Q2 STEM5 Past Paper - Biology PDF

SOLUTION - Mixture wherein 2 or more substances are mixed evenly CONCENTRATION - Amount of solute in a solution CONCENTRATION GRADIENT - The gradual difference in the concentration of solutes in a solution between 2 regions CELL MEMBRANE & CELL WALL - All cells have a cell membrane made o...

SOLUTION - Mixture wherein 2 or more substances are mixed evenly CONCENTRATION - Amount of solute in a solution CONCENTRATION GRADIENT - The gradual difference in the concentration of solutes in a solution between 2 regions CELL MEMBRANE & CELL WALL - All cells have a cell membrane made of proteins and lipids - Some cells have cell membranes and cell walls (ex: plants fungi, and bacteria) - Plant cells have a cell wall made of cellulose (fiber in our diet) - Bacteria and fungi also have cell walls, but they do not contain cellulose - Cell membranes and cell walls are porous allowing water, carbon dioxide, oxygen, and nutrients to pass through easily Functions of cell membrane: - Separates components of a cell from environment (surrounds cell) - “Gatekeeper” of cell (regulates flow of materials into and out of cell–selective permeable) - Helps cell maintain homeostasis (internal stable balance) M3L1: Transport Mechanisms PHOSPHOLIPIDS - Main component in cell membranes - Line up in a bilayer arrangement, acting as a barrier to water-soluble molecules - Amphipathic bc they have both hydrophilic and hydrophobic parts Structure: Head - Made of one molecule of glycerol and a phosphate group - Polar because of the phosphate group (which makes it hydrophilic and soluble in water) Tail - Two fatty acids - Non-polar and hydrophobic. Insoluble in water. TYPES OF TRANSPORT PASSIVE - No added energy - Ex: Diffusion, osmosis, facilitated diffusion 1  DIFFUSION OSMOSIS Movement of small particles across a Diffusion of water through a selectively permeable selectively permeable membrane like the membrane like the cell membrane cell membrane until equilibrium is reached High to low concentration High to low concentration Both solvent and solute are free to move Only the solvent crosses the membrane Occurs in all states of matter Only happens in liquid state FACILITATED DIFFUSION - Movement of larger molecules like glucose through the cell membrane (larger molecules must be “helped”) ➔ Proteins in the cell membrane form channels for large molecules to pass through ➔ Proteins that form channels (pores) are called protein channels - The spontaneous passage of molecules or ions across a biological membrane passing through specific transmembrane integral proteins. - Sugar molecules enter and exit a cell in this process TONICITY - A measure of the effective osmotic pressure gradient; the water potential of two solutions separated by a semipermeable cell membrane. 2 Outside: less concentrated Outside & inside: same Outside: more concentrated Inside: more concentrated concentration Inside: less concentrated Water enters cell No net movement of water Water leaves cell Contains a higher concentration of solute than the solution it is being compared with Having a lower osmotic having the same osmotic having a greater osmotic pressure than another; a cell pressure pressure than another in this environment causes water to enter the cell, causing it to swell. Cell intakes water from its Cell maintains water Cell loses water to its environment (plant cell content environment (plant cell becomes turgid when put into undergoes plasmalysis in a a hypotonic solution) hypertonic solution) Swollen red blood cell Normal red blood cell Red blood cell shrinks ACTIVE - Added energy required (molecules must be pumped against concentration gradient) - Movement of a substance across a cell membrane against its concentration gradient (from low to high concentration) facilitated by ATP conversion - Low concentration to high concentration “up” the concentration gradient 3 TYPES OF ACTIVE TRANSPORT: Membrane Pump (protein pumps) - A carrier protein uses energy from ATP to move a substance across a membrane, up its concentration gradient: Endocytosis - A type of active transport that moves particles, such as large molecules, parts of cells, and even whole cells, into a cell. - Cells take in (ingest) substances - Process 1. Depression in cell membrane folds in enclosing material from outside of the cell 2. Pinched off forming membrane-bound vesicle - Vesicle fuses with lysosomes - Fuse with other organelles ➔ Phagocytosis – The process by which large particles, such as cells or relatively large particles, are taken in by a cell. Exocytosis - Exporting large molecules outside of the cell - Process: 4  1. Packaged in Golgi Apparatus 2. Vesicle transports to the cell membrane 3. Vesicle fuses to membrane - Contents released - Vesicle becomes part of membrane CELL MEMBRANE COMPONENTS: 1. Cholesterol - manages the fluidity of the membrane and stops the phospholipids from sitting too closely together. This stabilizes them and reduces the chance of the membrane freezing in cold temperatures. M3L2: Biomolecules BIOMOLECULES (building blocks of life) - Lifeless organic compounds form the basis of life (they build up the living system and are responsible for their growth and maintenance ex: carbohydrates, proteins, vitamins, lipids, etc). - Large organic molecules that are normally present as essential components of living organisms - Biomolecules -> cells -> tissues -> organs -> living organism 1. CARBOHYDRATES - Organic molecules made up of C, H, and O - Important source of energy of many organisms including humans. 5  - Classified into the number of sugar compounds in their molecules - Also called saccharides, derived from the Latin word saccharum, which means sugar FUNCTIONS - Provide energy - Precursor of other biomolecules - Storage (energy reserve) - Part of nucleic acid structure - Component of cell membrane (with lipids) - Various cell-cell & cell-molecule recognition processes (with proteins) CLASSES a. MONOSACCHARIDES - Simplest carbohydrates - Monomer for carbohydrates - Classified by: a. Number of carbon atoms b. Functional group Aldose: contains an aldehyde group Ketose: contains a ketone group Monosacch Other name Info Pic aride Glucose Dextrose Found in large quantities D-glucose throughout the living world Blood sugar Primary fuel for living cells Its dietary sources include starch & disaccharides, lactose, maltose, and sucrose Most abundant monosaccharide Fructose Levulose Found in some vegetables and in Fruit sugar honey The sweetest sugar, twice sweet as sucrose 6  Sweetening agent in processed food products Can be found in semen Galactose Brain sugar Necessary to synthesized lactose, glycolipids, certain phospholipids, proteoglycans, and glycoproteins. Found in some plants and in dairy products Simple sugar that is normally transformed in the liver before being used up as energy. Crucial for human metabolism, with an established role in energy delivery and galactosylation of complex molecules. Although galactose is not considered an essential nutrient in general, it could be conditionally essential in infants in the context of rapid growth. 7 b. DISACCHARIDES - Formed when 2 monosaccharides are linked together, with water as the other product of the reaction - This reaction joins 2 monosaccharides and loses water Disaccha Other name Info Pic ride Sucrose Table sugar Produced in the leaves and stems of Cane sugar plants Beet sugar Contain both glucose and fructose residues linked through glycosidic bond between anomeric carbons Provides your body with the energy required to perform physical and mental functions Increases energy intake, body weight, fat mass, and blood pressure (adds sweetness but not healthy) Lactose Milk sugar Disaccharide composed of one molecule of galactose linked through the OH group on C1 in a B-glycosidic linkage to the OH of C4 of a molecule of glucose Ppl with this intolerance are unable to fully digest lactose in milk, which makes them have diarrhea, gas, and bloating 8  Maltose Malt sugar Intermediate product of starch hydrolysis Disaccharide with a glycosidic linkage between 2 glucose molecules During digestion, starch is partially transformed into maltose by the pancreatic or salivary enzymes called amylases; maltase secreted by the intestine then converts maltose into glucose One of the main sources of glucose (crucial nutrient bc it is used chiefly in energy metabolism) Glucose and maltose will raise blood glucose levels most rapidly of all sugars and therefore increase insulin secretion. Whereas fructose will have the least effect on glucose and insulin, but it will raise triglyceride levels c. OLIGOSACCHARIDES - Carbohydrates that contain 3-10 monosaccharides - The arrangement of these monosaccharides in the oligosaccharide determines the blood type of a person d. POLYSACCHARIDES (complex carbohydrates) - Long chains of monosaccharide units - Polymer of monosaccharides - Similar to disaccharides (the monosaccharides are linked through glycosidic bonds in polysaccharides) 9  Polysacch Other name Info Pic aride Starch Principal food reserve in plants - polymers of a-D-glucose units Glycogen Storage polysaccharides in animals Bush-like with a (1 -> 6) branch points Every 8-12 glucose residues for glycogen Cellulose Polysaccharide composed of glucose residues linked by glycosidic bonds Most important structural polysaccharide of plants Comprises one-third of plant biomass, hence it is the most abundant organic substance on earth Not digested by human beings but can be digested by some animal species using the enzyme cellulase Chitin Polysaccharide that is like cellulose, both in its biological function and its primary, secondary, and tertiary structure Present in the cell walls of fungi and is the fundamental material in the exoskeletons of crustaceans, insects, and spiders Structure of this (extended ribbon) is identical to cellulose, except that the -OH group on each C-2 is replaced by -NHCOCH3, so that the repeating units are N-acetyl-D-glucosamines in B(1,4) linkage 2. LIPIDS - Large, nonpolar biomolecules - Mainly composed of carbon, hydrogen, and oxygen - Includes fats, oils, some vitamins, and hormones - Functions as energy storage and as part of cell membrane 10  - Unlike proteins, nucleic acids, and carbohydrates, lipids do not have repeating basic structure Functions: - Source of energy - Protective coating of organisms - Cell membrane is made up of phospholipid bilayer - Serves as hormones and vitamins a. Fatty Acids - Essential components of some lipids - Long-chained carboxylic acids that have an even number of carbon atoms Fatty acid Info Pic Saturated Fatty acid chains that have predominantly single bonds Solid at room temp Unsaturated Has one or more double bonds Liquid at room temp Trans fat Raises Low-Density Lipoprotein (LDL) Decreases High-Density Lipoprotein (HDL) Increases risk of having type 2 diabetes 11 b. Waxes - Lipids that are produced by both plants and animals - Structurally related to the triglycerides because of the presence of fatty acids - Composed of a fatty acid with a long chain of alcohol - Nonpolar substances that have many different functions in the organisms that produce them c. Phospholipids - Lipids that contain phosphate groups and are biologically very important molecules - Composed of a phosphate “head” (hydrophilic) and a fatty acid “tail” (hydrophobic) 12  d. Steroids - Lipids without fatty acid chains - Built from the basic four-ring steroid structure, composed of 3 six-membered rings and a five-membered ring - Some steroids have hydroxyl groups that help balance their solubility in water Steroid Info Types hormone Sex Controls 1. Estrogens - female sex hormones hormones reproduction and 2. Androgens - male sex hormones secondary sex 3. Progestins - pregnancy hormones characteristics Adrenocorti Regulates 1. Mineralocorticoids - controls the balance of Na+ and coid numerous K+ ions in cells and body fluids hormons biochemical 2. Glucocorticoids - control glucose metabolism and processes in the counteract inflammation body 3. PROTEINS - Biomolecules composed of amino acid units - Essential in organisms because of their diverse functions - There are 20 common amino acids found in proteins and these are known as the essential amino acids - Comprise about 50% of our body weight - Most structurally complex polymer 13  - Helps in biochemical reactions - Helps our immune system, digestion of food, Blood clotting, Delivery of oxygen, and Body activity regulation Protein function Info Example Transport proteins carry small particles, such as food and Hemoglobin, a protein in waste, to different parts of the body. quaternary structure, is a respiratory pigment Structural These are responsible for the strength insect exoskeleton is made and shape of certain structures in the up of both chitin and protein body Antibodies Protein molecules produced by the immune system to fight off pathogens Receptors Proteins receive signals from other sources, and these signals are usually in the form of chemicals and compounds 4. NUCLEIC ACIDS - Biopolymers are usually found in the cell’s nucleus/nucleoid - Store and transmit genetic information - Made up of: a. 5 carbon sugar (ribose or deoxyribose) b. Phosphoric acid molecule c. Nitrogenous base 14 Nucleotides - Monomers of nucleic acids - Made up of a 5-carbon sugar, a phosphate, and a base Component DNA RNA Basic info Storage of genetic info Use protein-coding info of DNA Expression of genetic info Protein synthesis Ability to be replicated RNA production Variation through mutation mRNA, tRNA, rRNA Sugar Deoxyribose Ribose Nitrogenous A, G, T, C A, G, U, C bases Adenine, Guanine, Thymine, Uracil Cytosine Nucleotides Deoxyribonucleotides Ribonucleotides M3L3: Photosynthesis PHOTOSYNTHESIS - Process that converts solar energy into chemical energy that is used by biological systems (that means us). - Has 3 major events: 1. Sunlight is converted into chemical energy 2. Water is split into oxygen 3. Carbon dioxide is fixed into sugars 15  - Photosynthesis is carried out by certain bacteria, plants, most algae, cyanobacteria, and phytoplankton These organisms are known as photoautotrophs or producers meaning they make their own food and energy from the sun Consumers such as herbivores and carnivores depend on the products of photosynthesis that producers make to live GLUCOSE - Simple sugar because it is one of the smallest units of carbohydrates - During photosynthesis, plants produce glucose molecules when they convert light energy into chemical energy. The chemical energy is stored in the bonds of glucose - Plants also use the glucose they produce for energy. When plants produce excess glucose, they store it in their leaves - Plants produce sugars as a source of food. However, they produce way more than they need to survive. This is a great benefit for all the species that depend on glucose for energy - All biological energy comes from glucose - When animals digest plants, they break down the glucose bonds to release stored energy to power their bodies - Glucose molecules can be broken apart for energy to power reactions Plants can also make glucose into carbohydrate chains called polysaccharides. There are 2 polysaccharide chains in plants: 1. Cellulose - The structural component of cell walls 2. Starch - Long-term energy storage that the plant can use later Through evolution, plant cells, certain bacteria, and some algae have acquired chloroplasts to help carry out the photosynthetic reaction. CHLOROPLASTS - Where photosynthesis occurs - Plastid or plant cell organelle Thylakoids – round flattened discs, lined by pigments such as chlorophyll and cartenoids ➔ Chlorophyll – green pigment and is the most abundant. – absorbs all wavelength colors except green, which is reflected off giving plants their green appearance. – These pigments harvest light energy packets (photons) when they absorb sunlight. Granum – stack of thylakoids 16  Stroma – space inside chloroplasts ENDOSYMBIOTIC THEORY (endo = inside) - Plant cells were once ancient eukaryotic cells that had enveloped a cyanobacteria. Eventually, the cyanobacteria became a part of the cell and dependent upon it for life which in turn gave the cell the ability to photosynthesize. - Mitochondria are also believed to have been engulfed by ancient eukaryotic cells through endosymbiosis - There are many reasons why scientists believe this theory: Chloroplasts have their own DNA that is different from plant DNA but similar to bacterial DNA. CYANOBACTERIA (cyano = cyanin = aqua-colored) - Not all bacteria that undergo photosynthesis are cyanobacteria but all cyanobacteria are photosynthetic bacteria (purple bacteria are not cyanobacteria but were the first bacteria discovered that can photosynthesize) - Undergo photosynthesis in lakes, ponds, and oceans - Lack chloroplasts PHOTOSYNTHESIS REACTIONS Light reactions Dark reactions Light-dependent reactions capture light Light-independent reactions do not need light energy to power photosynthesis energy to power their reactions Occur during daytime Can occur day or night (occurs in every second of every day) Take place in thylakoids Occur in the stroma of chloroplasts Pigments in the thylakoid membranes form Fix carbon dioxide into glucose protein complexes called Photosystem I and Photosystem II. Discovered by 3 scientists: These photosystems harvest photons to “Calvin-Bensen-Bassham cycle / Calvin charge up energy-carrying molecules that will Cycle” power the dark reactions LIGHT REACTIONS 1. Energy absorbed by the chlorophyll during light reactions is used to power photosystem II that breaks the bonds of water absorbed through the plant’s roots 2. Freed oxygen atoms bind with each other to form the gas O2 O2 – byproduct of photosynthesis not used by the plant so it is released through the stomata of plants Stomata (greek “mouth”) – little pores in leaves that open and close to let oxygen our and carbon dioxide in 17  3. When water molecules break apart, the remaining 2 hydrogen atoms have a positive charge (protons). These protons are kept inside the thylakoid by the thylakoid membrane. 4. When there are more protons inside the thylakoid than in the stroma outside, protons want to leave the crowded thylakoid 5. When the protons (H+) cross the membrane to leave, a protein uses their passage to power ATP production 6. The ATP synthase attaches a phosphate group to ADP, making it ATP 7. Light energy absorbed by chlorophyll also powers photosystem I charges up the energy carrier molecule NADP+ to NADPH 8. NADPH then carries its energy over to power the dark reactions or Calvin Cycle DARK REACTIONS (start and end w the same products) 1. Starts with RuBP molecules and carbon dioxide molecules. An enzyme called Rubisco combines them into an unstable intermediate 2. Since the intermediate of combined RuBP and CO2 is unstable it quickly splits in half and forms 2 stable molecules of 3-PGA 3. The ATP and NADPH from the light reactions provide the energy to convert the 2 molecules of 3-PGA into their final form G3P 4. 2 G3P are joined to make a glucose molecule 5. The leftovers are reused in the light reactions to remake ATP and NADPH 6. Not all G3P is made into glucose 7. Most of the G3P made during the Calvin Cycle are made into RuBP, the starting molecule, with energy from ATP molecules. Calvin Cycle can begin again. 8. The spent ATP from the reaction leaves ADP and a phosphate group. These are reused in the light reactions to make more ATP. NADPH - nicotinamide adenine dinucleotide phosphate LIGHT REACTIONS SUMMARY DARK REACTIONS SUMMARY 1. Photons are absorbed by the pigments to power 1. Calvin Cycle photosystem I & II converts the carbon 2. Photosystem II splits water molecules into 2 protons from carbon dioxide (H+) and oxygen atoms are expelled as O2 gas through into glucose in the the stomata stroma (this is called 3. Protons cross the thylakoid membrane and power carbon fixation protein complex ATP synthase to make ATP because carbon is 4. NADP+ is powered up by photosystem I to make fixed into another NADPH to be used in dark reactions form) 5. Finish with charged NADPH, ATP, and released O2 PHOTOSYNTHESIS SUMMARY - Carried out in 2 steps 18  1. Two light-dependent photosystems 2. Light-independent carbon fixation cycle (Calvin Cycle) - Through these processes, the plant is able to convert sunlight, water, and CO2 into glucose and ATP - As a byproduct of these processes, O2 is released ENERGY-CARRYING MOLECULES - Used in photosynthesis and cellular respiration 1. ATP (adenosine triphosphate) - “Cellular currency” - Used to power all the reactions that take place in the cells of all living things - When ATP’s third phosphate is broken off, it releases energy that the cell can use - Made when a third phosphate is added to ADP (diphosphate) 2. NADP+ (nicotinamide adenine dinucleotide phosphate) - Can hold excited electrons charged from the light energy harvested by chlorophyll to become NADPH - NADPH passes electron its holding to power dark reactions and reverts back to NADP+ M3L4: Cellular Respiration CELLULAR RESPIRATION - Process by which the organisms obtain the energy available in the carbohydrates ATP - used as cellular energy currency 19  1. Aerobic respiration - A type of respiration which is carried on in the presence of oxygen by which the oxygen is obtained from air or from water in which is dissolved - Glucose + Oxygen -> Carbon dioxide + Water + Energy 2. Anaerobic respiration - Type of respiration in which a number of one-celled organisms, including yeast and many forms of bacteria, can carry on in the absence of oxygen - Glucose -> Lactic acid + Energy GLYCOLYSIS (glucose splitting reaction) - One molecule of glucose is broke down to form 2 molecules of pyruvic acid - Occurs in the cytoplasm of the cell - 4 ATP & 2 NADH are produced but this pathway produces a net gain of 2 ATP per molecule of glucose KREBS CYCLE (Citric Acid cycle) - Named after Hans Kreb - Occurs in the mitochondrion of a cell - For each turn of the cycle, 3 molecules of carbon dioxide are produced from one pyruvic molecules and 5 pairs of hydrogen atoms are removed by coenzymes NAD and FAD - Forms (per 2 molecules of pyruvic acid) carbon dioxide, 2 ATP molecules, 6 NADH molecules, and 2 FADH2 molecules 20 ELECTRON TRANSPORT CHAIN (ETC) - This occurs in the cristae of the mitochondria where a series of cytochromes and coenzymes exist - The electrons in NADH and FADH2 flow through a series of electron transport acceptors. The electron pass through a series of oxidation-reduction reaction, giving up energy to form ATP. 21 ATP Production Summary Cellular Respiration Step Energy Molecules ATP Totals Produced Glycolysis 2 ATP 2 ATP 2 NADH 4-6 ATP Oxidative Decarboxylation 2 NADH 6 ATP Krebs Cycle 6 NADH 18 ATP 2 FADH2 4 ATP 2 ATP 2 ATP TOTAL 36-38 ATP NOTE: Each ATP molecule is capable of releasing 7.3 kilocalories of energy per mole 22