h2 bio 9744 keyword bank

disclaimer: this keyword bank is far from comprehensive since i started it really late lol keywords topic stuff cell structure NUCLEUS - Protects DNA from degradation - presence of studded nuclear pores (transmembrane porin proteins) on nuclear envelope helps regulate the movement of substances into and out of the nucleus - nuclear envelope is a double membrane - 2 phospholipid bilayers - outer surface is studded with ribosomes - outer membrane is continuous with that of the endoplasmic reticulum - phosphate groups of outer membrane face the cytoplasm, those on the inner membrane face the nucleoplasm - phospholipid bilayer is held together by weak hydrophobic interactions between the non-polar hydrocarbon tails of phospholipids - CELL SURFACE MEMBRANE - phospholipid bilayer is held together by weak hydrophobic interactions between the non-polar hydrocarbon tails of phospholipids - cholesterol: carbon skeleton with 4 fused rings and a hydroxyl group at the end MITOCHONDRIA - inner mitochondrial membrane is thrown into many convoluted folds called cristae - high surface area to volume ratio for high rate of oxidative phosphorylation - cristae: high surface area for attachment of electron carriers and ATP synthase

SER - SER is made up of interconnected network of membrane-bound tubules - carbohydrate metabolism - Ca2+ store GA - GA is made up of flattened sacs called cisternae - RER - Ribosomes on RER synthesise polypeptides via translation - Polypeptides fold into native 3D conformation in the RER lumen - made up of an interconnected network of membrane-bound cisternae which is continuous with the outer membrane of the nuclear envelope - Tagging and packing of products for distribution to other parts of the cell such as the CSM and lysosomes via secretory vesicles - Carbohydrate metabolism - Synthesis of cell wall components - LYSOSOMES - autophagy - fuse with endocytic vesicles to form secondary vesicles TRANSPORT / MOVEMENT OF SUBSTANCES - diffusion: from a region of higher concentration to a region of lower concentration - hydrophobic core of the phospholipid bilayered cell surface membrane - Secretory / transport vesicles are transported along microtubules - transmembrane protein channels ADVANTAGES OF COMPARTMENTALISATION - Allows chemically incompatible reactions to be separated physically

- Reactions can take place simultaneously - Allows for accumulation of specific molecules in a specific organelle - Optimises conditions such as pH - Ensures high rate of reaction - standard questions - Advantages of compartmentalisation - Structure / functions of organelles - transport of glucose - fluid mosaic model - why are viruses considered living / non-living biomolecules 1. condensation reactions with the loss of one water molecule 2. glucose concentration gradient 3. glucose is polar, hence hydrophilic 4. weak hydrogen bonds / hydrophobic interactions / ionic bonds that stabilise the structure are broken SECONDARY STRUCTURE OF PROTEINS ALPHA-HELIX - formation of hydrogen bonds between the O atom of the C=O group with the H atom of an -NH group situated 4 amino acid residues ahead in the polypeptide - one turn every 3.6 amino acid residues BETA-PLEATED SHEETS - interchain or intrachain HAEMOGLOBIN - characteristics: 1) effective loading and unloading of oxygen, 2) soluble in aqueous blood, 3) maximized oxygen-carrying capacity, 4) cooperativity - each globin is folded into a specific 3D conformation with a deep hydrophobic cleft - Globular: amino acids with hydrophobic R groups are buried in the interior of the protein, those with hydrophilic R groups project outwards - each polypeptide has a haem group (prosthetic group, hydrophobic) with a central Fe2+ which can carry O2

- each molecule can carry 4 O2 - 4 subunits are loosely bound to each other - allows cooperativity - Dimers are held together by weak hydrogen bonds = can move with respect to each other = cooperativity - Mutation in sickle-cell anaemia: - T is replaced by A in the gene coding for the beta-globin chain - mRNA codon GAA → GUA - Glutamate (hydrophilic R group) → valine (hydrophobic R group) - HbA → HbS - At low oxygen concentrations, HbS molecules would clump together and polymerise to form fibres = circular biconcave shape → sickle shaped - Less flexible sickle shaped cells block narrow blood capillaries = low blood flow = reduced oxygen supply to tissues = tissue damage - COLLAGEN - characteristics: 1) large, long, fibrous, 2) insoluble, 3) stable triple helix, 4) high tensile strength - glycine present in every third residue - multiple hydrogen bonds form between the OH groups of hydroxylysine / hydroxyproline in the polypeptide chain - 3 helices are closely wound around each other to form a triple helix (tropocollagen) - compact - high tensile strength - tropocollagen molecules form cross-links via covalent bonds = high tensile strength - bundling of tropocollagen to form collagen fibrils, which bundle to form collagen fibres G PROTEIN LINKED RECEPTOR - characteristics: 1) embedding of receptor in plasma membrane to receive extracellular signals, 2) allows transmission of signals into cell

- activated G-protein binds to GPLR on the cytoplasmic side - extracellular signal binds to the receptor and triggers a change in the 3D conformation of the receptor - hydrophilic R groups of amino acids facing the exterior of the alpha helices interact with charged phosphate heads of the phospholipid bilayer by forming hydrogen bonds and ionic bonds - CELLULOSE - High tensile strength - Long straight chain - OH groups project outwards on both sides of the cellulose chain STARCH / GLYCOGEN - Starch is helical - Amylopectin is branched - Starch is compact = energy store - TRIGLYCERIDES - More energy-rich C-H bonds than an equivalent mass of glycogen = more energy can be stored and released in triglycerides - Solvent for fat-soluble vitamins - Long-term energy store - Heat insulator - Less dense than water = provides buoyancy PHOSPHOLIPIDS - Degree of saturation of fatty acid tails regulates membrane fluidity - Amphipathic standard questions - haemoglobin / cellulose / collagen / GPLR structure & function enzymes ENZYME MODE OF ACTION - Globular structure - Highly specific biological catalysts - Weak bonds such as hydrogen bonds and ionic bonds form

between the substrate and catalytic residues and binding residues at the enzyme active site - at high [substrate]: - active sites are saturated at any given moment in time - maximum rate of reaction is reached - as temperature increases, the molecules gain kinetic energy and vibrate faster - specific 3D conformation - at temperatures slightly above the optimum, the enzyme partially retains its specific 3D conformation - Rate of reaction is maximum at optimum temperature / pH - Acid-base catalysis - Strain effect: temporary weak bonds form between amino acid residues at the active site - Proximity effect: bind substrates next to each other temporarily to increase chance of reaction - Microenvironment effect: provides hydrophobic environment for non-polar substrates to react more readily - Serve as orientation surfaces for substrates to expose them for reaction - Lock and key hypothesis: active site of enzyme and substrate are exactly complementary - Induced fit model: active site of enzyme & substrate do not fit together exactly. Upon substrate binding, the active site undergoes a change in the 3D conformation to improve fit between substrate and enzyme - binding residues at active site form temporary bonds with the substrates - catalytic residues catalyse the enzymatic reaction - structural residues: maintain the structure of the enzyme’s active site DENATURATION - bonds holding the 3D conformation of the enzyme toge