Cell membrane and transport

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Approximately how thick is the plasma membrane?
7-8 nm
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What is a better name for the plasma membrane?
The phospholipid bilayer
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What are the two types of intrinsic proteins?
Channel proteins and carrier proteins
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What do channel proteins do?
They create a hydrophilic channel or pore. These allow water soluble molecules and polar molecules to pass through by facilitated diffusion
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What do carrier proteins do?
These carry water soluble molecules and ions through the membrane by active transport and facilitated diffusion as well as larger molecules like glucose.
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How do carrier proteins carry molecules through the membrane?
By changing shape to move the molecule across
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What are glycoproteins?
These are proteins with an attached carbohydrate chain. They act as hormone receptors and are involved in cell recognition.
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What is a glycolipid?
These are phosphate heads with a polysaccharide attached and is involved in cell recognition
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What is the role of cholesterol in the membrane?
It increases the flexibility and stability of membranes.
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Why must transport across the membrane occur?
To obtain nutrients, to excrete waste substances and secrete useful substance
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What does the rate of diffusion depend on?
The conc. gradient, temperature, surface area, size of the molecule, the length of the diffusion pathway
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What 3 things do molecules need to be in order to diffuse through the membrane?
Non-Polar (Polar molecules can diffuse though but either very slowly or not at all), Small, lipid soluble
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What is facilitated diffusion?
This is where molecules taht are too large to diffuse through the phospholipid bilayer diffuse through carrier or channel proteins, this is a passive process.
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What types of molecules pass through the membrane via facilitated diffusion?
Larger, water soluble, polar molecules and ions
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Why does the rate of facilitated diffusion, if shown on a graph, eventually level off?
Because all the available proteins become saturated with substrates
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What is co-transport?
This is a type of facilitated diffusion that brings molecules and ions into cells together on the same transport protein.
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How does co-transport work?
A glucose molecules and two sodium ions attach to a carrier protein, the carrier protein change shape and deposits them inside the cell, the glucose molecule and sodium ions separately diffuse though the cell.
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In co-transport how does each substance pass into the blood?
The glucose passes into it by facilitated diffusion and the sodium ions are carried by active transport
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What is water potential?
Water potential is a measure of free energy of water molecules and the tendency of water molecules to move out of the cell
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What is osmosis?
Osmosis is the movement of water from regions of high water potential to regions of low water potential across a partially permeable membrane
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What has the highest water potential and what is it's value?
Pure water, 0 kPa
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What is the equation to calculate water potential?
Water potential = solute potential + pressure potential
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How does the amount of solute effect the water potential?
Solute molecules form a weak bond with water molecules and slow down their movement, increasing the solute conc. results in less water molecules in any given space
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When pressure potential is at 0 Yp, what is this know as?
Incipient plasmolysis
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What is a hypotonic solution?
This is a solution that has a lower solute potential and therefore a higher water potential
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What is a hypertonic solution?
This is a solution that has a higher solute potential and a lower water potential.
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What is an isotonic solution?
This is where the solution has the same solute potential to water potential
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When a plant cell is unable to take up anymore water what is it said to be?
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When the plasma membrane starts to peel away from the cell wall what is this called?
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How does active transport work?
It uses energy supplied by ATP to move molecules and ions across cell membranes against a concentration gradient
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Where does active transport take place in a plasma membrane?
It takes place though carrier proteins which change shape
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What are the stages of active transport? Pt. 1
The ion combines with a carrier protein on the outside of the membrane, ATP transfers a phosphate group to the carrier protein on the inside of the membrane, the carrier protein changes shape and carries the ion across to the inside
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What are the stages of active transport? Pt. 2
the ion is released into the cytoplasm, the phosphate ion is released from the carrier protein back to the cytoplasm and recombines with ADP to make ATP
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Give an example of a respiratory inhibitor and explain what they do
Cyanide, prevent respiration from taking place.
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What is endocytosis?
This is the uptake of substances into the cell. It occurs when the material is engulfed by extensions of the plasma membrane
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What is phagocytosis?
A process by which large solid particles enter the cells
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What is pinocytosis?
A process by which liquid entry
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What is exocytosis?
When materials can be secreted out of the cell by exocytosis having be transported through cytoplasm in a vesicle which fuses with the membrane
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Why do endocytosis and exocytosis require ATP?
They change the shape of the membrane and so need energy
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In exocytosis does the membrane area increase or decrease?
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In endocytosis does the membrane area increase or decrease?
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Card 2


What is a better name for the plasma membrane?


The phospholipid bilayer

Card 3


What are the two types of intrinsic proteins?


Preview of the front of card 3

Card 4


What do channel proteins do?


Preview of the front of card 4

Card 5


What do carrier proteins do?


Preview of the front of card 5
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