Lipids Flashcards
Functions and properties of triglycerides
- Energy storage
- Are respired to release energy in the form of ATP
- Produces around twice as much energy as carbohydrates
- Insoluble so it doesn’t affect cell’s water potential
- Stored as adepose tissue when energy input is greater
- Adepose tissue provides layer of insulation
- Triglycerides provide protection for
Respiratory substrate
Substances used in respiration to release ATP
Types of cholesterol: bad cholesterol
Carried in LDL’s
Deposited in arteries
Leads to athlesclerosis
Leads to gallstones
Types of cholesterol: good cholesterol
Carried in HDL’s
Removes LDL’s from artery walls
Used to make cell membranes and organelle membranes
Maintains membrane fluidity
Deriratives of cholesterol
Testosterone
Oestrogen
Vitamin D
Vitamin A
Functions and properties of phospholipids
Form the membrane bilayer
Can change membrane fluidity by increasing he number of unsaturated fatty acids
May have carbohydrates attached to phosphate heads to form a glycolipid
Glycolipds are involved in cell signalling
Amphpathic nature (will mix with water)
Structure of triglycerides
Cosists of one olevule of glycerol and fatty acids that are linked to each carbon y ester bonds
Structure of glycerol
Has a propane parent chain with alcohol groups on each carbon
General formula for fatty acids
CH3(CH2)nCOOH where n>14
What are the two types of fatty acid
Saturated and unsaturated
Basic structure of a phospholipid molecule
Consists of a glycerol group with two fatty acids and one phosphate group attached
An alcohol group is also attached to the phosphate group
What is an ester bond?
The condensation link between an acid group (-COOH) and an alcool group (-OH) by the loss of water
What will a double bond cause in a fatty acid chain?
A kink in the chain
The main differences between a triglyceride and a phospholipid molecule
- A phospholipid moecule contains two fatty acid components but a triglyceride contains three
- A phospholipid contains a phosphate group
- A phospholipid contains an extra alcohol group attached to the phosphate group
- The third carbon in the glycerol of a phospholipid is rotated 180 degrees, the glycerol in a triglyceride has all three carbons the same way round
Why are phospholipid molecules amphipathic?
The phospholipid head has an alcohol group that can lose a H when in water so the O becomes negatively charged
Therefore the polar head can freely mix with water
What is the phospholipid bilayer chemical comoposition?
45% lipid
45% protein
10% polysaccharide
What is the thickness of a phospholipid bilayer?
7~8 nm
What is the impotance of phospholipid molecules in plasma membranes?
- They give the membrane a fluid mosaic structure
- Allows lipid soluble substances to cross plasma membrane
- Prevents passage of water soluble substances
- Phospholipids loosely bond to cholesterol making the membrane stronger and less permeable
Why do some membranes have a high proportion of unsaturated fatty acids?
The proportion of unsaturated fatty acids will influence flexibility and fluidity.
e.g. membranes of Golgi apparatus and SEM have a higher concentration of unsaturated fatty acids
Why are HDL’s better than LDL’s for you?
HDL’s remove cholesterol from cells and transport them to be excreted
LDL’s collect cholesterol from blood and deposit tem in cells
Too much cholesterol can lead to atheroma and CHD
The eight functions of lipids
Energy storage Strucutral components of membranes Thermal insulation Mechanical protection Electrical insulation Waterproofing Buoyancy Precursors
Why are lipids a good source of energy?
They contain a lot more energy than carbohydrates
How do animals obtain lipids?
Lipids are obtained through diet by hydrolysing lipids into glycerol and fatty acids using lipase
How and where is the digestion of lipids accelerated?
Since lipids are water insoluble, their digestion must be accelerated using bile salts in the large intestine
Bile salts emulsify lipids into smaller particles, greatly increasing the surface area on which lipase can act
What do you get when you hydrolyse fats?
Fats are hydrolysed to produce fatty acids, monoglycerides and cholesterol
How to the epithelial cells of the gut keep the concentration gradient low?
The reassembly of triglycerides in the epithelial cells keeps the concentration gradient between the ileum and the epithelial cells low
Describe the structure and function of epithelial cells in the gut
- Has many micro-villi to increase surface are to volume ratio
- Plasma membrane of epithelial cell has protein carriers for active transport
- Epithelial cells contain SEM for triglyceride sunthesis
What are the properties of fatty acids?
Can be saturated, monosaturated and polyunsaturated
Animal fats are mainly saturated and solid at room temperature
Unsaturated fats tend to be liquid
Function of fatty acids
Act as an energy store in most cells
Saturated fats contain more energy due to the increased number of H
Properties of triglycerides
Depends on the nature of the fatty acid
Animal triglycerides tend to have larger fatty acids and more saturated fatty acids compared to plant lipids
Properties of steroids
Has a polar head and a non polar tail so it therefore contributes to the membrane bilayer
How are trans fats produced?
By bubbling hydrogen through unsaturated fatty acids through a process called hydrogenation
Why do C=C bonds make a membrane more fluid?
C=C double bonds change the shape of the hydrocarbon
These changes in shape cause the molecules to move apart making the membrane more fluid
Test for lipids
Add ethanol to dissolve lipid and pour alcohol into water in another test tube
If the result tests positive, a white emulsion forms near the top of the water
What does essential mean?
We cannot make it ourselves so we have to obtain it through diet
Why is cholesterol carried as lipoprotein?
It is insouble
Why does pH fall during the hydrolysis of triglycerides?
The concentration of fatty acids increase
