Unit 2 Questions Bio

Front 1

Describe how haemoglobinnormally loads oxygen in the lungs and unloads it in a tissue cell.

Back 1

Oxygen combines(reversibly) to produce oxyhaemoglobin;

each haemoglobin molecule/ one haemoglobin may transport 4 molecules ofoxygen;high partial pressure of oxygen / oxygen tension / concentration in lungs;haemoglobin (almost) 95% / 100% saturated;unloads at low oxygen tension(in tissues);presence of carbon dioxide displaces curve further to right / increases oxygendissociation;allows more O2 to be unloaded;increase temp/ acidity allows more O2 to beunloaded;low pO2 /increase CO2 /increase term / increase acid occur in vicinity ofrespiring tissue;

Front 2

Describe how haemoglobin isinvolved in absorbing oxygen in the lungs and transporting it to respiringtissues.

Back 2

1. Diffusion of oxygen into red cell / haemoglobin in red cells;2. High affinity of haemoglobin in high oxygen concentration;3. (Therefore) loads / becomes saturated in lungs / where oxygen abundant;4. oxyhaemoglobin formed; 5. Reference to role of haem e.g. energy changes /role of Fe2+ ions /Hb molecule combines with fewer oxygenmolecules;6. Unloads / low affinity in low concentration;7. Explanation in terms of dissociation curve i.e. small changes inconcentration gives large changes in saturation;8. Respiration in tissues gives high CO2 concentration / high temperature / high H+ concentration / low pH9. Dissociation curve shifts to right / oxyhaemoglobindissociation at higher partialpressure

Front 3

During exercise, therate of respiration of muscle cells increases. Explain what causes humanhaemoglobin to unload more oxygen to these cells.

Back 3

Partial pressure on oxygen in muscle falls more;high / more carbon dioxide produced;lowers PH;increase in temperature;percentage saturation of Hb falls / lowers affinity /increase dissociation;displaces curve to right / results in Bohr shift;

Front 4

There is an advantage to theshrew in having haemoglobin with a dissociation curve shifted to the right.Explain this advantage

Back 4

(at the tissues at lowpp oxygen) the shrew’s haemoglobin is lesssaturated with oxygen / has reduced affinity;oxyhaemoglobin dissociates more readily / haemoglobin releasesoxygen more readily / more oxygen released;allowing greater demand / respiration rate

Front 5

Suggest the advantage to aground squirrel of having haemoglobin that has an oxygen dissociation curve tothe left of the curve for human haemoglobin.

Back 5

In ground squirrellower partial pressure of oxygen in lungs;Haemoglobin can be saturated/load more oxygen;at lower partial pressure of oxygen;

Front 6

Describe and explainhow the structure of the mammalian breathing system enables efficient uptake ofoxygen into the blood.

Back 6

. Alveoli provide a large surface area;2. Walls of alveoli thin to provide a short diffusion pathway;3. Walls of capillary thin/close to alveoli provides a short diffusion pathway;4. Walls (of capillaries/alveoli) have flattened cells;5. Cell membrane permeable to gases;6. Many blood capillaries provide a large surface area;7. Intercostal/chest muscles/diaphragm muscles / to ventilate lungs / maintain a diffusion/concentrationgradient;8. Wide trachea / branching of bronchi/bronchioles for efficient flow of air;9. Cartilage rings keep airways open;

Front 7

A fish uses its gills to absorb oxygen from water. Explain how the gillsof a fish are adapted for efficient gas exchange.

Back 7

1) Large surfacearea provided by lamellae/filaments;

2.Increasesdiffusion/makes diffusion efficient;

3) Thinepithelium/distance between water and blood;

4) Water and blood flowin opposite directions/countercurrent;

5) maintainsconcentration gradient (along gill)/equilibriumnot reached; Not enough to saygives steep concentration gradient

6) As water always nextto blood with lower concentration of oxygen;

7) Circulation replacesblood saturated with oxygen;

8) Ventilation replaceswater (as oxygen removed);

Front 8

Describe and explain howfish maintain a flow of water over their gills

Back 8

1. mouth opens,operculum/opercular valve shuts;

2. floor of mouth lowered;

3. water enters due to decreased pressure / increased volume;

4. mouth closes, operculum/opercular valve opens;

5. floor raised results in increased pressure / decreased volume;

6. high/increased pressure forces/pushes water over gills;

Front 9

Explain how thecountercurrent principle helps fish to extract oxygen from water

Back 9

Water flows inopposite direction to blood;across (gill) lamellae;so difference in concentration maintained;diffusion gradient maintained / diffusion over full length

Front 10

Insect havemore than 1.5 million tracheoles. The distance between the ends of thetracheoles in the muscle is approximately 4 µm. Explain how these featuresallow efficient oxygen supply.

Back 10

Large number giveslarge (total) surface area;For diffusion;Short distance between tracheoles gives short pathway;Movement/diffusion through muscle is slow;

Front 11

Insect have more than1.5 million tracheoles. The distance between the ends of the tracheoles in themuscle is approximately 4 µm. Explain how these features allow efficient oxygensupply.

Back 11

Large number giveslarge (total) surface area;For diffusion;Short distance between tracheoles gives short pathway;Movement/diffusion through muscle is slow;

Front 12

An insect lives in air.Describe how the insect is able to obtain oxygen and limit water loss.

Back 12

1 Air enters through (open) spiracles;

2 Through tracheae;

3 Diffusion gradient in trachea

4 Tracheae associated with all cells/closely associated with cells;

5 Oxygen diffuses into cells;

6 Ventilation replacing air in tracheae;

7 Body covered with (waterproof) waxy layer/cuticle;

8 Spiracles are able to close open in response to carbon dioxide at a criticallevels

Front 13

Describe how carbon dioxide in the air outside a leaf reaches mesophyllcells inside the leaf.

Back 13

1. (Carbon dioxide enters) via stomata;

2.(Stomata opened by) guard cells;

3.Diffuses through air spaces;

4. Downdiffusion gradient;

Front 14

The thickness of theaorta wall changes all the time during each cardiac cycle. Explain why.

Back 14

1) Aorta wall stretches;

2.Because ventricle/heart contracts / systole / pressure increases;

3.(Aorta wall) recoils;

4.Because ventricle relaxes / heart relaxes /diastole / pressure falls;

5.Maintain smooth flow / pressure

Front 15

Describe two ways by which blood flow in theveins is maintained.

Back 15

Valves preventbackflow;effect of (skeletal) muscle contraction Residual blood pressure from heart;negative pressure from thorax;‘suction effect’ from heart;

Front 16

Describeand explain ways in which a capillary adapts for exchange

Back 16

1. Permeable capillary wall/membrane;

2. Single cell thick/thin walls, reduces diffusion distance;

3. Flattened (endothelial) cells, reduces diffusion distance;

4. Fenestrations, allows large molecules through

; 5. Small diameter/ narrow, gives a large surface area to volume/ shortdiffusion distance;

6. Narrow lumen, reduces flow rate giving more time for diffusion;

7. Red blood cells in contact with wall/ pass singly, gives short diffusiondistance / more time for diffusion;

Front 17

Explain howtissue fluid is formed and how it may be returned to the circulatory system.

Back 17

1. (Hydrostatic) pressure of blood high atarterial end;2. Fluid/water/soluble molecules pass out (reject plasma);3. Proteins/large molecules remain;4. This lowers the water potential / water potential becomes more negative;5. Water moves back into venous end of capillary (reject tissue fluid);6. By osmosis / diffusion; 7. Lymph system collects any excess tissue fluid;8. (Lymph) returns to blood / circulatory system / link with vena cava/returnstissue fluid to vein;

Front 18

Describe the part played byproteins in the plasma in returning tissue fluid to the capillary.

Back 18

Produces lower waterpotential; Water moves into capillary;

By osmosis

Front 19

The tissues of people whoare starving often swell because of the accumulation of tissue fluid. Explainwhat causes this accumulation of tissue fluid.

Back 19

Starvation linked tolow protein content of diet/Low protein concentrationin plasma/blood;Water potential of blood higher/smaller water potential gradient;Tissue fluid formed faster than returned/less tissue fluid returned to blood;

Front 20

Suggest anexplanation for the link between high blood pressure and the accumulation oftissue fluid.

Back 20

High blood pressure increases rate of filtration / forces more fluidout;Lymph system cannot cope / higher pressure reduces reabsorption

Front 21

Explain how water enters aplant root from the soil and travels through to the endodermis.

Back 21

Water enters root hair cells;by osmosis;because active uptake of mineral ions has created a WP gradient;

water moves through the cortex;(by osmosis) down a WP gradient;t

hrough cell vacuoles and cytoplasms / symplastic pathway;

through cell walls / apoplastic pathway;

Not required here but remember that all water is forced into thesymplastic pathway at the endodermis because of the casparian strip

Front 22

Explain how the structure of the endodermis affects the passage of waterby this apoplastic pathway.

Back 22

Casparian bands; (accept ref to suberin)which are impermeable/waterproof;lower water potential in the cytoplasm of endodermis cell;enters symplastic pathway / cytoplasm of cell;by osmosis;

Front 23

Root pressure is a forcethat is partly responsible for the movement of water through xylem in stems.Explain how the active transport of mineral ions into xylem vessels in theroots results in water entering these vessels and then being moved up the xylemtissue.

Back 23

Water potential in xylem reduced (by entry of ions);Water potential gradient established between xylem and surrounding cells;Plasma membranes of surrounding cells are partially permeable;Water enters xylem by osmosis;Volume of water in xylem increases;Cannot move back due to gradient;Pressure in xylem increases (and forces water upwards)

Front 24

Explain how water enters xylem from the endodermis in the root and isthen transported to the leaves.

Back 24

(Inthe root)

1.Casparian strip blocks apoplast pathway / only allows symplast pathway;

2.Active transport by endodermis;

3.(Of) ions/salts into xylem;

4.Lower water potential in xylem / water enters xylem by osmosis /down a waterpotential gradient;

(Xylemto leaf)

5.Evaporation / transpiration (from leaves);

6.(Creates) cohesion / tension / H-bonding between water molecules / negativepressure; 7.Adhesion / water molecules bind to xylem; 8.(Creates continuous) water column;

Front 25

Describeways in which antibiotics can act against bacteria. Explain why this mode ofaction is effective against the bacteria.

Back 25

Prevent DNA replication - Bacterial cell unable to divide, prevents further growth of bacteria population, it will not increase

Prevent m-RNA synthesis (transcription) -No mRNA means code not passed to ribosomes form transcription;; no protein synthesismeans no new enzymes;

Prevent transfer of amino acids to ribosomes(translation) -No proteins made at ribosomes No translation means no enzymes / no proteinsstructures;

Preventcell wall synthesis - Water potential of bacterial cell lower thansurrounding solutionWater enters by osmosisOsmotic lysis occurs