surface area to volume ratio
As size increases, ratio (of surface area to volume) decreases;
Describe the relationship between size and surface area to volume ratio of organisms
Small leaves / surface area so (total) number of stomata is low.
Treatment 2 shows that even when the lower surface of the leaf is sealed there is still some uptake of carbon dioxide. Suggest how this uptake of carbon dioxide continues
(Highly) folded cell(-surface) membrane
What are microvilli?
Use a sharp scalpel/scissors
Wash hands/wear gloves
Disinfect bench/equipment
Cover any cuts
Cut away from self/others/on a hard surface
Give two safety precautions that should be followed when dissecting a heart.
Short diffusion pathway (to cells)
OR
It has a surface permeable (to water/ions into cells);
Ulva lactuca is an alga that lives on rocks on the seashore. It is regularly covered by seawater.Unlike plants, Ulva lactuca does not have xylem tissue. Suggest how Ulva lactuca is able to survive without xylem tissue.
1. Small SA:VOL
2. (So) reduces heat loss / (more) heat retained;
Explain how the body shape of a Weddell seal is an adaptation to living in a cold environment.
1. Flattened cells OR Single layer of cells;
2. Reduces diffusion distance/pathway;
3. Permeable;
4. Allows diffusion of oxygen/carbon dioxide;
Describe and explain one feature of the alveolar epithelium that makes the epithelium well adapted as a surface for gas exchange. Do not refer to surface area or moisture in your answer.
(Maintains/generates) a concentration/diffusion gradient for Na+ (from ileum into cell);. 2. Na+ moving (in) by facilitated diffusion, brings glucose with it OR Na+ moving (in) by co-transport, brings glucose with it
The movement of Na+ out of the cell allows the absorption of glucose into the cell lining the ileum. Explain how.
1. Carry/wash sharp instruments by holding handle OR Carry/wash sharp instruments by pointing away (from body)/down;
2. Disinfect instruments/surfaces;
3. Disinfect hands OR Wash hands with soap (and water);
4. Put organ/gloves/paper towels in a (separate) bag/bin/tray to dispose;
Describe two precautions the student should take when clearing away after the dissection.
1. Tracheole (wall) thin/one cell thick;
2. (So) rapid diffusion (into cells) OR (So) short diffusion pathway/distance;
OR
3. Tracheoles enter/supply tissues/muscle fibres;
4. (So) diffusion direct into cells OR (So) short diffusion pathway/distance
OR
5. Tracheoles are highly branched;
6. So) short diffusion distance/pathway
Chitin keeps the tracheae open in the tracheal system of gas exchange in an insect. Gas exchange does not occur in the tracheae. Explain the importance of one adaptation of the gas exchange surface in the tracheal system of an insect.
1. Mouse (Smaller so) larger surface area to volume ratio;
2. More/faster heat loss (per gram/in relation to body size);
3. (Faster rate of) respiration/metabolism releases heat;
Mammals such as a mouse and a horse are able to maintain a constant body temperature. Use your knowledge of surface area to volume ratio to explain the higher metabolic rate of a mouse compared to a horse
1. Less carbon dioxide exhaled/moves out (of lung) OR More carbon dioxide remains (in lung);
2. (So) reduced diffusion/concentration gradient (between blood and alveoli);
3. Less/slower movement of carbon dioxide out of blood OR More carbon dioxide stays in blood;
Tidal volume is the volume of air inhaled and exhaled during a single breath when a person is resting. The tidal volume in a person with emphysema is reduced compared with the tidal volume in a healthy person. Suggest and explain how a reduced tidal volume affects the exchange of carbon dioxide between the blood and the alveoli.
1. Combine/mix/join with bile salts;
2. Make (more) soluble (in water);
3. (Micelles) breakdown close to cells OR Maintain high(er) concentration at cell(-surface membrane) OR Transport to cells/lining;
4. Diffuses (into cells/ileum); Ignore facilitated Ignore micelles are absorbed
Vitamin A is a fat-soluble substance. Micelles are involved in the process of vitamin A absorption. Describe the process of vitamin A absorption into cells lining the ileum.
1. Renal vein;
2. Vena cava to right atrium;
3. Right ventricle to pulmonary artery;
Give the pathway a red blood cell takes when travelling in the human circulatory system from a kidney to the lungs. Do not include descriptions of pressure changes in the heart or the role of heart valves in your answer.
1. (Allows unbroken) water column 2. Cohesion from H bonds between (all) water (molecules) 3. Evaporation/transpiration creates tension (in column)
Lignin is a polymer found in the walls of xylem vessels in plants. Lignin keeps the xylem vessel open as a continuous tube. Explain the importance of the xylem being kept open as a continuous tube
1. Contraction of internal intercostal muscles;
2. Relaxation of diaphragm muscles / of external intercostal muscles;
3. Causes decrease in volume of chest / thoracic cavity;
4. Air pushed down pressure gradient.
Describe and explain the mechanism that causes forced expiration.
1. Hydrolysis; 2. (Of) glycosidic bonds; 3. (Starch) to maltose by amylase; 4. (Maltose) to glucose by disaccharidase/maltase; 5. Membrane-bound (disaccharidase/maltase); Other than 5.
Describe the complete digestion of starch by a mammal.
1. (Plasma) proteins remain;
2. (Creates) water potential gradient OR Reduces water potential (of blood);
3. Water moves (to blood) by osmosis;
4. Returns (to blood) by lymphatic system
Tissue fluid is formed from blood at the arteriole end of a capillary bed. Explain how water from tissue fluid is returned to the circulatory system.
1. In source / leaf sugars actively transported into phloem; 2. By companion cells; 3. Lowers water potential of sieve cell / tube and water enters by osmosis; 4. Increase in pressure causes mass movement (towards sink / root); 5. Sugars used / converted in root for respiration for storage.
Describe the mass flow hypothesis for the mechanism of translocation in plants
1. Spiracles, tracheae, tracheoles;
2. Spiracles allow diffusion (of oxygen) OR (Oxygen) diffusion through tracheae/tracheoles; 3. Tracheoles are highly branched so large surface area (for exchange);
4. Tracheole (walls) thin so short diffusion distance (to cells) OR Highly branched tracheoles so short diffusion distance (to cells) OR Tracheoles enter cells so short diffusion distance;
5. Tracheole walls are permeable to oxygen/air; If tracheae/tracheoles confused, penalise once only
6. Cuticle/chitin/exoskeleton (impermeable) so reduce water loss;
7. Spiracles (can) close so no/less water loss OR Spiracles have valves so no/less water loss;
8. Hairs around spiracles reduce water loss
Describe how the structure of the insect gas exchange system:
• provides cells with sufficient oxygen
• limits water loss. Explain your answers.
1. Hydrolysis of peptide bonds; 2. Endopeptidases break polypeptides into smaller peptide chains; 3. Exopeptidases remove terminal amino acids; 4. Dipeptidases hydrolyse / break down dipeptides into amino acids.
Describe how proteins are digested in the human gut.
1. Sucrose actively transported into phloem (cell); OR Sucrose is co-transported/moved with H+ into phloem (cell); Accept sieve (element/tube/cell) for phloem (cell)
2. (By) companion/transfer cells;
3. Lowers water potential (in phloem) and water enters (from xylem) by osmosis;
4. (Produces) high(er) (hydrostatic) pressure; OR (Produces hydrostatic) pressure gradient; Accept description of gradient, eg higher WP
5. Mass flow to respiring cells OR Mass flow to storage tissue/organ; Accept transport OR movement for flow Accept buds/young leaves/fruit/seeds/shoot tip/root tip/ meristems/root
6. Unloaded/removed (from phloem) by active transport; Accept facilitated diffusion
Describe the transport of carbohydrate in plants.