Lipids ,cell Membranes Flashcards
What are lipids?
Hydrophobic compounds made up of C,H and O,insoluble in water but soluble in organic solvents e.g ethanol
Two types of lipids?
Phospholipids and triglycerides
Function of triglycerides?
Used for storage insulation and protection in fatty (adipose) tissue found under the skin they include fats +oils
How are triglycerides formed?
When one glycerol molecule joins together with three fatty acid molecules via a condensation reaction
each fatty acid forms an.. bond?
ester bond
difference in the r group deterines
the differences in fats and oils
the r group is a…
hydrocarbon chain which varies in length 4-22 c atoms
saturated fatty acids?
mono-unsaturated fatty acids?
polyunsaturated fatty acids?
- no double c=c bonds in the hydrocarbon chain
- one double bond
- more than 1 double c=c bond in the h-c chain
How is the structure of triglycerides related to their properties
- Have a high ratio of energy storing C-H bonds to C atoms therefore an excellent source of energy
- They’re large non-polar molecules and insoluble in water so their storage doesn’t affect the water potential
- High ration of H-O atoms triglycerides release water when oxidised therefore provide an important source of water
What are phospholipids?
How’s re they formed?
- main components of the cell membrane
- similar to triglycerides but with a phosphate group in place of one fatty acid chain
Phospholipids have a … head so..
phospholipids have a … tail so..
The phosphate group is …
Hydrophilic head - so attracts water molecules .
Hydrophobic tail - so orients itself away from water molecules but mixes readily with fat
Highly polar - so attracts water molecules
When phospholipids are exposed to water they form either a ..?
In water they position themselves so that…?
Micelle or a bilayer
- hydrophobic heads are close to the water as possible and hydrophobic tails are away as possible
How is the structure of phospholipids related to their properties?
- phospholipids are polar molecules so in aqueous solution can form bilayer within a cell surface membrane therefore a hydrophobic barrier is formed between inside and outside of the cell so water soluble substances cant easily pass through
- the hydrophilic phosphate heads of phospholipid molecules help to hold at the surface of cell-surface membranes
- can form glycolipids by combining with carbohydrates within the cell-surface membrane which are important in cell recognition
- phosphate group is highly polar so attrcats water molecules
- fattu acids are non-polar so repel water
Importance of phospholipids in the cell surface membrane?
- makes cell selectively/partially permeable
- the smaller + less polar a substance the easier and faster it will diffuse across the the cell membrane
- allow lipid soluble substances to enter and leave the cell e.g vitamins
- prevent water soluble molecules entering and leaving the cell
- small molecules are able to pass through quickly
- charged particles unlikely to diffuse across the membrane even if they’re really small
Makes cell flexible and self-sealing
What are the components of the cell membrane?
Phospholipids, cholesterol , glycoproteins, glycolipids, Chanel proteins, carrier proteins, other proteins aswell
What are the many functions of the cell-surface membrane?
- Divided cells into different compartments to make functions more efficient
- controls what enters and leaves
- recognise chemical substances from other cells
- fold in the cell membrane may form microvilli which increases SA for diffusion
Extrinsic protein functions
- provide support and stability
- combine with carbohydrates to form glycoproteins and glycolipids which can act as chemical receptors
- cell recognition
- receptors sites for hormones
- protection
Example of intrinsic protein
Function of intrinsic protein?
- carrier/Chanel protein
- act as hydrophilic press through which water soluble substances can pass
- sites of facilitated diffusion, co-transport and active transport
- can be enzymes
What is a glycoprotein?
What is a glycolipids?
- proteins with attached carbohydrates chain
- lipids with attached carbohydrates chain
State the function of glycoproteins?
Receptor molecules bind with hormones or neurotransmitters which can trigger chemical reactions within the cell
- e.g insulin, only some cells within the body have insulin receptors therdore insulin can be released to the entire body and only cells with insulin receptors will be triggered
- cell recognition - provide support and stability
Function of cholesterol?
Control membrane fluidity - more cholesterol, less fluid therefore less permeable
Makes membrane stable at body temperature otherwise will burst
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