Topic 3- Transport And Cell Membranes Flashcards
How does the plasma membrane appear under a light microscope
As a double line
What are the two types of protein found in the plasma membrane
Intrinsic and extrinsic proteins
What are intrinsic proteins involved in
Transporting substances across the cell membrane
What are extrinsic proteins involved so
Act as receptors as they have a specific binding site, and are involved in cell to cell signalling and cell to cell recognition
What is the main function of the plasma membrane
Cell to cell recognition and cell to cell signalling
As well as controlling what substances enter and exit the cell
What is diffusion.
The movement of molecules from and area of high concentration to an area of low concentration down a concentration gradient
What molecules use simple diffusion
Lipid soluble molecules which are non polar and uncharged
Name substances that carry out simple lipid diffusion
Lipid soluble steroids
Oxygen
Carbon dioxide
What is facilitated diffusion
Passive transport of substances across a plasma membrane with the help of an intrinsic protein either through a carrier protein or a hydrophilic pore within a protein channel
What substances use facilitated diffusion
Large water soluble polar and charged molecules or ions
What are the two kinds of transport proteins
Channel proteins and Cartier proteins
What is active transport
An active process which moves against a concentration gradient from low to high concentration requiring an input of ATP energy
Name some examples of active transport
Transport of mineral ions in the root hair cells of plants
Glucose from kidney to the blood
How can active transport be stopped
By adding a metabolic poison called cyanide which stops the atp energy being produced, without atp active transport can not occur
How does phospholipids arrange themselves in water
As a Micelle, with the hydrophilic head facing outwards and the hydrophobic tails facing inwards
Why is structure of the plasma membrane described as a fluid mosaic structure
Fluid because all the parts move relative to each other and mosaic because all proteins are dotted through out the membrane like tiles
Describe the structure of the plasma membrane
Demi phospholipid bilayer composed of intrinsic and extrinsic proteins, glycolipids, glycoproteins and cholesterol arranged in a fluid mosaic structure
Who proposed the fluid mosaic structure of the plasma membrane
Singer and Nicholson
How are phospholipids arranged in water
As a Michelle with the hydrophilic heads outside and the hydrophobic heads facing in side
What are the main functions of the plasma membrane
Provide the cells structure, cell to cell signalling and cell to cell recognition
What does lipid bilayer mean
Two layers of phospholipid
What is a phospholipid
A molecule made of a hydrophilic glycerol phosphate head and two fatty acids forming a hydrophobic tail
What is the distance across the membrane
7-8 nm
How does an intrinsic protein differ from an extrinsic protein
Intrinsic proteins lie across both layers of the bilayer. Extrinsic proteins are in one of the layers on the surface of the membrane
What are intrinsic proteins
Proteins that lie across both the layers of the membrane
What are extrinsic proteins
Lay in one layer of the membrane or on the surface of the membrane.
What are glycoproteins
Proteins with a carbohydrate chain attached
What are glycolipids
Lipids with a carbohydrate chain attached
What are glycolipids involved with
Cell to cell recognition
What are glycoproteins involved with
Cell to cell recognition
What is the structure of the plasma membrane
A semi fluid phospholipid bilayer containing intrinsic and extrinsic proteins, glycoproteins and glycolipids and cholesterol
Why is the plasma membrane selectively permeable
It is able to control what substances enter and exit the cell
What is the role of cholesterol in the plasma membrane
Increase its rigidity
Name the model proposed by singer and Nicholson
Fluid mosaic model
What factors increase the rate of diffusion
Increasing temperature
Decreasing size
Increasing solubility in lipids
Increasing concentration
What is facilitated diffusion
A form of diffusion where the molecules move from an area of high concentration to an area of low concentration down a concentration gradient via a carrier protein or a hydrophilic pre within A channel protein
Does diffusion require ATP
No
What are the two kinds of transport proteins
Carrier protein and a channel protein
Draw a diagram to show diffusion
Draw
Draw a picture to show facilitated diffusion
Draw
Why is the partially permeable membrane important in osmosis
It ensures that large solutes do not diffuse and counteract the effect of osmosis
What is osmosis
The movement of water molecules from a high water potential to a low water potential across a partially permeable membrane
What is the equation that allows you to work out the water potential
¥cell = ¥s +¥p
What is the water potential of pure water
0kpa
Describe the relationship between the water potential the pressure potential and the solute potential
The water potential is equal to the solute potential plus the pressure potential
Is the highest possible water potential and what has this
Water and 0kpa
What is the solute potential generated by
The solutes dissolved in the water
What is the pressure potential generated by
THe cytoplasm pushing on the cell wall. As the cell wall is rigid it persists the pressure
During osmosis what is the solution with the highest water potential known as
Hypotonic solution
During osmosis what is the solution with the lower water potential called
Hypertonic
What is the word that describes when bin solutions have the same water potential
Isotonic
What happens when the solutions are isotonic
Both the solutions have the same water potential so there is no not movement
What happens when a plant cell is placed in a hypertonic solution
The solution will loose water and become flaccid and plasmolysed
What does plasmolysis mean
Where the cytoplasm shrinks and comes away from the cell wall causing the plant to wilt
What happens when plant cells are placed on a hypotonic solution
They will gain water, swell and become turgid
Why is it important that the cells become turgid
It ensures the plant will remain upright
What happens to plant cells that are placed in a hypertonic solution
Loose water and become shrivelled
What happens to animal cells when they are placed in a hypotonic solution
They will gain water swell and then burst
What is incipient plasmolysis
The point at which the cytoplasm behind to come away from the cell wall
How can incipient plasmolysis be found experimentally
Observing the solute potential at which half the plant cells in a sample are plasmolysis . At this point the solute potential is equal to the water potential - this is due to the pressure potential being zero as the cytoplasm is no knee pushing against the cell wall
Draw a plant cell in a hypotonic isotonic and hypertonic solution
Draw and check text book
Draw a plant cell in a hypotonic hypertonic and isotonic solution
Draw and check text book