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biology > 12.1 - Carbs & Lipids > Flashcards

12.1 - Carbs & Lipids Flashcards

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1
Q

What are monomers?

What are polymers?

A

Monomers are small, identical or similar molecules which can be joined together (condensed) to make larger molecules called polymers.

A large molecule made from the joining (by chemical bonds) of 3 or more similar or identical monomer molecules.

Formed by condensation reaction.

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2
Q

What is a condensation reaction?

What is a hydrolysis reaction?

A

A condensation reaction involves the formation of a chemical bond, removing a water molecule. Monomers -> polymers.

A hydrolysis reaction involves the breaking of a chemical bond, using a water molecule. Polymers -> Monomers.

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3
Q

What elements are found in all carbohydrates?

What is the ratio of H:O?

What are carbohydrate monomers called? + E.g

What are carbohydrate dimers called? + E.g

What are carbohydrate polymers called? + E.g

What are isomers?

A

C, H and O.

2:1.

Monosaccharides. (glucose, galactose, fructose)

Disaccharides. (maltose, lactose, sucrose)

Polysaccharides. (starch, glycogen, cellulose)

Molecules with the same molecular formula but a different arrangement of atoms.

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4
Q

How is a disaccharide formed?

What do Glucose + Glucose form? What enzyme speeds the hydrolysis of it?

What do Glucose + Galactose form? What enzyme speeds the hydrolysis of it?

What do Glucose + Fructose form? What enzyme speeds the hydrolysis of it?

A

Two monosaccharides can join together in a condensation reaction. This produces (uses) a water molecule. A glycosidic bond is formed between them.

Glucose + Glucose = Maltose. Hydrolysed by Maltase.

Glucose + Galactose = Lactose. Hydrolysed by Lactase.

Glucose + Fructose = Sucrose. Hydrolysed by Sucrase.

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5
Q

DRAW
ALPHA GLUCOSE, (penguin)
BETA GLUCOSE, (hieroglyphic)
GALACTOSE, (raver)
FRUCTOSE. (witch’s hat)

A

alpha - OHs at bottom
beta - one OH at top, other at bottom
galactose - both OH at top
fructose - o at top, 2 ch2oh groups

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6
Q

Give the structures and features of starch. (4)

MADE OF…

A

1) Helical/spiral - so compact, tightly packed, can fit lots into a small space.
2) Insoluble - so no osmotic effect, doesn’t affect WP + doesn’t leave cell.
3) Large molecule/long chains - doesn’t leave cell + large no. of glucose units.
4) Branched chains - Increased SA, rapid hydrolysis to remove glucose for respiration.

MADE OF ALPHA GLUCOSE.

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7
Q

Give the structures and features of glycogen.

MADE OF…

What is the difference between starch and glycogen? Glycogen has shorter…because…

Where are they found?

A

1) Insoluble - so no osmotic effect, doesn’t affect WP + doesn’t leave cell.
2) Large molecule/long chains - doesn’t leave cell + large no. of glucose units.
3) Branched chains - Increased SA, rapid hydrolysis to remove glucose for respiration.

MADE OF ALPHA GLUCOSE.

Glycogen has shorter chains = more rapidly hydrolysed to be used in respiration, animals require glycogen to be hydrolysed faster.

FOUND IN SKELETAL AND CARDIAC MUSCLES IN ANIMALS.

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8
Q

The structure of cellulose is related to its function in plant cell walls. Explain how. (4)

MADE OF…

A

1) Long straight unbranched chains of Beta Glucose
2) Joined together by many weak hydrogen bonds
3) Form micro/macrofibrils
4) Provide strength/support

MADE OF BETA GLUCOSE.

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9
Q

Hydrogen bonds are important in cellulose molecules. Explain why. (3)

A

1) Hydrogen bonds hold chains together / form cross links between chains of cellulose molecules
2) They provide strength + rigidity to cellulose/cell wall
3) Weak hydrogen bonds provide strength in large numbers.

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10
Q

Describe the test for reducing sugars (glucose, galactose, fructose, lactose, maltose.) (3)

A

1) Add Benedict’s solution/reagant
2) Heat to 95.C
3) Red/orange/yellow/green precipitate (depending on concentration)

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11
Q

Describe the test for non-reducing sugars (sucrose) (5)

A

1) Complete Benedict’s test for R.S and observe a negative result/stays blue.
2) Add acid and heat to 95.C
3) Neutralise with alkali
4) Add Benedict’s reagant and heat to 95.C
5) Red precipitate

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12
Q

Solutions are…

A precipitate is..

A

TRANSPARENT

a solid suspended in a liquid.

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13
Q

What is the test for starch?

A

1) Add potassium iodide (KI) solution
2) Solution turns blue/black colour if starch is present.

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14
Q

What is a quantitive test to measure the concentration of sugar in a solution?

How do you standardise this method? (3)

A

You can use a colorimeter, it measures the intensity of light passing through a solution.
Larger concentration of reducing sugar =
reduced transmission (au) / more absorbance

1) Samples should be shaken before testing.
2) Zero the colorimeter before use (with a control e/g water)
3) Use same volume for each reading.

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15
Q

Describe how you would produce a calibration curve for a reducing sugar of unknown concentration and use it to obtain results. (5)

A

1) Make up several known conentrations of a reducing sugar (e.g glucose).
2) Carry out the Benedict’s test on each sample.
3) Use a colorimeter to measure the colour intensity of each solution (absorbance/transmission) and plot a calibration curve.
4) Known concentration on X axis and Absorbance/transmission on Y axis.
5) Find the concentration of the unknown sample using the calibration curve.

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16
Q

Give two functions of lipids.

A

1) Conduct heat slowly, good thermal and electrical insulators.
2) Stored around delicate organs e.g kidney to protect them.

17
Q

Describe the test for lipids. (2)

A

1) Mix sample with ethanol, then add water and shake.
2) Cloudy white emulsion.

18
Q

Some seeds contain lipids. Describe how you could use the emulsion test to test for lipids. (4)

A

1) Crush/grind the seeds.
2) With ethanol to dissolve the lipid.
3) Then add water then shake.
4) Forms a white emulsion.

19
Q

What is a triglyceride made up of and how is it formed?

IT IS NOT A…

A

Made from one molecule of glycerol bonded to three fatty acids joined by ester bonds.
(NOT A POLYMER - not made of similar/same monomers.)

Formed by 3 condensation reactions, 3 ester bonds are formed and 3 water molecules are released.

20
Q

What is an unsaturated fatty acid?

A

Double bond(s)
Between carbon atoms in the hydrocarbon chain.

21
Q

Why are triglycerides good stores of energy and good source of water?

A

Energy - they have a low mass to energy ratio.

Water - storing them does not affect the water potential because they’re insoluble in water, they have a high H:O ratio, good source of water when broken down.

22
Q

What is a phospholipid made of and what is the main difference with a triglyceride?

A

Made up of two fatty acids, glycerol and a phosphate group. (while triglycerides have 3 FAs)

23
Q

How does the structure of a phospholipid allow it to form a bilayer in water?

The head and tails… (charges + properties)

They face… (direction)

A

The phosphate group head (PO4 3-) has a negative charge (polar) whereas the fatty acid tails have no charge, they are non-polar.

This makes the phospho-glycerol head hydrophilic (attracts water - soluble) and the FA tails hydrophobic (repels water - insoluble)

The hydrophobic tails face each other/away from the water (arranged in the middle)
The hydrophilic heads face the water.

24
Q

Compare and contrast the structure and properties of triglycerides and phospholipids. (8)

A

1) Both contain ester bonds
2) Both contain glycerol
3) Fatty acids on both can be saturated or unsaturated
4) Both are insoluble in water
5) Both contain C,H and O but phospholipids also contain P.
6) Triglycerides have 3 FAs, while phospholipids have 2 FAs and a phosphate group.
7) Triglycerides are hydrophobic/non-polar while phospholipids have a hydrophobic and hydrophilic region.
8) Phospholipids form a bilayer/micelle but triglycerides don’t.

25
Q

Describe the test for amylase. (2)

A

1) Add Biuret’s reagant and becomes violet/lilac
2) Add starch (leave for a time), then test for the absence of starch

26
Q

How can you measure the quantity of reducing sugar in a solution w/o colorimeter?

A

1) Filter and dry the precipitate
2) Find mass

biology (18 decks)

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