3.2.3 Transport across Cell Membranes Flashcards
True or false, the cell-surface membrane has the same basic structure as the membranes of organelles (for eukaryotic cells as prokaryotic cells don’t have membrane bound organelles) e.g the mitochondria/ Golgi apparatus etc
True
What are the 2 main component of the cell surface membrane
Phospholipid bilayer
Proteins
(All membranes have these 2 things)
Simple diffusion is the…
Net movement of particles from an area of high concentration to an area of low concentration down the concentration gradient until they are evenly distributed and doesn’t require ATP
The type of transport where substances pass directly through the membrane is called…
Simple diffusion
For simple diffusion, the substances that are passing directly through the phospholipid bilayer must be…, …. and …
Small
Non charged (non polar)
Lipid-soluble
E.g oxygen, urea, carbon dioxide
Oxygen, carbon dioxide and urea are all small, non polar (non charged) and lipid -soluble molecules so cross the cell membrane by…
Passive diffusion
(The movement of substances from an area of high concentration to an area of low concentration down the concentration gradient until they are evenly spread out and doesn’t require ATP)
Oxygen, carbon dioxide and urea are all small, non polar (non charged) and lipid -soluble molecules so cross the cell membrane by…
Passive diffusion
(The movement of substances from an area of high concentration to an area of low concentration down the concentration gradient until they are evenly spread out and doesn’t require ATP)
True or false, ions can pass directly through the phospholipid bilayer (passive diffusion)
False
Because they are charged (polar) so are repelled by the hydrophobic fatty acid tails
Why does simple diffusion only occur in liquids and gases
The substances must have kinetic energy to be able to move so that they can cross the cell membrane
(So even though simple diffusion doesn’t require external energy in the form if ATP, the substances still require energy)
Facilitated diffusion is…
the net movement of substances across the membrane using channel proteins and carrier proteins. The substances move from an area of higher concentration to an area of lower concentration down the concentration gradient until they are evenly spread out and no ATP is required.
Facilitated diffusion is how,..and…cross the membrane
Large particles
Charged particles
Both simple diffusion and facilitated diffusion are ..processes meaning no external energy is required in the form of ATP.
However the substances will have kinetic energy to allow them to move
Passive
In facilitated diffusion the 2 types of transport proteins used are…and…proteins
Carrier
Channel
2 similarities between simple diffusion and facilitated diffusion
Both are passive processes (don’t require any external energy in the form of ATP, only kinetic energy which the substances already have)
Both are the movement of substances down a concentration gradient
2 differences between simple diffusion and facilitated diffusion
Simple diffusion is for small, non polar (non-charged) and lipid soluble substances e.g carbon dioxide, oxygen and urea
Facilitated diffusion is for large and charged particles
For simple diffusion the substances cross directly through the phospholipid bilayer
For facilitated diffusion the substances cross the phospholipid bilayer using transport proteins (channel/ carrier) so don’t pass directly through
Out of channel proteins and carrier proteins, which requires ATP from hydrolysis
Carrier (but only for active transport, not for facilitated diffusion)
(Energy is needed to close the protein once the substance has entered and then to release the substance on the other side of the membrane (to change the shape of the protein))
Channel proteins don’t require energy in the form of ATP as they don’t need to move as they have a continuous pore/ column so are always open
In active transport, carrier proteins require energy in the form of ATP in order to transport the substance across the membrane. How will they get this energy
ATP will bind to the protein and be hydrolysed into ADP and Pi
This process of hydrolysis breaks a bond between 2 phosphate groups which releases energy
Channel proteins vs carrier proteins (both are used in facilitated diffusion to transport large and charged substances across the membrane)
Channel proteins are a continuous column/ pore and are always open so don’t require any energy in the form of ATP (they don’t need to move or do anything)
For active transport (not facilitated diffusion) carrier proteins require energy in the form of ATP by ATP hydrolysis in order to be able to move/ change shape (to close once the substance has entered the protein and then to release the substance on the other side of the membrane)
True or false, in facilitated diffusion, carrier proteins require energy in the form of ATP
False, they get their energy to be able to open/ close/ change shape from other mechanisms
Only carrier proteins used in active transport require energy in the form of ATP
Process of carrier protein allowing substance to pass through membrane
The substance binds to carrier protein which causes the protein to change shape so that the substance can be released on the other side of the membrane
(The carrier protein will always be open at one side of the membrane
The substance enters the protein where it’s open
The protein then closes to ‘enclose’ the substance in it
The substance is released on the other side of the protein to where it entered)
(This process requires energy in the form of ATP to allow the protein to move to let the substance pass through)
The main substance that passes through channel proteins is…
Ions
(As they are small and charged- remember they can’t pass directly through the phospholipid bilayer via passive diffusion as even though they’re small, they’re charged so will be repelled by the hydrophobic fatty acid tails)
If a charged particle tries to pass directly through the phospholipid bilayer via passive diffusion, it will be…by the hydrophobic fatty acid tails
Repelled
If a charged particle tries to pass directly through the phospholipid bilayer via passive diffusion, it will be…by the hydrophobic fatty acid tails
Repelled
The main substances that cross the membrane via carrier proteins is…and…substances
Larger
Charged (polar)
E.g glucose and amino acids
Carrier proteins are a continuous column/ pore filled with…which allows polar substances to pass through
Water
(As polar/ charged substances are water-soluble))
When a substance binds to a carrier protein, it causes the protein to change…so that the substance can be released on the other side of the membrane
Shape
Osmosis is …
The net movement of water from an area of high water potential to an area of low water potential down a water potential gradient and through a selectively permeable membrane until the water molecules are evenly spread out. The process is passive and doesn’t require energy in the form of ATP
Water potential is the…created by water molecules and is measured in…
Pressure
kPa (KiloPascals)
The highest value you can get for water potential is …where the water has no solute dissolved in it (it’s pure water)
0
(As soon as you add any solute to the water then the water potential becomes negative)
If the water potential is 0 it means that…
It’s pure water (there’s no solute dissolved in it)
The more negative the water potential is, the more…there is that’s dissolved in it
Solute
If cells are placed in an isotonic solution it means that…
The water potential inside the cells and inside the solution is the same so there will be no net movement of water in or out of the cells by osmosis
If cells are placed in an isotonic solution why is there no net movement of water in or out of the cell
The water potential inside the cells is the same as the water potential of the solution so there’s no water potential gradient
If cells are placed in an isotonic solution why is there no net movement of water in or out of the cell
The water potential inside the cells is the same as the water potential of the solution so there’s no water potential gradient
What does it mean if cells are placed in a hypotonic solution
The solution has a lower solute concentration than the cells so a higher water potential than the cells
So water will move into the cells from the solution via osmosis
A hypotonic solution has a low…concentration and a higher…
Solute
Water potential
A hypertonic solution has a high…concentration and a lower…
Solute
Water potential
What does it mean if cells are placed in a hypertonic solution
The solute concentration is higher outside of the cell than inside the cell
So the solution has a lower water potential than inside the cell
So water moves out of the cell into the solution via osmosis
Will water move by osmosis from a more negative water potential to a less negative water potential or the other way around
The other way around
Water will be move from a less negative water potential to a more negative water potential
(As a less negative water potential is higher so means that the water is purer and has a lower solute concentration)
What happens when an animal cell is placed in a hypotonic solution (the solution has a higher water potential than the cell)
Water will eneter the cell via osmosis
The cell could burst (lysis)
If an animal cell is placed in a hypotonic solution, water will move into the cell by osmosis which may cause the cell to burst (…)
Lysis
What happens when a plant cell is placed in a hypotonic solution (the solution has a higher water potential than the cell)
Water will enter the cell by osmosis and the cell will become turgid
(The cytoplasm and vacuole increase in size)
When water enters a plant cell (e.g when the plant cell is placed in a hypotonic solution), the …and…will increase in size making the cell turgid
Cytoplasm
Vacuole
What happens to animal cells vs plant cells when placed in a hypotonic solution
Animal cell= water enters cell by osmosis which may cause the cell to burst (lysis)
Plant cell= water enters the cell by osmosis which make the cell turgid (and the cytoplasm and vacuole increase in size)
(Plant cells don’t burst because of the cell wall which strengthens the cell)
What happens when an animal cell is placed in a hypertonic solution (the water potential is higher inside the cell than in the solution)
Water leaves the cell by osmosis
The cell will become shrivelled
What happens when a plant cell is placed in a hypertonic solution (the water potential is higher inside the cell than in the solution)
Water leaves the cell by osmosis
The cell becomes flaccid/ plasmolysed (the cytoplasm and vacuole decrease in size)
What happens when animal cells vs plant cells are placed in a hypertonic solution (water potential is higher inside the cell than in the solution)
Animal cell= water leaves the cell by osmosis, the cell becomes shrivelled
Plant cell= water leaves the cell by osmosis, the cell becomes flaccid/ plasmolysed (the cytoplasm and vacuole decrease in size)
True or false, the same thing happens to plant cells and animal cells when they’re placed in hypertonic/ hypotonic solutions
False (as plant cells have a cell wall which strengthens the cell)
E.g when animal cells are placed in a hypotonic solution they burst but plant cells just become turgid (the cytoplasm and vacuole increase in size)
E.g When animal cells are placed in a hypertonic solution they become shrivelled but plant cells become flaccid/ plasmolysed (the cytoplasm and vacuole decrease in size)
When cells are placed in a hypotonic solution, water…the cell by osmosis
Enters
When cells are placed in a hypertonic solution, water…the cell by osmosis
Leaves
Active transport is…
The movement of substances from an area of low concentration to an area of high concentration against the concentration gradient and requires carrier proteins and energy in the form of ATP
Facilitated diffusion uses both channel and carrier proteins but active transport only uses…proteins
Carrier
In active transport the carrier proteins act as…to move the substance across the membrane
Pumps
For a substance to move across the membrane via carrier proteins, it must be …in shape to the protein to be able to bind to it
Complementary
(This occurs for both facilitated diffusion and active transport as they both use carrier proteins)
For a substance to move across the membrane via carrier proteins, it must be …in shape to the protein to be able to bind to it
Complementary
(This occurs for both facilitated diffusion and active transport as they both use carrier proteins)
The …model describes the structure and properties of the cell membrane
Fluid mosaic
The cell membrane is described as being ‘fluid’ because…
The phospholipids are constantly moving laterally
The phospholipid bilayer is described as a ‘mosaic’ because…
There are glycoproteins, extrinsic proteins and phospholipids which provide a 3D surface
The role of glycoproteins in the phospholipid bilayer (which act as receptors) are…and…
Cell recognition
Binding to hormones
Role of cholesterol in cell membrane of animal cells
Adds structural support, strength and stability
Why does cholesterol make the cell membrane less fluid
It has a hydrophobic region which binds to the fatty acid tails of the phospholipids, causing the phospholipids to pack more closely together
In the cell membrane, …causes the phospholipids to pack more closely together
Cholesterol
(As the hydrophobic region of the cholesterol binds to the fatty acid tails of the phospholipids)
Co transport consists of 2 types of transport: .. and…
Active transport (of the sodium ions from the epithelial cells into the bloodstream using carrier proteins (the sodium potassium pump))
Facilitated diffusion (because of the sodium ions moving out of the cell by active transport it creates a low sodium concentration in the cell. This means that sodium ions then move from the lumen into the cell (from a high to low concentration) by facilitated diffusion via a co-transport protein and bring glucose with them (that’s attached))
Epithelial cells are the cells that line the villi. On one side of them there is the…and on the other side of them is the…
Lumen
Bloodstream
The cells that line the villi are called….cells
Epithelial
The first stage of co-transport is the active transport of sodium ions from the epithelial cells (that line the villi) into the…via carrier proteins called …
Bloodstream
The sodium potassium pump (as at the same time that sodium ions are moving out of the cell into the bloodstream, potassium ions are moving from the bloodstream into the cell. Both sodium and potassium ions move against the concentration gradient using sodium potassium pumps (carrier proteins)
As the first stage of co-transport, sodium ions move from the…to the…against the concentration gradient using carrier proteins (the sodium potassium pump). The sodium ions are transported via active transport
Epithelial cell (cells that line the villi)
Bloodstream
In the first stage of co-transport, sodium ions move from the epithelial cells into the bloodstream against the concentration gradient. They are transported by active transport and use carrier proteins (sodium potassium pump).
This creates a low sodium ion concentration in the…and a high sodium ion concentration in the…
Epithelial cell (as sodium ions are moving out of the cell)
Bloodstream (as sodium ions are moving into the bloodstream)
When in co-transport is the sodium potassium pump (a type of carrier protein) used
In the first stage to allow sodium ions to be transported out of the epithelial cell into the bloodstream against the concentration gradient by active transport
(At the same time potassium ions use the sodium potassium pump to move against the concentration gradient from the bloodstream into the epithelial cell by active transport)
In co transport what happens after there is a low sodium ion concentration in the epithelial cell
Sodium ions move from the lumen into the cell by facilitated diffusion using co-transport proteins (move from a high to low concentration down the concentration gradient)
Glucose moves into the cell alongside the sodium ions by attaching to the sodium ions
True or false, in co transport glucose is attached to the sodium ions when they move together from the lumen into the epithelial cell by facilitated diffusion
True
(The glucose then detaches from the sodium ions once they’ve entered the epithelial cell)
What happens in co- transport once the sodium ions and glucose have entered the epithelial cell from the lumen via facilitated diffusion
The glucose detaches from the sodium ions
Glucose is transported by facilitated diffusion from the epithelial cell into the bloodstream down the concentration gradient by carrier proteins
Sodium ions are transported by active transport from the epithelial cell into the bloodstream against the concentration gradient using the sodium potassium pump
What type of protein is the sodium potassium pump
Carrier protein
(As carrier proteins are the only proteins used in active transport and sodium ions and potassium ions use the sodium potassium pump in active transport e.g for sodium ions to be pumped out of the epithelial cell into the bloodstream against the concentration gradient)
Glucose and sodium ions are transported from the lumen into the epithelial cell by facilitated diffusion using …proteins
Cotransport
How does cholesterol in the cell membrane prevent the loss of water/ dissolved ions through the bilayer form the cell (how does it stop the membrane being too leaky/ permeable)
The hydrophobic region of the cholesterol binds to the fatty acid tails causing the phospholipids to pack more closely together
The presence of cholesterol affects the fluidity of the cell membrane as it makes it …fluid
Less (because the hydrophobic region of cholesterol binds to the fatty acid tails causing the phospholipids to pack more closely together so reduces their movement)
The presence of…in the cell membrane reduces the movement of the phospholipids as it causes them to pack more closely together
Cholesterol
…fatty acids are harder to pack together as they have branched hydrocarbon chains so this makes the membrane more fluid (there’s more free movement)
Unsaturated
2 things that can effect the fluidity of the membrane are…and…
Cholesterol (reduces movement of phospholipids by causing fatty acid tails to pack closely together so makes the membrane less fluid)
Unsaturated fatty acids (the unsaturated hydrocarbon chains are branched meaning the fatty acid tails can’t pack as closely together so it makes the membrane more fluid)
3 key things that can cause damage to the cell-surface membrane are… , … and …
Acid- causes proteins to denature
High temperatures- cause proteins to denature (so they can’t control what can enter the cell or not) and the membrane becomes more permeable
Ethanol- dissolves phospholipids
…damages the cell surface membrane as it dissolves phospholipids
Ethanol
Why does simple diffusion occur at a faster rate if the exchange surface is thinner
There is a shorter distance (shorter diffusion pathway) that the particles have to travel
Why does a larger surface area increase the rate of diffusion
It increases the number of particles that can move/ be exchanged in a given time
How is a substance transported across the membrane via carrier proteins in facilitated diffusion (correct/ updated flashcard)
The molecule binds to the protein, the protein changes shape which releases the substance on the opposite side of the membrane
(No energy in the form of ATP is required)
When glucose moves into the cell from the lumen alongside sodium ions, are they going down or against their concentration gradient
Against (so they use the concentration gradient of the sodium ions)
3 key features of epithelial cells to increase the rate of cotransport
Large number of transport proteins
Microvilli increases surface area
Large number of mitochondria to provide energy in the form of ATP for active transport of sodium ions (to then maintain the low sodium ion concentration inside the cell)
What is the mammalian ileum
Final section of small intestine in mammals
