Lipids and membranes Flashcards
What are fatty acids?
Long chain carboxylic acids
What can fatty acids be?
Saturated or unsaturated
What is a fat?
An ester between fatty acids and glycerol
What is an oil?
Fat made from unsaturated fatty acids
What are the two types of Unsaturated fatty acids?
Cis
Trans
How are lipids formed?
They are hydrolysed triglycerides
What are lipids?
Long carbon chains attached to a polar head
What is the simplest form of a lipid?
Salts of fatty acids (soap)
What are micelles?
Droplets of lipids where the hydrophilic heads point outwards and the hydrophobic tails point inwards
When do micelles form?
In water
Where are lipids in the cell membrane often derived from?
Triglycerides
What lipids form bilayers in water?
Phospholipids
Sphingolipids
What is found on the cell membrane?
Various proteins and enzymes
What lipids make up the cell membrane?
Phosphoglycerides
Sphingolipids
Sterols
What determines the properties of the cell membrane?
The composition
What effect do saturated lipids have on the cell membrane?
They form tightly packed bilayers with gel-like consistency
What effect do unsaturated lipids have on the cell membrane?
Unsaturated lipids can not pack as close and the bilayer becomes more fluid
Can cholesterol form micelles or bilayers?
No
What does small amounts of cholesterol do?
Makes the bilayer more fluid
What does large amounts of cholesterol do?
Anchors the lipid tails and makes parts of the membrane more gel-like
Can the lipids move within the bilayer?
Yes
How often does a lipid change place with it’s neighbour?
107 times/sec
What distance do lipids tend to move over?
0.5 μm
What does the cell membrane prevent?
Most molecules from freely passing through the membrane
What does the cell membrane allow to pass through the membrane?
Small, uncharged polar molecules
What two ways can transmembrane proteins be anchored?
α-helix
β-barrel
What are β-barrel anchored transmembrane proteins?
The β-sheets form a barrel like structure of hydrophobic amino acids
The hydrophobic side chains points to the outside of the barrel
What are α-helix anchored transmembrane proteins?
α-helix of about 20 hydrophobic amino acids
The hydrophobic side chains points to the outside of the helix
What are some examples of transmembrane proteins that transport molecules across the membrane?
Ion channels
Aquaporins
Glucose transporters
Amino acid transporter
What two things can transmembrane proteins do?
Transport molecules across the membrane
Relay signals across the cell membrane
What are examples of transmembrane proteins that can relay signals across the cell membrane?
G protein-couples receptors
Protein kinases
How can proteins be anchored to the membrane?
By lipids which attach to the protein
What are glycolipids?
Lipids with carbohydrates attached
Where are glycolipids found?
Only on the extracellular surface
What do glycolipids do?
They are active in cell recognition
They protect against harsh conditions
They maintain electrical gradients
What reactive oxygen species can oxygen form?
Hydroxyl radical: HO•
Hydroperoxide radical: HO-O•
What are reactive oxygen species used for?
To degrade unwanted proteins and molecules
How does lipid peroxidation occur?
Reactive oxygen species can react with unsaturated lipids in the cell membrane
What prevents lipid peroxidation?
antioxidants
They trap the intermediates
