A3 Transport Across Membranes Flashcards
Name the molecule shown in the diagram
Glycerol
Name the bond formed between a fatty acid and glycerol
Ester bond
Name the type of fatty acid shown in the diagram
Saturated fatty acid
Name the type of fatty acid shown in the diagram
Unsaturated fatty acid
Name the molecule shown in the diagram
Phospholipid
Name the structure labelled A on the diagram of a membrane
Phospholipid
Define diffusion?
The movement of a substance from a high concentration to a lower concentration
Give two differences between active transport and facilitated diffusion.
Active transport requires energy/ATP whereas facilitated diffusion is passive.
Active transport moves substances against the concentration gradient whereas facilitated diffusion moves substances down the concentration gradient.
Give a similarity between active transport and facilitated diffusion.
Both use carrier proteins.
Which type of molecule can diffuse across the phospholipid bilayer?
Non- polar or lipid soluble molecules.
Through what structure do water soluble molecules cross the membrane?
Through channel proteins/aquaporins
Name the structure labelled C on the diagram of a membrane
Glycoprotein
Name the structure labelled F on the diagram of a membrane
Extrinsic protein
Name the structure shown in the diagram
Phospholipid bilayer
Name the part of the membrane labelled A
Channel protein
Intrinsic protein
Which part of the phospholipid is hydrophobic?
Fatty acid tail.
Name the structure labelled E on the diagram of a membrane
Cholesterol
Protein molecules found on the surface of the membrane are called …
Extrinsic proteins
Give 2 differences between a triglyceride and a phospholipid.
Phospholipids contain a phosphate group whereas triglycerides do not.
Phospholipids have 2 fatty acids whereas triglycerides have 3 fatty acids.
What is the function of the carbohydrates found on the outer surface of the membrane?
Antigens
Each carrier proteins are specific. What does this mean?
Can only transport one type of molecule
Name the two carbohydrate containing chemicals found in cell membranes.
Glycoproteins and glycolipid.
What is the function of the microvilli?
Increase surface area for absorption of digested food by the small intestine.
What effect does cholesterol have on the fluidity of the membrane?
Reduces the fluidity/movement of phospholipids in the membrane.
How can the structure of the membrane be changed to make the diffusion of water soluble molecules more rapid?
Increase number of channel proteins
Increase surface area.
Give three ways in which the rate of gas exchange can be increased.
Increase the surface area.
Increase the concentration gradient.
Decrease the diffusion pathway/distance
Increase the temperature
Why is the term fluid mosaic used to describe the model for membrane structure?
Fluid - phospholipid move within the membrane.
Mosaic - proteins form blocks on the surface of the membrane.
The water potential of the cell cytoplasm is -5.
The cell is place in a solution with water potential of-10.
Which way will the water move?
Osmosis will cause water to leave the cell (water moves from high water potential to lower water potential).
A cell with a water potential of -5 is placed in a solution with a
water potential of -5.
Which way will the water move?
No net movement of water.
Water will still cross the membrane.
Same number of water molecules enter and leave the cell.
A cylinder of potato is placed into pure water.
Explain why the mass mass of the potato changes.
The cylinder will increase in mass.
Osmosis - water will enter the cylinder.
Water moves from high water potential to lower water potential through selectively permeable membrane.
Why should percentage change in mass be calculated when carrying out osmosis experiments.
Does not matter if the initial masses of the cylinders are not identical.
Allows comparison of results.
Calculating change in mass per gram of potato.
A proportion is calculated.
Give the equation for calculating the percentage change in mass.
% change in mass
= change in mass/initial mass X 100
Why is it important to dry the potato cylinders before placing them
in solutions of different water potential?
Removes the cytoplasm that has leaked out of the cut cells.
Only measuring the mass of the water inside the cells.
Why is it important to dry the potato cylinders when they have been removed from the different concentrations of salt solution?
Removes the salt solution on the outside of the cells/cylinder.
Only measure the mass of water that has entered the cylinder.
Ensure the experiment is valid.
Name the structure labelled G on the diagram of a membrane
Channel protein
Intrinsic protein
Define osmosis
Net movement of water from a high water potential to a lower water potential through a selectively/partially permeable membrane.
Name the two main chemicals found in the chloroplast
membranes.
Phospholipids and proteins (all membranes have the same structure)
Name a chemical that moves by osmosis into cells.
Water
Name 2 molecules that move into cells and are used in respiration.
Oxygen and glucose
What happens to ATP during active transport?
It is hydrolysed.
A phosphate group is removed.
Allowing the release of a small amount of energy.
What is formed when ATP is hydrolysed?
ADP and inorganic phosphate (Pi).
Describe how an ion is transported across a membrane by active transport.
Ion binds to a receptor site on the carrier protein on outside of membrane.
ATP in the cell binds to a receptor site on carrier protein.
ATP is hydrolysed
Causes carrier protein to change shape/open inside the membrane.
ADP is released
Ion released into cell.
Removal of Pi from carrier protein causes protein to revert to original shape.
Name the type of transport used to absorb glucose or amino acids into the epithelium cells lining the ileum.
Co-transport.
All membranes around and within cells (including those surrounding organelles) are called …
Plasma membrane
Describe how to carry out a biochemical test for a lipid
Add ethanol and shake gently
Pour into cold water
Positive result - white emulsion
Name the components of a cell surface membrane
Phospholipids
Proteins (extrinsic and intrinsic)
Glycoproteins
Glycolipids
Cholesterol
Name the type of reaction used to make a monoglyceride
Condensation reaction
Name the three molecules that make up a phospholipid
Phosphate
Glycerol
2 x Fatty acids
What are the functions of the phospholipids in the cell membrane?
Allow non-polar molecules cross the membrane
Prevent polar molecules crossing the membrane
Makes membrane flexible and self healing
What are the functions of proteins in the cell membrane?
Provide structural support
Act as channels to transport polar molecules/facilitated diffusion
What is the function of cholesterol in the cell surface membrane?
Reduces lateral movement of molecules in the membrane
Acts as a buffer against temperature changes
Prevent leakage of water and dissolved ions from the cell
What are the functions of glycoproteins in the cell surface membrane?
Act as recognition sites for hormones and neurotransmitters
Help cells attach and form tissues
In an investigation about diffusion diffusion and plasma membranes (beetroot discs) why would you ensure the temperature remained constant?
Maintain a constant rate of diffusion
Maintain constant fluidity of phospholipids
Prevent the denaturation of membrane proteins
How can you determine the water potential of plant material
Cut identical pieces of plant material
Measure the mass
Place in solutions of known concentration
Leave for 1 hour
Measure the mass of the plant material
Calculate % change in mass
Plot a graph (x axis concentration y-axis % change in mass)
Read off concentration resulting zero change in mass#
Convert to a water potential using a data table
What happens to red blood cells if placed in pure water?
Swell and burst/undergo lysis
What happens to a red blood cell placed in a strong sugar solution?
Shrinks
Becomes crenated
What happens to a plant cell when placed in pure water?
Swells and becomes turgid
What happens to a plant cells when placed in strong salt solution?
Plasmolysed
Define active transport
The movement of molecules or ions against a concentration gradient using ATP and carrier proteins.
What is the role of ATP in active transport?
Provide the energy needed to transplant a molecule against its concentration gradient.
ATP binds to carrier protein, ATP is hydrolysed causing the protein to change shape, allowing the entry of the molecule/ion
