BIOLOGY UNIT 1

Frage	Antworten
HOW ARE PHOSPHOLIPIDS ARRANGED IN A MEMBRANE?	IN A BILAYER HYDROPHOBIC FATTY ACID TAILS ON INSIDE HYDROPHILIC AND POLAR PHOSPHATE HEAD ON INSIDE
HOW IS THE GOLGI BODY INVOLVED IN SECRETION OF PROTEINS?	IT MODIFIES THEM AND PACKAGES THEM INTO VESICLES. IT THEN TRANSPORTS IT TO THE CELL SURFACE
WHY DO AREAS OF THE HEART DIE DURING A MYOCARDIAL INFARCTION?	THERE IS REDUCED BLOOD FLOW TO THE CORONARY ARERIES NOT ENOUGH OXYGEN IS SUPPLIED RESPIRATION STOPS SO CELLS DIE
WHY IS PRESSURE IN THE VENTRICLE RELATED TO THE THICKNESS OF THE VENTRICLE WALL	THICKNESS INCREASES AS VENTRICLES CONTRACT CONTRACTION CAUSES THE PRESSURE INCREASE
HOW IS PRESSURE IN THE VENTRICLE RELATED TO BLOOD FLOW IN THE AORTA?	PRESSURE IN VENTRICLE INCREASES, HIGHER THAN AORTA VALVES OPEN AND SO BLOOD MOVES IN
Describe how bacteria are destroyed by phagocytes.	1. (Phagocyte engulfs) to form vacuole / vesicle / phagosome; 2. Lysosome empties contents into vacuole / vesicle / phagosome; 3. (Releasing) enzymes that digest / hydrolyse bacteria;
Explain how fibrosis caused by tuberculosis could have produced the changes in FEV.	(Fibrosis causes / due to), 1. Development of scar tissue / scarring / connective tissue; 2. Loss of elasticity / elastic tissue / elastin in lungs; 3. Restricts inhalation; 4. Breathe out less / reduced FEV due to reduced lung elasticity / scar tissue does not recoil / is not elastic / lung tissue does not recoil;
People given whole-cell vaccines were more likely to develop harmful side effects than the people given the vaccines containing parts of the bacterial cells	(Whole-cell vaccine), 1. Heat(ing) supposed to kill bacteria; 2. Some might be alive / active/ viable; 3. (If so) bacteria could reproduce; 4. Bacterium makes or contains toxin; 5. Toxin might not be affected / all destroyed by heat; 6. Bacteria or toxins attacking / killing person’s cells;
) People given whole-cell vaccines produced a greater range of antibodies against the bacterium than the people given the vaccines containing parts of the bacterial cells	1. (Contains) many different / greater range of antigens; 2. Each antigen causes its own immune response / production of / has a specific (type of) antibody;
Infection by the cholera bacterium can cause acute diarrhoea. Explain how.	1. Toxin (produced by bacterium) causes (chloride) ions to move into (lumen of) intestine; 2. Water potential (of intestine contents) falls / water moves by osmosis into intestine/out of cells;
In areas where there are repeated outbreaks of cholera, most people who become infected by cholera bacteria do not become ill. Suggest and explain one reason why.	1. Have produced memory cells; 2. After previous infection/vaccination; OR 3. Different forms of cholera; 4. Some don't produce much/any toxins; OR 5. Few bacteria ingested; 6. Not enough toxin to produce symptoms; OR 7. Some people naturally resistant to bacterium; 8. Because of structure of cell membranes / amount of secretions eg bile/pancreatic juices;
Describe how you would test a sample of food for the presence of starch.	1. Add iodine/potassium iodide solution to the food sample; 2. Blue/black/purple indicates starch is present;
Microfold cells take up the antigens and transport them to cells of the immune system. Antigens are not able to pass through the cell-surface membranes of other epithelial cells. Suggest two reasons why.	1. Not lipid soluble; 2. Too large (to diffuse through the membrane); 3. Antigens do not have the complementary shape/cannot bind to receptor/channel/carrier proteins (in membranes of other epithelial cells);
Scientists believe that it may be possible to develop vaccines that make use of microfold cells. Explain how this sort of vaccine would lead to a person developing immunity to a pathogen.	1. (Vaccine contains) antigen/attenuated/dead pathogen; 2. Microfold cells take up/bind and present/transport antigen (to immune system/lymphocytes/Tcells); 3. T-cells activate B-cells; 4. B-cells divide/form clone/undergo mitosis; 5. B-cells produce antibodies; 6. Memory cells produced; 7. More antibodies/antibodies produced faster in secondary response/on reinfection;
Describe how a heartbeat is initiated and coordinated.	1. SAN sends wave of electrical activity / impulses (across atria) causing atrial contraction; 2. Non-conducting tissue prevents immediate contraction of ventricles/prevents impulses reaching the ventricles; 3. AVN delays (impulse) whilst blood leaves atria/ventricles fill; 4. (AVN) sends wave of electrical activity / impulses down Bundle of His; 5. Causing ventricles to contract from base up;
Explain how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the aorta.	1. Atrium has higher pressure than ventricle (due to filling/contraction); 2. Atrioventricular valve opens; 3. Ventricle has higher pressure than atrium (due to filling/contraction); 4. Atrioventricular valve closes; 5. Ventricle has higher pressure than aorta; 6. Semilunar valve opens; 7. Higher pressure in aorta than ventricle (as heart relaxes); 8. Semilunar valve closes; 9. (Muscle/atrial/ventricular) contraction causes increase in pressure;
Describe how the gut wall is adapted to push food down the oesophagus	Muscle (in walls); Circular and longitudinal; Contraction of circular (muscle pushes food down oesophagus);
Describe how gut wall is adapted to neutralise the stomach acid in the duodenum	Glandular cells/glands; Secrete alkali (mucus);
Describe how the gut is adapted to absorb the products of digestion in the iluem.	Villi/microvilli; (Many) capillaries/lacteals; Single cell layer; Channel/carrier proteins; Mitochondria; Enzymes in membrane; Muscles (in villi);
Describe how solubility in lipid affects the rate of diffusion through a membrane. Explain your answer.	As lipid solubility increases the rate increases; (Membrane consists of (double layer) of lipid/phospholipids;
Describe how molecular size affects the rate of diffusion. Suggest an explanation for your answer	Small molecules diffuse faster; Higher kinetic energy / easier to pass through pores / between phospholipid molecules;
Name two factors which affect the rate of facilitated diffusion of a substance through a membrane	Concentration/diffusion gradient; Number of carriers/channel/proteins; Temperature;
Describe how you would use a biochemical test to show that a solution contained a non-reducing sugar, such as sucrose.	Test for reducing sugar / Benedictís test is negative; Boil/heat with acid and neutralise / use NaOH / use alkali; OR Use enzyme hydrolysis;
Order in which pellets were produced by ultracentrifugation 1 2 3 Chloroplasts 4 5	1 Cell walls 2 Nuclei 4 Mitochondria 5 Ribosomes;
Suggest why the rate of oxygen uptake was measured when the mammals were at rest.	Allows comparison (between different animals); (Rate of) respiration varies if animal is not at rest / animal moving;
Explain the role of phospholipids in the structure and functioning of cell membranes.	1 Bipolar / hydrophobic and hydrophilic; 2 Forms bilayer; 3 Hydrophobic tail repelled by water / hydrophilic head attracted by water; 4 Allows movement of lipid soluble / non-polar molecules / water / gases / e.g. O2 and CO2 OR Prevents movement of water soluble/ polar molecules; 5 Allows membranes to fuse with other membranes / able to form vesicles / exocytosis and endocytosis; 6 Unsaturated fatty acids increase fluidity / flexibility / permeability; 7 Allows compartmentalisation / allows cells to maintain different concentrations of molecules on either side of the membrane;
Describe the processes involved in the digestion of triglycerides and the absorption of the products of this digestion in the small intestine.	1 Bile emulsifies triglycerides / large droplets to smaller droplets; 2 Smaller droplets provide large surface area / faster digestion; 3 Lipase breaks down triglycerides; 4 Into fatty acids and glycerol / monoglycerides; 5 By hydrolysis; 6 Diffusion (facilitated diffusion and active transport neutral); 7 Recombination (in epithelial cells); 9 (Move into) lymph vessels; 10 Fatty acids / glycerol move into blood (capillaries);
Describe how a sample consisting only of chloroplasts could be obtained from homogenised plant tissue.	use of differential centrifugation; first/low-spin pellet discarded / spin at low speed to remove cell wall material/cell debris; supernatant re-spun at higher speed / until pellet with chloroplasts is found; method of identifying chloroplasts e.g. microscopy;
What's the function of the fatty acid tail in the phospholipid membrane?	Form impermeable barrier to water-soluble substances / selectively permeable / allows non-polar molecules to pass through; allows cell to maintain different concentrations either side; makes membranes self-sealing/able to fuse with other membranes/able to form vesicles / gives flexibility/fluidity;
Explain how the cells of the cortex and the epidermis support the stem.	cortex (cells) take up water by osmosis (from vascular tissue); become turgid; cells expand and press against each other/epidermis; idea of epidermis restricting/preventing expansion of stem section; physical/mechanical support of stem in terms of vertical support/prevent bending;
Explain how the structures of the stomach wall and the ileum wall are related to the functions of these organs.	stomach 1. extra muscle layers; churning action; 4. mucus to protect stomach wall/ acid/HCl to kill bacteria or optimal pH/ pepsinogen or pepsin for (protein) digestion; 8. villi; 9. microvilli on epithelial cells; 10. larger surface area for absorption; 11. single layer of cells / capillary/blood vessels close to surface; 12. short diffusion pathway; 13. (extensive) capillary network / large number of blood vessels 14. maintain diffusion gradient; 15. feature of transmembrane/carrier/transport/intrinsic protein / many mitochondria; 16. active uptake/facilitated diffusion; 18. carry away lipids/fats or equivalent; 20. secrete alkaline fluid which neutralises acid (suitable environment for intestinal enzyme 21. correct named enzyme + location e.g. maltase in membrane of epithelial cells;
Bile is made in the liver. Explain one function of bile.	emulsifies fats; increases surface area for lipase / faster rate of digestion by lipase; OR bile (is alkaline) neutralises acidic material / chyme from the stomach; provides optimum pH for (digestive) enzymes;
Explain how three features of a plasma membrane adapt it for its functions.	1. phospholipid bilayer (as a barrier); 2. forms a barrier to water soluble / charged substances / allows non-polar substances to pass OR maintains a different environment on each side; 3. bilayer is fluid; 4. can bend to take up different shapes for phagocytosis / form vesicles; 5. channel proteins (through the bilayer)/intrinsic protein; 6. let water soluble/charged substances through / facilitated diffusion; 7. carrier proteins (through the bilayer); 8. allow facilitated diffusion / active transport; 9 surface proteins / extrinsic proteins, glycoproteins / glycolipids; 10 cell recognition / act as antigens / receptors; 11 cholesterol; 12 regulates fluidity / increases stability;

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