As Biology Organisms And Exchange

Front 1

What is the general formula for efficiency of gas exchange?

Back 1

Surface area x Concentration Gradient

---------------------------divided by -----------------------------

Thickness of membrane

Front 2

How are the alveoli adapted as a gaseous exchange surface?

Back 2

• Their shape and quantity means large surface area
• They have only 2 cell layers of 1 layer of flattened epithelial cells and 1 layer of endothelial cells. Meaning short diffusion pathway
• Fluid coating the inside of the alveoli. Allows gases to dissolve and diffuse across
• Extensive network of blood capillaries surrounds each alveolus. Large surface area for gas exchange.
• Circulation and Ventilation maintaining a high diffusion gradient for gaseous exchange by removing oxygenated blood and bringing in oxygen rich air.

Front 3

What happens during inspiration?

Back 3

• The external intercostal muscles contract while internal intercostal muscles relax
• This causes the ribs to be pulled upwards and outwards
• Diaphragm muscle contracts. So the diaphragm flattens.
• Both of these increase the volume of thorax and decrease pressure inside lungs below atmospheric pressure. Air enters along a pressure gradient

Front 4

What happens during expiration?

Back 4

• The internal intercostal muscles contract while external intercostal muscles relax
• This causes the ribs to be pulled inward and downwards
• Diaphragm muscle relaxes, causing the diaphragm to go into a dome shape.
• Both of these decrease the volume of thorax and increase pressure inside lungs above atm. pressure. Air is forced out along a pressure gradient
• ALSO, the lung tissue has ELASTIC RECOIL which helps to force air out.

Front 5

What is the formula for pulmonary ventilation and what are the units?

Back 5

Pulm.vent. = Tidal volume x Ventilation rate

dm³ / minute dm³ /min

Total volume of Volume of air Number of

air in one minute in one breath breaths per min

Front 6

Define Correlation

Back 6

Correlation is where a change in one of two variables is reflected by a change in the other variable.

Front 7

Define Cause (as in correlation/causal relationships)

Back 7

Cause means that a factor is directly responsible for a correlation/disease

Front 8

How is Relative Risk calculated?

give an example

Back 8

Comparing the likelihood of harm occurring in those exposed to a hazard to the likelihood in those not exposed to it.

e.g A smoker 15 times more likely for lung cancer than a non smoker.

Front 9

Describe the features of gas exchange systems in insects

Back 9

Network of tubes known as tracheal system.

Openings are called spiracles, with valves that close to reduce water loss.

Spiracles lead to Tracheae which are supported by spiral bands of cuticle.

Trachea branch into finer tubes called tracheoles.

The tracheoles penetrate body tissues.

They are thin for short diffusion pathway and numerous for large surface area.

Oxygen and Carbon dioxide diffuse in and out following a diffusion pathway.

Front 10

How are insects gas exchange systems adapted to be efficient and not lose too much water?

Back 10

1. There are valves on spiracles which open and close. During rest they close to prevent water loss from evaporation. During activity they open (open when high CO2 levels) to allow greater rate of diffusion.
2. During increased activity, anaerobic respiration makes lactic acid. This is soluble in cells, decreases water potential. So the liquid in the ends of the tracheoles is drawn in by osmosis, this allows more surface for oxygen to diffuse through but does mean more water is lost to evaporation
3. Have waterproof coverings, cuticle and chitin
4. Large or very active insects have body muscles lining the trachea. They contract to compress the trachea and force air out, then relax to allow the trachea to spring back into shape, drawing in O2 rich fresh air.

Front 11

How are the gills of fish adapted for gaseous exchange?

Back 11

1. Large Surface Area from large number of gill filaments and lamellae

2. Short Diffusion Pathway. 2 cell layers. Epithelial of lamellae and endothelial of blood capillaries

3.Ventilation mechanism provides continues flow of O2 rich water and removes CO2 rich water. High diffusion gradient.

4. Circulation continuous flow of blood. Absorbs oxygen and removes CO2. High Diffusion Gradient.

5. Blood and water flow in opposite directions across the lamellae. The countercurrent system

Front 12

Explain the countercurrent system in fish gas exchange.

Back 12

The flow of water over the gill lamellae and the flow of blood within them go in opposite directions.

Blood with little oxygen meets water with the least oxygen, so diffusion takes place.

Blood with the most oxygen meets water with the most oxygen, so diffusion can continue.

A diffusion gradient is maintained across the entire width of the gill lamellae so that more oxygen is absorbed than if they went the same direction. Which would mean they would reach equilibrium.

Front 13

How are plants adapted for efficient gas exchange?

Back 13

1. A large number of stomata to allow lots of air to diffuse in

2. Leaves are thin so there is a short diffusion pathway

4. Diffusion Gradient maintained by Using CO2 in Respiration and Producing O2

3. There are numerous air spaces inside the spongy mesophyll which allow gases to readily come into contact with mesophyll cells and diffuse to the palisade mesophyll which has more chloroplasts.

Front 14

Why do single celled or small and thin organisms not require specialised exchange structures?

Back 14

They have a large Surface Area to Volume Ratio which means that all parts of the organism have a short diffusion pathway for uptake of nutrients and oxygen and removal of waste products and heat.

Front 15

Describe the gas exchange system of a Human

Back 15

The Trachea, supported by incomplete rings of cartilage to prevent from collapsing.

Branches into two Bronchi which go to each lung.

Bronchi branch into smaller tubes, Bronchioles.

Alveoli are at the end of Bronchioles.

Lots of Capillaries surround each Alveolus which provide large surface area for diffusion of oxygen into Haemoglobin in the blood.

Front 16

How does oxygen diffuse through the leaf of a Mesophyllic plant

Back 16

Diffuses across the thin cell wall of the mesophyll cells where it is produced in Photosynthesis.

Diffuses across a concentration gradient from the mesophyll cells to the stomata through the air spaces in the spongy mesophyll.

They diffuse out, through the stomata.

Front 17

Define Ventilation

Back 17

The method by which air is passed over the respiratory surface