Topic 4 - Exchange and Transport

Question 1

What is diffusion?

Answer 1

the movement of particles down a concentration gradient.

Question 2

What is facilitated diffusion?

Answer 2

diffusion that occurs through carrier proteins or protein channels.

Question 3

Osmosis.

Answer 3

The net movement of water molecules from an area of high water potential to an area of low water potential through a partially permeable membrane.

Question 4

Endocytosis?

Answer 4

the movement of large molecules into cells through a vesicle.

Question 5

Exocytosis?

Answer 5

The movement of large molecules out of cells through vesicle formation.

Question 6

Active transport?

Answer 6

Movement of substances up a concentration gradient across a membrane using ATP.

Question 7

Describe the process of facilitated diffusion

Answer 7

1) - protein carriers of a specific shape to amino acids carry them across the membrane
2) the protein carrier changes shape and the molecules are passed into the cell
3) Protein carrier returns to its original shape to allow more molecules to enter.

(Passive process)

Question 8

What happens to a cell in an isotonic solution?

Answer 8

the osmotic concentration of the solute in the solution is the same as that in the cell

Question 9

What happens to a cell in a hypotonic solution?

Answer 9

The osmotic concentration of solutes in the solution is lower than that in the cytoplasm of the cell.
(will shrink)

Question 10

What happens to a cell in a hypertonic solution?

Answer 10

The osmotic concentration of solutes in the solution is higher than that in the cytoplasm
(become turgid)

Question 11

What is the equation for water potential of a cell?

Answer 11

water potential of a cell (-) = turgor pressure (+) + osmotic potential (-)

Question 12

What is turgor pressure?

Answer 12

A measure of the inward pressure exerted by the plant cell on the protoplasm of the cell as the cell contents expand and press outwards, which opposes the entry of water by osmosis.

Question 13

Osmotic potential?

Answer 13

A measure of the potential of the solution to cause water to move into the cell across a partially permeable membrane as a result of dissolved solutes.

Question 14

Factors that affect the rate of diffusion?

Answer 14

• surface area
• concentration gradient of the particles diffusing
• distance over which the diffusion is taking place

Question 15

Effective gas exchange features?

Answer 15

• Large surface area
• Thin layers to minimise diffusion distances
• Rich blood supply to respiratory surfaces, helps maintain steep concentration gradient
• Moist surfaces so the gases dissolve quicker
• Permeable surfaces

Question 16

Parts of the human gas exchange system and their function?

Answer 16

• Nasal cavity (air enters)
• Mouth (air enters more rapidly)
• Epiglottis (prevents food going wrong way)
• Larynx (voice box, uses air flow)
• Trachea (Major airway to bronchi)
• Incomplete rings of cartilage (prevents collapse, allows food to be swallowed)
• Left and right bronchus (tubes to lungs)
• Lung (where gas exchange happens)
• Bronchioles (small tubes in lungs to alveoli)
• Alveoli (main site of gas exchange)
• Ribs (protective cage)
• Intercostal muscles (between ribs for breathing)
• Pleural membranes (surround lungs and line chest cavity)
• Plueral cavity (space between above )
• Diaphragm (sheet of tissue floor of chest cavity)

Question 17

Alveoli features for efficient gas exchange

Answer 17

• large surface area
• short diffusion distance
• steep concentration gradient

Question 18

Describe inhalation

Answer 18

• intercostal muscles contract up and out
• muscles contract and flatten the diaphragm
• volume increases and the pressure lowers
• draws air in

Question 19

Describe exhalation

Answer 19

• intercostal muscles relax
• diaphragm relaxes into dome shape
• volume decrease
• air forced out

Question 20

What protects the lungs?

Answer 20

• mucus lines airways to trap particles
• cilia sweep upwards to back of throat
• swallowed
• stomach acid digests mucus

Question 21

Features of insect gas exchange

Answer 21

• Spiracles (site of entry and exit of gases)
• Tracheae (carry air directly into body)
• Tracheoles (spread throughout tissues of insect)

Question 22

Gas exchange in fish

Answer 22

• very active=high oxygen demand
• gills have large surface area for diffusion
• good blood supply to maintain conc gradient
• thin walls, short distances
• gills protected by operculum
• countercurrent exchange system
• overlapping gill filaments

Question 23

Layers of a plant leaf?

Answer 23

• Waxy cuticle (prevent water loss)
• Upper epidermis (transparent for light)
• Palisade mesophyll layer (cells stacked vertically)
• Spongy mesophyll layer (air to increase surface area)
• Lower epidermis, guard cells, stomata (guard cells open and close to prevent water losss from the stomata so need thick walls)

Question 24

Lenticels?

Answer 24

areas of loosely arranged cells which act as a pore to allow gas exchange in lignified (woody) plants

Question 25

Describe the structure of the heart

Answer 25

• 4 chambers
• pulmonary vein (heart to lungs)
• pulmonary artery (lungs to heart)
• Vena cava (body to heart)
• Aorta (heart to body)
• Atrioventricular valves - tricupsid/bicupsid prevent backflow from v to a
• Semilunar valves - pulmonary/aortic, prevent backflow from arteries to ventricles
• Tendinous chords - prevent atrioventricular valves turning inside out due to pressure when heart contracts
• Septum - muscle and connective tissue, prevents oxygenated/deoxygenated blood mixing
• Coronary arteries - wrapped around the heart to supply blood to cardiac muscle
• Cardiac muscle

Question 26

Single vs double circulatory system

Answer 26

Single - blood pumped once
Double - blood pumped twice

Question 27

Open vs closed circulatory system

Answer 27

Closed - blood confined to blood vessels only

Question 28

Advantage of a double circulatory system

Answer 28

• Concentration gradient is maintained
• Blood pressure to the body tissues is higher
• Blood pressure to lungs is lower, avoids damage to capillaries in lungs and increases time for gas exchange
• Organisms can develop larger bodies

Question 29

Why is the heart referred to as myogenic

Answer 29

Ability to initiate its own contraction

Question 30

How does the heart initiate its own heart beat

Answer 30

1) Depolarisation originates in the SAN (sinoatrial node)
2) Depolarisation spreads through the atria, causing atrial systole, can’t spread directly to the ventricles due to the region if nonconductive tissue - annulus fibrosus
3) Stimulates another region of conducting tissue - AVN (Atrioventricukar node)
4) Slight delay for atrial diastole, AVN passes depolarisation into the conducting fibres - Bundle of His
5) Bundle of His splits into two branches - Purkanje fibres. Causes ventricular systole

Question 31

3 stages of cardiac cycle

Answer 31

1) Atrial systole - during atrial systole the atria contract. This forces the atrioventricular valves open and blood flows into the ventricles
2) Ventricular systole - contraction of the ventricles causes the atrioventricukar valves to close and semilunar valves to open, allowing blood to leave the left ventricle through aorta and right ventricle through pulmonary artery
3) Cardiac diastole - atria and ventricles relax and pressure inside the heart chambers decreases. Causes semilunar valves in the aorta and pulmonary arteries to close, preventing backflow

Question 32

Functions of blood

Answer 32

• Transport
• Defence against pathogens
• Formation of lymph
• Tissue fluid