Biology 3.1.1 Exchange Surfaces

Question 1

Explain why multicellular organisms need specialised gas exchange systems

Answer 1

Diffusion across the outer membrane is too slow as multicellular organisms have a low surface area to volume ratio and high metabolic activity.

Question 2

State the features of an efficient gas exchange surface and give examples.

Answer 2

Large surface area - Root hair cells
Short diffusion pathway - Alveoli
Steep concentration gradient - Large capillary network of the alveoli/gills

Question 3

Describe the function of the following in the mammalian exchange system: goblet cells, cilia, elastic fibres, smooth muscle and cartilage

Answer 3

Goblet cells - secrete mucus to trap particles
Cilia - beat and waft the mucus upwards
Elastic fibres - stretch and recoil to aid in ventilation
Smooth muscle - relax to allow diameter of structures to be controlled
Cartilage - Strong and flexible to prevent collapse of structures as pressures changes

Question 4

Describe the structure and function of the trachea

Answer 4

Trachea carries air to bronchi
C-shaped cartilage rings
Smooth muscle
Elastic fibres
Goblet cells
Ciliated epitheium

Question 5

Describ the structure and function of bronchi

Answer 5

Bronchi carries air to bronchioles
Smaller rings of cartilage
Smooth muscle
Elastic fibres
Goblet Cells
Ciliated epithelium

Question 6

Describe the structure and function of bronchioles

Answer 6

Bronchioles carry air to the alveoli
No cartilage
Minimal smooth muscle, elastic fibres, goblet cells and ciliated epithelium

Question 7

Describe the structure and function of the alveoli

Answer 7

Alevoli is the site of gas exchange in the mammalian exchange system
Squamous epithelium and elastic fibres
No cartilage, muscle fibres, ciliated epithelium and goblet cells

Question 8

Describe the mechanism of inspiration in mammals

Answer 8

Diaphragm contracts and flattens
External intercostal muscles contract
Ribcage moves up and out
Thorax volume increases and pressure decreases
Air flows in, down the pressure gradient
Inspiration is an active process

Question 9

Describe the mechanism of expiration in mammals

Answer 9

Diaphragm relaxes and curves
External intercostal muscles relax
Ribcage moves down and in
Thorax volume decreases and pressure increases
Air is forced out, down the pressure gradient
Expiration is a passive process

Question 10

Describe the mechanism of forced expiration in mammals

Answer 10

Internal intercostal muscles contract
Ribcage moves down and in
Thorax volume decreases and pressure increases
Air is forced out of lungs, down the pressure gradient

Question 11

Describe how a spirometer works

Answer 11

A person breathes through a tube which is connected to an oxygen-filled chamber with a moveable lid with a pen attached
The lid moves up and down as the person breathes
These movements produce a spirometer trace on a rotating drum

Question 12

Explain why the total volume of gas in a spirometer chamber will decrease over time

Answer 12

Oxygen is being used up by respiration
Carbon dioxide is absorbed by soda lime

Question 13

Define tidal volume
Explain how it is found on a spirometer trace

Answer 13

The volume of air in one breath at rest
The difference between one peak and trough

Question 14

Define vital capacity

Answer 14

The maximum volume of air that can be breathed in or out

Question 15

Define breathing rate
Explain how it is found on a spirometer trace

Answer 15

The number of breaths taken per minute
Count the number of peaks in one minute

Question 16

Define oxygen uptake
Explain how it is found on a spirometer trace

Answer 16

The volume of oxygen used by an organism per minute
Calculate the decrease in the volume of gas in the chamber in one minute

Question 17

Describe the mechanism of inspiration in bony fish

Answer 17

Mouth opens
Buccal cavity volume increases and pressure decreases
Water is sucked in, down the pressure gradient

Question 18

Describe the process of expiration in bony fish

Answer 18

Mouth closes
Buccal cavity volume decreases and pressure increases
Water is forced out across gill filaments
Operculum opens and water leaves the gills

Question 19

Describe the process of gas exchange in bony fish

Answer 19

Four gills on each side of head, supported by a bony arch

Gills contain stacks of gill filaments - large surface area

Gill filaments contain gill plates with a large network of capillaries - large surface area, steep concentration gradient and thin diffusion pathway

Question 20

Explain counter-current flow in bony fish

Answer 20

Blood flows through gill plates in one direction and water flows over gill plates in the opposite direction

The concentration of oxygen in the water is always higher than in the blood.

The concentration gradient allows maximum amount of oxygen to diffuse from water into blood .

Question 21

Explain the process of gas exchange in insects

Answer 21

Air moves into pores on insect surface
Trachea branch into many smaller tracheoles
Tracheoles have thin, permeable walls and directly contact cells
Tracheoles contain tracheal fluid, in which gases dissolve
Oxygen diffuses from fluid into body cells, carbon dioxide diffuses from body cells into fluid

Question 22

Explain the mechanism of ventilation in insects

Answer 22

Mechanical ventilation - Abdominal/thoracic pumping movements change the volume and pressure of their bodies, moving air in and out of the body

Air sacs/collapsible enlarged tracheae - act as air reservoirs and increase the volume of air within the gas exchange system