Biology Unit 1.5 Marks

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  • Created by: bethk100
  • Created on: 14-01-14 11:59

Question 1

The structure of a cholera bacterium is different from the structure of an epithelial cell from the small intestine. Describe how the structure of a cholera bacterium is different.

1. Cholera bacterium is prokaryote;

2. Does not have a nucleus/nuclear envelope/ has DNA free in cytoplasm/has loop of DNA;

3/4. Any two from... No membrane-bound organelles / no mitochondria / no golgi / no endoplasmic reticulum / etc;

5. Small ribosomes only 70s

6/7. Any two from... Capsule / flagellum / plasmid / cell wall / etc;

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Question 2

Scientists use optical microscopes and transmission electron microscopes (TEMs) to investigate cell structure. Explain the advantages and limitations of using a TEM to investigate cell structure.


1. Small objects can be seen;

2. TEM has high resolution;

3. Wavelength of electrons shorter;  



4. Cannot look at living cells;

5. Must be in a vacuum;

6. Must cut section / thin specimen;

7. Preparation may create artefact

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Question 3

Describe the role of the enzymes of the digestive system in the complete breakdown of starch.

Starch;  Amylase;  Maltose:


Pancreas;  Amylase;  Maltose:  


Maltase;  Epithilial lining of cells;  Glucose;  


Hydrolysis; of glycosidic bond;

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Question 4

Describe the processes involved in the absorption of the products of starch digestion.  

Glucose moves in with sodium (into epithelial cell);

Via (carrier/channel) protein/symport;

Sodium removed (from epithelial cell) by active transport/sodium-potassium pump;

Into blood;

Maintaining low concentration of sodium (in epithelial cell) / maintaining sodium concentration gradient (between lumen and epithelial cell);

Glucose moves into blood;

By (facilitated) diffusion;

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Question 5

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


1. SAN initiates heartbeat;

2. SAN sends wave of electrical impulses across atria, causing atrial contraction;

3. AVN delays electrical impulses

4. Allowing atria to empty before ventricles contract / ventricles to fill before they contract;

5. AVN sends wave of electrical impulses down Bundle of His / Purkyne fibres;

6. Causing ventricles to contract from base up

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Question 6

What is atheroma and how may it cause myocardial infarction?

1. Cholesterol;

2. in artery wall/ under lining;

3. Atheroma linked to blood clot;

4. (Blocks) coronary artery / artery supplying heart muscle;

5. Reduces oxygen / glucose supply (to heart muscle);

6. (Heart muscle) unable to respire / dies;

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Question 7

Many different substances enter and leave a cell by crossing its cell surface membrane.

Describe how substances can cross a cell surface membrane.

1. (Simple / facilitated) diffusion from high to low  concentration;

2. Small molecules pass via  phospholipids / bilayer;


Large 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;

5. Active transport / facilitated diffusion involves carrier protiens;

6. Active transport requires energy / ATP;

7. Ref. to Sodium / glucose co-transport;

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Question 8

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.

1. Many alveoli provide a large surface area;

2. Many capillaries provide a large surface area;

3. (So) fast diffusion;


4. Alveoli or capillary walls are thin / short distance between alveoli and blood;

5. Flattened / squamous epithelium;

6. (So) short diffusion distance;

7. (So) fast diffusion;


8. Ventilation / circulation;

9. Maintains a diffusion / concentration gradient;

10. (So) fast diffusion;

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Question 9

Pulmonary tuberculosis is a disease of the lungs.

Describe the transmission and course of infection of pulmonary tuberculosis

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);

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Question 10

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

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;

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Question 11

Different cells in the body have different functions.

Some white blood cells are phagocytic. Describe how these phagocytic white blood cells destroy bacteria.

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;

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Question 12

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

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

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Question 13

Vaccines protect people against disease. Explain how

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;

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Question 14

Oral rehydration solutions (ORS) are used to treat diarrhoeal disease. What does an

ORS consist of and how does it work?

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;

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Question 15

The heart controls and coordinates the regular contraction of the atria and ventricles.

Describe how.

1. SAN → AVN → bundle of His /Purkyne fibres;

2. Impulses / electrical activity (over atria);

3. Atria contract;

4. Non-conducting tissue (between atria and ventricles);

5. Delay (at AVN) ensures atria empty/ ventricles fill before ventricles contract;

6. Ventricles contract from apex upwards;

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Question 16

The diet of a person can increase the risk of coronary heart disease.

Explain how.

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;

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Question 17

Some substances can cross the cell-surface membrane of a cell by simple diffusion through the phospholipid bilayer.

Describe other ways by which substances cross this membrane.

1. (By osmosis)  From a high water potential to a low water potential/down a water potential gradient;

2. Through aquaporins/water channels;

3. (By facilitated diffusion) Channel/carrier protein;

4. Down concentration gradient;

5. (By active transport)  Carrier protein/protein pumps;

6. Against concentration gradient;

7. Using ATP/energy (from respiration);

8. (By phagocytosis/endocytosis) Engulfing by cell surface membrane to form vesicle/vacuole;

9. (By exocytosis/role of Golgi vesicles) Fusion of vesicle with cell surface membrane.

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Question 18

Atheroma formation increases a person’s risk of dying.

Explain how.

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;

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