AS Biology OCR Unit 1 Module 2, OCR, AS, Biology, Exchange and Transport

AS Biology OCR Unit 1 Module 2, OCR, AS, Biology, Exchange and Transport notes (summarised from textbook)

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Key Words
Exchange Surfaces ­ a specialised area that is adapted to make it easier for
molecules to cross from one side to the other.
Gaseous Exchange ­ the movement of gases by diffusion between an organism and
its environment across a barrier e.g. the alveolus wall.

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Inspiration (or inhalation) and Expiration (or exhalation) are the terms used to
describe breathing in and out.
Transport ­ the movement of oxygen, nutrients, hormones and water and heat
around the body.
Heart ­ a muscular pump that creates pressure to propel blood through the
arteries and around the body.
Cardiac Cycle ­ the sequence of events in one heartbeat.
Sinoatrial Node ­ the heart's pacemaker.…read more

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Keywords
An exchange surface is a specialised area that is adapted
to make it easier for molecules to cross from one side of
the surface to the other.…read more

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Gaseous Exchange is the movement of gases by diffusion
between an organism and its environment across a
barrier such as the alveolus wall.
Inspiration (or inhalation) and Expiration (or exhalation)
are the terms used to describe breathing in and out.
1.…read more

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Organisms may absorb these from surrounding environment, or make them inside their
cytoplasm as part of cell metabolism. All living cells also need to remove waste products
from the metabolic activities occurring in their cytoplasm, these include: CO2, oxygen,
and other wastes such as ammonia or urea, which contain excess nitrogen.
Single cell and small organisms can exchange gases, nutrients and wastes across the
outer surfaces.…read more

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Gasses pass both ways through wall of alveoli. Oxygen passes from air in alveoli to blood in
capillaries, CO2 passes from blood to alveoli.
How Lungs Are Adapted For Exchange.
Large Surface Area- provides more space for molecules to pass through, individual alveoli very
small but numerous thus total surface area of lung much larger.
Barriers permeable to oxygen and carbon dioxide- plasma membranes that surround thin
cytoplasm of cells form barrier and readily allow diffusion of oxygen and CO2.…read more

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Tissues in the Lungs
The Lungs
The trachea, bronchi and bronchioles are airways that allow passage of air into the lungs
and out again. To be effective certain requirements must be met firstly, the larger
airways must be large enough to allow sufficient air to flow without obstruction these
must also divide into smaller airways to deliver air to alveoli.…read more

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Measuring Lung Capacity
Breathing
When resting air moves in and out of your lungs about 12 times per min as your diaphragm
and intercostal muscles contract and relax. Each breath refreshes some of the air in your
lungs and carries away some of the CO2 generated by your body. If you exercise or are
frightened you breathe more deeply and more quickly. This gets more oxygen rich air in
and removes more CO2 rich air out.…read more

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Measuring Oxygen Uptake
If someone breathes in and out of spirometer for a period of time the CO2 level increases
dangerously. To avoid this, soda lime is used to absorb the CO2 exhaled, meaning the
total volume of gas in spirometer will go down because the volume of CO2 breathed out
equals the volume of oxygen breathed in, as carbon is removed this total reduction is
equal to volume of oxygen used up by the person breathing in or out.…read more

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