Topic 3.1 - Exchange Surfaces

Question 1

What becomes essential as animals grow larger and more active?

Answer 1

Ventilation and gas exchange systems become essential to supply oxygen and remove carbon dioxide from their bodies

Question 2

What are examples of animals that demonstrate properties and functions of exchange surfaces?

Answer 2

Ventilation and gas exchange system in mammals, bony fish, and insects are examples of the properties and functions of exchange surfaces in animals

Question 3

Why do organisms require specialised exchange surfaces?

Answer 3

Due to the differences in their surface area to volume ratio (SA:V), metabolic activity, and whether they are single-celled or multicellular

Question 4

What does the surface area to volume ratio affect in organisms

Answer 4

The surface area to volume ratio affects the efficiency of the exchange of substances (e.g., oxygen, carbon dioxide, nutrients, and waste).

Question 5

What is the formula for calculating the SA:V ratio?

Answer 5

Ratio = Volume / Surface Area

Question 6

Why can smaller organisms like bacteria rely on diffusion?

Answer 6

Smaller organisms (e.g., bacteria) have a large SA: V ratio, which allows for efficient diffusion across their surface

Question 7

Why is diffusion alone insufficient for larger organisms?

Answer 7

Larger organisms (e.g., mammals) have a small SA: V ratio, meaning diffusion alone is insufficient to meet metabolic demands

Question 8

How does an increase in size affect the SA: V ratio and diffusion efficiency?

Answer 8

As size increases, SA: V decreases, making diffusion across the outer membrane insufficient

Question 9

Why do organisms with higher metabolic rates require more efficient gas exchange?

Answer 9

Organisms with higher metabolic rates (e.g., mammals and birds) require more oxygen and nutrients for respiration

Question 10

Why do active organisms need a higher rate of gas exchange?

Answer 10

Active organisms need a higher rate of gas exchange to support increased ATP production in aerobic respiration

Question 11

Why is diffusion alone too slow in large or active organisms?

Answer 11

Diffusion alone is too slow to supply the necessary oxygen and glucose in large or active organisms

Question 12

What are examples of single-celled organisms and how do they exchange substances?

Answer 12

Examples: Bacteria, Amoeba

• Have a large SA: V, so diffusion alone is sufficient to exchange gases and nutrients
• Short diffusion distances ensure rapid exchanges

Question 13

What are examples of multicellular organisms and what do they require for exchange?

Answer 13

Examples: Humans, fish, plants

• A small SA: V means diffusion is too slow to meet cellular demands
• Require specialised exchange surfaces (e.g., alveoli in lungs, gills in fish) to increase efficiency

Question 14

How do root hair cells demonstrate increased surface area?

Answer 14

Root hair cells have long, thin extensions that increase surface area.
This maximises the absorption of water and mineral ions from the soil.
Higher surface area enhances diffusion/ osmosis rates

Question 15

What feature of alveoli allows for faster gas exchange?

Answer 15

Alveoli have a single layer of squamous epithelial cells, this reduces the diffusion distance for oxygen and carbon dioxide.
Faster gas exchange occurs due to the short diffusion pathway

Question 16

How do alveoli maintain a steep concentration gradient for gas exchange?

Answer 16

• Surrounded by a dense capillary network, ensuring continuous removal of oxygen into the blood and CO2 out
• Ventilation replenishes oxygen and removes CO2, maintaining a steep concentration gradient

Question 16

How do gills maintain a steep oxygen diffusion gradient?

Answer 16

• A rich capillary network ensures efficient oxygen uptake into the blood and the removal of CO2
• Counter current flow maintains a steep oxygen diffusion gradient

Question 17

Why do mammals require an efficient gas exchange system?

Answer 17

Mammals are relatively large - they have a small SA:V ratio and a very large volume of cells. They also have high metabolic rates because they are active and maintain their body temperature independently of the environment. As a result, they need lots of oxygen for cellular respiration and produce carbon dioxide, which needs to be removed

Question 18

Where does the exchange of gases take place in mammals?

Answer 18

The exchange of gases takes place in the lungs

Question 19

What are the lungs and where are they located?

Answer 19

The lungs are a pair of structures with a large surface area located in the chest cavity that can inflate.

Question 20

What protects the lungs?

Answer 20

The lungs are surrounded by the rib cage, which serves to protect the,

Question 21

What prevents friction between the lungs and rib cage?

Answer 21

A lubricating substance is secreted to prevent friction between the rib cage and lungs during inflation and deflation

Question 22

What muscles are involved in moving the rib cage during the breathing?

Answer 22

External and internal intercostal muscles between the ribs, which contract to raise and lower the ribcage respectively

Question 23

What separates the lungs from the abdomen?

Answer 23

A structure called the diaphragm separates the lungs from the abdomen area

Question 23

Where does gaseous exchange occur within the lungs?

Answer 23

The gaseous exchange takes place in the walls of alveoli, which are tiny sacs filled with air

Question 24

How does air enter the lungs?

Answer 24

The air enters through the nose and along the trachea, bronchi, and bronchioles, which are structures well adapted to their role in enabling the passage of air into the lungs

Question 25

What is the role of cartilage in the gas exchange system?

Answer 25

- Found in the walls of the trachea and bronchi - Provides structural support to keep the airways open, preventing collapse during inhalation when air pressure decreases - The cartilage rings are strong yet flexible, ensuring the trachea and bronchi remain patent

Question 26

What is the function of ciliated epithelium?

Answer 26

- Lines the trachea, bronchi, and larger bronchioles - Contains cilia that are involved in moving mucus along to prevent lung infection by moving it towards the throat

Question 27

What do goblet cells do in the respiratory system?

Answer 27

- Scattered among the ciliated epithelium in the trachea and bronchi - Secretes mucus to trap inhaled particles, such as bacteria and dust, preventing them from reaching the alveoli

Question 28

What is the function of smooth muscle in the airways?

Answer 28

- Present in the walls of the trachea, bronchi, and bronchioles - Allows regulation of airway diameter by contracting or relaxing, controlling airflow resistance - During exercise, the smooth muscle relaxes to widen the airways, facilitating increased airflow

Question 29

What role do elastic fibres play in the respiratory system?

Answer 29

- Located in the walls of the trachea, bronchi, bronchioles, and alveoli - Enable the stretching and recoiling of lung tissues during breathing - When inhaling, elastic fibres stretch to accommodate air; during exhalation, they recoil to help expel air

Question 30

What is the trachea and what is its structure like?

Answer 30

- The main airway carries from nasal passages down to the bronchi - Wide tube supported by flexible cartilage, which prevents the trachea from collapsing - The trachea and branches are lined with a ciliated epithelium with goblet cells between and below epithelial cells

Question 31

What is the role and structure of the bronchi?

Answer 31

- Conducts air from the trachea into each lung; the trachea divides into two bronchi, each leading to a lung - Similar to the trachea, bronchi are reinforced with cartilage to maintain open airways. through the cartilage is arranged in smaller plates than rings - Ciliated epithelium and goblet cells continue to trap and move particles out of the respiratory system

Question 32

What are bronchioles and what is their function?

Answer 32

- Further conducts air to the alveoli; regulates airflow resistance and distribution within the lungs - Contains smooth muscle that can contract or relax to adjust the diameter of bronchioles - Elastic fibres present in the walls to aid in the recoil of bronchioles during exhalation

Question 33

What are alveoli and what adaptations make them efficient for gas exchange?

Answer 33

- Serves as the primary site for gas exchange between the air and the bloodstream. - Thin walls composed of a single layer of squamous epithelial cells, minimising the diffusion distance for gases - Numerous alveoli provide a vast surface area to maximise gas exchange efficiency - Surrounded by a dense network of capillaries to maintain concentration gradients for oxygen and carbon dioxide, facilitating efficient diffusion - Elastic fibres allow alveoli to stretch during inhalation and recoil during exhalation.

Question 34

Explain the mechanism of inhalation (inspiration - active process) in mammals

Answer 34

1. The dome-shaped diaphragm contracts, flattening, and lowering. 2. The external intercostal muscles contract, moving the ribs upwards and outwards 3. The volume of the thorax increases so the pressure in the thorax is reduced - lower than atmospheric pressure 4. Air is drawn into the lungs through the nasal passages, trachea, bronchi, and bronchioles, down the pressure gradient 5. This equalises the pressure inside and outside the chest.

Question 35

Explain the mechanism of exhalation (expiration- passive process) in mammals

Answer 35

1. External intercostal muscles relax, causing the ribcage to move downwards and inwards 2. Internal intercostal muscles contract (only during forced expiration), pulling ribs further down 3. The diaphragm relaxes and returns to its domed shape, reducing the thoracic cavity volume 4. Decreased thoracic volume causes an increase in pressure - above atmospheric pressure 5. Air is forced out of the lungs down a pressure gradient, from high pressure in the lungs to lower atmospheric pressure

Question 36

Define tidal volume

Answer 36

The volume of air that moves into and out of the lungs with each resting breath

Question 37

Define vital capacity

Answer 37

The maximum volume of air that can be exhaled after a maximal inhalation, encompassing the inspiratory reserve volume, tidal volume, and expiratory reserve volume

Question 38

Define breathing rate

Answer 38

The number of breaths per minute

Question 39

Define oxygen uptake

Answer 39

The rate at which oxygen is consumed by the body, reflecting metabolic activity

Question 40

Define inspiratory reserve volume

Answer 40

The maximum volume of air you can breathe in over and above a normal inhalation

Question 41

Define expiratory reserve volume

Answer 41

The extra amount of air you can force out of your lungs over and above the normal tidal volume of air you can breathe out

Question 42

Define total lung capacity

Answer 42

The sum of the vital capacity and the residual volume

Question 43

What is a spirometer and how is it used?

Answer 43

A spirometer is a device used to measure lung volume. A person using a spirometer breathes in and out of the airtight chamber, causing the air to move up and down, leaving a trace on a graph that can then be interpreted

Question 44

What specialised structured do bony fish use for gas exchange and how is efficiency maximised?

Answer 44

Bony fish utilise gills for gas exchange, employing a counter-current flow system to maximise oxygen uptake

Question 45

Describe how volume changes in the buccal cavity help ventilate the gills in a bony fish

Answer 45

Fish actively change the volume of their buccal (mouth) cavity to facilitate water movement over the gills. By lowering the floor of the buccal cavity, they increase its volume, causing water to flow in. Raising the floor decreases the volume, pushing water over the gills for gas exchange.

Question 46

How do gill filaments and lamellae support efficient gas exchange?

Answer 46

Gill filaments are thin projections that increase the surface area for gas exchange. Each filament is lined with lamellae ( gill plates), which are primary sites where oxygen and carbon dioxide diffuse between water and blood.

Question 46

What is the role of the operculum in fish ventilation?

Answer 46

The operculum, a bony flap covering the gills, plays a crucial role in maintaining a continuous flow of water over the gill surfaces. By opening and closing, it helps regulate water pressure and ensures efficient ventilation

Question 47

Explain the counter-current flow system in fish gills and its significance.

Answer 47

Blood flows through the gill lamellae in the opposite direction to water passing over them. This counter-current arrangement maintains a concentration gradient, allowing for efficient oxygen uptake and carbon dioxide removal.

Question 48

What prevents water from flowing backwards during fish ventilation?

Answer 48

The operculum operates in tandem with buccal movements. During buccal cavity expansion, the operculum remains closed to prevent backflow. As the buccal cavity compresses, the operculum opens, allowing water to exit after passing over the gills

Question 49

Why is counter-current flow more efficient than parallel flow?

Answer 49

Blood flows through the gill lamellae in the opposite direction to water passing over them. This counter-current arrangement maintains a concentration gradient, allowing for efficient oxygen uptake and carbon dioxide removal.

Question 50

What gas exchange system do insects use, and how is oxygen delivered?

Answer 50

Insects rely on a tracheal system for gas exchange, delivering oxygen directly to tissues without the use of blood as a transport medium.

Question 51

What are spiracles and what function do they serve in insect gas exchange?

Answer 51

These are small openings along the thorax and abdomen that allow air to enter and exit the tracheal system. Spiracles can be opened or closed to regulate gas exchange and minimise water loss

Question 52

What structural feature of insects prevent uncontrolled gas exchange through the body surface?

Answer 52

All insects possess a rigid exoskeleton with a waxy coating that is impermeable to gases

Question 52

Describe the structure and role of the trachea and tracheoles in the insect gas exchange system.

Answer 52

A network of trachea extends from the spiracles throughout the insect's body, branching into finer tubes called the tracheoles that reach individual cells, facilitating direct oxygen delivery. The large number of tracheoles that are in contact with the muscle cells provides a large surface area for gas exchange.

Question 53

How is tracheal fluid involved in the gas exchange process in insects at rest and during activity?

Answer 53

At rest, the ends of tracheoles contain tracheal fluid, facilitating the diffusion of gases. During activity, this fluid can be withdrawn to increase the air-filled volume of the tracheoles, reducing diffusion distance and enhancing oxygen delivery to tissues

Question 54

What is the role of spiracles in the inset ventilation mechanism?

Answer 54

Insects have openings called spiracles along their thorax and abdomen. These can open and close to regulate air entry, minimising water loss.

Question 55

Describe how air moves through the insect body to reach tissues.

Answer 55

Air enters through spiracles into a network of tubes called trachea, which branch into finer tracheoles reaching individual cells. This system facilitates direct gas exchange with tissues

Question 55

How do insects ventilate their tracheal system actively?

Answer 55

Muscular contractions of the thorax and abdomen alter body volume, creating pressure changes that drive air in and out of the tracheal system. This active ventilation enhances efficient gas exchange.