Humans

Question 1

What are the substances plasma is important for the transport of

Answer 1

CO2, Digested food, Urea, Heat energy and hormones

Question 2

Role of plasma in transporting CO2

Answer 2

hTe waste product of respiration, dissolved in the plasma as hydrogencarbonate ions and transported from respiring cells to the lungs

Question 3

Role of plasma in transporting digested food

Answer 3

dissolved particles absorbed from the small intestine and delivered to requiring cells around the body

Question 4

Role of plasma transporting urea

Answer 4

the waste substance produced in the breakdown of proteins by the liver. Urea is dissolved in the plasma and transported to the kidneys

Question 5

Role of plasma transporting hormones

Answer 5

chemical messengers released into the blood from the endocrine organs (glands) and delivered to target tissues/organs of the body

Question 6

Role of plasma transporting heat energy

Answer 6

created in respiration (an exothermic reaction), heat energy is transferred to cooler parts of the body or to the skin where heat can be lost

Question 7

Why don’t red blood cells have a nucleus

Answer 7

More space for haemoglobin to be packed

Question 8

What is haemoglobin

Answer 8

A protein that binds to oxygen to form oxyhaemoglobin

Question 9

Why does the red blood cell have a biconcave shape

Answer 9

This gives them a large surface area to volume ratio to maximise diffusion

Question 10

How do phagocytes deal with pathogens

Answer 10

They engulf and digest pathogens.
1) They have a sensitive cell surface membrane that can detect chemicals produced by pathogenic cells
2) Once they encounter the pathogenic cell, they will engulf it and release digestive enzymes to digest it

Question 11

How do lymphocytes deal with pathogens

Answer 11

Lymphocytes produce antibodies
Antibodies are Y-shaped proteins with a shape that is specific to the antigens on the surface of the pathogen

Question 12

How do antibodies work

Answer 12

Antibodies attach to the antigens and cause agglutination (clumping together). This means the pathogenic cells cannot move very easily
At the same time, chemicals are released that signal to phagocytes that there are cells present that need to be destroyed

Question 13

How do vaccinations work

Answer 13

Lymphocytes recognise the antigens in the bloodstream
The lymphocytes produce antibodies specific to the antigen encountered
Memory cells and antibodies subsequently remain circulating in the blood stream

Question 14

How do platelets clot blood

Answer 14

Platelets release chemicals that cause soluble fibrinogen proteins to convert into insoluble fibrin and form an insoluble mesh across the wound, trapping red blood cells and therefore forming a clot
The clot eventually dries and develops into a scab to protect the wound from bacteria entering

Question 15

Where does blood enter from in the heart

Answer 15

Oxygenated blood from the lungs enters the left side of the heart and is pumped to the rest of the body

Question 16

Which ventricle has a thicker muscle wall and why

Answer 16

The left ventricle has a thicker muscle wall than the right ventricle as it has to pump blood at high pressure around the entire body.

Question 17

Where does deoxygenated blood enter from and where does it go to

Answer 17

Deoxygenated blood from the body enters the right side of the heart and is pumped to the lungs

Question 18

Which ventricle pumps blood at lower pressures to the lungs

Answer 18

The right ventricle is pumping blood at lower pressure to the lungs

Question 19

What muscle separates the two sides of the heart

Answer 19

septum

Question 20

What do valves do

Answer 20

prevent blood flowing backwards

Question 21

Whats the pathway of blood through the heart

Answer 21

• Deoxygenated blood coming from the body flows through the vena cava and into the right atrium
• The atrium contracts and the blood is forced through the tricuspid (atrioventricular) valve into the right ventricle
• The ventricle contracts and the blood is pushed through the semilunar valve into the pulmonary artery
• The blood travels to the lungs and moves through the capillaries past the alveoli where gas exchange takes place
• Low pressure blood flow on this side of the heart prevents damage to the capillaries in the lungs
• Oxygenated blood returns via the pulmonary vein to the left atrium
• The atrium contracts and forces the blood through the bicuspid (atrioventricular) valve into the left ventricle
• The ventricle contracts and the blood is forced through the semilunar valve and out through the aorta
• Thicker muscle walls of the left ventricle produce a high enough pressure for the blood to travel around the whole body

Question 22

How does the heart rate change during exercise and why

Answer 22

Heart rate increases to deliver oxygen and glucose and remove waste more frequently
The volume of blood pumped out of the heart also increases to deliver bigger quantities of oxygen and glucose

Question 23

How is oxygen debt paid off

Answer 23

At the end of a period of exercise, the heart rate may remain high for a period of time as oxygen is required in the muscles to break down the lactic acid from anaerobic respiration