SA:V
As size increases, ratio of (surface area:volume) decreases
Describe the relationship between size and surface area to volume ratio of organisms
(Simple) diffusion
Name the process by which oxygen passes from an alveolus in the lungs into the blood.
Amylase and disaccharidases eg maltase
What enzymes break down starch
Binding of first oxygen changes tertiary / quaternary (structure) of haemoglobin which uncovers another binding site
Suggest how binding of one molecule of oxygen to haemoglobin makes it easier for a second oxygen molecule to bind.
Phloem pressure falls as (rate of) water movement (in xylem) increases
Describe the relationship between phloem pressure and the rate of water movement in xylem in this plant
Larger organisms have a smaller surface area:volume (ratio)
For Faster diffusion
Explain the advantage for larger animals having a specialised system that facilitates oxygen uptake?
Thin walls / cells
Surface area is large
Describe two adaptations of the structure of alveoli for efficient gas exchange
A concentration/diffusion gradient for Na+ (from ileum into cell);
Na+ moving (in) by facilitated diffusion, 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
(smooth)Muscle contracts;
Constricts/narrows arteriole/lumen;
Explain how an arteriole can reduce the blood flow into capillaries
Mitochondria release energy / ATP / site of respiration;
For active transport / uptake against concentration gradient
Suggest and explain one way in which companion cells are adapted for the transport of sugars between cells
As surface area to volume ratio increases, metabolic rate increases
A larger surface area to volume ratio will lose more heat
A higher rate of metabolism/respiration maintains body temperature
Describe and explain the relationship between surface area to volume ratio of the human body and metabolic rate
Water and blood flow in opposite directions;
Maintains concentration / diffusion gradient
Along whole / length of gill
Describe and explain how the countercurrent system leads to efficient gas exchange across the gills of a fish.
1.Droplets increase surface areas (for lipase / enzyme action);
2. (So) faster hydrolysis / digestion (of triglycerides / lipids);
3. Micelles carry fatty acids and glycerol to (epithelial) cell.
Explain the advantages of lipid droplet and micelle formation.
Increases dissociation of oxygen(because of a lower partial pressure of Oxygen);
For aerobic respiration at the tissues/muscles/cells
Anaerobic respiration delayed so less lactate at the cells.
Describe the advantage of the Bohr effect during intense exercise.
Sucrose actively transported (into phloem);
Lowering/reducing water potential
Water moves (into phloem) by osmosis (from xylem)
Use your understanding of the mass flow hypothesis to explain how pressure is generated inside this phloem tube
Large(r) cells have small(er) surface area to volume ratio;
(Takes) longer for oxygen to diffuse (to mitochondria)
Because diffusion pathway is longer
Why are mitochondria placed near the membrane in larger cells whilst they are distributed evenly in smaller cells?
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.
Breathing out as hard as you can is called forced expiration. Describe and explain the mechanism that causes forced expiration
1. Hydrolysis of peptide bonds
2. Endopeptidase act in the middle of protein/polypeptide
3. Exopeptidases act at end of protein/polypeptide
4. Dipeptidase acts on dipeptide/between two amino acids
Describe the role of enzymes in the digestion of proteins in a mammal.
(Plasma) proteins remain;
(Creates) water potential gradient by reducing water potential of the blood
Water moves (to blood) by osmosis;
Excess tissue fluid returns by lymphatic system
Explain how water from tissue fluid is returned to the circulatory system.
In source / leaf sugars actively transported into phloem;
By companion cells;
Lowers water potential of sieve cell / tube and water enters by osmosis;
Increase in pressure causes mass movement (towards sink / root);
(Sugars used / converted in root for respiration for storage.)
Describe the mass flow hypothesis for the mechanism of translocation in plants.
(Smaller so) larger surface area to volume ratio;
More/faster heat loss (per gram/in relation to body size)
(Faster rate of) respiration/metabolism releases heat
Explain the higher metabolic rate of a smaller organism compared to a larger one.
Single layer of cells;
Reduces diffusion distance/pathway;
So increases rate of diffusion
Permeable;
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
1. Micelles contain bile salts and fatty acids/monoglycerides
2. Make fatty acids/monoglycerides (more) soluble (in water)
3. Fatty acids/monoglycerides absorbed by diffusion;
4. Triglycerides (re)formed (in cells)
5. Vesicles move to cell membrane;
Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels.
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.
Water lost from leaf because of transpiration
Lowers water potential of mesophyll / leaf cells;
Water pulled up xylem (creating tension);
Water molecules cohere / ‘stick’ together by hydrogen bonds;
(forming continuous) water column;
Adhesion of water (molecules) to walls of xylem
Describe the cohesion-tension theory of water transport in the xylem.