maintain high surface areas with relatively little change to their volume. This allows for more space to perform metabolic activities leading to greater efficiency. 10. In petri dish A, is a cell with size s=5µm. In petri dish B there are 125 cells with size s=1µm. Calculate the surface area to volume ratio for each petri dish. Which petri dish contains cells with a more optimal surface area to volume ratio? SHOW YOUR WORK Surface area = 6s2 ; Volume = s3 ; Surface area to volume ratio = 6s2 / s3 Dish A Surface area = 6(5)2 = 150 ; Dish A Volume = 53 = 125 ; SA to Vol RatioA = 150/125 = 1.2 Dish B Surface area = 125 * 6(1)2 = 750 ; Dish B Volume = 125 * 13 = 125 ; SA to Vol RatioB = 750/125 = 6 The cells of dish B have a more optimal surface area to volume ratio (higher SA to Vol Ratio) 4.2 Passive Transport 11. Which of the two major types of cell transport DO NOT require an expenditure of energy? Passive transport does not require energy input to make molecules move. Active transport does require energy input to make molecules move. 12. Describe the direction of the movement of molecules or ions as they diffuse, in reference to concentrations. In diffusion, a type of passive transport, molecules/ions move from areas of high concentration to areas of low concentration spontaneously. Another way to say this is that molecules/ions diffuse down or with their concentration gradient. 13. Is diffusion a form of passive or active transport? Diffusion is a form of passive transport. 14. Is diffusion spontaneous or non-spontaneous? Diffusion is spontaneous, meaning that the process occurs without any external influence, like energy input. 15. What is a concentration gradient? Does diffusion move molecules down/with their concentration gradient or up/against the gradient? Concentration gradients exist when there is a difference in the concentration of a particle in one area versus another. As molecules diffuse, they move down/with their concentration gradient, from high to low concentration. This idea is similar to a ball rolling down a hill – the ball spontaneously rolls from a higher elevation to a lower elevation. 16. Describe dynamic equilibrium. When is dynamic equilibrium achieved in reference to passive transport? Dynamic equilibrium is achieved when molecules have completely diffused down their concentration gradients, resulting in an equal concentration of molecules in a given volume. When molecules are in dynamic equilibrium, they are still moving around, but there is not net change in concentration from one area to another. (NOTE: equilibrium does not always mean that concentrations are equal. Equilibrium means there are no more changes in concentration and the system is its most stable state.) 17. Nitric oxide gas (NO) is a small non-polar molecule. Outside of the cell the concentration of NO is 0.6µM, while inside the cell the concentration of NO is 0.2µM. a) Will NO diffuse through the membrane directly? How do you know? Yes. NO is a small non-polar molecule and thus will utilize simple diffusion to pass directly through the membrane’s hydrophobic barrier b) What is this type of diffusion called? Diffusion of non-polar molecules directly through the cell membrane is called simple diffusion c) Will NO diffuse in to or out of the cell? NO is more concentrated outside of the cell than it is inside of the cell. Therefore, the concentration gradient of NO goes from outside to inside. NO is diffuse into the cell. d) Is ATP required for this process? No, simple diffusion is a type of passive transport and will not require energy (will not require ATP). 18. Will hydrophilic molecules or ions utilize simple or facilitated diffusion? Explain your answer. Hydrophilic molecules or ions will utilize facilitated diffusion to pass through the membrane. Because the membrane is a hydrophobic barrier, hydrophilic molecules can not utilize simple diffusion to pass directly through the membrane. Therefore, hydrophilic molecules must use transport proteins that are embedded in the cell membrane to facilitate the transport of these molecules. Transport proteins provide a small hydrophilic corridor through the membrane, allowing hydrophilic molecules to pass through. 19. The difference between simple and facilitated diffusion is: a) facilitated diffusion allows molecules to pass directly through membrane, simple utilizes protein channels/carriers b) simple diffusion allows molecules to pass directly through the membrane, facilitated utilizes protein channels/carriers c) facilitated diffusion transports non-polar molecules, simple diffusion transports polar molecules d) both b & c 20. What are the two types of membrane transport proteins? The two types of transport proteins are channel proteins and carrier proteins. Both are involved in facilitated diffusion. 21. Why is it crucial for cells that membrane transport proteins are highly specific about the types of molecules that will transport? Because in order to maintain homeostasis, the cell must be able to regulate which molecules are allowed to pass through the membrane. The specificity of membrane proteins allows for cells to carefully pick and choose what type of molecules can pass through and when they are allowed to pass through. 4.3 Osmosis 22. Is water capable of diffusing directly through the cell membrane? Explain your answer No. Water is a polar molecule and as such is unable to pass through the membrane utilizing simple diffusion. Water must utilize facilitated diffusion. 23. What is an aquaporin? An aquaporin is a channel protein that allows for water to be transported in to or out of the cell. 24. A beaker has a solution that is separated by a membrane that is permeable to water but not NaCl. The left side of the membrane has a solute concentration of 5M NaCl, while the right side has a solute concentration of 10M NaCl. Which side of the membrane is hypertonic and which side is hypotonic? The right side of the membrane is hypertonic because it has a higher solute concentration (10M) compared to the left side of the membrane (5M). 25. The beaker described in question 22 is not in a state of equilibrium, meaning that something must happen for the system to achieve a more stable state. What will happen in this beaker for dynamic equilibrium to be achieved? The membrane in this example is permeable to water but not to NaCl. As stated in the previous question, the right side of the membrane is hypertonic to the left side. Using the rule that water will always diffuse toward the hypertonic side of a membrane that is impermeable to certain solutes, water will diffuse from the left side to the right side of the membrane to achieve dynamic equilibrium. 26. If solutes are blocked from diffusing down their concentration gradient, water will always flow toward the hypertonic side of a membrane. 27. Describe what could happen to a red blood cell if the cell is placed in a hypertonic solution. If the solution surrounding a red blood cell is hypertonic, then water will flow out of the cytoplasm of the cell into the extracellular fluid, causing crenation, or shriveling up of the cell. 28. Describe what could happen to a red blood cell if the cell is placed in a hypotonic solution. If the solution surrounding a red blood cell in hypotonic, then water will diffuse into the cytoplasm of the cell, causing the cell to swell up and potentially lyse (burst). 29. Describe what could happen to a red blood cell if the cell is placed in an isotonic solution. In an isotonic solution, there will be no net movement of water into or out of the cell. The red blood cell will retain normal shape. 30. Animal cells have high solute concentrations in the cytoplasm. Why do they not burst inside of our bodies? We have organs (kidneys) that control the solute concentration of our extracellular fluids. Our bodies maintain isotonicity between the cytoplasm of our cells and the extracellular fluids surrounding our cells. 31. Plant cells are usually hypertonic compared to their surroundings. Explain the direction of osmosis in plant cells. Because plant cells are usually hypertonic compared to their surroundings, water will flow into plant cells, causing them to swell up. 32. What does it mean to say a plant cell is turgid? What role does the large central vacuole and cell wall play in maintaining turgor pressure? In reference to the previous questions, when plant cells swell up with water, something called turgor pressure is produced in the cell. As water fills the hypertonic plant cytoplasm, the large central vacuole collects the water, creating pressure inside of the plant cell that pushes the cell membrane up against the cell wall of the plant. The cell wall protects the plant cell from bursting from this turgor pressure. As it turns out, plants have evolved to require this turgor pressure to maintain healthy shape. 33. Protozoans are normally found in freshwater that is hypotonic compared to the cytoplasm of the cell. Explain the role of the protozoan contractile vacuole in maintaining water balance. In protozoans, the cytoplasm is hypertonic to the surroundings, meaning water will flow into the cell, again causing the cell to swell up. In protozoans, the contractile vacuole collects this excess water and then expels the water from the cytoplasm, relieving the internal osmotic pressure. 34. Is osmosis a form of passive or active transport? Osmosis is a form of passive transport. 35. In the image to the right, the membrane is permeable to both glucose and fructose, but NOT sucrose. Use the image to the right to answer A-C A) Draw an arrow showing the direction of glucose diffusion Glucose will diffuse out of the cell B) Draw an arrow showing the direction of fructose diffusion Fructose will diffuse into the cell C) Draw an arrow showing the direction of osmosis. Glucose & fructose are balanced, but sucrose is not. The inside of the cell is hypertonic, so water will flow into the cell. 4.4 Active Transport 36. Explain the direction of the movement of molecules in active transport, in reference to concentrations. In active transport, molecules move from areas of low concentration to areas of higher concentration – the exact opposite of passive transport. This can be described as molecules moving AGAINST their concentration gradients. (Picture a fish trying to swim against the stream – it takes a low of energy to do) 37. True or false: Active transport builds a concentration gradient True – biological concentration gradients would not exist without active transport. 38. As concentration gradients develop, is potential energy being stored or released in the gradient? (THIS IS CRUCIAL TO UNDERSTANDING OUR NEXT UNIT ON ENERGY CONVERSION IN CELLS) Active transport builds concentration gradients, requiring energy to push molecule from low to high concentrations. Some of this energy becomes STORED in the concentration gradient. 39. When a concentration gradient dissipates (molecules diffuse down a concentration gradient) is potential energy stored or released from the gradient? (THIS IS CRUCIAL TO UNDERSTANDING OUR NEXT UNIT ON ENERGY CONVERSION IN CELLS) As molecules/ions diffuse down their concentration gradients, energy is RELEASED from the gradient. 40. Which situation is active transport analogous to: allowing a ball to roll downhill or pushing a ball uphill? Explain your answer. Active transport is analogous to pushing a ball up hill – it takes a lot more work than simply letting a ball roll downhill. 41. What do we call proteins that engage in active transport of molecules and ions? These proteins are called protein pumps 42. What two forms of bulk transport in the cell? The two major forms of bulk transport are exocytosis and endocytosis. Both are forms of active transport, meaning they require energy to happen. 43. Describe the difference between endocytosis and exocytosis Endocytosis is bulk transport into the cell. Large particles accumulate outside of the cell membrane. The membrane senses these particles and begins to form a vesicle around them, which then pinches off in the cytoplasm of the cell. Exocytosis is bulk transport out of the cell. Large particles are contained inside a vesicle in the cytoplasm which then fuses to the cell membrane, spilling all of the particles to the outside of the cell. 44. A neuron utilizes complex cellular transport mechanisms to send signals to other neurons. Answer the questions below to understand how. a) Na+ ions have an extracellular concentration of 145mM, and an intracellular concentration of 20mM. When a signal, called an action potential, reaches the neuron, Na+ specific ion channels open in the cell membrane. In what direction will Na+ diffuse? Na+ is more concentrated outside of the cell than inside of the cell. The direction of diffusion will be to the inside of the cell. b) The movement of Na+ triggers the opening of K+ channels. K+ has an intracellular concentration of 100mM and an extracellular concentration of 5mM. In what direction will K+ diffuse? K+ is more concentrated inside the cell than it is outside. Thus, when K+ channels open, K+ will be allowed to diffuse out of the cell. c) The movement of Na+ and K+ ions create what we call an action potential, an electrochemical signal which travels down the neuron that allows one neuron to “talk” to an adjacent neuron. Once one action potential is complete, the neuron needs to prepare for another action potential to come. To do this, the original Na+ and K+ concentration gradient must be restored. A special protein called the sodium-potassium pump restores this gradient. Will the sodium- potassium pump utilize active or passive transport? Does this require energy? To restore the concentration gradients, the sodium-potassium pump will utilize active transport to push Na+ back out of the cell and K+ back into the cell. This process requires energy in the form of ATP. Another action potential may now initiate. 5.1 Energy Conversion Molecules 1. What is cellular respiration? Briefly describe the process and write the full chemical equation. Cellular respiration is a process that converts the chemical energy stored in glucose to chemical energy stored in ATP. The equation for cellular respiration is: C6H12O6 + 6O2 → 6H2O + 6CO2 + ATP + Heat 2. Referring the kingdoms of life, what kingdoms of organisms perform cellular respiration? All eukaryotic kingdoms perform cellular respiration: plantae, animalia, fungi, protista  3. What role does glucose play in cellular respiration? What role does ATP play in cellular respiration. Is glucose more analogous to a bar of gold or more like cash money? Glucose is a reactant that is the source of energy for cellular respiration. ATP is a product that absorbs some of the energy stored in glucose. Glucose is more like a bar of gold because it is very energy-rich, but can’t be used for cell processes. 4. Draw the structure of ATP and label each chemical group and label the high energy bond. 5. Explain ATP hydrolysis and whether it results in a net release or net storage of chemical energy. ATP hydrolysis is when water is used to break the bond between the last two phosphates on ATP. ATP hydrolysis results in a net release of energy that can be harnessed for cellular work. 6. Explain ADP phosphorylation and whether it results in a net release or net storage of energy. ADP phosphorylation is the reverse reaction of ATP hydrolysis. A third phosphate group is added to ADP, producing ATP and water. This reaction requires a net absorption of energy that comes from glucose. 7. ADP + Pi → ATP + H2O requires a net input of energy. Where does this energy come from in mitochondria? This reaction requires energy from the oxidation of glucose. 8. On the following diagram label ATP, ADP, Hydrolysis, and Phosphorylation Phosphorylation Hydrolysis 9. How does the 2nd law of thermodynamics aid in our understanding of cellular respiration? The second law states that no energy transfer is 100% efficient and that when energy is transferred, some of it is lost as heat. This is the reason that we produce body heat: cells constantly convert glucose to ATP, transferring energy and releasing heat. 10. Define the following terms: oxidation and reduction Oxidation: A reaction resulting in the loss of electrons to another molecule. Reduction: A reaction resulting in the gain of electrons from another molecule. For every oxidation, there is a reduction. 11. Is NAD+ + 2e- + H+ → NADH an oxidation or reduction reaction? What about FADH2 → FAD + 2e- + 2H+ ? NAD+ + 2e- + H+ → NADH is a reduction reaction (gain of electrons) FADH2 → FAD + 2e- + 2H+ is an oxidation reaction (loss of electrons) NOTE THAT BOTH REACTIONS ARE REVERSIBLE 5.2 Cellular Respiration Overview & Glycolysis 12. Cellular respiration involved oxidative phosphorylation. Define what this term means. Oxidative phosphorylation means that the energy release from the oxidation of glucose provides energy to power the phosphorylation of ADP to ATP. 13. What is the difference between aerobic and anaerobic processes? Aerobic refers to a process that only occurs in the presence of oxygen. Anaerobic processes do not need to happen in the presence of oxygen. 14. List the 3 stages of cellular respiration in order. 1) Glycolysis 2) Citric Acid Cycle or Krebs Cycle (used interchangeably) 3) Electron Transport Chain (ETC) 15. Where in the cell does glycolysis take place? Is glycolysis aerobic or anaerobic? Glycolysis happens in the cytoplasm of the cell. It is an anaerobic process. 16. What are the three products of glycolysis and how many of each product are produced? The products of glycolysis are 2 pyruvate, 2 NADH, and a net gain of 2 ATP 17. In glycolysis, is glucose oxidized or reduced? What about NAD+? Glucose is oxidized to pyruvate in glycolysis. NAD+ is reduced to NADH in glycolysis. 18. Label each box in image showing the overall reactants and products of glycolysis 19. Where is pyruvate shuttled to after glycolysis, in the presence of oxygen? In the presence of oxygen, pyruvate is shuttled to the mitochondria after glycolysis to enter pyruvate oxidation and the citric acid cycle. 20. Why is it said that there is a net gain of ATP in glycolysis? There is a net gain of 2 ATP because 2 ATP are used to begin glycolysis and later another 4 ATP are produced. -2 + 4 = 2 21. Where is NADH shuttled to after glycolysis, in the presence of oxygen? In the presence of oxygen, NADH is shuttled to the electron transport chain to drop off its high energy electrons to help make ATP. 5.3 Citric Acid (Krebs) Cycle 22. Draw the mitochondria. Label the outer membrane, inner membrane, mitochondrial matrix, and intermembrane space.  Intermembrane Space 23. Where does the citric acid cycle take place? Is it an aerobic or anaerobic process? The mitochondrial matrix is the site of the citric acid cycle. The citric acid cycle is aerobic. 24. What are the products of pyruvate oxidation and the citric acid cycle, per glucose? What about per pyruvate? Fill out the table below to answer the question. CO2 3 6 NADH 4 8 FADH2 1 2 ATP 1 2 25. Before entering the citric acid cycle, pyruvate from glycolysis is oxidized to what molecule? Before entering the citric acid cycle, 2 pyruvate molecules are oxidized to 2 molecules of Acetyl-CoA, per glucose. 26. What is the primary purpose of the citric acid cycle? Specifically, how is the citric acid cycle related to the electron transport chain? The purpose of the citric acid cycle is primarily to produce electron carriers NADH and FADH2 for the electron transport chain. NADH and FADH2 carry high energy electrons from the citric acid cycle to the ETC. 27. Are NAD+ & FAD oxidized or reduced in the citric acid cycle? Where are they shuttled to following the citric acid cycle? Both NAD+ and FAD are reduced to NADH and FADH2 respectively. Citric acid is oxidized. NADH and FADH2 are both shuttled to the electron transport chain to drop off their high energy electrons to help make ATP. 28a. By the end of both glycolysis and citric acid cycle, how many total ATP, CO2 NADH, and FADH2 have been produced, per glucose? By the end of glycolysis and the Krebs cycle the cell has produced 4 ATP, 8 NADH, 2 FADH2, and 6CO2. 28b. What happens to the CO2 produced by animal cells? It is exhaled from our bodies. 5.4 Electron Transport Chain 29. Where does the electron transport chain take place? Is this process aerobic or anaerobic? The electron transport chain takes place primarily in the inner mitochondrial membrane. This process is aerobic. 30. Given what we know about the first step in the electron transport chain, why are NADH and FADH2 referred to as “electron carriers”? NADH and FADH2 are electron carriers because they carry high energy electrons, obtained by the oxidation of glucose, from glycolysis and the citric acid cycle to the electron transport chain to make, where the electrons are used to help make ATP. 31. Are NADH and FADH2 reduced or oxidized by the ETC? NADH and FADH2 are oxidized by the ETC (recall that they are reduced in glycolysis & citric acid cycle) 32. Explain how active transport is involved in the electron transport chain? The high energy electrons gained from oxidation of NADH and FADH2 are used to build a concentration gradient of H+ protons, storing potential energy between the intermembrane space and mitochondrial matrix. 33. Describe the H+ (proton) concentration gradient between the mitochondrial matrix and intermembrane space. The proton gradient goes from a high concentration of H+ protons in the intermembrane space to a low concentration of H+ protons in the mitochondrial matrix. 34. Recall from Unit 4 – does the concentration gradient between the matrix and intermembrane space store potential energy or release potential energy? The concentration gradient between the high H+ intermembrane space and low H+ matrix stores potential energy that will be harnessed by ATP synthase to phosphorylate ADP + P → ATP 35. Recall from Unit 4 – why can’t H+ ions (protons) diffuse directly through the inner membrane of the mitochondria? H+ ions cannot diffuse directly through the inner membrane of the mitochondria because they are hydrophilic ions. As we learned in unit 4, hydrophilic ions are blocked from permeating through the hydrophobic barrier put up by the membrane. 36. Describe the role of ATP synthase in the passive transport of H+ (protons) in the electron transport chain. Be sure to reference the energy dynamics of passive transport in your explanation H+ are free to diffuse through ATP synthase, which harnesses the energy release of diffusion to phosphorylate ADP to ATP. Recall that phosphorylation requires an energy input. Thus, glucose transferred energy to NADH and FADH2 which transferred the energy to the H+ proton concentration which ATP then uses to make ATP. 37. How many ATP are produced by ATP synthase per glucose in the electron transport chain? Roughly 28-32 ATP are produced per glucose by ATP synthase alone. 38. What molecule is known as the final electron acceptor of cellular respiration? What does this molecule become reduced to when it accepts electrons from the ETC? O2 (oxygen gas) is the final electron acceptor in cellular respiration. O2 has the highest affinity for electrons in the mitochondria. Electron movement that powers active transport of the H+ gradient is driven by the presence of O2. Therefore, O2 is absolutely required for electron transport function. When O2 accepts these electrons, it becomes reduced to H2O 39. Compare the total ATP output of glycolysis, the citric acid cycle, and the electron transport chain (use the table on slide 58 for help) Glycolysis gives net of 2 ATP Citric Acid cycle gives 2 ATP Electron Transport chain gives 28-32 ATP Total: 32-36 ATP per glucose 5.6 Fermentation 40. Is fermentation considered a stage of cellular respiration? Defend your answer. No fermentation is more of a short-term backup plan for cells when oxygen is not available. Fermentation and cellular respiration have completely different chemical equations and are therefore completely separate, albeit related, processes 41. When you are performing heavy exercise, the citric acid cycle and electron transport chain in your muscle cells will shut down and your muscles will kick into fermentation. Why does this happen? Your muscles can become depleted of oxygen quickly during exercise. The electron transport chain becomes inactive because oxygen is required to be the final electron acceptor and influence the movement of electrons. The citric acid cycle is aerobic because the citric acid cycle relies on the electron transport chain for the regeneration of NAD+. If there is not ETC, then there is no NAD+ in the mitochondria. If there is no NAD+, the citric acid cycle won’t happen. Aerobic. 42. Where does fermentation happen in the cell? Is it an aerobic or anaerobic process? Fermentation is anaerobic and it happens in the cytoplasm 43. The electron transport chain is responsible for oxidizing NADH back to NAD+, which can be shuttled back to the cytoplasm to become re-reduced in glycolysis and allow the cell to continue making ATP. However, in anaerobic conditions, the electron transport chain becomes inactive. What role does fermentation play in relieving this problem? Use the diagram below to aid you. The cell still must find a way to make some ATP in anaerobic conditions when the electron transport chain is inactive. Glycolysis produces a net gain of 2 ATP and is anaerobic. However, glycolysis also requires NAD+ to be active. Fermentation takes the pyruvate produced by glycolysis and uses NADH to reduce pyruvate, regenerating NAD+. To put it concisely fermentation regenerates NAD+ for glycolysis in the absence of oxygen. 44. Compare the ATP output of cellular respiration versus glycolysis & fermentation. Given your answer, can cells survive for long periods of time in anaerobic conditions? Cellular respiration as a whole produces roughly 32-36 ATP at a time. Glycolysis and fermentation only produce a net gain of 2 ATP. Given this information, cells cannot survive for long in the absence of oxygen. 45. What type of organisms perform alcoholic fermentation? Give the equation for alcoholic fermentation. Yeasts and some bacteria perform alcoholic fermentation. + Pyruvate + NADH → Ethyl Alcohol + CO + NAD 2 46. What type of organisms perform lactic acid fermentation. Give the equation for lactic acid fermentation. Lactic acid fermentation happens in the muscles of animal. Pyruvate + NADH → Lactic Acid + NAD+ 5.6 Photosynthesis Overview 1. In one sentence, explain the purpose of photosynthesis Photosynthesis is the process by which photoautotrophs convert sunlight energy and CO 2 into the energetic carbohydrate glucose, producing oxygen as a byproduct. 2. Life on Earth can be broken in to two groups, heterotrophs and autotrophs. Which of these types of organisms perform cellular respiration? Which of these types of organisms perform photosynthesis? Both eukaryotic heterotrophs and autotrophs perform cellular respiration. Only autotrophs perform photosynthesis. 3. Photosynthesis is the lynch pin of nearly all ecosystems on Earth. Describe the flow of energy in to and through the biosphere. Sunlight shines down on Earth. Photoautotrophs convert sunlight to food. Heterotrophs eat the food. Every energy transfer involves some energy being lost as heat to the environment. 4. What is carbon fixation? The process of converting gaseous carbon in CO2 into solid carbon in the form of glucose, C6H12O6. 5. What does it mean to say photosynthesis is an anabolic chemical process? Do anabolic processes require an absorption of energy, or do they release energy? Anabolic processes build larger, more complex molecules from smaller, less simple molecules. This process requires energy to be absorbed. 6. Label each section of the chloroplast to the right. Your labeling should include: Thylakoid Outer membrane, inner membrane, stroma, granum, thylakoids Outer Membrane Inner Membrane Granum Stroma 7. Which type of plant cells generally contain the most chloroplasts? Cells of the leaf 8. Define pigment. Where are pigments found in chloroplasts? Pigments are molecules that absorb and reflect light, producing color. Pigments are found in the thylakoid membranes 9. Give two examples of pigments found in chloroplasts Chlorophyll and carotenoids are major photosynthetic pigments 10. The graph on the right shows the electromagnetic absorption spectra of different pigments. Interpret the graph. What kind of colors would these these pigments produce? The higher the peak, the more a certain wavelength is absorbed. Both chlorophyll a and b absorb wavelengths in the violet, blue, orange, and red sections of the spectrum, but have very low absorption in the green section of the spectrum. Thus, chlorophyll will reflect green, and appear green to the eye. Carotenoids absorb violets, blues, and some green, but reflect yellow, oranges, and reds. Thus, carotenoids will appear yellow, orange, or red, to the eye. 11. What are the two stages of photosynthesis and where in the chloroplast do they take place? The light dependent reactions, or light reactions, take place in the thylakoid membranes. The Light independent reactions, or Calvin Cycle, take place in the stroma of the chloroplast 5.7 Light Dependent Reactions 12. What are the molecular and energetic requirements of the light dependent reactions? The LDR require, photons (light), water, ADP, and NADP+ 13. What are the products of the light dependent reactions? The products of the LDR are O2, ATP, and NADPH. 14. What stage of cellular respiration are the light dependent reactions most similar to? The LDR are most similar to the electron transport chain in cellular respiration. 15. Label photosystem I, photosystem II, and ATP synthase in the image to the right. 16. In the image on the right, which of these membrane proteins are filled with pigments like chlorophyll and carotenoids? Photosystems II and I 17. What happens to the special pair of electrons in chlorophyll when they absorb sunlight? The special pair of electrons in chlorophyll becomes excited – meaning they absorbed energy. 18. Does electron excitation immediately cause chlorophyll to become oxidized or reduced? What happens to these excited electrons? Electron excitation causes for chlorophyll to become oxidized. The excited electrons are passed from the photosystem to the photosynthetic ETC. 19. Chlorophyll is highly unstable in the oxidized form. Explain what this has to do with the production of O2 gas in the light dependent reactions. Chlorophyll is highly unstable in the oxidized form, so photosystem II uses a nearby H 2O molecule and oxidizes it, forming O2 gas. The electrons from water are used to re-reduce chlorophyll, stabilizing chlorophyll. 20. What happens to oxygen after being produced in the light dependent reactions? It diffuses from the leaf cell, eventually exiting the plant through stomata in the leaves. 21. Explain how active transport is involved in the light dependent reactions. Your response should include the following vocabulary: H+, stroma, thylakoid space, electrons, proton pump, electron transport chain, concentration gradient. As excited electrons are passed from PSII through the ETC, H+ ions are pumped via protein pumps from a low concentration in the stroma to a high concentration in the thylakoid space. Therefore, a proton concentration gradient has been formed, very similar to the one built in cellular respiration. 21. Explain how passive transport is involved in the light dependent reactions. Your response should include the following vocabulary: H+, ATP synthase, stroma, thylakoid space, diffusion, ADP, ATP, photophosphorylation Due to the concentration gradient formed during active transport, H+ ions naturally will diffuse through ATP synthase from the thylakoid space to the stroma. This process releases energy from the concentration gradient, and this energy is harnessed by ATP synthase to phosphorylate ADP to ATP. This specific type of phosphorylation in called photophosphorylation because the energy used to build the concentration came from photons (sunlight) 22. What happens to ATP after it is produced in the light dependent reactions? ATP is produced in the stroma and will participate in the next stage of photosynthesis, the Calvin Cycle, which also happens in the stroma. 23. Happens to the special pair of electrons in chlorophyll when photosystem I absorbs photons? Does chlorophyll become oxidized or reduced in this process? Just like in PSII, the electrons in chlorophyll become excited and chlorophyll becomes oxidized. 24. What electron carrier is reduced following the excitation of electrons from photosystem I? The high energy electrons from PSI’s chlorophyll are used to reduce NADP+ to NADPH. 25. What happens to NADPH after being produced in the light dependent reactions? NADPH is produced in the stroma and will participate in the Calvin Cycle, which also takes place in the stroma. 5.8 The Light Independent Reactions (The Calvin Cycle) 26. What are the requirements of the Calvin Cycle? The Calvin Cycle requires CO2, ATP, and NADPH 27. What are the products of the Calvin Cycle? The Calvin Cycle produces G3P (used to make glucose), ADP, and NADP+ 28. Where do the Light Independent Reactions take place in the chloroplast? The stroma of the chloroplast. 29. Remind yourself, what is carbon fixation? Carbon fixation is the process of converting gaseous CO2 in to solid glucose. 30. How are stomata involved in the exchange of gases by the leaf and the environment? Stomata allow for carbon dioxide to enter the leaves of the plant, while oxygen is released from the leaves. 31. The Calvin Cycle has three phases. What is the first phase called? The first phase is called carbon fixation 32. In carbon fixation, one CO2 is bonded to one 5-carbon molecule called RuBP. This reaction is catalyzed by an enzyme called RuBisCO. The six-carbon product immediately breaks down into two 3-carbon molecules called 3PG. 33. What is the second phase of the Calvin Cycle called? Reduction of 3PG 34. In the second phase of the Calvin Cycle, two 3PG are reduced to two G3P by two molecules of NADPH. Two ATP are also hydrolyzed in this process. Therefore, energy has been transferred from NADPH and ATP to G3P. 35. So far from questions 31-34, we have generated two molecules of high energy G3P. G3P is a precursor to glucose. G3P has 3 carbons each. Glucose has 6 carbons. How many G3P are needed to make glucose? 2 G3P are required to make glucose. G3P = 3 carbons each, glucose = 6 carbons 36. Given your answer to question 35, is there enough G3P left over after making glucose to regenerate the 5-carbon molecule RuBP for the Calvin Cycle? What is the solution to this problem? (Hint: How many Calvin Cycles must be happening simultaneously in order to produced 1 glucose and regenerate RuBP?) No, the way we described the Calvin Cycle only gives a total of 6 carbons in the form of 2 G3P. We need both of those G3P to make glucose. Therefore there is no carbon left over to regenerate the 5-carbon RuBP. In reality, there are 6 Calvin Cycles working in coordination with each other. 6 Calvin Cycles produce 12 G3P which is equal to 36 carbons. Two of those G3P can be used to make glucose, leaving 10 G3P (30 carbons) left over. Those 30 carbons can be rearranged to form six molecules of 5-carbon RuBP, replenishing all 6 Calvin Cycles. 37. In the Light Independent Reactions, CO2 is reduced to glucose. 5.9 Environmental Influences on Photosynthesis 38. Describe the role of H2O in photosynthesis. How is it practically the reverse of the role of O2 in cellular respiration? H2O is the initial electron donor of photosynthesis, becoming oxidized to O2. In cellular respiration, O2 is the final electron acceptor, becoming reduced to H2O. 39. Draw a graph to the right showing the relationship between carbon dioxide concentration and the rate of photosynthesis. Don’t forget titles and axis labels. You do not need to include numbers or units. 40. Which molecule binds more tightly to the active site of RuBisCO, O2 or CO2? O2 binds more tightly to the active site of RuBisCO than CO2 does. 41. Describe how your answer to question 40 is related to the problematic process of photorespiration? If O2 binds to RuBisCO instead of CO2, this means the carbon fixation step of the Calvin Cycle can’t happen. This means less glucose will be produced by the plant, which comes at high metabolic cost. The plant will suffer. 42. In what type of climates are plants at most risk of photorespiration? This happens in hot, arid climates where plants must balance keeping their stomata open for gas exchange with keeping their stomata closed to reduce the rate of transpiration (water loss) from leaves. At high temperatures, plants want to limit water loss by keeping stomata closed, but closed stomata also mean O2 gas will build up in plant cells. 43. What adaptations have C4 and CAM plants evolved to limit photorespiration? C4 plants, like sugar cane, can store CO2 in special cells called bundle sheath cells, which allows the Calvin Cycle to be totally separated from the light dependent reactions where oxygen is produced. By isolating the Calvin Cycle from high oxygen concentrations, photorespiration is limited. CAM plants close their stomata during the day when it is hot outside to limit transpiration, and then open their stomata at night when temperatures are cooler, allowing for gas exchange to occur.