topic 3 Flashcards
Surface area to volume ratio
As size increases, ratio (of surface area to volume) decreases;
Comparison required, e.g., smaller organisms have a larger ratio
Insect – structural adaptations
- Tracheoles have thin walls so short diffusion distance to cells;
- Highly branched / large number of tracheoles so short diffusion distance to cells;
- Highly branched / large number of tracheoles so large surface area (for gas exchange);
- Tracheae provide tubes full of air so fast diffusion (into insect tissues);
- Fluid in the end of the tracheoles that moves out (into tissues) during exercise so faster diffusion through the air to the gas exchange surface;
OR
Fluid in the end of the tracheoles that moves out (into tissues) during exercise so larger surface area (for gas exchange); - Body can be moved (by muscles) to move air so maintains diffusion / concentration gradient for oxygen / carbon dioxide;
Fish – structural adaptation
- Many lamellae / filaments so large surface area;
- Thin (surface) so short diffusion pathway;
Fish - Countercurrent mechanism
- Water and blood flow in opposite directions;
Allow diagram showing counter-flow - Blood always passing water with a higher oxygen concentration;
- Diffusion gradient maintained throughout length (of gill)
OR
Diffusion occurs throughout length of gill
OR
If water and blood flowed in same direction equilibrium would be reached
Gas exchange system
- Named structures – trachea, bronchi, bronchioles, alveoli;
- Above structures named in correct order
- Breathing in – diaphragm contracts and external intercostal muscles contract;
- (Causes) volume increase and pressure decrease in thoracic cavity (to below atmospheric, resulting in air moving in);
- Breathing out - Diaphragm relaxes and internal intercostal muscles contract;
- (Causes) volume decrease and pressure increase in thoracic cavity (to above atmospheric, resulting in air moving out);
For thoracic cavity accept ‘lungs’ or ‘thorax’.
Inhalation mechanism
- Diaphragm (muscle) contracts and external intercostal muscles contract;
- (Causes volume increase and) pressure decrease;
- Air moves down a pressure gradient
OR
Air enters from higher atmospheric pressure
Lung gas exchange adaptation
- (The alveolar epithelium) is one cell thick;
Reject thin membrane - Creating a short diffusion pathway / reduces the diffusion distance;
Leaf adaptations for gas exchange
- (Carbon dioxide enters) via stomata; Reject stroma
- (Stomata opened by) guard cells;
- Diffuses through air spaces;
- Down diffusion gradient;
Haemoglobin structure and binding
- Binding of first oxygen changes tertiary / quaternary (structure) of haemoglobin;
- Creates / leads to / uncovers second / another binding site
OR
Uncovers another iron / Fe / haem group to bind to;
Bohr shift
1. Increases/more oxygen dissociation/unloading
OR
Deceases haemoglobin’s affinity for O2;
2. (By) decreasing (blood) pH/increasing acidity;
Oxygen dissociation (shift to left)
- lower affinity for O2 at low partial pressures;
OR
lower affinity for oxygen at pp found in tissues; - Easier unloading of O2 ;
- For aerobic respiration at the tissues/muscles/cells
OR
Anaerobic respiration delayed at the tissues/muscles/cells
OR
Less lactate at the tissues/muscles/cells;
Oxygen dissociation – high metabolism organism
- Curve to the right so lower affinity / % saturation (of haemoglobin);
- Haemoglobin unloads / dissociates more readily;
- More oxygen to cells / tissues / muscles;
- For greater / more / faster respiration;
Idea of a higher rate of respiration
What is digestion?
- Hydrolysis (of);
- (Large / insoluble substances) to small(er) / soluble substances;
Starch digestion
- Maltose;
- Salivary amylase breaks down starch
Protein digestion
1. (Reference to) hydrolysis of peptide bonds;
2. Endopeptidase act in the middle of protein/polypeptide
OR
Endopeptidase produces short(er) polypeptides/ increase number of ends;
3. Exopeptidases act at end of protein/polypeptide
OR
Exopeptidase produces dipeptides/amino acids;
4. Dipeptidase acts on dipeptide/between two amino acids
OR
Dipeptidase produces (single) amino acids
Lipid digestion adaptations – bile salts
- Small droplets have a larger surface area to volume ratio;
- More surface for lipase (to act), leading to faster digestion of triglycerides;
Lipid absorption
- Micelles contain bile salts and fatty acids/monoglycerides;
- Make fatty acids/monoglycerides (more) soluble (in water) OR Bring/release/carry fatty acids/monoglycerides to cell/lining (of the iluem) OR Maintain high(er) concentration of fatty acids/monoglycerides to cell/lining (of the ileum);
- Fatty acids/monoglycerides absorbed by diffusion;
- Triglycerides (re)formed (in cells);
- Vesicles move to cell membrane;
Golgi and lipid absorption
- Modifies / processes triglycerides;
- Combines triglycerides with proteins;
- Packaged for release / exocytosis
OR
Forms vesicles;
Ventricular systole
- Atrium has higher pressure than ventricle (due to filling / contraction) causing atrioventricular valves to open;
- Ventricle has higher pressure than atrium (due to filling / contraction) causing atrioventricular valves to close;
- Ventricle has higher pressure than aorta causing semilunar valve to open;
Points 1, 2 and 3 must be comparative: eg higher - Higher pressure in aorta than ventricle (as heart relaxes) causing semilunar valve to close;
- (Muscle / atrial / ventricular) contraction causes increase in pressure
Name the blood vessel that carries the blood to:
The heart
The kidneys
The lungs
Coronary arteries
Renal artery
Pulmonary artery
Artery and arteriole structure
Elastic tissue
1. Elastic tissue stretches under pressure / when heart beats then recoils / springs back;
2. Evens out pressure / flow;
Muscle
3. Muscle contracts to reduce diameter of lumen / vasoconstriction / constricts vessel;
4. Changes flow / pressure;
Epithelium
5. Epithelium smooth;
6. Reduces friction / blood clots / less resistance
Aorta structure to function
- Elastic tissue to allow stretching / recoil / smoothes out flow of blood / maintains pressure;
- (Elastic tissue) stretches when ventricles contract
OR Recoils when ventricle relaxes; - Muscle for contraction / vasoconstriction;
- Thick wall withstands pressure OR stop bursting;
- Smooth endothelium reduces friction;
- Aortic valve / semi-lunar valve prevents backflow
Explain how the atrioventricular valve maintains a unidirectional flow of blood
1. Pressure in (left) atrium is higher than in ventricle/B causing valve to open;
OR
(When) pressure above valve is higher than below valve it opens;
2. Pressure in (left) ventricle/B is higher than in atrium causing valve to close;
OR
(When) pressure in below valve is higher than above valve it closes;
Tissue fluid formation and high blood pressure
- High blood pressure = high hydrostatic pressure;
- Increases outward pressure from (arterial) end of capillary / reduces inward pressure at (venule) end of capillary;
- (So) more tissue fluid formed / less tissue fluid is reabsorbed.
Allow lymph system not able to drain tissues fast enough
Dissection safety
Use a sharp scalpel/scissors
Wash hands/wear gloves
Disinfect bench/equipment
Cover any cuts
Cut away from self/others/on a hard surface
Safe disposal
Transpiration
- Stomata open and photosynthesis increases / transpiration increases;
- More water pulled up due to cohesion between water molecules / by cohesion tension;
- Water pulled up trunk / moves up at fast rate under tension;
- Sticking / adhesion (between water and) cells / walls / pulls xylem in;
Factors affecting rate of transpiration
Light;
Humidity / moisture in air;
Air movement / wind;
Temperature;
Xerophyte adaptations
- Hairs so ‘trap’ water vapour and water potential gradient decreased;
- Stomata in pits/grooves so ‘trap’ water vapour and water potential gradient decreased;
- Thick (cuticle/waxy) layer so increases diffusion distance;
- Waxy layer/cuticle so reduces evaporation/transpiration.
- Rolled/folded/curled leaves so ‘trap’ water vapour and water potential gradient decreased;
- Spines/needles so reduces surface area to volume ratio
Translocation
- (At source) sucrose is actively (transported) into the phloem/sieve element/tube;
- By companion/transfer cells;
- Lowers water potential in phloem/sieve element/tube and water enters by osmosis;
- (Produces) high (hydrostatic) pressure;
- Mass flow/transport towards sink/roots/storage tissue;
- At sink/roots sugars are removed/unloaded;
Evidence for mass flow
In support of mass flow hypothesis
1. phloem is involved;
2. respiration / active transport is involved (in flow / movement);
3. Because 4 °C / cooling reduces / slows / stops flow / movement;
4. The agar block is the source;
5. Roots are the sink;
Against the mass flow hypothesis
6. No bulge above ringing ;
7. No (role for) osmosis / hydrostatic pressure / water movement;
8. Movement could be due to gravity;
9. Roots still grow without (intact/functioning) phloem;
10. No leaves / sugars / photosynthesis to act as a source;
heart rate equation
cardiac output ÷ stroke volume
