Cell Membranes

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Why is the phospholipid bilayer described as fluid?
The phospholipids are constantly moving.
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What is a glycoprotein?
A protein with a carbohydrate attatched.
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What does the term 'hydrophobic' mean?
Repels water.
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What does the term 'hydrophilic' mean?
Attracts water.
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Explain why a cell membrane is an effective barrier against water-soluble substances.
The centre of the phospholipid bilayer is hydrophobic, so water-soluble substances cannot pass through.
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How does the cell surface membrane control what enters and leaves the cell?
Some proteins in the membrane allow the passage of large or charged particles that would otherwise find it difficult to cross the membrane.
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Describe the role of cholesterol in the cell membrane.
It helps the membrane become more stable and less fluid.
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What is diffusion?
The net movement of movement from an area of high concentration to an area of low concentration.
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Is simple diffusion a passive or active process?
Passive (does not require energy)
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Give 3 factors that affect the rate of simple diffusion.
1) concentration gradient 2) surface area 3) thickness of exchange surface.
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Is facilitated diffusion a passive or active process?
Passive.
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What is a channel protein?
Proteins within a cell membrane that form pores.
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Describe the role of channel proteins in the transport of particles across a cell membrane.
They allow charged particles to pass through a cell membrane via facilitated diffusion.
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Define osmosis.
The diffusion of water molecules from an area of high water potential to an area of low water potential across a partially permeable membrane.
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Define water potential.
The potential of water molecules to diffuse into or out of a solution.
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Give 3 factors that affect the rate of osmosis.
1) water potential gradient 2) thickness of exchange surface 3) surface area of the exchange surface.
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Describe a chemical reaction that occurs to release energy from ATP.
Hydrolysis reaction. Splits ATP into ADP and p!.
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Describe how carrier proteins are used to transport substances across a cell membrane during active transport.
A molecule attaches to a carrier protein in the membrane. The protein then changes shape and releases the molecule on the opposite side of the membrane. This process requires energy.
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Describe how co-transporters are used to transport substances across a cell membrane during active transport.
They bind 2 molecules at a time.The concentration gradient of one of the molecules is used to move the other molecule against its own concentration gradient.
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Why are sodium ions important in the transport of glucose from the ileum into the blood?
Sodium ions diffuse from the ileum into the intestinal epithelium cells down their concentration gradient, through a sodium-glucose co-transporter.The co-transporter carries glucose into the epithelium cell which enables it to diffuse into the blood.
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Will the rate of active transport increase or decrease with an increasing number of carrier proteins?
Increase
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Other cards in this set

Card 2

Front

What is a glycoprotein?

Back

A protein with a carbohydrate attatched.

Card 3

Front

What does the term 'hydrophobic' mean?

Back

Preview of the front of card 3

Card 4

Front

What does the term 'hydrophilic' mean?

Back

Preview of the front of card 4

Card 5

Front

Explain why a cell membrane is an effective barrier against water-soluble substances.

Back

Preview of the front of card 5
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