Explain how ventilation helps to maintain the concentration gradients at the alveoli.

Breathing brings in fresh air with a high oxygen and low carbon dioxide concentration and removes air that has equilibrated with the blood, so the gradients are kept steep.

OCR A-Level Biology B H422

The Developing Cell: Cell Division and Cell Differentiation

Topic overview The cell cycle and mitosis Apoptosis in growth and repair Stem cells and cell differentiation

The Developing Individual: Meiosis, Growth and Development

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Gas Exchange in Mammals and Plants

Topic overview Tissues of the mammalian gas exchange system Gas exchange in the alveoli Pulmonary ventilation and lung volumes Expired air resuscitation Gas exchange and stomata in terrestrial plants

Transport Systems in Plants

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Gas Exchange in Mammals and Plants

Gas exchange in the alveoli

3 things to know
Components 01, 02 and 03

Overview

Recall questions on the thin barrier and large surface area of the alveoli, the factors setting the rate of diffusion, how ventilation and blood flow keep gradients steep, surfactant and premature babies, elastic fibres, smooth muscle and cilia, the moist surface, and emphysema.

What you need to know

Answer each one before you reveal it.

Your recallNot started

Key term

Which two cell layers must oxygen cross to pass from alveolar air into the blood?

Key term

State the three factors that determine the rate of diffusion across a gas exchange surface.

Key term

Explain how blood flow through the alveolar capillaries helps maintain the concentration gradients.

Questions from this subtopic

Each one with the model answer underneath.

1
Which two cell layers must oxygen cross to pass from alveolar air into the blood?
Model answer
The squamous epithelium of the alveolus wall and the endothelium of the capillary wall.
2
State the approximate thickness of the barrier between alveolar air and the blood.
Model answer
About 0.3 μm.
3
State the approximate total surface area of the alveoli in a pair of adult human lungs.
Model answer
About 70 m².
4
State the three factors that determine the rate of diffusion across a gas exchange surface.
Model answer
The rate is proportional to the surface area multiplied by the difference in concentration, divided by the thickness of the surface.
5
Explain how ventilation helps to maintain the concentration gradients at the alveoli.
Model answer
Breathing brings in fresh air with a high oxygen and low carbon dioxide concentration and removes air that has equilibrated with the blood, so the gradients are kept steep.
6
Explain how blood flow through the alveolar capillaries helps maintain the concentration gradients.
Model answer
The circulation constantly carries away oxygenated blood and brings deoxygenated blood, so the alveolar air always has more oxygen and less carbon dioxide than the blood arriving.

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The Developing Cell: Cell Division and Cell Differentiation

The Developing Individual: Meiosis, Growth and Development

The Development of Species: Evolution and Classification

Cells and Microscopy

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measles and .

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Gas exchange in the alveoli

Overview

What you need to know

Which two cell layers must oxygen cross to pass from alveolar air into the blood?

State the three factors that determine the rate of diffusion across a gas exchange surface.

Explain how blood flow through the alveolar capillaries helps maintain the concentration gradients.

Questions from this subtopic

Which two cell layers must oxygen cross to pass from alveolar air into the blood?

State the approximate thickness of the barrier between alveolar air and the blood.

State the approximate total surface area of the alveoli in a pair of adult human lungs.

State the three factors that determine the rate of diffusion across a gas exchange surface.

Explain how ventilation helps to maintain the concentration gradients at the alveoli.

Explain how blood flow through the alveolar capillaries helps maintain the concentration gradients.

Other ways to work this

What is inside Levo

The 3-step method, run for you

Cram a whole paper in one sitting

Blank Blitz makes facts automatic

Build It gets the exam shape right

Test It catches misconceptions

Brain Breaks between sessions

Every question in Gas Exchange in Mammals and Plants, on a schedule.