Mass transport (Human & Plant) Flashcards
Explain how an arteriole can reduce the blood flow into capillaries (2)
- Muscle contracts;
- Constricts/narrows arteriole/lumen;
Describe how the heart muscle and the heart valves maintain a one-way flow of blood from the left atrium to the aorta (9)
- Atrium has higher pressure than ventricle (due to filling / contraction);
- Atrioventricular valve opens;
- Ventricle has hi**gher pressure than atrium (due to filling / contraction);
- Atrioventricular valve closes;
- Ventricle has higher pressure than aorta;
- Semilunar valve opens;
- Higher pressure in aorta than ventricle (as heart relaxes);
- Semilunar valve closes;
- Muscle / atrial / ventricular) contraction causes increase in pressure
Describe how the movement of the diaphragm leads to air movement into the lungs (4)
- Diaphragm contracts and flattens.
- Volume of lungs increases.
- Pressure inside the lungs is lower than
atmospheric pressure. - Air moves into the lungs.
Describe and explain how the lungs are adapted to allow rapid exchange of oxygen between air in the alveoli and blood in the capillaries around them (5)
- Many alveoli/ alveoli walls folded provide a large surface area;
- Many capillaries provide a large surface area So fast diffusion
- Alveoli or capillary walls/ epithelium/ lining are thin/ one cell thick / short distance between alveoli and blood;
- Flattened/ squamous epithelium So short diffusion distance/ pathway / So fast diffusion
5.* Ventilation / circulation; So Maintains a diffusion / concentration gradient So fast diffusion;
Describe the gross structure of 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 – Diaphragm contract and external intercostal muscles contract
- Volume increases and pressure decreases in thoracic cavity.
- Breathing out – Diaphragm relaxes and internal intercostal muscles contract
- Volume decrease and pressure increase in thoracic cavity
Describe the pathway taken by an oxygen molecule from an alveolus to the blood (2)
- (Across) alveolar epithelium;
- Endothelium of capillary;
Arteries and arterioles take blood away from the heart. Explain how the structures of the walls of arteries and arterioles are related to their functions. (6)
Elastic tissue
**1. Elastic tissue stretches under pressure/when heart contracts;
2. Recoils/springs back;
3. Evens out pressure/flow;
Muscle
4. Muscle contracts;
5. Reduces diameter of lumen/vasoconstriction/constricts vessel;
6. Changes flow/pressure;
**Epithelium
7. Epithelium smooth;
8. Reduces friction/blood clots/less resistance;
The thickness of the aorta wall changes all the time during each cardiac cycle.
Explain why. (5)
- (Aorta wall) stretches;
- Because ventricle/heart contracts / systole / pressure increases;
- (Aorta wall) recoils;
- Because ventricle relaxes / heart relaxes /diastole / pressure falls;
- Maintain smooth flow / pressure;
Describe how tissue fluid is formed and how it is returned to the circulatory system. (8)
**Formation
**1. High blood / hydrostatic pressure / pressure filtration;
2. Forces water / fluid out;
3. Large proteins remain in capillary;
Return
4. Low water potential in capillary / blood;
5. Due to (plasma) proteins;
6. Water enters capillary / blood;
7. (By) osmosis;
8. Correct reference to lymph;
Heat from respiration helps mammals to maintain a constant body temperature.
Use this information to explain the relationship between the surface area to volume ratio of mammals and the oxygen dissociation curves of their haemoglobins. (5)
- Smaller mammal has greater surface area to
volume ratio; - Smaller mammal/larger SA:Vol ratio more
heat lost (per unit body mass); - Smaller mammal/larger SA:Vol ratio has
greater rate of respiration/metabolism; - Oxygen required for respiration;
(Haemoglobin) releases more oxygen / oxygen released more readily / haemoglobin has lower affinity;
Explain how water enters xylem from the endodermis in the root and is then transported to the leaves. (6)
In the 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 water potential gradient;
Xylem to leaf)
5. Evaporation / transpiration (from leaves);
6. (Creates) cohesion / tension / H-bonding between water molecules / negative pressure;
7. Adhesion / water molecules bind to xylem;
8. (Creates continuous) column of water
Root pressure moves water through the xylem. Describe what causes root pressure. (4)
- Active transport by endodermis;
- ions/salts into xylem;
- Lowers water potential (in xylem);
- (Water enters) by osmosis;
Name a factor that can affect transpiration (4)
Light (intensity)
temperature
air movement
humidity;
Give two precautions the students should have taken when setting up the potometer to obtain reliable measurements of water uptake by the plant shoot (8)
- Seal joints / ensure airtight / ensure watertight;
- Cut shoot under water;
- Cut shoot at a slant;
- Dry off leaves;
- Insert into apparatus under water;
- Ensure no air bubbles are present;
- Shut tap;
- Note where bubble is at start / move bubble to the start position;
Describe the mass flow hypothesis for the mechanism of translocation in plants (5)
- 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;
