3: Organisms exchange substances with their environment Flashcards
Explain the advantage for larger animals of having a specialised system that facilitates oxygen uptake [2]
- Large(r) organisms have a small(er) surface area:volume (ratio); OR Small(er) organisms have a large(r) surface area:volume (ratio);
- Overcomes long diffusion pathway OR Faster rate of diffusion;
How does oxygen move through the insect? [4]
- Oxygen diffuses in through the spiracles;
- Spiracle closes;
- Oxygen diffuses through the trachea into the tracheoles;
- Oxygen delivered directly to the respiring tissues;
Explain three ways in which an insect’s tracheal system is adapted for efficient gas exchange. [3]
- 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);
4.Tracheae provide tubes full of air so fast rate of 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;
Describe how the structure of the insect gas exchange system:
* provides cells with sufficient oxygen
* limits water loss.
Explain your answers. [6]
- Spiracles, tracheae, tracheoles;
- Spiracles allow diffusion (of oxygen)
OR (Oxygen) diffusion through tracheae/tracheoles; - Tracheoles are highly branched so large surface area (for exchange);
- 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;
- Tracheole permeable to oxygen/air;
- Cuticle/chitin/exoskeleton (impermeable) so reduce water loss;
- Spiracles (can) close so no/less water loss OR Spiracles have valves so no/less water loss;
- Hairs around spiracles reduce water loss;
Describe and explain the advantage of the counter-current principle in gas exchange across a fish gill. [3]
- Water and blood flow in opposite directions;
- Maintains diffusion/concentration gradient of oxygen OR Oxygen concentration always higher (in water);
- (Diffusion) along length of lamellae/filament/gill capillary;
A fish uses its gills to absorb oxygen from water.
Explain how the gills of a fish are adapted for efficient gas exchange. [6]
1 Large surface area provided by many lamellae over many gill filaments;
2 Increases diffusion/makes diffusion efficient;
3 Thin epithelium/distance between water and blood;
4 Water and blood flow in opposite directions/countercurrent;
5 (Point 4) maintains concentration gradient (along gill)/equilibrium not reached;
6 As water always next to blood with lower concentration of oxygen;
7 Circulation replaces blood saturated with oxygen;
8 Ventilation replaces water (as oxygen removed);
Describe the gross structure of the human gas exchange system and how we breathe in and out. [6]
- Named structures – trachea, bronchi, bronchioles, alveoli;
- Above structures named in correct order OR Above structures labelled in correct positions on a diagram;
**Breathing in **
3. Diaphragm (muscles) contract and diaphragm flattens;
4. External intercostal muscles contract and ribcage pulled up/out;
5. (Causes) volume increase and pressure decrease in thoracic cavity (to below atmospheric pressure);
**Breathing out **
6. Diaphragm (muscles) relaxes and diaphragm moves up;
7. External intercostal muscles relax and ribcage moves down/in;
8. (Causes) volume decrease and pressure increase in thoracic cavity (to above atmospheric pressure);
Describe how carbon dioxide in the air outside a leaf reaches mesophyll cells inside the leaf. (4)
- (Carbon dioxide enters) via stomata;
- (Stomata opened by) guard cells;
- Diffuses through air spaces;
- Down diffusion gradient;
Explain why plants grown in soil with very little water grow only slowly. [2]
- Stomata close;
- Less carbon dioxide (uptake) for less photosynthesis/glucose production;
Describe the process of starch digestion. [5]
(salivary/pancreatic) Amylase;
Starch to Maltose;
Maltase;
Maltose to glucose;
Hydrolysis;
Glycosidic bonds;
Describe the processes involved in the absorption and transport of digested lipid molecules from the ileum into lymph vessels. [5]
- 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 SER);
- Vesicles move to cell membrane;
Describe the role of micelles in the absorption of fats into the cells of the ileum. [5]
- Micelles include bile salts and fatty acids;
- Make the fatty acids (more) soluble in water;
- Bring/release/carry fatty acids to cell/lining (of the ileum);
- Maintain high(er) concentration of fatty acids to cell/lining (of the ileum);
- Fatty acids (absorbed) by diffusion;
Describe the role of enzymes in the digestion of proteins in a mammal. [4]
- (Reference to) hydrolysis of peptide bonds;
- Endopeptidase act in the middle of protein/polypeptide OR Endopeptidase produces short(er) polypeptides/ increase number of ends;
- Exopeptidases act at end of protein/polypeptide OR Exopeptidase produces dipeptides/amino acids;
- Dipeptidase acts on dipeptide/between two amino acids OR Dipeptidase produces (single) amino acids;
The action of endopeptidases and exopeptidases can increase the rate of protein digestion. Describe how. [2]
- Exopeptidases hydrolyse peptide bonds at the ends of a polypeptide/protein AND endopeptidases hydrolyse internal peptide bonds within a polypeptide/protein;
- More ‘ends’ OR More surface area;
Describe and explain two features you would expect to find in a cell specialised for absorption. [2]
- Folded membrane/microvilli so large surface area (for absorption);
Accept ‘brush border’ for ‘microvilli’. - Large number of co-transport/carrier/channel proteins so fast rate (of absorption) OR
Large number of co-transport/carrier proteins for active transport OR
Large number of co-transport/carrier/channel proteins for facilitated diffusion; - Large number of mitochondria so make (more) ATP (by respiration) OR
Large number of mitochondria for aerobic respiration OR
Large number of mitochondria to release energy for active transport; - Membrane-bound (digestive) enzymes so maintains concentration gradient (for fast absorption);
Describe the absorption of glucose (Cotransport) [3]
- Sodium ions actively transported from ileum cell in to the blood;
- Maintains / forms diffusion gradient for sodium to enter cells from gut (and with it, glucose);
- Glucose enters ileum cell by facilitated diffusion with sodium ions;
Describe the mechanism for the absorption of amino acids in the ileum [4]
- Facilitated diffusion of amino acid (into cell when higher concentration in lumen);
- Co-transport;
- Sodium ions actively transported from cell to blood/capillary/tissue fluid;
- Creating sodium ion concentration/diffusion gradient;
- Facilitated diffusion of amino acid into blood/capillary;
Explain how an arteriole can reduce the blood flow into capillaries. [2]
- Muscle layer contracts;
- Constricts/narrows arteriole/lumen;