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A-Level Biology ISOMER > Biological Molecules - glucose, starch Monosaccharides > Flashcards

Biological Molecules - glucose, starch Monosaccharides Flashcards

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1
Q

Define monomer

A

Monomers are the smaller units from which larger molecules are
made.

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2
Q

Define polymers

A

Polymers are molecules made from a large number of monomers
joined together.

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3
Q

Examples of monomers

A

Monosaccharides, amino acids and nucleotides are examples of
monomers

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4
Q

what is a condensation reaction

A

A condensation reaction joins two molecules together with the
formation of a chemical bond and involves the elimination of a
molecule of water.

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5
Q

what is a hydrolysis reaction

A

A hydrolysis reaction breaks a chemical bond between two
molecules and involves the use of a water molecule.

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6
Q

what is a monosaccharide

A

Monosaccharides are the monomers from which larger
carbohydrates are made

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7
Q

examples of carbohydrates

A

sugars and starch

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8
Q

where are sugars found e.g. sucrose

A

sucrose is found in cakes and biscuits

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9
Q

where is starch found

A

starch is found in foods such as pasta and rice

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10
Q

Describe the structure of glucose

A

Glucose has a ring shape
Glucose contains 6 carbon atoms

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11
Q

What do all carbohydrates contain

A

All carbohydrates including glucose contain only the elements carbon, hydrogen and oxygen

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12
Q

What are sugars /monosaccharides with six carbon atoms called

A

Sugars with six carbon atoms are called hexose sugars/monosaccharides

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13
Q

What type of sugar is glucose and why?

A

Glucose is a hexose sugar/monosaccharide because it contains six carbon atoms

A single sugar molecules (a monosaccharide)

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14
Q

Draw the structure of glucose

A

https://static.aqa.org.uk/assets/image/0018/235440/00055366-DA00046397-DB.png

write 1 - 6 on the inside of the hexagon
then 6 on the left of the stick

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15
Q

Give examples of a monosaccharide

A

glucose, galactose, fructose

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16
Q

describe a key feature of monosaccharides - explain using the structure of glucose

A

Monosaccharides are soluble in water
Monosaccharides including glucose have a large number of OH groups.
OH groups are called hydroxyl groups

Hydroxyl groups are polar due to the small negative charge in the oxygen atom and the small positive charge on the hydrogen atom.
This means that Hydroxyl groups can form hydrogen bonds with water molecules
Due to this, monosaccharides are soluble in water

These molecules are hydrophilic

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17
Q

What are hydrophilic molecules

A

Hydrophilic (water loving)
Hydrophilic molecules all dissolve in water

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18
Q

Monosaccharides are ______ molecules

A

Monosaccharides are hydrophilic molecules

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19
Q

State the two forms of glucose

A

Alpha glucose
Beta glucose

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20
Q

The two different forms of glucose can also be called ______ of glucose

A

The two different forms of glucose can also be called ISOMERS of glucose

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21
Q

Draw the structures of alpha and beta glucose

A

https://static.aqa.org.uk/assets/image/0018/235440/00055366-DA00046397-DB.png

https://static.aqa.org.uk/assets/image/0008/235439/00055366-DA00046396-DB.png

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22
Q

Describe the similarity between alpha and beta glucose

A

In both isomers of glucose, carbon 1 is bonded to a hydrogen atom and also to an OH (hydroxyl) group.

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23
Q

Describe the difference between alpha and beta glucose

A

The key difference between the two isomers of glucose is the position of the hydroxyl group on carbon 1

If the carbon 1 hydroxyl group
points below the plane of the ring, then this isomer is called alpha glucose

If the carbon 1 hydroxyl points above the plane of the ring, this this isomer is called beta glucose

https://encrypted-tbn1.gstatic.com/images?q=tbn:ANd9GcQtVcnkOpYu6-eFvrKkMGS7Zeacf_nG260b7BNijnErTnPs5fFs - beta glucose

https://www.youtube.com/watch?v=8GDXf2LrrUg&list=PL9IouNCPbCxVF0IVlwiILW-TmAMYX5OO7&index=4 at 1:43

24
Q

Describe how disaccharides are formed from monosaccharides

A

Disaccharides are formed by the condensation of two
monosaccharides:

25
Q

Describe what happens when two molecules of alpha glucose react together

A

When two molecules of alpha glucose react together, the disaccharide maltose is made.

Also when the disaccharide is made, a molecule of water is also produced

The water molecules is formed from a hydrogen atom from one of the monosaccharides and a hydroxyl group from the other

This reaction is called a condensation reaction since the reaction forms a water molecule

The glycosidic bond is formed between carbon 1 on one alpha glucose and carbon 4 on the other alpha glucose

26
Q

When a disaccharide is made from two monosaccharide was is also produced and how?

A

Also when the disaccharide is made, a molecule of water is also produced

The water molecules is formed from a hydrogen atom from one of the monosaccharides hydroxyl group and a hydroxyl group from the other

This reaction is called a condensation reaction since the reaction forms a water molecule

27
Q

a disaccharide is formed from two monosaccharides. What type of reaction is this and why?

A

This reaction is called a condensation reaction since the reaction forms a water molecule

28
Q

What is a glycosidic bond

A

The chemical bond formed between the two molecules of alpha glucose

29
Q

A condensation reaction between two monosaccharides forms a _____________

A

A condensation reaction between two monosaccharides forms a
glycosidic bond.

30
Q

Draw the reaction for the formation of maltose

A

https://o.quizlet.com/pVG3e0ugJZiYwjQlseKHVw.jpg

31
Q

How are the two alpha glucose molecules bonded together

What type of glycosidic bond is in the disaccharide maltose

A

Maltose has a 1,4 glycosidic bond

32
Q

Explain how maltose has a 1,4 glycosidic bond

Why it is called a 1,4 glycosidic bond

A

The glycosidic bond is between carbon 1 on one alpha glucose and carbon 4 on the other alpha glucose

33
Q

What type of reaction a disaccharides formed in

A

Disaccharides are formed in a condensation reaction (water molecule is also produced)

34
Q

Describe what happens when you add water to a disaccharide

A

If water is added to the disaccharide, the glycosidic bond breaks.
This converts the disaccharide back to the original monosaccharides
This is called a hydrolysis reaction

35
Q

What is a hydrolysis reaction

A

A reaction where water is added to the disaccharide which breaks the glycosidic bond
This converts the disaccharide back to the original monosaccharides

36
Q

Where are hydrolysis reactions normally carried out and by what

A

In cells this reaction is normally carried out by enzymes

37
Q

State some disaccharides

A

Maltose
Sucrose
Lactose

Are examples of disaccharides.

38
Q

How is sucrose made

A

Glucose (alpha) + fructose = sucrose

The disaccharide sucrose is formed from the monosaccharides glucose and fructose

39
Q

How is lactose made

A

Glucose (alpha) + galactose = lactose

The disaccharide lactose is formed from the monosaccharides glucose and galactose

40
Q

Why is glucose being extremely soluble in water a problem

A

If a cell contains a large amount/(high conc. of in cell) dissolved glucose, this can cause water to move into the cell by osmosis

41
Q

How do plant cells solve the problem of water moving into cells by osmosis (due to glucose’s solubility) and why?

A

To solve this problem, plant cells store glucose as starch - because starch is insoluble

42
Q

What is a polysaccharide

A

Polysaccharides are formed by the condensation of many glucose
units.

Polysaccharides are formed when more than two monosaccharides are joined together by condensation reactions

43
Q

What two molecules/polysaccharides does starch consist of

A

Amylose
Amylopectin

44
Q

Describe the structure of amylose

A

Amylose is an unbranched polymer of alpha glucose molecules (joined by 1,4 glycosidic bonds)
If a large number of alpha glucose molecules are joined together, then the polysaccharide amylose is made.

The alpha glucose molecules are joined by 1,4 glycosidic bonds
Each bond forms in a condensation reaction producing a molecule of water

The amylose molecule then twists into a compact helix with hydrogen bonds forming between glucose molecules along the chain

Amylose forms a helix which is held in place by hydrogen bonds between glucose molecules

This helical shape helps to make starch a very compact molecule

45
Q

In amylose how does each bond form

A

Each bond forms in a condensation reaction producing a molecule of water

46
Q

What is starch

A

Starch is a store of glucose

47
Q

If a cell needs glucose, what happens

A

If a cell needs glucose, water is used to break the glycosidic bonds

This converts the polysaccharide back to the original monosaccharides (glucose)

This is called a hydrolysis reaction

When the cell needs glucose, enzymes are used to break the glycosidic bonds in starch
This is a hydrolysis reaction and requires water
The enzymes that break down starch act at the ends of the molecules
Because amylopectin has a large number of branches, this means that it has a large number of ends.
Because of this the enzymes can break down starch rapidly

48
Q

Draw the structure of amylose

A

https://o.quizlet.com/pVG3e0ugJZiYwjQlseKHVw.jpg

but many

49
Q

Where do we find starch

A

We find starch in starch grains. /plants

50
Q

State the advantage of the structure of amylose in starch / structure relate to function

A

Amylose twists into a helix
This helical shape helps to make starch a very compact molecule

SO A lot of it can be stored in a small space

51
Q

Describe the structure of amylopectin

A

Amylopectin is a polymer of alpha glucose molecules joined by 1,4 glycosidic bonds

Amylopectin chains have a branch every 25-30 glucose molecules

A branch is another chain of alpha glucose molecules joined by 1,4 glycosidic bonds

The branch is connected to the main chain by a glycosidic bond.

The glycosidic bond is between carbon 1 of one of the alpha glucose molecules and carbon 6 of the other alpha glucose molecules.
This is called a 1,6 glycosidic bond

The glucose molecules at the branch points are joined by 1,6 glycosidic bonds.

Amylopectin is a heavily branched molecule

52
Q

Regarding amylopectin, what is a branch

A

A branch is another chain of alpha glucose molecules joined by 1,4 glycosidic bonds

53
Q

In amylopectin, how is the branch connected to the main chain

A

The branch is connected to the main chain by a glycosidic bond.

54
Q

Describe the glycosidic bond between the branch and main chain in amylopectin

A

The branch is connected to the main chain by a glycosidic bond.

The glycosidic bond is between carbon 1 of one of the alpha glucose molecules and carbon 6 of the other alpha glucose molecules. This is called a 1,6 glycosidic bond

55
Q

Draw the structure of amylopectin

Draw a simplified structure of amylopectin

A
56
Q

Which polysaccharide is unbranched and which polysaccharide is branched

A

Amylose - unbranched polysaccharide
Amylopectin - branched polysaccharide

57
Q

How is the structure of starch related to its function in cells

A

Amylose forms a tight helix. This makes starch compact
This means/allows for starch can store a large amount of glucose molecules for its size

Starch is insoluble in water
This means that starch does not cause water to enter the cell by osmosis
Because amylose and amylopectin are polymers, they are two large to diffuse through the cell membrane and pass out of the cell

When the cell needs glucose, enzymes are used to break the glycosidic bonds in starch
This is a hydrolysis reaction and requires water
The enzymes that break down starch act at the ends of the molecules
Because amylopectin has a large number of branches, this means that it has a large number of ends.
Because of this the enzymes can break down starch rapidly

insoluble - therefore doesnt affect water potential - so water is not drawn into cells by osmosis - means cell does not cell - makes it good for storage
being large and insoluble - does not diffuse out of cells
compact - a lot of it can be stored in a small placed
when hydrolysed forms alpha glycose - which is easily transported and readily used in resp.

branched form has many ends, each of which can be acted on by enzymes simultaneously meaning that glucose monomers are released very rapidly

has lots of branches (more than starch), so has more ends that can be acted on simultaneously by enzymes.
it is therefore more rapidly broken down to form glucose molecules, which are used in respiration

A-Level Biology ISOMER (4 decks)

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