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Biology > 2.2. 6-7 Lipids > Flashcards

2.2. 6-7 Lipids Flashcards

1
Q

What are Lipids?

A

a group of substances that are soluble in alcohol rather than water. These include triglycerides, phospholipids, glycolipids and cholesterol.

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2
Q

What is a macromolecule?

A

very large, organic molecule

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3
Q

What is a phospholipid

A

molecule consisting of glycerol, two fatty acids and one phosphate group

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4
Q

What do Lipids contain?

A

Large amounts of Carbon, hydrogen and smaller amounts of oxygen.

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5
Q

Why are lipids insoluble in water?

A

They are not polar which means that they do not attract water molecules but do dissolve in alcohol

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6
Q

What are the three most important lipids in living things?

A

Triglycerdies, phospholipids and steriods. They are not polymers but do have different components bonded together thus being examples of macromolecules

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7
Q

Describe the structure of a Triglyceride

A
  • Made up of glycerol and fatty acids.
  • There are many different types of fatty acids and we can make many of them in our body but some mustt be ingested complete
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8
Q

What is glycerol

A

It has 3 bonded atoms with 3 OH groups (its an alcohol)

- Which are important to the structure of triglycerides

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9
Q

Describe the structure of Fatty Acids

A
  • Carboxyl group (-COOH) on one end attached to a hydrocarbon tail, made of only Carbons and Hydrogens.
  • The Carobxyl group ionises into H+ and a COO- group
  • Structure is therefore an acid as it produces free H+ ions
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10
Q

What is the difference between a saturated and a unsaturated Fatty Acid

A

There is a C=C bond in the unsaturated fatty acid

There is no C=C bond in the unsaturated fatty acid

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11
Q

What is a single C=C bond in a fatty acid called?

A

Monounsaturated fatty acid e.g oleic acid

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12
Q

What is a fatty acid with more than 1 C=C bond called?

A

Polyunsaturated e.g linoleic acid

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13
Q

Describe the structure of a triglyceride molecule

A
  • 1 Glycerol molecule bonded to three fatty acids
  • Because there are three -OH groups of a Glycerol, 3 fatty acids will bond hence the name TRIglyceride
  • Covalent bond formed is known as an ESTER bond
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14
Q

What are the functions of triglycerides

A
  1. Energy Source - Triglycerides can be broken down in respiration to release energy and generate ATP, by hydrolising the ester bonds then both the glycerol and the fatty acid into CO2 and H2O.
    - Respiration of a lipid produces more water than respiration of a sugar
  2. Energy store - Triglycerides are insoluble in water —> Can be stored without affecting the water potential of a cell.
    - 1g of fat releases twice as much energy of 1g of carbohydrates —> lipids have more hydrogens and carbon atoms than carbohydrates and almost no oxygen atoms
  3. Insulation - Adipose tissue is a storage location for lipid in whales, acting as a heat insulator.
    - Lipid in nerve cells act as an electrical insulator.
    - Animals preparing for hibernation store extra fat.
  4. Buoyancy - Fat is less dense than water, it is used by aquatic mammals to help them stay afloat
  5. Protection - Humans have fat around delicate organs such as their kidneys to act as a shock abosrber.
    - Peptidoglycan cell wall of some bacteria is covered in a lipid-rich outer coat
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15
Q

Where do Mammals store fat?

A

Adipose cells under the skin

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16
Q

What is the structure of a Phospholipid

A
  1. Same structure as a triglyceride however ONE of the fatty acids is replaced by a phosphate group.
  2. One of the -OH groups form an ester bond
  3. Most of fatty acids found in phospholipids have an even number of carbon atoms. Commonly one of these chains is saturated and one of them is unsaturated
17
Q

How do Phospholipids react in water?

A
  1. When surrounded by water the phosphate group (hydrophillic) has a negative charge making it polar (attracted to water)
  2. Fatty acid tails (hydrophobic) are non polar and so are repelled by water.
  3. -The molecule is amphipathic
    - Membrane lipids tend to be amphipathic where as storage lipids are not
18
Q

Phospholipids that are amphipathic have very distinct properties, what are they?

A
  1. May form a layer on the surface of the water with the heads in the water and tails sticking up out of the water
  2. May form micelles (tiny balls with tails tucked away inside, and the heads pointing outwards into water
19
Q

Why are Amphipathic phospholipids excellent at forming membranes around cells and organelles.

A
  • Inside and outside of a cell membrane is an aqueous solution. —> The Phospholipids form a bilayer with two rows of phospholipids, tails pointing inwards and heads pointing outwards
  • 20 to 80% of membranes in plant and animal cells are made of phospholipids.
  • Bacterial membranes tend to contain greater proportions of protiens
  • Selectively permeable membrane: Only possible for small and non polar molecules to move athrogh the tail in the bilayer, such as oxygen and CO2. This lets the membrane control what goes in and out of the cell and keeps it functioning properly
20
Q

How does the membrane receive stability

A
  • Individual phospholipids are free to move around in their layer, but will not move into any position where their hydrophobic tails are exposed to water
21
Q

What is cholesterol?

A
  1. A steroid alcohol
  2. Type of lipid which is not made from glycerol or fatty acids
  3. Small hydrophobic molecule, which means it can sit in the middle of the hydrophobic part of the bilayer
  4. The steroid hormones testosterone, oestrogen and vitamin D are all made from cholesterol. —> Because they are small they can pass through the hydrophobic parts of the cell membrane
22
Q

What is cholesterol made out of?

A

Four carbon atom based rings or isoprene units

23
Q

What is the function of cholesterol?

A
  1. Regulates the fluidity of the membrane, preventing it from becoming too fluid or stiff
24
Q

Where is cholesterol made?

A
  1. Liver in animals

2. Plants also have cholesterol properties in their membranes

Biology (12 decks)

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