Chapter 2: Cell Membranes

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What is the difference between the outer surface and inner surface of a plasma membrane?
The outer surface has chains of sugars - carbohydrate - that are part of the gylcolipid and gylcoprotein molecules.
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Name some of the functions of a cell membrane
Produce compartments inside cell, control what passes in and out of cell, involved in cell signalling, allow electrical impulses to pass through and attachment of enzymes.
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What are the three types of cell signalling?
Receptor opens a channel, receptor activates a g-protein and receptor acts as enzyme.
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Phago is ___ material. Pino is ____ material.
Solid;Liquid
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What is an example of a receptor activating a g-protein?
Fight of flight response; adrenaline
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What is an example of a receptor opening a channel?
Synapse
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What is an example of a receptor acting as an enzyme?
Insulin.
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What type of diffusion requires ATP?
Active Transport
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Which two types of diffusion do not require a transporter protein?
Osmosis and Diffusion
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When a protein changes shape, it is known as ____ ____, going from inactive to active.
Conformational change
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What is the definition of facilitated diffusion?
The diffusion of a substance through protein channels in a cell membrane. The proteins provide hydrophilic areas that allow the molecules or ions to pass through a membrane that would otherwise be less permeable to them.
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What is the definition of endocytosis?
Movement of bulk liquids or solids into a cell by the indention of the plasma membrane to form vesicles containing a substance (active transport using ATP)
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What is the definition of active transport?
The movement of molecules or ions through a transport protein across a cell membrane against the concentration gradient.
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What is the function of the glycolipid?
Help the cell to recognise other cells of the body.
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What is the function of cholesterol?
Help make up the bilayer.
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Describe why the plasma membrane is said to be a "fluid mosaic model"
Fluid refers to the fact that the molecules in the membrane are in constant motion. Mosaic refers to the way the model would look like from above.
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Give 3 reasons why cells need membranes
1. Sets boundaries for the cell. 2. Controls what comes in and out. 3. Gives structure to the cell.
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What is the phospholipid bilayer made up of?
Hydrophilic heads and hydrophobic tails.
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What is an example of when a membrane allows electrical signals to pass along it?
The membrane of an axon of a motor neurone transmits action potentials from the central nervous system
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Many of the lipid molecules and protein molecules have short strings of sugar molecules attached to them, forming ____ and ____.
Glycolipids and glycoproteins.
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Describe the process of cell signalling.
Signal arrives at the plasma membrane from outside the cell as particular substances or changes in electrical potential. A receptor in the cell's plasma membrane picks up these signals and brings about actions within the cell.
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What is the role of cholesterol in the cell membrane?
Helps to maintain the fluidity of the membrane, preventing it from becoming too stiff when temperatures are low, or too fluid when temperatures are high.
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What is the role of the phospholipid bilayer in a cell membrane?
Forms the bilayer which is the fundamental basis of the membrane in which all other components are embedded and provides a barrier to water soluble substances, such as ions and molecules that carry a charge.
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What is the role of proteins and glycoproteins in a cell membrane?
Form channels which hydrophilic substances can pass, act as transporters that can move substances using ATP, act as receptor sites allowing molecules from outside to bind, act as recognition sites (precise structure=specific cell) and act as enzymes.
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Describe the mechanism of a receptor acting as an ion channel.
The signal is a chemical that attaches to a protein or glycoprotein acting as an ion channel. When the chemical attaches to the receptor, it makes the channel open and let ions into the cell, bringing about a response.
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Describe the mechanism of a receptor activating a g-protein.
The receptor in the plasma membrane interacts with another molecules, a g-protein. When the signal molecule attaches to the receptor, the g-protein is activated, which then activates an enzyme, which brings about the reaction.
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Describe the mechanism of a receptor acting as an enzyme.
The receptor is made up of two parts. When the signal molecule arrives, it slots into both of these parts, connecting them to one another and forming them into an active enzyme. The enzyme then brings about a reaction in the cell.
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Facilitated diffusion uses ___ ___ as the pathway for diffusion.
Channel proteins
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What happens to an animal cell when it takes up too much water?
It swells, bursts and dies (lysis)
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What happens to an animal cell when it loses too much water?
It becomes crenated.
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How does high temperature affect permeability?
If you heat cells they become much more permeable as a rise in temp. on the phospholipids cause the molecules to vibrate more leaving temporary gaps in the membrane. Proteins come apart and lose their shape.
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How does low temperature affect permeability?
It decreases membrane permeability. Phospholipids vibrate much less, package together tightly and rarely provide pathways. Transporter proteins do not work well because it makes it hard to provide ATP. Molecules and ions move around less, so few pass
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A solution containing dissolved substances and little water has a ___ water potential.
Low
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Pure water has a ___ water potential.
High
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When a plant cell is full of water it is said to be ____. When the cell loses water the cell contents shrinks and becomes ____ and the cell is called ___.
Turgid: Plasmolysed: Flaccid
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What is the definition of water potential?
The tendency of a solution to lose water. Water moves from high water potential to low. Water potential is decreased by the addition of a solute and increased by application of pressure.
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Card 2

Front

Name some of the functions of a cell membrane

Back

Produce compartments inside cell, control what passes in and out of cell, involved in cell signalling, allow electrical impulses to pass through and attachment of enzymes.

Card 3

Front

What are the three types of cell signalling?

Back

Preview of the front of card 3

Card 4

Front

Phago is ___ material. Pino is ____ material.

Back

Preview of the front of card 4

Card 5

Front

What is an example of a receptor activating a g-protein?

Back

Preview of the front of card 5
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