Mass Transport

Question 1

First Phase of the Cardiac Cycle

Answer 1

Atrial systole

Question 2

Atrial Systole

Answer 2

Atria contract

Blood is forced through the atrioventricular valves into the ventricles

Atrioventricular valves open when atrial pressure > ventricular pressure

Ventricles remain relaxed

Question 3

Second Phase of the Cardiac Cycle

Answer 3

Ventricular Systole

Question 4

Ventricular Systole

Answer 4

Atria relax

Ventricles contract

Blood is pushed away from the heart through pulmonary arteries and aorta

Semi-lunar valves open when ventricular pressure > atrial pressure

Blood forced into arteries

Question 5

Third Phase of the Cardiac Cycle

Answer 5

Diastole

Question 6

Diastole

Answer 6

Atria are relaxed and fill with blood

Ventricles are relaxed

Semi-lunar valves closed

Atrioventricular valves open

Question 7

When do the semi-lunar valves open?

Answer 7

When ventricular pressure>atrial pressure

Question 8

When do the atrioventricular valves open?

Answer 8

When arterial pressure>ventricular pressure

Question 9

Role of Aorta

Answer 9

Takes blood from left ventricle to body

Question 10

Role of Pulmonary Artery

Answer 10

Takes blood from right ventricle to lungs

Question 11

Role of Vena Cava

Answer 11

Carries blood from the body to the right atrium

Question 12

Role of Pulmonary Veins

Answer 12

Carry blood from the lungs to the left atrium

Question 13

Role of Coronary Arteries

Answer 13

Supply the heart muscle with oxygen

Question 14

Where do veins carry blood

Answer 14

Into the atria

Question 15

Where do arteries carry blood

Answer 15

Away from the ventricles

Question 16

Double Circulatory System

Answer 16

Blood confined to vessels and passes through heart twice

Pulmonary circulation -> Right side pumps blood to lungs & oxygenates blood & removes CO2

Systematic circulation -> Left side pumps blood rapidly at a higher pressure to the body

Question 17

The Human Heart Has 4 Chambers:

Answer 17

2 thin-walled & elastic atria on top, which receive blood

2 thick-walled ventricles underneath, which pump blood

Question 18

Arteries

(In depth)

Answer 18

Carry blood away from the heart and into arteries rapidly, under high pressure

Muscle layer is thick, smaller arteries can be constricted & dilated to control volume of blood passing through them

Elastic layer is thick to keep high blood pressure, stretches at the systole and recoils at the diastole

Overall thickness resists the vessel bursting under pressure

No valves as the high pressure prevents backflow

Question 19

Arterioles

(In depth)

Answer 19

Carry blood (under lower pressure than arteries) from arteries -> capillaries

Muscle layer thicker than in arteries (contraction allows constriction of the lumen of the arteriolar, restricting blood flow & controls the movement into the capillaries)

Elastic layer thinner than in arteries (blood pressure is lower)

Question 20

Veins

(In depth)

Answer 20

Transport blood slowly, under low pressure from capillaries -> heart

Muscle layer=thin compared to arteries (carry blood away from tissues, constriction&dilation can’t control the flow of blood->tissues)

Elastic layer thin, low pressure will not cause them to burst and pressure too low to create a recoil action

Overall thickness small -> pressure is too low to create any risk of bursting

Valves so blood doesn’t flow backwards

Question 21

Equation for Cardiac Output

Answer 21

Cardiac Output = Stroke Volume x Heart Rate

Question 22

Cardiac Output Definition

Answer 22

Volume of blood pumped by 1 ventricle per minute

Question 23

Stroke Volume Definition

Answer 23

Volume pumped out per minute

Question 24

Heart Rate Definition

Answer 24

Beats per minute

Question 25

When does Ventricular Pressure Increase?

Answer 25

As the ventricles fill with blood and the atria contract When the left atrioventricular valves close

Question 26

Why is Atrial Pressure Relatively Low And When Does It Drop More?

Answer 26

Relatively low because the thin walls of the atrium cannot create much force Drops when the left atrioventricular valve closes and its walls relax

Question 27

When Does Aortic Pressure Rise?

Answer 27

When ventricles contract as blood is forced into the aorta Recoil action also produces temporary rise

Question 28

When Does Ventricular Volume Rise? When Does It Suddenly Drop?

Answer 28

As the atria contract and the ventricles fill with blood When blood is forced out into the aorta when the semi-lunar valves open

Question 29

Cohesion Tension Theory

Answer 29

Water evaporates from the mesophyll cells within the leaf through the stomata (transpiration), creating a negative water potential (tension). Cohesion: Water molecules stick together due to hydrogen bonding, forming a continuous water column in the xylem. Tension: The tension created by transpiration pulls water upwards through the xylem, drawing water from the roots. Adhesion: Water molecules also adhere to the walls of the xylem vessels, further aiding in the upward movement of water. Xylem is under so much tension that the vessels are pulled inwards and get narrower.

Question 30

Movement of water across the cells of a leaf

Answer 30

Mesophyll cells lose water to the air spaces by evaporation due to heat from the sun These cells now have a low water potential, water enters by osmosis by nearby cells Loss of water from nearby cells lowers their water potential, so they take in water from those nearby cells by osmosis

Question 31

What is the xylem made of

Answer 31

Lignin which is found in cell walls and is a waterproof substance

Question 32

Xylem cells are dead, hollow, continuous tubes:

Answer 32

Cell wall ends break down so cells form continuous, hollow tubes No organelles to restrict water flow so water flows easily

Question 33

Water movement through the roots

Answer 33

Root hair cell function= absorption of water & mineral ions

Question 34

Root hair cell adaptations

Answer 34

Hair projection: Large SA for absorption Many mitochondria: ATP

Question 35

Root hair cells

Answer 35

Take up mineral ions by active transport so the root hair cell has a lower water potential than the soil so water enters by osmosis

Question 36

4 factors affecting the rate of transpiration

Answer 36

Temperature Humidity Light Wind

Question 37

How does an increased temperature affect the rate of transpiration

Answer 37

Increases rate of transpiration because kinetic energy of water molecules increases so more likely to pass through stomata

Question 38

How does increased humidity affect the rate of transpiration

Answer 38

Decreases transpiration because there would be a reduced WP gradient between leaf & air spaces so water diffuses slower

Question 39

How does increased light intensity affect the rate of transpiration

Answer 39

Increases transpiration Indirect effect as stomata are open more when there is more light and so more gas exchange is needed for photosynthesis

Question 40

How does increased wind affect the rate of transpiration

Answer 40

Radioactive carbon incorporated into plant and forms glucose/sucrose Tracked around the plant X-Ray film-autoradiography

Question 41

Ringing experiments

Answer 41

Removed phloem of tree Area above removed phloem bulges if filled with sugar solution, evidence for translocation occurring in phloem Heat killed phloem or cooled phloem -> reduced rate of translocation, enzymes and ATP required for translocation are denatured so rate is slowed

Question 42

Radioactive tracers

Answer 42

Radioactive carbon incorporated into plant and forms glucose/sucrose Tracked around the plant X-Ray film-autoradiography

Question 43

Translocation

Answer 43

Sucrose made from photo products in cells facilitated diffusion down a gradient from these to companion cells H+ ions actively transported from companions into spaces in cell wall using ATP H+ ions diffuse though co-transport proteins into sieve tube and elements, carrying sucrose with them Sieve tubes have lower WP so water moves in from xylem by osmosis, creating high hydrostatic pressure, sucrose actively transported in from sieve tube and WP lowers - water also moves in Hydrostatic pressure of sieve lowers at the sink and higher at the source

Question 44

Ultrafiltration (Tissue Fluid Formation)

Answer 44

Tissue fluid contains oxygen, glucose, amino acids & supplies these to the tissues & cells of the body Beating of the heart creates high hydrostatic pressure at the arterial end of the capillaries Tissue fluid moves out the blood plasma This pressure is opposed by the lower WP of blood due to the plasma proteins Water moves back into ththe blood Overall pressure pushes tissue fluid out the capillaries (but only small molecules e.g. oxygen, amino acids) Large cells and proteins are left in the blood

Question 45

Return of tissue fluid to the circulatory system

Answer 45

Loss of tissue fluid from capillaries reduces hydrostatic pressure inside them Blood reaches Venus end of the capillaries - hydrostatic pressure lower than that of the tissue fluid Tissue fluid is forced back into the capillaries by the higher hydrostatic pressure outside them Plasma lower WP than tissue fluid Water leaves the tissue fluid by osmosis down a WP gradient