Lipids Flashcards
What are the 3 types of lipids?
- Triglycerides
- Phospholipids
- Sterols
What are the 5 functions of triglycerides?
- Major source of energy
- Source of metabolic water
- Makes up adipose tissue
- provides thermal insulation under skin of animals
- Provides protection around internal organs
How do triglycerides compare to carbohydrates in terms of energy?
-Per g triglycerides release more energy
Being a source of metabolic water makes them useful for organisms in what kind of environment?
Desert
Give an example of an animal that uses triglycerides as thermal insulation
Killer whale in the form of blubber
When are triglycerides stored as adipose tissue?
When energy input is greater than energy output
Why is cholesterol transported as a lipoprotein?
They allow lipids and cholesterol to dissolve in the blood
What are the functions of sterols (2 functions)?
-Cholesterol used in cell membranes to give stability and regulate fluidity -Used to make steroid hormones
Give 2 examples of steroid hormones
Testosterone and oestrogen
Where is cholesterol manufactured?
The liver and intestines
What is the function of HDL?
-used to make cell membranes and organelle membranes -decreases membrane fluidity
Which is ‘good’ cholesterol; HDL or LDL?
HDL
What does too much LDL lead to?
-atherosclerosis (deposits in artery walls) -gall stones
How are triglycerides formed?
A condensation reaction between a glycerol molecule and 3 fatty acids
What kind of bonds are formed when a triglyceride is formed?
Ester bonds
Which part of a glycerol molecule takes part in the condensation reaction to form a triglyceride?
The hydroxyl groups
What is the structure of a glycerol molecule?
How many molecules of water are formed from the condensation reaction to form a triglyceride?
3
What does a hydrolysis reaction of a triglyceride produce?
A glycerol molecule and 3 fatty acids
i) How are phospholipids formed? ii) What kind of bonds are formed?
i) A condensation reaction between a glycerol molecule, 2 fatty acids, and a phosphate group ii) Ester bonds
What property does the head of a phospholipid have?
It is hydrophillic and polar
What property does the tail for a phosphlipid have?
It is hydrophobic and non-polar
Explain the differences between phospholipids and triglycerides
-Triglycerides contain 3 fatty acids but phospholipids only contain two and a phosphate group - Triglycerides contain 3 ester bonds but phospholipids only contain 2 - Phospholipids have a hydrophilic head
Draw a simplified version of a phospholipid
Draw a phospholipid bilayer
Explain why membranes exist as bilayers
-Both the inside and outside of cells are aqueous -therefore a single layer would repel on one side -Bilayers mean that hydrophilic heads can face into the tissue fluid and cytoplasm -with the hydrophobic tails facing away from the aqueous environments
How does cholesterol sit in phospholipid bilayers?
With the hydroxyl group in contact with the Phosphate head
What are sterols made up of?
Large alcohol molecules
As cholesterol increases membrane fluidity ____
Decreases
A decrease in cholesterol ____ fluidity
Increases
How can you test for the presence of lipids?
Add ethanol first and then the resulting mixture add to water and shake
State two roles of cholesterol in living organisms
1) Increases stability of phospholipds in cell membrane 2) Waterproofing to skin
Name two molecules that combine with cholesterol to form LDLs
1) Saturated fatty acids 2) Triglycerides/lipids
