Biology Unit 1

Front 1

The cardiac cycle is controlled by the sinoatrial node (SAN) and the atrioventricular node (AVN). Describe how. (5 marks)

Back 1

1. SAN initiates heartbeat / acts as a pacemaker /myogenic;
2. (SAN) sends wave of electrical activity / impulses (across atria) causing atrial contraction;
3. AVN delays (electrical activity / impulses);
4. (Allowing) atria to empty before ventricles contract / ventricles to fill before they contract;
5. (AVN) sends wave of electrical activity / impulses down Bundle of His / Purkyne fibres;
6. (Causing) ventricles to contract (from base up) / ventricular systole;

Front 2

What is atheroma and how may it cause myocardial infarction? (5 marks)

Back 2

1. Cholesterol / plaque / lipoprotein / LDL / fatty material / cells;
2. In artery wall / under lining / endothelium of artery / blood vessel;
3. Atheroma linked to blood clot / thrombosis;
4. (Blocks) coronary artery / artery supplying heart muscle / tissue / cells;
5. Reduces oxygen / glucose supply (to heart muscle / tissues / cells);
6. (Heart muscle / tissue / cells) unable to respire / dies;

Front 3

Many different substances enter and leave a cell by crossing its cell surface membrane. Describe how substances can cross a cell surface membrane. (5 marks)

Back 3

1. (Simple / facilitated) diffusion from high to low concentration / down concentration gradient;
2. Small / non-polar / lipid-soluble molecules pass via phospholipids / bilayer; OR Large / polar / water-soluble molecules go through proteins;
3. Water moves by osmosis / from high water potential to low water potential / from less to more negative water potential;
4. Active transport is movement from low to high concentration / against concentration gradient;
5. Active transport / facilitated diffusion involves proteins / carriers;
6. Active transport requires energy / ATP;
7. Ref. to Na+ / glucose co-transport;

Front 4

Describe and explain how the lungs are adapted to allow rapid exchange of oxygen between air in the alveoli and blood in the capillaries around them. (5 marks)

Back 4

1. Many alveoli / alveoli walls folded provide a large surface area;
2. Many capillaries provide a large surface area;
3. (So) fast diffusion;
4. Alveoli or capillary walls / epithelium / lining are thin / short distance between alveoli and blood;
5. Flattened / squamous epithelium;
6. (So) short diffusion distance / pathway;
7. (So) fast diffusion;
8. Ventilation / circulation;
9. Maintains a diffusion / concentration gradient;
10. (So) fast diffusion;

Front 5

Pulmonary tuberculosis is a disease of the lungs. Describe the transmission and course of infection of pulmonary tuberculosis. (5 marks)

Back 5

1. (Bacteria transmitted in) droplets / aerosol;
2. (Bacteria) engulfed / ingested by phagocytes / macrophages;
3. (Bacteria) encased in named structure e.g. wall / tubercle / granuloma / nodule;
4. (Bacteria) are dormant / not active / not replicating;
5. If immunosuppressed, bacteria activate / replicate / released;
6. Bacteria destroy alveoli / capillary / epithelial cells;
7. (Leads to) fibrosis / scar tissue / cavities /calcification;
8. (Damage) leads to less diffusion /less surface area / increases diffusion distance;
9. (Activation / damage allows bacteria) to enter blood / spreads (to other organs);

Front 6

Emphysema is another disease of the lungs. People with emphysema may feel weak and tired. Explain why. (5 marks)

Back 6

1. Alveoli break down / collapse / rupture / walls thicken;
2. Less surface area / increases diffusion distance / less diffusion;
3. Loss of elastin / elastic tissue / elastase involved;
4. (Alveoli / lungs) cannot recoil / spring back / have reduced elasticity / more difficult to expel air;
5. Reduced diffusion gradient / air not replenished / less air leaves lungs;
6. Less oxygen enters blood / tissues;
7. Less respiration / less energy released / less ATP produced;

Front 7

Different cells in the body have different functions. Some white blood cells are phagocytic. Describe how these phagocytic white blood cells destroy bacteria. (5 marks)

Back 7

1. Phagocyte attracted to bacteria by chemicals / recognise antigens on bacteria as foreign;
2. Engulf/ingest bacteria;
3. Bacteria in vacuole / vesicle;
4. Lysosome fuses with / empties enzymes into vacuole;
5. Bacteria digested / hydrolysed;

Front 8

The epithelial cells that line the small intestine are adapted for the absorption of glucose. Explain how. (5 marks)

Back 8

1. Microvilli;
2. Large/increased surface area;
3. Many mitochondria;
4. (Mitochondria/respiration) produce ATP / release or provide energy (for active transport);
5. Carrier proteins for active transport;
6. Channel / carrier proteins for facilitated diffusion;
7. Co-transport of sodium (ions) and glucose or symport / carrier protein for sodium (ions) and glucose;
8. Membrane-bound enzymes digest disaccharides / produce glucose

Front 9

Vaccines protect people against disease. Explain how. (5 marks)

Back 9

1. Vaccines contain antigens / antigens are injected;
2. Dead pathogens / weakened pathogens;
3. Memory cells made;
4. On second exposure memory cells produce antibodies / become active / recognise pathogens;
5. Rapidly produce antibodies / produces more antibodies;
6. Antibodies destroy pathogens;
7. Herd effect / fewer people to pass on disease;

Front 10

Oral rehydration solutions (ORS) are used to treat diarrhoeal disease. What does an ORS consist of and how does it work? (5 marks)

Back 10

1. Contains glucose/starch/ carbohydrate / sugar;
2. Sodium/salt;
3. Co-transport / symport;
4. Sodium and glucose taken up (from lumen);
5. Lowers water potential in cells/ increases water potential gradient;
6. Water taken up by osmosis;

Front 11

The heart controls and coordinates the regular contraction of the atria and ventricles. Describe how. (5 marks)

Back 11

1. SAN initiates heartbeat / acts as a pacemaker /myogenic;
2. (SAN) sends wave of electrical activity / impulses (across atria) causing atrial contraction;
3. AVN delays (electrical activity / impulses);
4. (Allowing) atria to empty before ventricles contract / ventricles to fill before they contract;
5. (AVN) sends wave of electrical activity / impulses down Bundle of His / Purkyne fibres;
6. (Causing) ventricles to contract (from base up) / ventricular systole;

Front 12

The diet of a person can increase the risk of coronary heart disease. Explain how. (5 marks)

Back 12

1. Too much saturated fat/ cholesterol in diet;
2. Increase in LDL/ cholesterol in blood;
3. Atheroma/ fatty deposits/ plaques in artery walls;
4. Reduces diameter of / blocks coronary arteries;
5. Less oxygen/ glucose to heart muscle /tissue/ cells;
6. Increase in blood pressure;
7. (Increased risk of )clot / thrombosis / embolism/ aneurysm;

Front 13

Some substances can cross the cell-surface membrane of a cell by simple diffusion through phospholipid bilayer. Describe other ways by which substances cross this membrane. (5 marks)

Back 13

By osmosis (no mark)
1. From a high water potential to a low water potential/down a water potential gradient;
2. Through aquaporins/water channels;
By facilitated diffusion (no mark)
1. Channel/carrier protein;
2. Down concentration gradient;
By active transport (no mark)
3. Carrier protein/protein pumps;
4. Against concentration gradient;
5. Using ATP/energy (from respiration);
By phagocytosis/endocytosis (no mark)
8. Engulfing by cell surface membrane to form vesicle/vacuole;
By exocytosis/role of Golgi vesicles (no mark)
9. Fusion of vesicle with cell surface membrane;

Front 14

Atheroma formation increases a person's risk of dying. Explain how. (5 marks)

Back 14

1. Atheroma is fatty material/cholesterol/foam cells/plaque/calcium deposits/LDL;
2. In wall of artery;
3. (Higher risk of) aneurysm/described;
4. (Higher risk of) thrombus formation/blood clot;
5. Blocks coronary artery;
6. Less oxygen/glucose to heart muscle/cells/tissue;
7. Reduces/prevents respiration;
8. Causing myocardial infarction/heart attack;
9. Blocks artery to brain;
10. Causes stroke/stroke described;