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Biology > Biological Molecules - Lipids > Flashcards

Biological Molecules - Lipids Flashcards

1
Q

What are triglycerides made up of?

A

Contains 1 glycerol molecule and 3 fatty acids

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2
Q

What if there’s a practical where there’s mixed oil and ph indicator and you are asked to explain the drop in pH after mixing in lipase?

A

Remember triglyceride is broken down by lipase to release glycerol and fatty acids and the fatty acids are what makes the mixture acidic

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3
Q

DRAW THE STRUCTURE OF A TRIGLYCERIDE

+ the condensation reaction between the glycerols and fatty acids

A

(Check in biology book pg10)

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4
Q

What bond is formed after a condensation reaction?

A

An ester bond (formed between organic alcohol and acid)

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5
Q

Whats the reverse of a condensation reaction?

A

Hydrolysis reaction

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6
Q

What does a saturated fatty acid chain mean? + draw example

A

Means each carbon is saturated aka filled with carbon on each side and means there are no double bonds

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7
Q

What is meant by an unsaturated fatty acid?

A

Only 1 on each end because each carbon can only make 4 bonds and means they have double bonds

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8
Q

Whats a polyunsaturated fatty acid?

A

Even more than one double bond

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9
Q

What do the double bond fatty acids have?

A

Kinks

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10
Q

Whats a phospholipid?

A

Another type of lipid which makes up the plasma membrane

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11
Q

Whats a phospholipid made up of?

A

Hydrophilic (charged and binds to water easily) phosphate group

Fatty acids 2x

Glycerol

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12
Q

How will it organise itself in a plasma membrane (phospholipids)?

A

It’ll organise itself into a bilayer

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13
Q

Whats the phosphate head like?

A

Hydrophilic aka water loving

It can deal with charge stuff as water is a polar molecule

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14
Q

What are the fatty acid tails like?

A

Are hydrophobic (hate water)

Humans are mainly made up of water. So in membranes that separate or compartmentalise stuff they will have the phosphate bit facing the outside or towards the aqueous bit, whereas fatty acids will face one another, shielding themselves away from it

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15
Q

Why do we get an oil layer when we mix water and oil?

A

Because similar properties will go together whereas stuff will opposite properties will not mix very well

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16
Q

Can lipid soluble (non polar) molecules diffuse through cell membrane?

A

Yes, via simple diffusion eg O2 steroid hormones

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17
Q

Can polar / charged molecule diffuse through the membrane?

A

No

18
Q

What can go through the cell membrane via diffusion?

A

Anything that is non polar or hydrophobic can happily sit in between, but stuff that is polar or charged will have to channel but stuff that is polar or charged will have to channel proteins or carrier proteins that sit in the membrane as well

19
Q

Draw the structure of a plasama membrane with cholesterol and a protein channel and a phospholipid bylayer and a hydrophobic layer

A

Pg 10

20
Q

What is cholesterol for in a plasma membrane?

A

It has a 4 ring structure

Dual hydrophilic/phobic properties

Provides stability to plasma membrane

The more cholesterol the less fluid the membrane is (increases packing)

21
Q

What is the protein channel for plasma membrane?

A

( allows Water to pass through )

22
Q

Draw the protein channel with the hydrophobic amino acids and the hydrophilic amino acids

A

Pg 10

(Hydrophilic is what allows the polar molecules to pass through)

23
Q

What are sterols?

A

Cholesterol is an example, them having dual hydrophilic and hydrophobic characteristics (the one hydroxyl group is the only part that’s hydrophilic and function in membrane (maintains fluidity)

24
Q

What do you need to make fat (triglyceride) into fatty acids + glycerol ?

A

Lipase

25
Q

What are fatty acids?

A

Macromolecules consisting of long hydrocarbon chains with a hydroxyl group attached

26
Q

How are the hydrocarbon chains of fat acids variable?

A
  1. The length; from 12 to 20 carbon atoms long
  2. The degree of saturation ; the number of double bonds along the chain
27
Q

What happens if there’s a double bond between the carbons…

A

There are fewer hydrogen atoms and the chain bends. This is an unsaturated fatty acid

28
Q

What do double bonds result in

A

Kinky tails in fatty acid chains

  • less H bonding
  • lower melting point
  • liquid at room temperature (oils)eg sun flower oil
29
Q

Give another example of condensation reactions that happen in living things?

A

The formation of glycosidic bon between two sugars (or a peptide bond between two amino acids)

30
Q

How do the properties of carbon, hydrogen and oxygen in a triglyceride differ from their proportions in a carbohydrate such as glucose?

A

A glucose molecule has twice as many hydrogens as carbons, and the triglyceride also has nearly twice as many. But whilst the glucose molecule has the same number of carbon atoms and oxygen atoms, the triglyceride has more than 7 times as many carbons as oxygen

31
Q

Roles of lipids are

A
  • main energy store in human adipose tissue (the layer of fat under your skin)
  • store of fat and fat-soluble vitamins A and D in the liver cells
  • acts as a heat insulator (under the skin)
  • acts as an insulator around nerve cells axons, preventing ions leaking
  • protects delicate organs eg kidneys
  • cholesterol is a sterol which is important in cell membranes. Steroids such as the sex hormones are synthesised from cholesterol . Cholesterol is not a triglyceride but is often included with lipids as it is lipid soluble
32
Q

Why do triglycerides make good storage substances?

A

Because their molecules do not dissolve in water.

As they are hydrophilic which means the molecules tend to clump together inside cells, making as little contact with the watery cytoplasm as possible. They keep out of the way taking up little space and they don’t absorb water

33
Q

How are triglycerides good at heat insulation?

A

They are store inside the cells which make up adipose tissue under our skin.

It is a poor conductor of heat and it reduces heat loss from ski

When our surroundings are particularly cold, the arterioles supplying blood to the skin capillaries close of, diverting the blood to flow in capillaries beneath the adipose tissue

34
Q

How are triglycerides a good storage site for fat soluble vitamins?

A

Lipid globules containing triglycerides in the cytoplasm of cells in the liver contain dissolved fat soluble vitamins such as Vitamins D and A. They act as a store for these vitamins

35
Q

What is cholesterol made of?

A

Four carbon based rings not made from glycerol and fatty acids

36
Q

What is the role of cholesterol?

A

Is a major constituent of cell membranes where it gives stability and helps to regulate the fluidity of the membrane. Because the molecule has a narrow structure and is hydrophobic in nature, it is able to fit between the phospholipid hydrocarbon tails

37
Q

Whats the cholesterol and other substances with similar structures which are formed from it called?

A

Steroids. The hormones testosterone and oestrogen are made from cholesterol

38
Q

Give the method for the emulsion test for lipids

A
  1. Label the test tubes suitably for the foods to be tested
  2. Chop solid food on a tile or grind with a mortar and pestle
  3. Add the food to a labelled test tube to a depth of about 1cm. For olive oil, add two drops.
  4. Add 3cm3 of ethanol to each test tube
  5. Put a clean bung into each test tube and shake carefully at least 10 times. This will help any lipids dissolve in the ethanol
  6. Allow time for food particles to settle. You may proceed when the ethanol above the food has cleared
  7. Use the wash bottle to dispense about 3cm depth of distilled water into the test tubes
  8. Observe and note any changes in the test tube contents. Record your results in a suitable table
39
Q

Give possible results for the emulsion test

A
  • confirmation of lipids: a white emulsion floating at or near the top of the water
  • confirmation of the absence of lipids (or levels below the sensitivity of the test): no white emulsion at or near the top of the water
40
Q

Give the explanation for the emulsion test for lipids

(+do exam qs in booklet, cover answers)

A

Lipids are soluble in organic solvents such as ethanol but they are not soluble in water or in dilute ethanol. Any dissolved lipid will precipitate in the diluted ethanol when added to water. The lipid will form a white emulsion, which is a mixture of two immiscible liquids

41
Q

What is cholesterol?

A

Cholesterol is a sterol. The body manufactures cholesterol primarily in the liver and intestines. It is important in the formation of cell membranes , as it becomes positioned between the phospholipids with the hydroxyl group at the periphery of the membrane

This adds stability to the cell membrane and regulates their fluidity, by keeping membranes fluid at low temperatures and stopping them becoming too fluid at high temperatures

Biology (14 decks)

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