Unit 2 Cell Cycle and Cancer Cellular Respiration and Photosynthesis PDF

Cell Cycle How it begins: - Sperm fertilizes the egg, the fertilized egg (zygote) goes through cell division repeatedly - Cell division through mitosis gives rise to many identical cells - Differentiation: a process that creates special structures and functions (specilized cells...

Cell Cycle How it begins: - Sperm fertilizes the egg, the fertilized egg (zygote) goes through cell division repeatedly - Cell division through mitosis gives rise to many identical cells - Differentiation: a process that creates special structures and functions (specilized cells become tissues -> organs -> organ system Cell differentiation Stem cells - undifferentiated cells that can become differentiated into one or more types of specialized cells - Organogenesis - process of body organ and organ system formation that follows gastrulation Two types: - Embryonic stem cells (cells that have never differentiated) cells that are inside a human embryo when it is a blastocyst and Implanted blastocyst becomes a gastrula = embryo with 3 differentiated germ layers - Adult stem cells aka somatic stem cells (cells found in adult bone marrow that are partially differentiated and can become bone, blood, cartilage, fat, and connective tissue) cells that are doing the replacement of the old cells and reparing of the damaged tissue Body system from most complex to most basic: Organism - one individual member of a species (example: human) Organ system - set of organs working together for a common function (example: digestive system) Organ - set of tissues working together for a common function (example: stomach) Tissue - group of cells working together for a common function (example: muscle tissue) Cell - most basic unit of life that has all characteristics of life (example: muscle cell) DNA vocab: - Chromosome: one long continuous thread of DNA that consists of thousands of genes and regulatory information - Gene: a section of DNA that contains the instructions for making a protein - Each human body cell has all of the DNA organized into 46 chromosomes (in normal body cells, chromosomes always occur in pairs of homologous chromosomes) (the DNA organized in 46 chromosomes and thousands of genes, provides the instructions for making proteins, which run your body) - Chromatid: one half of a duplicated chromosome - Sister chromatids: two identical chromatids - Centromere: region of the condensed chromosomes that looks pinched - Telomere: ends of the DNA molecule Cell cycle - repeated pattern of growth, DNA duplication, cell division that occurs in eukaryotic cells - Holds 2 purposes: (growth and repair) - Consists of 3 main phases: - Interphase: cell growth - Mitosis: cell division - Cytokinesis: cytoplasm separation which begins at the end of mitosis Interphase - growth phase of the cell cycle has 3 parts: - G1 phase = Gap 1 phase = cell grows and makes proteins - S phase = Synthesis phase = DNA replication occurs, doubling the number of chromosomes - G2 phase = Gap 2 phase = more cell growth and protein synthesis ***At the end of the interphase: the cell has 2 full sets of chromosomes*** Mitosis - the division phase of the cell cycle (1 cell becomes 2 identical daughter cells Prophase: - Chromosomes are condense and are visible as sister chromatied (in X’s) - Nuclear membrane disappears - Spindle fibers form *out of centrioles* Metaphase: - Spindle fibers connect to the centromere of each sister chromatid - Chromosomes line up in middle of the cell Anaphase: - Sister chomatids separate, pulling away from each other + becoming individual chromosomes - Chromatids move to opposite ends of the cell Telophase: - Chromosomes decondense and start to look like chromatin again - Nuclear membrane re-froms around chromosomes at each pole - Spindle fibers break down - Cytokinesis begins Cytokinesis: - The division of the cytoplasm into 2 individual cells - PLANT CELLS - cell plate forms midway between divided nuclei and gradually develops into a membrane - ANIMAL CELLS - forms a cleavage furrow that pinches the cell to 2 equal parts - End result -> 2 identical body cells How often do cells divide? - Every cell divides at different rate based on its need - Examples: Internal lining of intestines = 5 days Skin cells = every 2 weeks Red blood cells = 4 months Liver cells = 1 year Why do body cells divide? - Growth and repair - Cells can’t just get bigger to grow either - they have to stay sall to maintain a high surface area to volume ratio (this is most efficient energy-wise + allowos substances to move ina nd out of the cell more easily) Regulation (how do cells know when to divide and when not to?) (what happens if this regulation fails?) - Cell cycle is controlled by a chemical control system that starts and stops events in the cell cycle (PROTEINS PLAY A KEY ROLE!) - Regulation is: - External - signals that come from outside of the cell (example: hormone, nutrients) - Internal - signals that come from the cell’s own nucleus (example: DNA) Checkpoint - critical point where “stop” and “go” signals can regulate the cycle Apoptosis - programmed cell death - internal/external signals activate genes that produce self-destructive enzymes - Nucleus shrinks and breaks apart Cancer - uncontrolled cell division - Happens when the regulation of the cell cycle breaks down - Cancer cells divide much more often than healthy cells do - Leads to formation of tumors Tumors - clumps of cells that divide uncontrollably - Benign - abnormal cells typically remain clustered together - Malignant - cancer cells that break away from the tumor and move to other parts of the body (metastasize - spreading of disease from one organ to others) Causes of cancer: - Biological factors (age, inhertited genes) - Lifestyle choices (diet, exposure to UV radiation) - Viruses and other infections (HPV can cause cervial cancer) - Exposure to carcinogens - cancer causing agents; chemicals that cause cancer by mutating DNA (tobacco smoke) Revision cell cycle formative document: 1. What is the purpose of the cell cycle and mitosis? The cell cycle consists of a repeated pattern of growth, DNA duplication, and cell division that occurs in eukaryotic cells. Mitosis is cell division. Simply put, it is the process where cells divide themselves and multiply the number of cells. The purposes are the growth and repair of cells. 2. What happens during S-phase of the cell cycle? If a cell fails to go through S-phase before going through mitosis, what might be wrong with the daughter cells? During S phase of the cycle also known as the synthesis phase, DNA replication occurs, doubling the number of chromosomes. The S phase of the cell cycle is significant for DNA replication. If a cell skips through this phase before mitosis, the daughter calls could lack a complete set of chromosomes, which might possibly lead to genetic instability and possible chance of death. 3. Which phase of the cell cycle would be easiest to identify under a light microscope? Explain your reasoning. The mitosis phase, more specifically the metaphase phase of the cell cycle would be the easiest to identify under a light microscope. During the phase, chromosomes are maxmially condensed, hence, most noticeable under the light microscopy. 4. Explain the main difference between cytokinesis in plant cells and cytokinesis in animal cells. Cytokinesis in plant cells and animal cells differs in the mechanism of cell division. For plant cells, cytokinesis is involved in the formation of a cell plate, which eventually develops into a new cell wall. On the other hand, for animal cells, a cleavage furrow forms, and the cell membrane is pinched to form two daughter cells. 5. What can go wrong if the cell cycle runs out of control? Mutations in genes can cause cancer if the cell cycle runs out of control, more specifically accelerating cell division rates or inhibiting normal controls on the system, such as cell cycle arrest or programmed cell death. This can result in a mass of cancerous cells growing, which can develop into a tumor. Enzymes and Biochemical Reactions Metabolism - all of the chemical reactions within each cell of an organism - Provide energy for life’s processes - Create key molecules Overall, reactions absorb energy or release energy - Breaking a bond requires energy to be absorbed - Forming a bond allows energy to be released Due to the law of conservation of energy, no energy in the system is lost -> it just changes forms Biochemical reactions are either… - Catabolic - break down larger molecules into simpler compounds -> release in energy = exergonic - Anabolic - build larger molecules from smaller ones -> requires consuming energy to do it = endergonic All reactions require energy to happen… - activation energy - the amount of energy needed to make a chemical reaction to start Chemical Reactions (breaking + forming of bonds between different substances during chemical changes) - Reactants (substrate) - substances that are changed during a chemical reaction - Products - substances that are made by a chemical reaction Types of reactions 1. Endothermic: Absorbs energy (in the form of heat or light) - Example: photosynthesis 2. Exothermic: Releases energy (in the form of heat or light) - Example: Cellular respiration Key Biochemical Reactions: 1. Photosynthesis: 6CO2 + 6H2O → C6H12O6 + 6O2 Light energy is stored as chemical energy in sugar, therefore it is an endothermic reaction 2. Cellular respiration: C6H12O6 + 6O2 → 6CO2 + 6H2O Chemical energy in sugar is converted to chemical energy released as ATP, therefore it is an exothermic reaction Enzymes (Metabolic reactions are controlled by enzymes) - Enzymes are mostly proteins that speed up biochemical reactions by lowering the activation energy - Because they speed up reactions, they are also known as catalysts, which are substances that speed up reactions without being permanently altered More about Enzymes - They are very specialized molecules that bind two reactants and help to break or form bonds, which leads to the release of newly created products - They are not changed in a reaction and can be used over and over again - They are critical for the regulation of life’s processes in all organisms - Enzymes are very specific: - They have an active site that fits only one reactant - Once the reactant connects, the bond tightens = an induced fit - They can break bonds in a substrate to form two products __ - They can make bonds between substrates to form one product __ Denaturation - Enzyme’s active site gets deformed and loses its specific shape -> loss of biological activity (caused by environmental changes such as: extreme changes in pH, temperature, ion strength and solubility) - Some enzymes can be “renatured” to their original shape, but it is not common Ways to change the rate of a chemical reaction: 1. Temperature = increasing temperature increases the rate of the reaction. But if the temperature change is too high, the enzyme can denature (molecules are moving FASTER and colliding more with each other) 2. pH = how acidic a solution is (most enzymes only work at very specific pH, so if the pH changes it can affect the speed of reaction) 3. Reactant concentration = higher the amount of reactants the faster the reaction (more particle collisions) 4. Catalysts = (enzymes) speed up reactions (lower activation energy needed for the reaction to start) 5. Competitive Inhibitor = slows down reaction (competes with reactant for the active site on enzyme) Adenosine Triphosphate (ATP) Some backgound info: - Body need energy to run the cells - Body cannot directly use the food consumed for energy - The energy you CAN use in the food you eat is stored in its chemical bonds - To convert the energy into a form you body can directly use, the bonds have to be broken (energy is absorbed), and new bonds have to be formed (energy is released) - Once energy is converted into a more usable form, ATP carries it to be used for cell functions - ATP - an energy-carrying molecule that carries/stores energy for cell functions - It is the main energy currency for the cell Structure of ATP - Consists of… 1. Nitrogen base (adenine) 2. Sugar ring (ribose) 3. 3 phosphate groups held together by high energy bonds ATP - ADP Cycle - A lot of energy is stored in the bond between the last two phosphates - Energy is released when a phosphate group is removed (and added to another molecule) - ADP becomes ATP when a phosphate group is added - ADP is recycled - This is a chemiosmotic process (chemiosmosis - movement of ions down a concentration gradient) - Enzyme ATP synthase is used to add the third phosphate to ADP to make ATP, using energy from the food consumed Summary: When ATP is broken down, it releases energy for the cell to use and become ADP and a phosphate - Chemical equation: ATP → ADP + P + energy - Because more energy is given off than required, this is overall an exothermic reaction To make ATP, cells must join together ADP and a phosphate using energy from food - Chemical equation: ADP + P + energy → ATP - Because energy is taken in (it takes a lot of energy to attach the 3rd phosphate) this is overall an endothermic reaction Where does the energy come from? - Carbohydrates (most commonly broken down for ATP) - Lipids (broken down after carbs) - Proteins (least likely to be broken down for energy) Background info for Photosynthesis - All organisms need a constant supply of energy to survive - For most life on earth, the ultimate source of energy is the sun - Converting that energy source into something usable is accomplished by photosynthesis Photosynthesis - overall process by which sunlight (solar/light energy), water and carbon dioxide are chemically converted into chemical energy stored in glucose (a sugar/carbohydrate) - Water absorbed through the roots - CO2 absorbed through stomata - Chemical equation: 6CO2 + 6H2O → C6H12O6 + 6O2 Structure of a chloroplast - Photosynthesis takes place in the chloroplast which has 2 main parts - Grana = pancake-like stacks of thylakoid membrane - Stroma = fluid-like substance that fills the space between the grana Why are plants green? Because of the presence of the pigment chlorophyll - Chlorophyll a, chlorophyll b and other pigments called carotenoids absorb every color of light in sunlight except green Therefore, green is leftover and is reflected and is what we see How is light absorbed? Photosystems absorb light - Clusters of chlorophyll and proteins that trap energy from the sun - Chlorophyll is a pigment that can absorb sunlight - Energy is transferred to electrons -> makes excited electrons What are electron carriers? - Molecules that carry electrons in order to pass on their energy (example: Compound (NADP+) that can accept a pair of high-energy electrons and transfer them to another molecule) (NADP+ grabs/carries 2 electrons and a H+ -> becomes NADPH) - ATP and NADPH carry energy from the light-dependent rxn to the light-independent rxn Rate of photosynthesis Speed if affected by 3 factors: 1. Light intensity (excites more e- causing light reactions to happen faster) 2. Amount of CO2 (more ingredients to work with and process through cycle) 3. Temperature (increased temperature accelerates chemical reactions to a degree) Why would root cells in a plant do NOT need chloroplasts? - Chloroplasts catch sunlight, since roots are underground, they are not exposed to sun and therefore, the sunlight, so they cannot do photosynthesis Alternate Pathways Stomata = pores on underside of the leaf where… - Plants lose water - CO2 enters - O2 exits If it is too hot or fry out, the plant will close its stomata so that it doesn’t lose too much water and become dehydrated. If that happens then… levels of CO2 drop and the levels of O2 increase… Photorespiration: - Adds oxygen to the Calvin Cycle instead of carbon dioxide - This makes NO sugar or ATP (bad) - Wastes all of the plants' resources (bad) Two types of alternative pathways in plants to avoid this: 1. CAM: - Done by cacti and pineapples - Causes them to grow slowly - In CAM photosynthesis, plants can open their stomata at night (not so hot) and they can capture carbon dioxide and chemically store it 2. C4: - Done by corn and sugar cane - Partially close stomata during the hottest part of day - Allows them to only need ½ as much water as normal plants Stages of photosynthesis Photosynthesis can be divided into 2 sets of reactions 1. Light dependent reaction (requires solar energy) (aka the electron transport chain or light reaction) 2. Light independent reaction (does not require any solar energy) (aka the calvin cycle or dark reaction) Light-dependent reaction Purpose: capture energy from the sun and store energy in “energy-carrying molecules” (ATP + NADPH) Location: occurs in the thylakoid -> occurs in the Granum (stacks of thylakoid) -> occurs in the Grana (multiple stacks of thylakoid) Summary: - Water molecules are split into hydrogen and oxygen - Oxygen is released as a waste product - ATP and NADPH are “charged up” by the sun Details: - Energy from the sun is passed down the electron transport chain and is stored in the bonds of ATP and NADPH (light energy excites e- -> e- move down -> combine with the “final electron acceptors/carriers” of NADP+ and ADP, making NADPH and ATP) - That is a chemiosmotic process because H+ ions move down the gradient to make ATP - ATP, NADPH ,and H+ leave the grana and go into the stroma for the next stage Light-Independent Reaction Purpose: use the energy from the “energy-carrying molecules” from the light-dependent reaction to make sugar (glucose) Location: occurs in the stroma Summary: (Calvin cycle) - Series of enzyme-assisted chemical reactions powered by ATP and NADPH that produce three-carbon (3-C) (G3P) sugars from CO2 and the H from the water - Then these 3-C (G3P) sugars combine to make 1 glucose (C6H12O6) Details: (Calvin cycle) 1. Carbon fixation a. CO2 diffuses into stroma b. Enzyme Rubisco attach to 6CO2 to RuBP c. Produce 12 3-PGA 2. ATP and NADPH a. Energy from the ATP (phosphate groups) and NADPH transfer electron, H+ ions and electrons 12 G3P 3. Leave a. Two G3P leaves the cycle to become glucose b. The other G3P moves on to next step 4. Reboot a. The remaining 10 G3P converts back to RuBP by using phosphate from ATP and the cycle starts again  Cellular respiration Structure of mitochondria: - Cellular respiration take solace in the mitochondria which has 2 main parts 1. Inner membrane: Folded membranes 2. Matrix: fluid-like substance that fills the space Glycolysis - 1st stage in cellular respiration - Breakdown of glucose Purpose - 10 step process of splitting the 6-carbon molecule of glucose in half -> to form 2 3-carbon molecules called pyruvate - Occurs in the cytoplasm - Requires no oxygen (ANAEROBIC) - Produces a total of: 2 ATP and 2 NADH (1 glucose -> 2 pyruvate molecules and 4 ATP, but it uses 2 to get the process done, so only a total of 2) Decision time - After glycolysis, the cell must make a decision - If oxygen IS present: then the cell will go through a two step process (AEROBIC RESPIRATION) to obtain energy - If oxygen is NOT present: then the cell will go through the process of (ANAEROBIC RESPIRATION) aka fermentation, to obtain energy Photosynthesis Cellular respiration Equation 6CO2 + 6H2O → C6H12O6 + 6O2 C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP Type of reaction Endothermic (Light energy is stored as chemical energy) Exothermic (Chemical energy in sugar is converted to chemical energy released as ATP) Step 1 ETC (electron transport chain) Krebs Cycle Occurs in Grana, Uses and splits H2O, Makes O2 Occurs in Mito Matrix, Uses C6H12O6, makes CO2 Step 2 Calvin Cycle ETC (electron transport chain) Occurs in Stroma, Uses CO2, Makes C6H12O6 Occurs in Inner Membrane of Mito, Uses O2, Makes H2O Aerobic respiration 1. Citric Acid Cycle (Krebs Cycle) Purpose: - Make electron carries NADH and FADH2 to move on to the ETC Location: - Mitochondrial Matrix Process: - 8 steps of chemical reactions where 2 pyruvate molecules from glycosis are chemically converted to make 2 ATP (and some NADH and FADH2) - Releases CO2 as a waste product Details: - Pyruvate from glycolysis are converted into acetyl-CoA, which will then enter the Citric Acid Cycle - NAD+ and FAD act as electron carries and become NADH and FADH2 which carry electrons into the final step - The cycle happens for 2 times - 1 pyruvate → 4 NADH, 1 ATP, 1 FADH2, and 3 CO2 - Therefore, TOTAL = 8 NADH, 2 ATP, 2 FADH2 and 6 CO2 2. Electron Transport Chain (oxidative phosphorylation and chemiosmosis) Location: - Inner membrane of the mitochondria (called cristae) Process: - A series of reactions using the e- and hydrogens carried by NADH and FADH2 formed in the Krebs cycle - Enzyme ATP SYnthase helps to assemble ATP - Final electron acceptor after the e- have gone down the ETC is oxygen (oxygen combines with e- and H+ to make water) - Makes 32 ATP and H2O (when hydrogen bonds to oxygen) most ATP comes from this step Anaerobic Respiration (fermentation) 1. Lactic Acid Fermentation - Occurs in some bacteria and animal cells - Pyruvate from glycolysis is converted into lactic acid and 2 ATP 2. Alcohol Fermentation - Occurs in yeast when oxygen is not available - Pyruvate from glycolysis is broken down into alcohol, CO2 and 2 ATP Total ATP produced: Aerobic Respiration = 32-38 ATP (2 from glycolysis, 2 from krebs cycle, 34 from ETC) Anaerobic Respiration = 2-4 ATP