EKQu's | Mass Transport in Animals

How many oxygen molecules can a haemoglobin molecule carry?

4

An arteriole is described as an organ. Explain why.

Made of (different) tissues / more than one tissue;

Explain how haemoglobin transports oxygen (5)

-4 haem groups attach to oxygen - loads/associates under high partial pressures of oxygen at gas exchange surface - cooperative binding – binding of 1st oxygen increases the affinity for oxygen/makes binding easier - due to change of shape - unloads/disassociates under low partial pressures of oxygen at respiring tissue - bohr effect – carbon dioxide lowers the pH of blood - changes the shape of haemoglobin lowering its affinity/increases unloading

An arteriole contains muscle fibres. Explain how these muscle fibres reduce blood flow to capillaries

1.      (Muscle) contracts; 2.      (Arteriole) narrows / constricts / reduces size of lumen / vessel / vasoconstriction;

The elastin fibres in the wall of the artery help to smooth out the flow of blood. What happens to these fibres as the pressure of the blood in the artery changes?

Stretch as pressure increases; Recoil / spring back as pressure drops;

What is meant by the term    ‘cooperative binding’ in simple terms

AS….

As one oxygen molecule binds to haemoglobin, the haemoglobin changes shape which makes it easier for subsequent oxygens to bind

Why do large organisms need a circulatory system?

sa:vol is too small to be able to rely on diffusion to get  oxygen/glucose to all parts of the organism quickly enough

What is a double circulatory system?

Blood passes twice through the heart for  each complete circuit of the body

Name the arteries which supply the heart muscle with oxygenated blood.

coronary arteries

What prevents blood being forced back into the atria during  ventricular systole?

The atrioventricular (AV) valves close.

How is the structure of an artery related to its function?

Thick wall and elastic fibres – can withstand high pressure; allows artery to recoil and maintain high pressure. smooth muscle – contracts to control blood flow

How is the structure of a capillary related to its function?

Capillary endothelium is one cell thick – short diffusion path; has small gaps between endothelial cells to allow exchange of substances.

Explain the role of the heart in the formation of tissue fluid.

1.      Contraction of ventricle(s) produces high blood / hydrostatic pressure; 2.      (This) forces water (and some dissolved substances) out (of blood capillaries);

in a healthy person, blood moves in one direction as it passes through the heart. Give two ways in which this is achieved.

1.      Pressure gradient / moves from high to low pressure; 2.      Valves stop backflow;

S3 Explain how tissue fluid is formed and how it may be returned to the circulatory system. (5)

1. (hydrostatic) pressure of blood high at arterial end; 2. fluid / water / soluble molecules pass out (reject plasma); 3. proteins / large molecules remain; 4. this lowers the water potential / water potential becomes more negative; 5. water moves back into venous end of capillary (reject tissue fluid) by osmosis / diffusion; 6. lymph system collects any excess tissue fluid which returns to blood

S3 Explain how the structures of the walls of arteries and arterioles are related to their functions (5)

Elastic tissue 1. Elastic tissue stretches under pressure / when heart beats then recoils / springs back; 2. Evens out pressure / flow; Do not allow credit for expands / contracts / relaxes in this context. 3. Muscle contracts to reduce diameter of lumen / 4. Changes flow / pressure; Epithelium 5. Epithelium smooth; 6. Reduces friction / blood clots / less resistance;

S3 explain how the structures of the walls of arteries, veins and capillaries are related to their functions.(6)

Artery 1. thickest wall, enabling it to carry blood at high pressure / withstand pressure surges; 2. most elastic tissue, which smoothes out flow / maintains pressure; 3. most muscle which maintains pressure; 4. muscle in wall to control blood flow; Vein 5. thin wall does not have to withstand high pressure; Capillary 6. thin wall, allowing diffusion / exchange; 7. only endothelium present, allowing short diffusion pathway; All vessels 8. have endothelium that reduces friction;

The oxygen dissociation curve for haemoglobin shifts to the right during vigorous exercise. Explain the advantage of this shift. (3)

Bohr shift - Respiration produces carbon dioxide Lower affinity for oxygen / releases more oxygen / oxygen is released quicker / oxygen dissociates / unloads more readily; 2. (To) muscles / tissues / cells 3. (For) high / rapid respiration;

Explain how the heart muscle and the heart valves maintain one-way flow of blood from the left atrium to the aorta. (cardiac cycle)(5)

1. Atrium has higher pressure than ventricle (due to filling contraction) causing atrioventricular valves to open; (Muscle / atrial / ventricular) contraction causes increase in pressure; 2. Ventricle has higher pressure than atrium (due to filling contraction) causing atrioventricular valves to close; 3. Ventricle has higher pressure than aorta causing semilunar valve to open; 4. Higher pressure in aorta than ventricle (as heart relaxes) causing semilunar valve to close;

S3 Explain how oxygen is loaded, transported and unloaded in the blood.(5)

1. Haemoglobin carries oxygen / has a high affinity for oxygen 2. Loading / uptake / association in lungs; 3. at high p.O2; Cooperative binding means the binding of the first oxygen increases its affinity (attraction) by changing its shape 4. Unloads / dissociates / releases to respiring cells / tissues; 5. at low p.O2; 6. Unloading linked to higher carbon dioxide (concentration); Bohr effect

S3 Describe and explain four ways in which the structure of a capillary adapts it for the exchange of substances between blood and the surrounding tissue.(4)

1. permeable capillary wall / membrane; 2. single cell thick / thin walls, reduces diffusion distance; 3. flattened (endothelial) cells, reduces diffusion distance; 5. small diameter / narrow, gives a large surface area to volume / short diffusion distance; 6. narrow lumen, reduces flow rate giving more time for diffusion; 7. red blood cells in contact with wall / pass singly, gives short diffusion distance / more time for diffusion;

Arteriole

carry blood from arteries to capillaries. Arterioles are very similar to arteries. They are different in that they are smaller in diameter and have a thinner muscle layer and lumen. The muscle layer is thicker and elastic layer is thinner than in arteries.

Haem group

The iron-containing group in haemoglobin that binds to oxygen molecules.

Cooperative binding

When the binding of one oxygen molecule to haemoglobin increases the affinity of haemoglobin for additional oxygen molecules.

Bohr effect

The phenomenon where increased levels of carbon dioxide lower the pH of blood, reducing haemoglobin's affinity for oxygen.

Elastic fibres

Fibres in the artery walls that allow them to stretch when blood pressure increases and recoil when pressure drops.

Muscle fibres (in arterioles)

Muscle fibres (in arterioles)

Muscle cells that allow the arteriole to constrict and reduce blood flow.

Atrioventricular (AV) valves

Valves that prevent the backflow of blood into the atria during ventricular systole.

Double circulatory system

A system in which blood passes through the heart twice for each complete circuit around the body.

Coronary arteries

Arteries that supply oxygenated blood to the heart muscle.

Tissue fluid

Fluid that surrounds tissues, formed when blood pressure forces water and small molecules out of the capillaries.

Hydrostatic pressure

Pressure exerted by a fluid within the blood vessels, forcing substances out of the capillaries.

Endothelium

The thin layer of cells that lines the inside of blood vessels, reducing friction and allowing smooth blood flow.

Semilunar valve

Valves that prevent the backflow of blood from the arteries into the ventricles after ventricular systole.

Capillary

Small blood vessels where exchange of gases, nutrients, and waste products occurs between blood and tissues.