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Biology Mock 2019


Define homeostasis. The maintenance of a relatively constant internal environment within small tolerance limits, despite changes in the external environment.
What are the 5 points in the stimulus response model? 1. stimulus 2. receptor 3. processing centre 4. effector 5. response
What are the 5 types of receptors? 1. Mechanoreceptor 2. Photoreceptor 3. Chemoreceptor 4. Nocireceptor 5. Thermoreceptor
Name and describe the 2 types of metabolic reactions. Anabolic: small molecules into larger molecules eg. amino acids --> proteins Catabolic: large/complex molecules into smaller molecules eg. starch --> glucose
Differentiate between a Sensory neuron and a motor neuron. Sensory neurons: Soma = side bulge along the axon. Dendritic terminals end in sensory receptors. Axon terminals end in many synapses. Motor neurons: Soma at dendritic end. The axon terminates in end plates and the dendritic terminals end in synapses.
Describe and explain the passage of a nerve impulse. (think sodium-potassium pump) Initially the membrane is polarised -resting potential: 3 Na+:2 K+. Impulse is triggered - depolarisation. Membrane becomes permeable to Na+ (action potential), Na+ diffuses into cell. Resting potential restored by membrane --> impermeable and Na-K pump.
What is the role of myelin? Insulates the axon against other impulses and speeds up transmission of the signal - signal is forces to leap from node to node.
What is the first step of signal transmission between neurons? (ie. Signal transduction) Impulse makes calcium ion channels open and calcium ions diffuse into the presynaptic cleft - stimulating exocytosis of secretory vesicles containing neurotransmitters.
What is the second step of signal transmission between neurons? (ie. Signal transduction) Vesicles release neurotransmitters into the synaptic cleft. The neurotransmitters bind to receptor binding sites on sodium channels.
What is the third step of signal transmission between neurons? (ie. Signal transduction) Binding of neurotransmitters opens sodium channels so sodium flows into the postsynaptic neuron, generating action potential. (Sodium-potassium pump).
What is the fourth step of signal transmission between neurons? (ie. Signal transduction) Neurotransmitter degrades so sodium channels close. Some neurotransmitter molecules are recycled back into the presynaptic neuron via endocytosis.
Why is the pituitary gland known as the 'master gland'? It produces so many hormones that affect hormone production by other endocrine glands.
Properties of Hydrophilic hormones. Water soluble, polar molecules derived from amino acids. Cannot pass through cell membrane unassisted so bind to receptors on the outside of the cells.
Properties of Hydrophobic hormones. Fat soluble, non-polar molecules derived from cholesterol. Need a companion molecule to pass through blood bu can detach and pass through cell membrane by independently. Binds to intracellular receptors.
What is upregulation? When a cell is prompted to produce more of a particular cellular component such as enzymes.
What is downregulation? When a cell is prompted to produce less of a particular cellular component such as enzymes.
Name the three types of extracellular receptors. (Hydrophilic hormones) Ion channel receptors, G protein receptors and Tyrosine Kinase receptors.
Differentiate Osmoregulators and Osmoconformers. Osmoregulators regulate their osmotic concentration to be higher or lower than their external environment whereas Osmoconformers allow their osmotic concentration to be equal to their external environment.
Name some of the structural features for osmoregulation. Waterproof/impermeable outerlayer: scales, hair and feathers *keratin Kidneys: removal of waste, regulation of blood water concentration & maintaining ion levels in blood.
Name some behavioural responses in Osmoregulation. Hiding in burrows. Water-conserving cocoons. Highly concentrated urine. Creating a microclimate ie. wrapping bushy tail around face
Name some physiological responses in Osmoregulation. Reptiles & birds: reabsorb water from their cloaca. Terrestrial vertebrates: Slow prod. of urine by <-- rate of glom. filtr. Camels: metabolise fat. Marine vert: isotonic w. environ. Freshwater vert: high kidney filtr. Actively absorb saltr. from envi.
Describe the homeostatic mechanism for osmoregulation in humans. (stimulus response model) Osmotic pressure rises/falls Osmoreceptors in hypothamalus more/less stimulated Pituitary gland secretes more/less ADH Kidneys absorb more/less water OP rises/falls
What are xerophytes? Plants that grow in dry conditions.
What are the three types of plants? (in regards to environments) Mesophytes: adequate water. Hydrophytes: on or in water. Halophytes: salty conditions.
What is the homeostatic mechanism in plants for osmoregulation? Abscisic acid accumulates in guard cells. The rapid alteration in osmotic pressure means the guard cells lose turgidity and stomata close. Transpiration in reduced and water is being conserved.
Differentiate between an infection and non-infections disease. A non-infectious disease is not caused by a pathogen and not communicable whereas an infectious disease is caused by pathogens and is communicable.
Name the key characteristics of a virus. Has viral DNA. A Phospholipid envelope. Viral proteins Core proteins.
Describe the process of a viral infection. 1. Virus attaches to specific host via receptors 2. Virus injects its DNA/RNA into the cell 3. Virus DNA uses host cell's machinery/DNA to make copies of itself 4. The host cell undergoes lysis - releasing multiple copies that infect nearby cells
Describe prions. (characteristics and method) Has no genetic material and is much smaller than viruses. Converts normal proteins into harmful prion proteins upon encounter. Prions are resistant to high temperatures, strong enzymes and UV radiation.
Describe bacteria. (characteristics and method) very small and has a cell wall. Some have protective capsules. flagellum and endospores. Have different shapes: spherical, rod-shaped bacillus, spiral, vibrio.
Describe Fungi. (characteristics and method) Eukaryotes. Cell walls made of chiton.
What is the first step of malaria? (Zygotes) 1. zygotes of the malarial parasite develop in the gut of the mosquito then migrate into her salivary gland.
What is the second step of malaria? (sporozoites) 2. Mosquito bites a human; sporozoites enter blood stream and move to the liver.
What is the third step of malaria? (sporozoites) 3. Sporozoites reproduce asexually in liver cells.
What is the fourth step of malaria? (Merozoites) 4. Merozoites move into bloodstream and from there enter red blood cells where they reproduce asexually.
What is the fifth step of malaria? (Merozoites) Merozoites released from red blood cells can infect and multiply in other red blood cells.
What is the sixth step of malaria? (Gametocytes) Some merozoites can form male and female gametocytes. These are released into the blood stream.
What is the seventh step of malaria? (transmission) Blood is sucked from an infected human by a female mosquito. Gametocytes travel to the mosquitoes gut where they mature into gametes and fuse to form zygotes.
Differentiate endoparasites and ectoparasites. Endoparasites are multicellular internal parasites. Ectoparasites are parasites that live on the surface of another organism.
Name the virulence factors. Adhesins, invasion factors ie. enzymes secreted by bacteria, toxins (Endotoxins, exotoxins: cytotoxins, neurotoxins, enterotoxins), and lifestyle changes.
Name the 5 modes of disease transmission. Direct contact, body fluids, foodborne transmission, waterborne transmission and vectors.
What is the first line of defence? Physical barriers and chemical barriers eg. skin, sweat, stomach acid etc.
What is the second line of defence? White blood cells (Phagocytes/Macrophages) that ingest foreign materials. Histamines signal phagocytes. Antibodies on pathogens attract phagocytes - die after killing pathogen.
What is the second line of defence (inflammatory response)? Macrophages release cytokines and that signal mast cells to release histamines and prostaglandins which causes vasodilation. Phagocytes engulf foreign particles.
Differential between natural/artificial and passive/active immunity. Artificial immunity is from a vaccine. Natural is from being naturally exposed to the pathogen. Passive immunity is gained from a source ie. mother to foetus. Active immunity --> specialised lymphocytes and antibodies are produced upon primary exposure.
What is the third line of defence (Adaptive immunity)? Humoral immunity: B lymphocytes produce antibodies in bone marrow. Divides rapidly in presence of antigens. Becomes plasma cells or Memory B cells. Plasma secretes antibodies. Memory produces antibodies on secondary exposure.
What are the first 2 antibody kill methods? 1. Start a cascade effect: complement activation. 2. Opsonisation: Coats antigen in "non-self" substance which attracts phagocytes.
What are the 3rd and 4th antibody kill methods? 3. Neutralisation: neutralises pathogenic toxin. Pathogens are unable to bind to cells. 4. Agglutination: Binds pathogens to antibodies to prevent spreading. Phagocytosis can take place.
What is Cell mediated immunity? Tcells produced in bone marrow: release soluble proteins > attract&activate phagocytes- may become mem. cells. KillerTcells kill pathogens. Other Tcells helper Ts boost activity of immune cells > release cytokines. Regulatory Ts suppress/control response.
Name the physical defence strategies in plants. Thick outer bark on stems and roots: has high amounts of waxy water-proof substances. Cell wall. Callose - polysaccharide: impedes cellular penetration at site on infection. shed infected parts. Plug wounds with resin.
Name the chemical defence strategies in plants. Defensins: small, stable peptides. Some chemicals act as toxins to pathogens.
Created by: Caitlyn_01