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A-level Biology - 3.1.4 Transport into and out of Cells Part 1

Biology20 CardsCreated about 2 months ago

This deck covers key concepts related to the structure and function of cell membranes, including the roles of phospholipids, cholesterol, and proteins in the transport of substances into and out of cells.

What is a cell-surface membrane?

(Partially permeable) barrier between cell and its environment, controlling which substances enter and leave the cell
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Key Terms

Term
Definition
What is a cell-surface membrane?
(Partially permeable) barrier between cell and its environment, controlling which substances enter and leave the cell
What is the functions of membranes around organelles?
Act as barriers between organelle and cytoplasm Also control what comes in and out + partially permeable

Describe the phospholipids arrangement in a plasma membrane

Bilayer Hydrophobic tails to inside Hydrophilic heads to outside

Describe how the plasma membrane acts as a barrier to water-souble substances
Centre of bilayer is hydrophobic ∴ membrane doesn’t allow water-souble substances (like ions) through it
Name 3 functions of phospholipids in plasma membranes
Allow lipid-soluble substances to enter & leave the cell Prevent water-soluble substances entering and leaving the cell Makes membrane flexible
Cholesterol is present in all cell membranes expect _____ ____ ________
bacterial cell membranes

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TermDefinition
What is a cell-surface membrane?
(Partially permeable) barrier between cell and its environment, controlling which substances enter and leave the cell
What is the functions of membranes around organelles?
Act as barriers between organelle and cytoplasm Also control what comes in and out + partially permeable

Describe the phospholipids arrangement in a plasma membrane

Bilayer Hydrophobic tails to inside Hydrophilic heads to outside

Describe how the plasma membrane acts as a barrier to water-souble substances
Centre of bilayer is hydrophobic ∴ membrane doesn’t allow water-souble substances (like ions) through it
Name 3 functions of phospholipids in plasma membranes
Allow lipid-soluble substances to enter & leave the cell Prevent water-soluble substances entering and leaving the cell Makes membrane flexible
Cholesterol is present in all cell membranes expect _____ ____ ________
bacterial cell membranes
Where are cholesterol molecules found in cell membranes?
Between phospholipids
What is the role of cholesterol in cell membranes?
Controls the fluidity of the membrane (provides stability e.g. helps to maintain shape of animal cells)
Describe how cholesterol gives cell membranes stability
Cholesterol molecules bind to hydrophobic tails of phospholipids = causes them to pack more closely together Restricts movement of phospholipids Makes membrane less fluid and more rigid
What model is used to describe the arrangement of molecules in membrane?
Fluid mosaic model
Why is the bilayer is ‘fluid’?
∵ phospholipids are constantly moving
How are proteins arranged in the cell membrane?
They’re scattered through bilayer (like tiles in mosaic)
What are extrinsic proteins?
Proteins are partly embedded in bilayer (occur either on surface of it)
What are intrinsic proteins?
Proteins that span entire bilayer from one side to the other
What do channel proteins and carrier proteins allow?
Allow large molecules and ions to pass through membrane
What do receptor proteins on the cell-surface membrane do?
Detect chemicals released from other cells (chemicals signal to cell to respond in some way)
Some proteins can ___ _______ through bilayer & others are _____ __ _____
Some proteins can move sideways through bilayer & others are fixed in position
What are glycoproteins?
Proteins that have a polysaccharide chain attached
What are glycolipids?
Lipids that have a polysaccharide chain attached
Increasing the temperature ____ membrane permeability
INCREASES