3. Lipids, membranes and transport Flashcards
(47 cards)
What elements are in Lipids
C H O
What are lipids
Group of non-polar molecules
Insoluble in water
dissolve easily in organic solvents
What are the important groups of lipids
Triglycerides and phospholipids
What is a triglyceride
Made of 3 fatty acids and 1 molecule of glycerol
How is a triglyceride formed
Glycerol has 3 OH- groups.
Each bind to a fatty acid
Condensation reaction
Produce 3 molecules of H2O
Ester bonds between OH and COOH
What is a fatty acid made from
A COOH- group and a long hydrocarbon chain (Unsaturated or Saturated)
Why are triglycerides not classified as polymers
They are not made of monomers.
They are made of 2 different types of molecules
What are the biological roles of triglycerides
Storage of energy
Insulation - electrical and heat
Protection
How do the structure and properties of a triglyceride relate to its function
High ratio of energy storing C-H bonds to C atoms = good source of energy
Low mass to energy ratio = Good storage molecules as lots of energy stored in small volume
Large, non-polar, insoluble in water molecules = no osmotic effect and dont effect water potentiels
What is a phospholipid
Lipids where one fatty acid is substituted for phosphate group
- Polar/hydrophilic head (Glycerol and phosphate)
-2 Non-Polar/hydrophobic tails (Fatty acids)
What is the test for lipids
Ethanol emulsion test
- Add ethanol to the sample to be tested
- Shake thoroughly to dissolve any lipid in sample
- Then add water to sample and shake gently
-A milky white emulsion indicates the presence of lipid
What are the 3 functions of plasma membranes
- Control the transport of substances into and out of cell or organelle - Partially permeable
- Act as a receptor site - Recognise chemicals that need to enter the cell
- Separate off the cell from the environment and the different reactions - Different concs can be maintained
What molecules do plasma membranes not let through
Water-soluble
Charged
Polar
What molecules are in a membrane structure
- Phosphlipids
- Membrane proteins
-Glycoproteins - Glycolipids
-Cholesterol
What do phospholipids do in the membrane structure
Form a bilayer
Hydrophobic tails point towards eachother
Hydrophilic head point out into the water
What do membrane proteins do in the membrane structure
Float about in bilayer - fluid mosaic structure
May be in one layer (Extrinsic) or across the whole membrane (Intrinsic) .
May be fixed in one place or float about
Often have hydrophilic channels in the middle
What is the function of an Intrinsic protein
Transport - channels and carriers
What is the function of extrinsic proteins
Enzymes
Receptors
Antigens
What is a glycoprotein and its function in the membrane structure
Short, branching carbohydrate chains attached to proteins in the membrane.
Act as receptors for hormones and neurotransmitters or antigens
What is a glycolipid
Made of a carbohydrate covalently bonded to a lipid.
Act as recognition sites
Help maintain stability of the membrane and help cells attach to one another forming tissues
What is cholesterol
Restrict the movment of other molecules in the membrane
Increase the strength and stability of membranes by making them less flexible
Prevents loss of water and dissolved ions
What is the fluid mosaic structure
Fluid = All different molecules can move
Mosaic = Different types of molecules. Some can float within the bilayer
What can molecules in the plasma membrane do
-Move sideways
-Leave the membrane to form vesicles
-Join memranes from vesicles
Why does should a membrane be fluid
Cells can change their shapes e.g phagocytes
