3.5 Lipids Flashcards
What is a lipid?
A non-polar macromolecule containing carbon, hydrogen and oxygen
What are the 2 types of lipids? What are they at room temperature?
Fats - solid at room temperature
Oils - liquid at room temperature
What is a triglyceride made up of?
1 glycerol molecule + 3 fatty acids
What group does glycerol belong to?
Alcohols
What group do fatty acids belong to?
Carboxylic acids
What are fatty acids made up of?
A carboxyl group with a hydrocarbon chain
What groups do fatty acids and glycerol molecules contain?
Hydroxyl groups
What do the hydroxyl groups do?
Hydroxyl groups interact, forming 3 water molecules and bonds between the fatty acids and glycerol
What are the bonds between fatty acids and glycerol called? What is the reaction called?
Ester bonds
Esterification - A condensation reaction
What’s needed when triglycerides are broken down?
3 water molecules are required to reverse the reaction that formed the triglyceride
What are saturated fatty acid chains?
No double bonds between carbon atoms - all carbon atoms form the maximum amount of bonds with hydrogen atoms
Chains are straight
What are unsaturated fatty acid chains?
Contain double bonds between some carbon atoms
Chains have a bending point
What are monounsaturated fatty acid chains?
Contain only one double bond
What are polyunsaturated fatty acid chains?
Contain 2 or more double bonds
What is the effect of a double bond?
Causes the molecule to bend, therefore the molecule can’t be packed closely together
What triglycerides do plants contain? Elaborate on it
Unsaturated triglycerides
- Occur as oils
- Healthier than saturated fats
What are phospholipids and what do they contain?
- Modified triglycerides
2. Contain phosphorus, carbon, hydrogen and oxygen
Where are inorganic phosphate ions found?
In the cytoplasm of every cell
Describe the phosphate ions
Have extra electrons so are negatively charged, making them soluble
How is a triglyceride made into a phospholipid? (*Refer to Figure 3 on p.g.55)
One fatty acid chain in the triglyceride is replaced with a phosphate group to form a phospholipid
Describe the structure of a phospholipid
Non-polar tail, the fatty acid chains
Charged head, the phosphate group
Describe the non-polar tails
- Repelled by water so are hydrophobic
- Mix easily with fat
Describe the charged heads
Attracted by water so are hydrophilic
What happens when phospholipids mix with water? What are they called because of this?
- Form a layer on the water’s surface with phosphate heads in the water and fatty acid tails sticking out of the water
- Surface active agents (Surfactants)
Explain what sterols are
- Also known as steroid alcohols
- Another type of lipid found in cells
- Not fats or oils
- Complex alcohol molecules
- Made of a 4 carbon ring structure with a hydroxyl (OH) group at one end
- Have hydrophilic+hydrophobic properties (OH group = hydrophilic, rest of molecule - hydrophobic)
Give an example of a sterol
Cholesterol
Where is cholesterol made?
Liver and intestines
What role does cholesterol have?
What is the result of this?
- Role in formation of membranes, becoming positioned between phospholipids w/ hydroxyl group on the outside of the membrane
- Adds stability to membranes
- regulates membrane fluidity by keeping membrane fluids at low temperatures + stopping them become too fluid at high temperatures
Give examples of what can be made using cholesterol
- Vitamin D
- Steroid hormones
- Bile
What roles do lipids play?
- Membrane formation + creation of hydrophobic barriers
- Hormone production
- Electrical insulation for impulse transmission
- Waterproofing e.g. bird feathers + plant leaves
Where else are lipids stored? What does this provide?
- Under skin
- Around vital organs
Provides: - Thermal insulation to reduce heat loss e.g. in penguins
- Cushioning to protect vital organs e.g. heart and kidneys
- Buoyancy for aquatic animals e.g. whales
What test is used to identify lipids?
Emulsion test
How is the test for identifying lipids carried out? What indicates the presence of a lipid?
- Mix sample with ethanol
- Mix resulting solution with water + shake
White emulsion forming as a layer on top of the solution means lipids are present
If the solution remains clear, results are negative
What is food synergy?
The belief that nutrients work collectively, not in isolation
