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Biology A-Level ♡ > Biological Molecules > Flashcards

Biological Molecules Flashcards

1
Q

What shape does glucose have?

A

A ring shape

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2
Q

what elements do all carbohydrates have?

A

carbon, hydrogen and oxygen

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3
Q

Glucose has 6 carbon atoms and therefore is a….

A

Hexose sugar/monosaccharide

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4
Q

Glucose is a single sugar molecule and single sugar molecules are called….

A

Monosaccharides

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5
Q

Name 3 types of monosaccharides

A

Glucsoe, fructose, galactose

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6
Q

Why are monosaccharides soluble in water

A

They contain many OH groups (hydroxyl groups) allowing them to form hydrogen bonds with water molecules

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7
Q

Hydrophilic molecules are…

A

Molecules which are soluble in water

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8
Q

Glucose is a hexose sugar/monosaccharide, what does this mean

A

It has 6 carbon atoms

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9
Q

Which monosaccharide has 5 carbon atoms

A

Ribose

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10
Q

How can disaccharides and polysaccharides (larger carbohydrates) be formed

A

formed by the condensation of glucose molecules and the glucose molecules are joined by a glycosidic bond and a water molecule is formed too.

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11
Q

What glucose is it when the carbon-1 hydroxyl group points below the ring

A

Alpha glucose

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12
Q

What glucose is it when the carbon-1 hydroxyl group points above the ring?

A

Beta glucose

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13
Q

What are isomers?

A

Sams formula but different structure and properties

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14
Q

Alpha and beta glucose are called

A

Isomers of glucose

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15
Q

When do disaccharides form?

A

When 2 monosaccharides are joined together by a glycosidic bond in a condensation reaction

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16
Q

What is made when 2 alpha glucose molecules react?

A

Maltose

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17
Q

What is also made when we make a disaccharide?

A

A water molecule.

One hydrogen from one monosaccharide and one hydroxyl group from the other

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18
Q

What is it called when a reaction forms a water molecule

A

A condensation reaction

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19
Q

When we make maltose (disaccharide) what bond is formed?

A

A 1,4 glycosidic bond between the 2 alpha glucose molecules

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20
Q

In what reaction are disaccharides and polysaccharides formed in?

A

Condensation reaction because a molecule of water is produced

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21
Q

What happens when we add water to disaccharides or polysaccharides?

A

The glycosidic bonds break and this converts it back to the original monosaccharides

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22
Q

What is it called when we add water to a disaccharide/polysaccharide

A

Hydrolysis reaction

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23
Q

In cells hydrolysis reactions are normally carried out by

A

Enzymes

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24
Q

Monosaccharide + monosaccharide =

A

Disaccharide + water

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25
Q

Alpha glucose + alpha glucose =

A

Maltose + water

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26
Q

Glucose + fructose =

A

Sucrose + water

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27
Q

Glucose + galactose =

A

Lactose + water

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28
Q

Examples of disaccharides are

A

Maltose,sucrose,lactose

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29
Q

Examples of monosaccharides are

A

Glucose, fructose, galactose

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30
Q

Glucose is produced by plant cells…

A

Using light energy trapped from photosynthesis

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31
Q

Glucose is a store of energy which can be released during….

A

Respiration

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32
Q

Why is glucose extremely soluble

A

It has a lot of hydroxyl groups which form hydrogen bonds with water molecules

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33
Q

Why are hydroxyl groups polar?

A

Due to small negative charge on the oxygen atom and the small positive charge on the hydrogen atom

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34
Q

Due to the hydroxyl groups being polar in glucose they can form hydrogen bonds with water molecules which makes….

A

Glucose highly soluble in water (hydrophilic)

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35
Q

What are the problems with the solubility of glucose? (plant cell)

A

If a cell contains a lot of dissolved glucose then water will move into the cell via osmosis

Instead the cell stores glucose as starch which is insoluble

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36
Q

Where is starch found?

A

In starch grains

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37
Q

How many molecules is starch consisted of?

A

2

Amylose and amylopectin

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38
Q

What is amylose?

A

An unbranched chain/polysaccharide of alpha glucose molecules formed in a condensation reaction

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39
Q

What happens when we join many alpha glucose molecules together to form amylose?

A

The amylose molecules twists into a compact helix with hydrogen bonds forming between molecules

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40
Q

What happens when the plant cell needs glucose?

A

Enzymes are used to break the glycosidic bonds in starch by adding water (hydrolysis)

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41
Q

What is amylopectin?

A

Amylopectin is a branched polymer of alpha glucose joined together by 1,4 glycosidic bonds and is made in a condensation reaction

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42
Q

Amylopectin has branches every….

A

25-30 glucose molecules

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43
Q

What are the branches in amylopectin

A

The branches are chains of alpha glucose molecules joined by 1,4 glycosidic bonds

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44
Q

How do amylopectin branches join to the main branch?

A

By a 1,6 glycosidic bond

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45
Q

Amylose forms a tight helix and so….

A

Makes starch a very compact compound

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46
Q

Starch is insoluble in water and so…

A

Does not cause water to move into the cell via osmosis

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47
Q

Amylose and amylopectin are polymers and so….

A

They are too big to diffuse out the cell membrane and out the plant cell

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48
Q

What happens when a plant cell needs glucose?

A

Enzymes are use to break the glycosidic bonds in starch by adding water (hydrolysis)

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49
Q

Where do enzymes break down the starch?

A

At the ends of the molecules

And because the amylopectin has a lot of branches it therefore has a lot of ends and so because of this emzymes can break down starch rapidly

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50
Q

What is the glucose storage molecule in animals?

A

Glycogen

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51
Q

Where are the major glycogen stores found?

A

Liver and muscle cells

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52
Q

What is glycogen?

A

A storage molecule in animal cells

Glycogen is a branched polymer of alpha glucose joined by 1,4 glycosidic bonds and it is formed in condensation reactions

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

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53
Q

What is more branched, glycogen or amylopectin?

A

Glycogen

Which makes it a VERY COMPACT MOLECULE

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54
Q

Glycogen has many branches and therefore many free ends which means…

why is this important?

A

That enzymes can break down glycogen into glucose very rapidly

This is important as animals have high rates of respiration

And the energy needs of an animal can change rapidly (running away from a predator)

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55
Q

Why is it good that glycogen is insoluble?

A

No water is drawn into the cell via osmosis

56
Q

Why is it good that glycogen is a large molecule?

A

Because it cannot diffuse out the cell

57
Q

What is a major part of the cell wall in plant cells?

A

Cellulose

58
Q

What is cellulose

A

Cellulose is an unbranched polysaccharide of beta glucose and every 2nd beta glucose is flipped

It is flipped so it can form 1,4 glycosidic bonds

59
Q

Cellulose forms a straight chain without any branches and so…

A

This allows cellulose molecules to get close together

And hydrogen bonds can form between neighbouring chains

A lot of these hydrogen bonds are formed which makes cellulose STRONG

60
Q

What is it called when lots of cellulose chains group together?

A

A microfibril

Then microfibrils group together to form larger structures called MACROFIBRILS

and finally macrofibrils group together to form a cellulose fibre

61
Q

What forms the cellulose cell wall

A

Cellulose fibres

62
Q

What is the key feature of cellulose

A

Strength

63
Q

Is the cell wall permeable to molecules like water?

A

Yes

64
Q

Under normal conditions, do plant cells contain a lot of water?

A

Yes

65
Q

What happens when water moves into a plant cell by osmosis?

A

The plant cells contents push OUTWARDS against the cellulose cell wall

The cellulose cell wall is strong enough to resist the outward pressure of the cell contents

This prevents the cell from bursting

66
Q

What is it called when a plant cell is full of water?

A

Turgid

67
Q

What gives plants an upright structure?

A

Turgid plant cells

68
Q

Who loves you more?

A

Me (you can delete after u see this so it doesnt ruin ur flashcard 😭)

69
Q

what is the scientific name for the molecules found in fats and oils?

A

lipids

70
Q

lipids are a major source of ___ in the human body

A

energy

71
Q

where do we find lipids?

A

in oils (olive oil) and solid fats (butter)

⬆️ both of these are rich sources of energy

72
Q

as well as lipids being a source of energy, lipids are also used to ….

A

store energy

eg: adipose tissue in humans

73
Q

where is adipose tissue found ?

A

under skin and around internal organs like the kidneys

74
Q

explain adipose tissue

A

adipose tissue acts as an energy store and it also insulates the body reducing heat loss to the environment

75
Q

lipids are used as w…..

A

waterproofing

for example: the oils that coat the feathers of aquatic birds

76
Q

lipids are a major part of the structure of what?

A

membranes

eg the membranes that surround cells and mitochondria

77
Q

what are the 2 main categories of lipids

A

TRIGLYCERIDES and PHOSPHOLIPIDS

78
Q

what molecules do triglycerides contain ?

A

1 molecule of glycerol bonded to 3 molecules of fatty acids

79
Q

what are the 2 parts of fatty acid molecules

A

at the end of the fatty acid we have a carboxylic group

the rest of the chain consists of a long chain of carbon atoms bonded to hydrogen

80
Q

what do saturated fatty acids contain?

A

contain only single covalent bonds between the carbon atoms

81
Q

what do unsaturated fatty acids contain

A

they contain at least 1 double covalent bond between the carbon atoms

82
Q

what do monounsaturated contain?

A

only 1 double covalent bond in the carbon chain

83
Q

what do polyunsaturated fatty acids contain ?

A

more than one double covalent bond in the carbon chain

84
Q

imagine the structure of glycerol

A

…

85
Q

how many hydroxyl groups do glycerol molecules have?

A

3 hydroxyl groups

86
Q

glycerol and fatty acid molecules can react together to form a bond between eachother called a ___

and what is this process called ?

and 3 molecules of water are formed so what reaction is this?

A

ester bond

and this process is called esterification

condensation reaction

87
Q

describe the process where fatty acids and glycerol are released in the digestion system .

how is this a hydrolysis reaction ?

A

in the digestion system lipase enzymes break ester bonds releasing fatty acid and glycerol molecules

⬆️ this reaction requires 3 water molecules and therefore it is a a hydrolysis reaction

88
Q

are triglycerides polar or non polar

A

they are NON POLAR so they do not dissolve in water (hydrophobic) which explains why triglycerides are used for waterproofing

89
Q

because triglycerides contain a large amount of carbon and hydrogen atoms ….

A

a lot of energy can be released from them

90
Q

what does non-polar mean?

A

doesn’t dissolve in water (hydrophobic)

molecule is uncharged

91
Q

how is the structure of PHOSPHOLIPIDS different to the structure of TRIGLYCERIDES?

A

phospholipids have 1 glycerol molecule bonded to 2 fatty acid molecules. and the glycerol molecule is also bonded to PHOSPHATE

92
Q

what charge is the phosphate in a molecule of PHOSPHOLIPID

and is this part of the phospholipid (phosphate) hydrophilic or hydrophobic

A

the phosphate is negatively charged

in other words this part of the molecule is POLAR

because of this the phosphate is HYDROPHILIC (attracts water molecules/dissolves in water)

93
Q

what is a simpler way to represent a phospholipid molecule?

A

a circle (the polar hydrophilic head) and 2 tails (non polar hydrophobic tails)

  • the head group is the polar hydrophilic part of the molecule (phosphate)
  • the tails represent the 2 fatty acid molecules which are non polar and hydrophobic
94
Q

do phospholipids contain both a hydrophilic and hydrophobic region ?

A

yes

95
Q

how do phospholipids act in water ?

and what do scientists call this structure ?

A

in water, phospholipids molecules position themselves so that the hydrophilic head groups can interact with water molecules while the hydrophobic tails cluster together, well away from water molecules

⬆️ scientist call this structure a PHOSPHOLIPID BILAYER

96
Q

why is the phospholipid bilayer useful in cells?

A

the property is extremely useful as it allows phospholipids to form the membranes that we find around cells and within cells

97
Q

what are all proteins formed from?

A

amino acids

98
Q

how many amino acids are there?

A

20

99
Q

what are the 3 parts of an amino acid?

A

amine group, carboxyl group and the R (variable) group

100
Q

what is the “R” group in an amino acid?

A

it is a variable .

the R group is different for each of the 20 amino acids

101
Q

Looking at the general formula of an amino acid, what elements do they contain?

what is the element that some amino acids contain ?

A

Carbon, Hydrogen, Oxygen and Nitrogen

Sulfur

102
Q

how are dipeptides formed ?

where does this reaction take place?

how can this reaction be catalysed?

A

by the condensation of 2 amino acids and they are bonded by a peptide bond. and since it’s a condensation reaction a molecule of water is formed too

in the ribosomes

by a SPECIFIC enzyme

103
Q

how do we make a polypeptide?

how many molecule of water are formed?

A

if we join 3 or more amino acids, then we make a polypeptide

we make a molecule of water for each peptide bond we make

104
Q

how do we break a peptide bond?

A

to break a peptide bond, we need a molecule of water (hydrolysis reaction) and this reaction is carried out by the protease enzymes in the digestive system

or this hydrolysis reaction can take place by heating proteins with acid

105
Q

what is the difference between an polypeptide and a protein

A

in order to be classed a protein, a polypeptide has to fold into a complex 3-dimensional structure

once it is folded into the correct shape, it can then carry out its function (for example a hormone or enzyme)

at this point we would refer to it as a PROTEIN MOLECULE

106
Q

can proteins consist of several different polypeptides?

and can proteins contain other molecules helping them to carry out their function?

A

yes many proteins consist of many different polypeptides forming a large and complex molecule

yes proteins often contain other molecules helping them to carry out their function (haemoglobin)

107
Q

how many levels are there in protein structure ?

A

4

108
Q

what is the primary structure of a protein?

A

the primary structure is simply the specific order of amino acids in a polypeptide

109
Q

why is the primary structure of a protein important?

A

because the primary structure determines the final 3 dimensional shape of the protein molecule

110
Q

is the shape of a protein important for its function?

explain

A

yes

even changing a single amino acid in the primary structure can change the final shape of the protein

and this can prevent the protein from carrying out its function effectively

111
Q

how is the primary structure of a polypeptide determined?

A

it is determined by the DNA sequence of the gene that encodes for that polypeptide

112
Q

how do we form hydrogen bonds in a polypeptide chain?

what do hydrogen bonds cause polypeptides to do

A

looking at the polypeptide chain we can see that we have C=O groups and N-H groups.

the oxygen atoms have a small negative charge and the hydrogen atoms have a small positive charge

this means these charges can attract each other to form hydrogen bonds between amino acids all along the polypeptide chain

these hydrogen bonds cause the polypeptide to twist and fold into shapes and scientists call these twists and folds SECONDARY STRUCTURE

113
Q

what is the most common secondary structure

and how is it formed

A

alpha-helix

the polypeptide is twisted into a helical shape held in place by hydrogen bonds

114
Q

what is another secondary structure except alpha-helix?

and explain how it’s formed

A

beta pleated sheet

polypeptide folds into a flatter, sheet like structure again with hydrogen bonds between the amino acids holding it in shape

115
Q

do many proteins have regions with alpha-helixes and beta pleated sheets ?

A

yes

the type of secondary structure formed depends on the primary structure in the region

certain amino acids are found in alpha helix regions and certain amino acids are found in beta pleated sheets regions

116
Q

what does a molecule of water consist of?

what are the bonds between the oxygen and hydrogen atoms?

A

1 atom of oxygen chemically bonded to 2 atoms of hydrogen

covalent bonds

117
Q

what are the charges in a water molecule?

because of these charges, what type of molecule is it?

what do the opposite charges mean?

A

the hydrogen atoms have a small positive charge and the oxygen atoms have a small negative charge

a polar molecule

opposite charges mean that water molecules are attracted to eachother and these forces out attraction are called HYDROGEN BONDS

118
Q

are hydrogen bonds strong or weak?

A

weak

119
Q

does a small volume of water have little or many hydrogen bonds

A

many

120
Q

does water have a very high specific heat capacity ?

what happens when we heat water?

and because of this what does water act as?

this is an ideal habitat for which organism and why?

A

yes (we have to put in or take out a lot of energy to the change the temperature of water

when we heat water, the heat energy is used to break/weaken the hydrogen bonds rather than increase the kinetic energy of the water molecules

because of this water acts a buffer against rapid temperature changes, in other words the temperature of water tends not to change rapidly

this is ideal for aquatic organisms as they will not be able to function if the temperature of water changed rapidly in hot/cold days

121
Q

which is less dense : liquid water or ice?

A

ice (ice floats)

122
Q

ice is a HABITAT for a number of organisms what else does it do?

A

as well as acting as a habitat, ice also insulates the water below and prevents it from freezing and this means organisms can continue living

123
Q

water has a very high latent heat of…

and what does allow organisms to do?

A

vapourisation (takes a large amount of heat energy to evaporate water)

to cool themselves without losing a great deal of water (sweating)

124
Q

is one role of water as a solvent?

A

yes, water is an excellent solvent (lots of substances can dissolve in water)

125
Q

do eukaryotic and prokaryotic cells contain a large amount of dissolved substances ?

like what ?

A

yes such as the chemicals in metabolic reactions such as respiration as well as the enzymes needed to carry out these reaction

126
Q

what do bodies of water such as ponds and rivers contain?

A

dissolved oxygen and this is used by organisms in the water to carry out respiration

this makes water an excellent habitat for organisms

127
Q

because water is a good solvent it is used to…

such as …

A

transport substances

for example blood plasma is the liquid part of blood and contains dissolved substances such as co2, ions (sodium ions) and chemicals such as glucose and amino acids

128
Q

what is used to transport substances in the xylem vessels of plants ?

A

water

water in the xylem contains mineral ions such as the magnesium ion, magnesium ions pass through the plant roots from the soil. they are transported in the xylem from the roots to the leaves.
once in the leaves magnesium ions are used to make chlorophyll for photosynthesis

129
Q

water molecules tend to stick together and scientists call this.?

and why does this happen

A

cohesion

this happens due to the hydrogen bonds between water molecules

130
Q

what does cohesion allow in xylem tubes?

what else does cohesion cause? and why is it useful?

A

it allows long columns of water to travel in the xylem tubes and this makes water ideal as a transport medium in plants

SURFACE TENSION when water meets air,

it allows the surface of water to act as a habitat

131
Q

is water important in metabolic reactions ?
how?

A

water is reactant and product in many metabolic reactions such as

hydrolysis
photosynthesis
respiration
condensation reactions

132
Q

how can we hydrolyse disaccharides

A

by heating with acid or by an enzyme

133
Q

how can lipids be hydrolysed into fatty acids and glycerol (3 ways)

A

1) heating with acid
2) heating with alkali
3)using the enzyme lipase at optimum temperature and pH

134
Q

how can we hydrolyse proteins

A

heating w acid
by using protease enzymes

135
Q

what are the products of enzyme reaction near to

A

they are near to specific carrier proteins used to absorb them

Biology A-Level ♡ (9 decks)

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