Crossing the Plasma Membrane Flashcards
Lipids are made of which elements?
Carbon, Hydrogen and Oxygen.
State three examples of lipids
Fats, oils and waxes.
How are lipids different to carbohydrates in terms of their molecular structure?
Lipids contain less oxygen atoms. Lipids also have long tails made up entirely of C and H.
Difference between fats and oils?
Fats are solid at room temperature whilst oils are liquid.
State two properties of lipids.
Non-polar and insoluble in water. Poor conductors of heat, which means they are good insulators.
What are the subunits of a triglyceride molecule?
One glycerol and three fatty acids.
What is the name of chemical bond that holds the subunits of a triglyceride together?
Ester bond
How many hydroxyl groups does a glycerol contain?
Three hydroxyl groups allowing three fatty acids to attach to the glycerol molecule.
How do fatty acids attach to the glycerol?
The carboxyl group of the fatty acid joins with the hydroxyl group of the glycerol.
Difference between saturated and unsaturated fats?
Saturated fats have no double bonds between carbon atoms in their fatty acid tails, whereas unsaturated fats have double bonds between carbon atoms in their fatty acid tails.
Describe the structure of a phospholipid
Hydrophilic polar phosphate head
Hydrophobic non-polar fatty acid tails
Difference between phospholipids and triglycerides
A phospholipid contains a phosphate group and two fatty acid tails, whereas a triglyceride contains three fatty acid tails.
What is the function of phospholipids?
They form an integral part of all cell membranes.
How do phospholipids form a bilayer?
Two layers of phospholipids come together with phosphate heads facing the water rich environments (i.e. extracellular space and cytoplasm) and fatty acid tails facing towards the centre, forming the core of the phospholipid bilayer.
What is the function of cholesterol?
It is a lipid found in the plasma membrane that provides stability and flexibility.
What is the function of triglycerides? State at least three functions.
Any three of the following:
Source of energy, Insulation, Protection of vital organs, To prevent evaporation in plants, form myelin sheath around neurons, Source of water (metabolic water produced in respiration).
What are steroids?
Steroids are lipid-based hormones; they act as signalling molecules that cause a response in the body of an organism.
How do steroids move into or out of the cell?
Because they are lipid-based, they can freely move across the phospholipid bilayer.
Protein channels are involved in?
Facilitated diffusion
Protein pumps are involved in?
Active transport
How are glycoproteins and glycolipids formed?
When a carbohydrate chain attaches to a protein & When a carbohydrate chain attaches to a phospholipid.
What is the function of glycoprotein and glycolipid?
Cell communication and recognition.
What is the fluid mosaic theory about?
It states that membranes are made up of small, varying components like a mosaic. In addition, these components are able to move across the plasma membrane.
Define diffusion
Net movement of particles from a high concentration to a low convention down a concentration gradient
Define facilitated diffusion
Facilitated diffusion is the net movement of particles from a high concentration, to a low concentration, down a concentration gradient, through a protein channel.
State the properties of molecules that will pass through a protein channel or pump and how you know if they will cross by facilitated diffusion or active transport
Hydrophilic (either charged or polar).
Large in size.
If down a concentration gradient = facilitated diffusion through a protein channel
If up a concentration gradient = active transport through a protein pump
Describe which types of molecules can cross the phospholipid bilayer directly
Small, non-polar, hydrophobic molecules can pass through the phospholipid bilayer directly.
Small, polar molecules (like water and ethanol) can also pass through the phospholipid bilayer directly.
Describe a hypertonic solution.
A solution that is higher in solute in comparison to another solution.
Describe a hypotonic solution.
A solution that is lower in solute in comparison to another solution.
Describe steps in osmosis using the scaffold provided (OTTO).
- osmosis has occurred.
- Water has moved from the hypotonic solution (+ context)
- through the partially membrane of (+ context)
- to the hypertonic solution (+ context)
- outcome (e.g. the animal cell swells and lyses)
Describe an isotonic solution.
A solution that has the same solute concentration as another solution.
Define osmosis
The net movement of water molecules from a hypotonic solution to a hypertonic solution.
Define active transport
the net movement of particles from a low concentration, to a high concentration, against the concentration gradient, through a protein pump using ATP .
Define exocytosis
Bulk movement of large molecules OUT of the cell. (This is primarily proteins but can be other polymers or molecules too big to pass through a protein pump or channel)
Define endocytosis
Bulk movement of large molecules INTO the cells.
Define pinocytosis
Bulk movement of liquids into the cell.
Define phagocytosis.
Bulk movement of solids into the cell.
