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Revision:AQA Biology Synoptic Paper - Linking of Topics
From The Student RoomTSR Wiki > Study Help > Subjects and Revision > Revision Notes > Biology > AQA Biology Synoptic Paper - Linking of Topics Tertiary structure of proteinsShape determined by sequence of amino acids. The secondary structure is produced by hydrogen bonds between the amino acid residues. TERTIARY STRUCTURE when the secondary structure is further folded to give a complex globular shape. Enzymes such as carbonic anhydrase, in acrosome, digestive enzymes, neurotransmitter.
Membrane receptorsProteins function as receptors/channels etc to allow movement of ions. Humoral immunity (complementary T-helper cells to the antigen presented on macrophage). Beta blockers block beta receptors so agonists cannot bind to it. Monoclonal antibodies attach only to tumour markers, so attach to cancer cells. Synapses, epithelial cells, receptors for hormones.
Movement across membranesMovement across membranes facilitated diffusion - Large molecules and charged ions cross through proteins - unlike oxygen and carbon dioxide. Formation of tissue fluid. Calcium ions enter sperm membrane during acrosome reaction - releases enzymes to digest jelly coat. placenta - villi folded into microvilli, counter-current system, short diffusion path. Contains mitochondria for ATP needed for AT of amino acids. Senescence causes myelin sheath surrounding axon to become thinner - more ions leak out of nerve cell. Water potential in small intestine lower in the first part due to Na+ and Cl- ions, water added to gut. Then ions pumped out into epithelial cells à raising water potential. So water moves back out by osmosis. Amino acids pass into epithelial cells via facilitated diffusion with Na+ ions. Glucose absorbed by AT - passes into capillaries via facilitated diffusion. Lipids pass into epithelial cells via micelles, resynthesised then into lacteals. resting potentials maintained by: phospholipid bilayer, voltage-sensitive gates shut. Large negatively charged protein molecules prevent incoming Cl- ions. Sodium-potassium pump. Saltatory conduction caused by myelin sheath preventing diffusion of ions, so AP jumps from one node to another.
EnzymesEnzyme reduced activation energy. ES Complex and induced fit theory. Competitive inhibitors. To diagnose and control disease e.g. glucose oxidase & peroxidase, absence of enzymes in faeces - chronic pancreatitis. High levels of enzymes in blood - acute pancreatitis. saprobionts secrete enzymes onto compounds to break them down. Nitrogenase catalyses reduction of nitrogen to ammonia. (nitrogen fixation). Hydrolases such as maltase/lactase/dipeptidase/proteases/lipase.
SA/Volume ratioThe larger the animal the smaller it is. Large animals need body shape with large surface area / specialised gas exchange system or a blood system. Affects BMR of people - large = more heat lost.
DNA/genetic codeNucleotides joined up by hydrogen bonds. Non overlapping and degenerate. Carcinogens make mutation of tumour suppressor genes more likely. Gametogenesis = mitosis-growth-meiosis-maturation. Oogenesis not completed until fertilisation and is unequal (polar bodies). In haemoglobin, DNA substitution causes sickle cell anaemia.
Translation/transcriptionTranslation/transcription mRNA to proteins with help of tRNA. Antibiotics can prevent DNA transcription/mRNA translation in bacterial cells.
Basic geneticsDNA replication via DNA polymerase. DNA à enzymes à metabolic pathway influences phenotype. Inheritance - co dominance/multiple alleles/dihybrid/sex linkage.
Genetic engineeringIsolating gene via complementary DNA, reverse transcriptase and mRNA, DNA probes. Cutting gene out through restriction endonucleases (sticky ends). Vector = plasmids. Antibiotic gene for resistance.
Transport principlesDiffusion and water potential. Haemoglobin pigment transports o2. Made of 4 subunits containing -haem and globin. Bohr shift (increases pp of CO2). Carbon dioxide reacts with water to form carbonic acid. Catalysed by carbonic anhydrase in red blood cells à splits into hydrogen ion and hydrogencarbonate ion. ß diffuse out into plasma, to correct this Cl- ions move into red blood cell. H+ ions carried by buffer solution haemoglobin.
Use of tracersDNA probes - electrophoresis separates DNA fragments by their size. (fragments made by restriction enzymes).
Photosynthesis/respirationLight dependent reaction - ATP & reduced NADP. Light independent - Carbohydrate. Respiration - glycolysis = glucose into private. Link reaction produces acetylcoenzyme A. Krebs cycle produces reduced coenzymes, co2 and ATP . Electron transport chain produces ATP and water. Respiratory quotient
Stimulus/responseAccelerator/vagus nerve affect heart rate. FSH, oestrogen and LH in menstrual cycle. Baby suckles, sending impulse to hypothalamus, prolactin & oxytocin, producing milk. nervous reflex =saliva, conditioned reflexes = smell of food causes secretion of gastric juice. Hormones Food in stomach causes release of gastrin - gastric juice. Food in small intestine causes secretion of CCKPZ (pancreatic enzymes and bile) and secretin (alkaline fluid). Action potential brought about stimulus opening voltage-sensitive Na+ gates. Disturbs adjacent membrane causing its Na+ ions to open as well. Synapses neurotransmitter causes AP in postsynaptic membrane. Pacinian corpuscle transduces mechanical pressure into nerve impulse. Rod and cone cells. Sliding filament theory during depolarisation, Ca2+ ions enter sarcoplasm, bind to complex and so reveal binding site. ATPase activity on myosin head occurs, cross-bridge forms and “power-stroke”. COLD - vasoconstriction, hair raising, shivering and increased metabolic rate. HEAT- vasodilation, increased sweating, decreased metabolic rate.
Negative feedbackControl of CO2 detected by chemoreceptors (medulla). à breathing rate. Blood cholesterol controlled by liver - changes how much it makes according to levels. Islets of Langerhans in pancreas control glucose conc. Hypothalamus detects temperature of blood flowing through it, initiates response via autonomic nervous system.
VariationIndependent assortment and chiasmata in meiosis 1 produce variation. Normal distribution = same mean/mode/median. GENE mutation - base deletion or substitution. Polygenic inheritance. SPECIES defined by being similar to each other but different to other species, and being able to produce fertile offspring.
Natural selectionStabilising e.g. birth mass. Directional e.g. warfarin resistance in rats. Disruptive selection e.g. peppered/black morphs.
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