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Topic 2 - practice questions and answers
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A-level Biology Edexcel A Topic 2 practice questions and answers.
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A level Biology Edexcel ATopic 2 - Practice Questions & Answers
1. What are the properties of gas exchange surfaces
in living organisms?
a. Gas exchange surfaces in living organisms
typically have a large surface area to volume
ratio, thin surfaces to minimise diffusion
distance, and a concentration gradient to drive
diffusion
2. How is the rate of diffusion dependent on these
properties and calculated using Fick’s law?
a. The rate of diffusion is directly proportional to
the surface area and the difference in
concentration, and inversely proportional to
the thickness of the surface.
,3. How does the surface area to volume ratio impact
gas exchange?
a. As organisms increase in size, their surface
area to volume ratio decreases. Larger
organisms have evolved adaptations (such as
alveoli in mammalian lungs) to increase the
surface area available for gas exchange.
4. How is the structure of the mammalian lung
adapted for efficient gas exchange?
a. The mammalian lung has several adaptations:
b. Alveoli: These tiny air sacs increase the surface
area for gas exchange.
c. Bronchioles: Smaller tubes branching from
bronchi take air deeper into the lungs.
d. Intercostal Muscles and Diaphragm: These
muscles aid in breathing.
e. Thin Diffusion Pathway: The alveolar
membrane is thin, allowing rapid diffusion of
gases.
f. Rich Capillary Network: Surrounding alveoli,
capillaries facilitate gas exchange.
, 5. What are the main components of cell
membranes?
a. Phospholipids: Form a lipid bilayer with
hydrophilic heads and hydrophobic tails.
b. Cholesterol: Helps maintain membrane
stability and fluidity.
c. Proteins: Integral proteins transport molecules
across the membrane, while peripheral
proteins assist with communication and
transport.
6. What is the fluid mosaic model of cell membranes?
a. The fluid mosaic model describes the cell
membrane as a dynamic structure composed
of various molecules (lipids, proteins, and
carbohydrates) distributed across the
membrane. It emphasises the fluidity and
mosaic-like arrangement of these
components.
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