A Level Biology : Module 3 - Exchange and Transport

Question 1

What happens to the SA : V ratio as an organism increases in size?

Answer 1

• SA : V ration decreases
• Greater volume means a longer diffusion distance to cells and tissues of the organism

Question 2

Why do we need a gas exchange system?

Answer 2

• To supply oxygen (which through aerobic respiration produces ATP)
• To remove CO2 (toxic waste produce of aerobic respiration which alters pH of cells)

Question 3

What do effective exchange surfaces have

Answer 3

• Large surface area
• Thin diffusion distance
• Good ventilation mechanism
• Good blood supply

Question 4

What are root hair cells

Answer 4

• Specialised cells found in roots of plants.
• They play an important role in the absorption of water and mineral ions from the soil
• Presence of root hairs increases the surface area
• So the water update by osmosis is greater

Question 5

What are alveoli and how do they work

Answer 5

• Small air sacs in the lungs where gaseous exchange happens with the capillaries
• Alveoli has a high concentration of O2, and a low concentration of CO2
• Capillaries have a low concentration of O2 and a high concentration of CO2
• Diffusion occurs across this concentration gradient (high to low) and exchange of gases occurs

Question 6

Features of Alveoli

Answer 6

• Thin walls (cells are flattened and walls are one cell thick, creating a small diffusion distance)
• Lots of alveoli (higher SA)
• Lots of capillaries (maintains high concentration gradient via constant blood flow) (capillaries are also 1 cell thick)
• Liquid surfactant in alveoli reduces surface tension between alveolar walls and gases. prevents atelectasis

Question 7

Features Fish Gills

Answer 7

• Lots of capillaries
• There is a counter current system (blood flow is opposite to water flow, ensuring the concentration gradient is maintained along the whole length of the capillary)
• Each gill arch contains gill filaments, with lamellae on them. increasing surface area for which O2 can diffuse across

Question 8

Cartilage

Answer 8

• Strong and flexible tissue
• Seen in rings around the trachea (tracheal rings)
• Helps to support trachea, ensuring it stays open while allowing it to move and flex while breathing
• In Bronchi, they are full circles of cartilage (rather than C shaped)

Question 9

Ciliated Epithelium

Answer 9

• Found in trachea, down to the bronchi
• Each cell has small projections called cilia
• Cilia sweeps mucus, dust and bacteria up the throat and away from the lungs

Question 10

Goblet Cells

Answer 10

• Found in ciliated epithelium and trachea
• PRODUCE MUCUS, (mucus traps dust and prevents them from reaching lungs)
• Mucus swept by cilia upwards where it is swallowed, then mucus and microbes are destroyed by the acid in the stomach

Question 11

Squamous Epithelium

Answer 11

• Makes up wall of alveoli
• Thin, allowing smaller diffusion distance

Question 12

Smooth Muscle

Answer 12

• Found throughout walls of bronchi and bronchioles
• Regulates flow of air
• Dilates when air is needed, constricts when air is less needed

Question 13

Elastic Fibres

Answer 13

• Present in all lung tissue
• Allow lungs to stretch and recoil, and the ability to recoil makes expiration a passive process

Question 14

mucus glands

Answer 14

• Works with goblet cells to secrete mucus

Question 15

Passage of air in the human body

Answer 15

1. nose / mouth
2. Trachea (windpipe)
3. Bronchi
4. Bronchioles
5. Alveoli

Question 16

What happens as we inhale?

Answer 16

• Diaphragm contracts and flattens
• Increasing chest volume
• Decreasing pressure in lungs below atmospheric pressure
• Drawing air in down the pressure gradient

DURING EXERCISE
- External intercostal muscles contract, moving ribcage upwards and outwards, increasing thoracic cavity

Question 17

What happens when we breathe out?

Answer 17

At Rest
- Breathing out occurs due to reoil of lungs after being stretched

• Diaphragm relaxes (becoming dome shaped)
• Decreasing volume of chest
• Increasing pressure
• Forcing air out

WHEN EXERCISING
- Internal intercostal muscles contract to pull the ribs down and back
- Abdominal muscles contract to push organs upwards against diaphragm, decreasing volume in lungs, increasing pressure and this forcing exhalation

Question 18

What are the 4 main ways to measure breathing

Answer 18

• Vital Capacity
• Tidal Volume
• Breathing rate
• Oxygen Uptake

Question 19

Vital Capacity

Answer 19

• Maximum volume of air that can be breathed in or out in 1 breath

Question 20

Tidal Volume

Answer 20

• Normal volume of air breathed in or out of the lungs at normal breathing rate

Question 21

Breathing Rate

Answer 21

• Breaths per minute

Question 22

Oxygen Uptake

Answer 22

• Volume of oxygen used up by someone in a given time

Question 23

How does a Spirometer Work?

Answer 23

• Breathe into a tube
• CO2 is absorbed from exhaled air by soda lime (stops concentration of CO2 being too high, coz it will cause respiratory distress)
• Trace is drawn as person breathes into tube (rotating drum of paper or a graph is formed digitally)
• From the trace, tidal volume, vital capacity and breathing rate can be calculated
• Oxygen uptake can be measured by observing change in volume from total volume and CO2 removed

Question 24

Tracheal System of Insect

Answer 24

• Rigid exoskeleton, waxy coating IMPERMEABLE to gases
• Spiracles are openings to exoskeleton, (they have valves, allows air to enter and flow into tracheal system
• Trachea are tubes, which lead to tracheoles (held open by RIGID RINGS OF CARTILAGE)
• Lots of tracheoles run between cells and muscle fibres, which is where gas exchange takes place
• This works for smaller insects (provides sufficient oxygen)
• Tracheal fluid at the end of tracheoles allows O2 to dissolve and then diffuse into cells

Question 25

Ventilation mechanism in Insects

Answer 25

Whilst Flying
- They create a mass flow of air into tracheal system
- By closing their spiracles
- Using abdominal muscles creating a pumping movement for ventilation

• During flight, tracheal fluid is drawn into respiring muscle so gas diffuses across quicker (because of a shorter diffusion distance)

Question 26

Structure of Fish Gills

Answer 26

• Gills either side of head
• Gill arch attached to 2 stacks of filaments
• Each filament has lamellae in rows lined on the surface

Question 27

Counter Current Flow

Answer 27

• Capillary system in lamellae ensures blood flows in the opposite direction to water (COUNTER CURRENT FLOW)
• Counter Current flow ensures concentration gradient is maintained along the whole length of the capillary

Question 28

Ventilation Mechanism in Fish

Answer 28

• Constantly pushes water over surface of gills, ensures supply of oxygen rich water (concentration gradient maintained)
• Fish opens mouth
• Buccal cavity floor lowers
• Increasing volume of buccal cavity
• Decreasing pressure within cavity
• Drawing water in (because pressure outside mouth is greater, so water flows into buccal cavity)
• Fish raises floor of buccal cavity to close mouth, increasing pressure in buccal cavity
• Water flows from buccal cavity into gill cavity (across pressure gradient)
• As water enters, pressure begins to build up in gill cavity, causing operculum (a flap of tissue covering gills) to be forced open and allowing water to exit the fish
• Operculum is pulled shut when fish next opens its mouth