Section 8 Exchange and transport in animals p.59-65

Question 1

Exchanging with the environment

Answer 1

Take in what we need….give out waste.
e.g. oxygen for respiration by diffusion
water is taken up by osmosis
Urea diffuses from cells to blood plasma

Question 2

Surface area to Volume Ratio

Answer 2

Larger the organism the smaller its surface area to volume ratio.
The smaller the ratio the slower exchange of substances will be.

Question 3

Multicellular organisms
Alveoli

Answer 3

Single- celled organisms can diffuse substances directly across the membrane. Multicellular need an exchange surface
The lungs transfer oxygen to the blood and carbon dioxide from the blood. The lungs contain millions of alveoli. Due to the high concentration gradient diffusion can occur fast.
Alveoli adaptations
• Moist lining for dissolving gases
• Good blood supply to maintain gradient
• Very thin walls to minimise distance
• Large surface area (75m² in humans)

Question 4

Red blood cells

Answer 4

Carry oxygen. In lungs a red pigment haemoglobin binds with oxygen to form oxyhaemoglobin.
Biconcave shape to give large surface area
No nucleus allowing more room for oxygen

Question 5

White blood cells

Answer 5

Phagocytes change shape to engulf microorganisms – phagocytosis

Question 6

Platlets

Answer 6

Small fragments of cells with no nucleus. Help to clot the blood

Question 7

Plasma

Answer 7

Pale liquid that carries substances: red cells, white cells, platelets, nutrients, carbon dioxide, urea, hormones, proteins, antibodies and antitoxins.

Question 8

Arteries

Answer 8

Carry blood away from the heart. Due to high pressure artery walls are strong, thick and elastic.

Question 9

Capillaries

Answer 9

Arteries branch into capillaries.
• Very small and narrow to go between cells.
• Permeable walls for exchange.
• One cell thick to speed up diffusion.

Question 10

Veins

Answer 10

• Blood at lower pressure than arteries so walls are not as thick.
• Bigger lumen (hole in the middle) to help blood flow
• Valves to help blood flow in the right direction – prevent back flow

Question 11

Double Circulation

Answer 11

Two circuits. First – the heart pumps deoxygenated blood to the lungs to take in oxygen which then returns to the heart.
Second – heart pumps oxygenated blood to all other organs of the body to deliver oxygen and returns deoxygenated blood to the heart.

Question 12

Circuit of blood

Answer 12

Deoxygenated blood into right atrium (via vena cava) – then to right ventricle – to lungs (via pulmonary artery) – oxygenated blood goes into left atria (via pulmonary vein) –then to left ventricle – then to rest of body (via aorta)
Left ventricle has thicker wall as it needs to pump at higher pressure. Valves prevent backflow.

Question 13

Cardiac output
(equation)

Answer 13

Cardiac output = heart rate x stroke volume

Question 14

Respiration
respiration

Answer 14

Takes place in the mitochondria.
Releases energy in an exothermic reaction. Energy for; metabolic processes, contracting muscles, maintaining body temperature.

Question 15

Aerobic

Answer 15

With oxygen

Question 16

Anerobic

Answer 16

Not enough oxygen. Lactic acid builds up. Painful. Less energy released
Oxygen is used to break down the lactic acid – known as oxygen debt
Glucose à lactic acid

Question 17

Anaerobic respiration in plants

Answer 17

Instead of lactic acid they produce ethanol
Measuring respiration using a respirometer.