Topic 8 Exchange and Transport in Animals

Question 1

Do larger organisms have a higher or lower SA:V ratios generally?

Answer 1

Lower

Question 2

Why don’t single-celled organisms need exchange organs?

Answer 2

Gases and substances can diffuse directly in and out of the cell across cell membrane because they have a large SA:V so enough substances can be exchanged across the membrane to supply the volume of the cell.

Question 3

Why do multi-cellular organisms need exchange surfaces?

Answer 3

They have a small SA:V so it’s difficult to exchange enough substances to supply the entire volume of the organism.
Exchange surfaces are needed that have efficient diffusion and a transport system to move substances from the exchange surfaces to the rest of the body.

Question 4

Ways alveoli maximise diffusion

Answer 4

A good blood supply arriving from rest of body to high concentration gradient for diffusion of both CO2 and O2.
Moist lining for dissolving gases.
Very thin walls to minimise distance gases have to move.
Large surface area.

Question 5

3 factors of rate of diffusion

Answer 5

Distance - quicker diffusion with less travel distance.
Concentration gradient - big difference means more particles to move across from one side.
Surface area - more surface available for molecules to move across.

Question 6

Rate of diffusion (Fick’s Law)

Answer 6

Rate of diffusion is proportional to surface area and concentration difference and inversely proportional thickness of membrane.
Rate of diffusion will double if difference in concentration or surface doubles or thickness of membrane halves.

Question 7

When and where is respiration happening

Answer 7

In every living cell of all living organisms all the time.

Question 8

Uses of respiration

Answer 8

Metabolic processes - making larger molecules from smaller ones (e.g. proteins from amino acids).
Contracting muscles.
Maintaining a steady body temperature.

Question 9

Equation for aerobic respiration

Answer 9

Glucose + oxygen -> carbon dioxide + water

Question 10

When does anaerobic respiration happen?

Answer 10

When the body cannot supply enough oxygen to your muscles for aerobic respiration during vigorous exercise even though your heart rate and breathing rate is at maximum. It happens at the same time as aerobic respiration.

Question 11

How efficient is anaerobic respiration and what does it cause?

Answer 11

It is not as efficient as it transfers much less energy than aerobic respiration.
The glucose is only partially broken down and lactic acid is produced.
The lactic acid build up can become painful and lead to cramp.

Question 12

Word equation for anaerobic respiration

Answer 12

Glucose -> lactic acid

Question 13

Word equation for anaerobic respiration in plants

Answer 13

Glucose -> ethanol + carbon dioxide

Question 14

How to measure rate of respiration in a respirometer

Answer 14

Measure the rate oxygen is used up in a given time.
The oxygen used up decreases the pressure in the tube so the coloured liquid moves toward the test tube containing the organism.
The distance moved is measured and volume of oxygen taken in can be found per minute.

Question 15

How is the carbon dioxide absorbed from the tube

Answer 15

Using soda lime

Question 16

Structure and features of red blood cell

Answer 16

Biconcave disc shape to give large surface area for absorbing oxygen.
No nucleus allow more room to carry oxygen.
Contain haemoglobin which contains iron which binds to oxygen in lungs to become oxyhemoglobin and splits at body cells to release oxygen.

Question 17

Phagocytes

Answer 17

White blood cells that engulf microorganisms (phagocytosis).

Question 18

Lymphocytes

Answer 18

White blood cells that produce antibodies and antitoxins.

Question 19

Features and purpose of platelets

Answer 19

Small fragments of cells that have no nucleus.

They help blood clot at wounds.

Question 20

Plasma features and function

Answer 20

Straw-coloured liquid that carries everything: red and white blood cells and platelets, nutrients such as glucose and amino acids, carbon dioxide, urea, hormones, antibodies and antitoxins.

Question 21

Arteries

Answer 21

Carry blood away from heart.
Pumps blood at high pressure to go around whole body, strong and elastic walls.
Have thick layer of smooth muscle wall with small lumen.
Have elastic fibres to allow muscle to stretch and spring back.

Question 22

Capillaries

Answer 22

Narrow to fit between cells to carry blood to every cell in body to exchange substances.
Permeable walls so substances can diffuse through them.
Supply glucose and oxygen and take away CO2.
Have 1 cell thick walls to increase rate of diffusion.
Small lumen to slow blood flow so more substances diffuse.

Question 23

Veins

Answer 23

Carry blood back to heart.
Blood is at lower pressure so walls don’t need to be as thick.
Bigger lumen to help blood flow at lower pressure.
Have valves to make sure blood flows in right direction.

Question 24

Right side of the heart

Answer 24

Right atrium receives deoxygenated blood from the vena cava and it is pumped to the right ventricle which pumps it to the lungs.

Question 25

Left side of the heart

Answer 25

Receives oxygenated blood from the lungs through the pulmonary vein.
Blood moves through to left ventricle and is pumped around the whole body via the aorta.

Question 26

Purpose of valves

Answer 26

Prevent backflow of blood

Question 27

Why has the left ventricle a thicker wall?

Answer 27

If needs more muscle to pump the blood around the whole body at high pressure.

Question 28

Formula for cardiac output

Answer 28

Cardiac output = heart rate * stroke volume

Question 29

Stroke volume definition

Answer 29

Volume of blood pumped by one ventricle each time it contracts.

Question 30

Cardiac output definition

Answer 30

The total volume of blood pumped by a ventricle every minute.