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;
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
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;
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;
Maintaining low concentration of sodium (in epithelial cell) / maintaining sodium concentration gradient (between lumen and epithelial cell);
Glucose moves into blood;
By (facilitated) diffusion;
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
What is atheroma and how may it cause myocardial infarction?
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;
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;
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;
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);
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;
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;
The epithelial cells that line the small intestine are adapted for the absorption of glucose. Explain how.
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
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;
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;
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;
The heart controls and coordinates the regular contraction of the atria and ventricles.
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;
The diet of a person can increase the risk of coronary heart disease.
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;
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.
Atheroma formation increases a person’s risk of dying.
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;