Mass Transport

Question 1

List the 4 components of blood

Answer 1

1. Plasma (transports glucose, amino acids, urea, mineral ions and hormones)
2. Red blood cells (transports oxygen & carbon dioxide)
3. White blood cells (lymphocytes & phagocytes to fight infection)
4. Platelets (blood clotting with fibrin)

Question 2

Describe arteries

Answer 2

• Thick elastic walls
• High b.p.
• Smooth endothelium contains flattened cells
• Muscle cells & elastic fibre which recoils and expands
• Narrow lumen
• Carries blood away from heart

Question 3

Describe capillaries

Answer 3

• One cell thick walls
• Low b.p.
• Big SA

Question 4

Describe veins

Answer 4

• Think walls
• Low b.p.
• Wide lumen
• Not elastic/muscular
• Contains valves to prevent backflow
• Carries blood towards the heart

Question 5

Describe the cardiac cycle (3 steps)

Answer 5

1. Blood flows through atria about to flow through ventricles (atrial diastole and ventricular diastole)
2. Atrial walls contract, blood flows through ventricles (atrial systole and ventricular diastole)
3. Ventricular walls contract, SL valves open, AV valves close (atrial diastole and ventricular systole)

Question 6

Define diastole

Answer 6

At rest

Question 7

Define systole

Answer 7

Contraction / muscular movement

Question 8

Equation for cardiac output

Answer 8

Cardiac Output = heart rate (bpm) x stroke volume (mm)

Question 9

What factors affect heart rate?

Answer 9

• Age
• Hormones
• Fitness

Question 10

What factors affect stroke volume?

Answer 10

• Heart size
• Fitness
• Gender
• Heart contractility

Question 11

Risk factors of coronary heart disease with reason

Answer 11

• Age (increases with age)
• Sex (Men are more susceptible)
• Genetic (lifestyle/family)
• High bp (genetic, narrow lumen, high salt intake
• High conc. of low density lipoproteins

Question 12

Why is the increase in low density lipoproteins a risk factor of CHD?

Answer 12

• LDL leads to atheroma
• LDL also transports cholesterol
• low LDL = high HDL
• HDL absorbs excess cholesterol
• Therefore, high LDL = CHD

Question 13

During translocation in the phloem, how is a high pressure generated?

Answer 13

1. Water potential lowers as sugar enters phloem
2. Water enters phloem by osmosis;
3. Increased vol. (of water) causes increased pressure.

Question 14

Describe cohesion in the xylem

Answer 14

• Water molecules are polar
• O (d-) is attracted to H (d+) of H2O
• This pulls up water

Question 15

Describe adhesion in the xylem

Answer 15

• Water is attracted to the xylem walls
• As water is pulled up, walls drawn inward slightly (also because of transpiration)
• Water moves faster

Question 16

What is the function of the pits in the xylem?

Answer 16

They allow water to change direction if vessels are damaged

Question 17

Describe the ‘mass flow’ hypothesis (6 points)

Answer 17

• sucrose move from sources to phloem
• active transport of sucrose into phloem companion cells and passed to sieve tubes
• water follows by osmosis
• vol. of water increases, increasing pressure
• creates hydrostatic pressure
• sugars removed from phloem at sink and water follows;
• hydrostatic pressure gradient btwn source and sink creates mass flow

Question 18

How is a heartbeat initiated and coordinated?

Answer 18

• SA node sends an electrical impulse causing atrial contraction
• Non conducting tissue delays ventricular contraction
• AV node delays impulse whilst ventricles fill up
• AV node sends impulse down impulse down Bundle of His
• Causes ventricular contraction from base up

Question 19

What is the equation for pulmonary ventilation rate?

Answer 19

PVR = tidal volume × breathing rate

Question 20

Why would rate of water uptake not be equal to transpiration rate?

Answer 20

1. Water used for
turgidity
2. Water used in photosynthesis
3. Water used in hydrolysis
4. Water produced during respiration