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1. Biology A-level > 1. 1. Chemical elements are joined together to form biological compounds > Flashcards

1. 1. Chemical elements are joined together to form biological compounds Flashcards

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1
Q

carbs contain 3 elements

A

carbon

hydrogen

oxygen

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2
Q

monosaccharide

A

The simplest sugars, consist of a single monomer

General formula (CH2O)n

All carbohydrates contain the elements carbon, hydrogen and oxygen.

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3
Q

two isomers of glucose (a monosaccharide)
1. alpha

A
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4
Q

two isomers of glucose (a monosaccharide)
2. beta

A
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5
Q

difference of hydroxyl group alpha vs beta glucose

A
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6
Q

difference of hydroxyl group alpha vs beta glucose

A

The only difference in the alpha (α) and beta (β) ring isomers is the position of the OH group on carbon atom 1.

To remember which ring form is which, use ABBA:

Alpha OH Below – Beta OH Above

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7
Q

glucose

A

Glucose is a polar molecule – hydrogen bonds can form between the Oδ- on C2 of one glucose molecule and C3δ+ of the next glucose molecule in the chain. As a result, the amylose molecule coils up to form a helix.

This makes starch a compact molecule that is less soluble in water - an ideal properties for storage of glucose.

Also, because starch is insoluble it does not affect the water potential of the cell in which it is stored. This means that starch is osmotically stable.

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8
Q

alpha glucose

A

function
- energy storage (found in starch)
- energy source (easily broken down in cellular respiration, providing ATP)

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9
Q

beta glucose

A

function
-structural component in plants, found in cellulose, beta links create long, straight chains which are rigid
-fiber in diet, in cellulose, aids digestion

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10
Q

EDITTTT glucose in nature

A

36% α glucose
-more reactive as more hydroxyl groups on bottom
-delta charge on O and H
-charge is unevely distributed on molecule

64% β glucose

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11
Q

classification of monosaccharides

A

3 carbons Triose

5 carbons, pentose eg ribose, deoxyribose

6 carbons, hexose eg glucose

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12
Q

eg of monosaccharide

A

glucose

fructose

galactose

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13
Q

structural isomers

A

Molecules with the same molecular formula but with different arrangements of their atoms are called structural isomers.

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14
Q

fructose vs glucose vs galactose

A
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15
Q

all types of carbs diagram

A
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16
Q

glycosidic bonds

A

type of covalent bond, forms between two monosaccharides,

formed by condensation

two types
-Alpha Glycosidic Bond
- Beta Glycosidic Bond

roles
-allow molecules to store energy efficiently
-create rigid structures, essential for plant cell walls
-breakdown via hydrolysis releases monosaccharides, used for energy production in cellular respiration

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17
Q

naming glycosidic bonds

A
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18
Q

glucose

fructose

galactose

A

isomers

C6H12O6

same molecular formula

different structural formula

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19
Q

disaccharide

A

class of carbohydrates made up of two monosaccharide subunits

general molecular formula is C 12 H 22 O 11 .

formed by a condensation reaction (i.e., loss of water)

The bond that holds them together is called a glycosidic bond.

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20
Q

hydrolysis reaction.

A

The glycosidic bond can be broken by the chemical insertion of water – this reforms the OH groups and is called a hydrolysis reaction.

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21
Q

eg of disaccharide

A

sucrose = α glucose + fructose

maltose = α glucose + α glucose

lactose = α or β glucose + galactose

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22
Q

condensastion reaction of two monosaccharides

A
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23
Q

condensation reaction of two molecules of alpha glucose

A
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24
Q

polysaccharide

A

Polysaccharides are complex carbohydrates. They are large molecules, or polymers, consisting of chains of monosaccharides linked together by glycosidic bonds.

formed by condensation reactions, to form chains

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25
Q

2 functions of polysaccharides

A

Some polysaccharides have metabolic functions and others have structural functions in cells and organisms.

metabolic eg starch (plants) and glycogen (animals) made of a-glucose

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26
Q

function of polysaccharides

A

energy storage (starch in plants, glycogen in animals)

structural (cellulose) (chitin)n

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27
Q

oligosaccharides

A

short chain polysaccharides

8-10 monosacharide residues

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28
Q

eg of polysaccharide

A

Starch

glycogen

cellulose

heparin

peptidoglycan

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29
Q

starch

A

consists of polymers:

amylose
-polymer of α glucose, linked by 1,4 glycosidic bonds
-unbranched helical molecule
-most -OH groups are capable of forming H bonds with H2O in aqueous environments
-forms coiled molecules

amylopectin
- the bonds between glucose molecules within a branch are α-1,4 glycosidic bonds but at branching points, the bonds are α-1,6 glycosidic bonds.
-gives more ends to hydrolyse, enables faster metabolic rate

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30
Q

glycogen

A

has side branches

glycosidic bonds forming between OH groups on C1 and C4 but also C1 and C6. Glycogen can form granules in cells and act as a carbohydrate/energy store.

supports higher metabolic rate of animals (as more ends avaliable to hydrolyse)

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31
Q

branches in amylopectin and glycogen

A

make them better for the release of glucose. This is because there are more ‘ends’ where glycosidic bonds can be hydrolysed and glucose released, which can be used in respiration to produce ATP.

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32
Q

cellulose

A

ellulose is a complex carbohydrate made of a polymer of β-glucose molecules. The β-1,4 glycosidic linkages result in the −CH2OH groups being on opposite sides of the chain of adjacent glucose molecules.

Within a cellulose chain, adjacent glucose molecules are rotated 180° relative to each other. This means that OH groups are aligned and a water molecule can be removed to form a glycosidic bond.

Therefore, hydrogen bonds do not form between glucose molecules within the same chain, but between glucose molecules in different chains.

The hydrogen bonds form cross-linkages which hold the chains together. This makes cellulose form into long threads called microfibrils.

Cellulose is completely insoluble and the microfibrils are laid down in overlapping layers in plant cell walls.

most abundant structural polysaccharide in plant cell walls

distribution of hydroxyl groups, means cross links between cellulose molecules can occur, procides support and strength

hydrogen bonds form between adjacent -OH groups on cellulose molecules

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33
Q

cellulose is what type of polysaccharide

A

Cellulose is called a structural polysaccharide. It is very difficult to digest because of the very high numbers of hydrogen bonds between the chains of beta glucose. This also gives cellulose very high tensile strength; it is difficult to break when stretched. This means that cells with cellulose in their cell wall are more resistant to osmotic lysis (they are not likely to burst because cellulose stops too much water entering the cell).

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34
Q

chitin

A

amino acid side chains

used for exoskeletons

Chitin is found in the cell walls of fungi and in the exoskeletons of insects. It is not a true polysaccharide as it contains the element nitrogen – it is called a heteropolysaccharide.

It has a similar structure and function as cellulose but because it contains side groups containing N, more hydrogen bonds can form. Chitin microfibrils, therefore, have greater tensile strength than those of cellulose.

The diagram shows two of the monosaccharides (N-acetyl glucosamine) found in chitin joined together by a β-glycosidic bond.

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35
Q

why is cellulose less reactive than other polysaccharides

A

due to hydrigen bonds and cross linking between chains

hydroxyl groups on adjacent cellulose molecules form hydrogen bonds

strong cross links between cellulose fibers makes structure rigid

36
Q

lignin

A

polymer of sugar and amino acids

deposited between cellulose molecules to lignify tissue

37
Q

macromolecules

A

giant molecules

some are polymers

38
Q

labelled lipid

triglyceride

A

three condensation reactions, forming ester bonds

Triglycerides have key roles in respiration and energy storage due to its insolubility and high carbon to hydrogen ratio.

39
Q

lipids

A

Lipids are organic compounds made of carbon, hydrogen and oxygen. All lipids contain a high proportion of CH2 groups. Phospholipids also contain phosphorus.

All lipids have a low solubility in water but a high solubility in organic solvents (e.g., ethanol, tetrachloromethane).

long term store of energy (high energy density 9kcal per gram, hydrophobic, stored compactly)

not polymers

made of glycerol and fatty acids

too small to be macromolecules

40
Q

Triglycerides

A

molecules that form fats or oils depending on the size of the molecule. The more carbon atoms, the higher the melting point because the intermolecular forces are stronger and more energy is required to overcome them.

Each triglyceride is made from glycerol combined with three fatty acids through a condensation reaction with the release of three molecules of water.

The fatty acids bind to the glycerol by means of ester bonds.

Triglycerides are broken down in a hydrolysis reaction with the chemical insertion of three molecules of water.

41
Q

The diagram shows how triglycerides are formed and are broken down.

A
42
Q

fatty acids diagram

A

R group can be saturated or unsaturated

43
Q

glycerol diagram

A
44
Q

condensation glycérol and fatty acids

A
45
Q

phospholipid

A

hydrophillic head - allows exchange of substances between cell and environment

hydrophobic tail

fat and water soluble, can form lipid bilayer, crucial for role in cell membranes

46
Q

function of a phospholipid

A

The different properties of the phosphate heads and the fatty acids affect how easily different molecules can cross a cell membrane (see Unit 1.3: Cell membranes and transport).

If phospholipids are poured into water, the molecules arrange themselves in a single layer. But in cell membranes, phospholipids form a bilayer.

The hydrophilic phosphate groups are attracted to water molecules in the cytoplasm and outside the cell.

The hydrophobic tails are repelled by water molecules and ‘hide’ from water in the cytoplasm and outside the cell.

47
Q

what affects fluidity of membrane

A

The different properties of the phosphate heads and the fatty acids affect how easily different molecules can cross a cell membrane (see Unit 1.3: Cell membranes and transport).

If phospholipids are poured into water, the molecules arrange themselves in a single layer. But in cell membranes, phospholipids form a bilayer.

The hydrophilic phosphate groups are attracted to water molecules in the cytoplasm and outside the cell.

The hydrophobic tails are repelled by water molecules and ‘hide’ from water in the cytoplasm and outside the cell.

48
Q

difference between phospholipid and triglyceride

A

triglyceride - 3 fatty acids, and no phosphate

phospholipid - 2 fatty acids and a phosphate group

49
Q

elements in aminoacids

A

N
C
H
O

50
Q

amino acids

A

essential - obtained in diet

non-essential - synthesised

51
Q

zwitterion

A
52
Q

condensation réaction

A
53
Q

condensation réaction

A
54
Q

hydrogen bonding

A

weak

55
Q

ionic bonding

A

between R groups

56
Q

disulphide bridge

A

amino acids oxidise to form disulphide bridge

57
Q

hydrophobic interactions

A

non-covalent bonds

between water and hydrophobes

58
Q

primary structure of proteins

A

sequence of amino acids determined by DNA coding

59
Q

secondary structure of proteins

A

Secondary structure - interactions with peptide backbone forms beta pleated sheets and alpha helices

Beta pleated sheets are parallel or antiparallel depending on direction of polypeptide chain
Alpha helices - have a helical structure, formed by hydrogen bonds between layers of the helix, creating a spiral shape (hydrogen bonds stabilise the helical structure)
Hydrogen bonds are crucial for the formations of secondary proteins

60
Q

tertiary structure of proteins

A

Tertiary structure - influenced by interactions of the side chains, inc hydrophobic and hydrogen bonds

61
Q

quarternary structure of proteins

A

Quaternary structure - involves arrangement of multiple polypeptide chains

62
Q

denaturation of proteins

A

breaking down of weak bonds

covalend bonds between amino acids

hydrogen bonds

active site changes shape, interactions can’t occur

BUT peptide bonds not broken

secondary and tertiary structures not destoryed
primary structure destroyed - proteins can refold

63
Q

renaturation of proteins

A

hydroken bonds reformed

if primary structure disrupted, can’t occur

64
Q

factors affecting denaturation

A

change in pH

increase in temp

heavy metals

ionising radiation

65
Q

carbs and triglycerides

A

long term energy store

66
Q

Adenine Triphosphate

A

ATP captures chemical energy obtained from the breakdown of food molecules and releases it to fuel other cellular process

67
Q

nucleotide of ATP

A
68
Q

hydrolysis of ATP

A

breaks last covalent bond between phosphate groups

releases chemical energy

energy used for: active transport, muscle contraction, formation of large molecules

69
Q

uses of ATP

A

muscle contraction
active transport
DNA replication
cell divison

70
Q

nucleotide

A
71
Q

nucleotide

A
72
Q

polynucleotide

A
73
Q

While ions are all charged, molecules can have:

A

no charge – non-polar

or a slight charge – polar.

74
Q

ions, non-polar and polar behaviour

A

Ions and polar compounds attract oppositely charged particles and play important roles in the structure of molecules.

Non-polar compounds do not dissolve in water but will dissolve in lipids (fats/oils) – they are said to be lipid-soluble.

75
Q

ions

A
76
Q

Organic compounds

A

Organic compounds always contain the elements carbon and hydrogen, and many contain oxygen and/or nitrogen.

77
Q

Inorganic compounds

A

also contain carbon, hydrogen, oxygen and nitrogen, but can be made without the involvement of living organisms.

78
Q

water properties

A

Water is a polar molecule – it has no overall charge, but the hydrogen atoms have a partial positive charge and the oxygen atoms have a partial negative charge.

A water molecule is usually drawn using solid lines for the bonds between the hydrogen and oxygen atoms.

The partial charges are shown as δ+, delta positive and δ−, delta negative.

Because of their polarity, water molecules attract each other by forming hydrogen bonds. This is usually represented by a series of vertical lines as shown in the diagram.

79
Q

water properties 2

A
80
Q

water diagram

A
81
Q

why is water known as a universal solvent

A

Because of their polarity, water molecules are attracted to other water molecules and charged particles. This helps charged particles dissolve in water.

For this reason, water is sometimes referred to as the universal solvent as a large number of substances can dissolve in water.

82
Q

letter R

A

The carbon chain in fatty acids is often represented by the letter R, a variable group containing a chain of between 4 and 24 carbon atoms.

83
Q

state of lipid at room temp

A

Lipids with long hydrocarbon chain fatty acids are more likely to be solid at room temperature – these are fats.

Those with short hydrocarbon chains form oils which are liquid at room temperature.

This is because there are weak forces of attraction between the fatty acid chains – the longer the carbon chain, the greater the force of attraction, so the higher the melting point. Some examples of different fatty acids and their melting points are shown below.

84
Q

Functions of triglycerides

A

Triglycerides are efficient energy storage molecules. They are more efficient than carbohydrates:

1 g fat provides about 38 kJ energy
1 g carbohydrate provides about 17 kJ energy.
Because of this, fats and oils are the preferred energy storage molecule in animals and many seeds (lipids store twice as much energy per gram than carbohydrates).

Triglycerides are also good thermal insulators and provide mechanical protection for delicate organs.

Because fats are less dense than water, they are used to provide buoyancy for many aquatic animals.

Some animals spread oil onto their fur or feathers because this makes them waterproof. This is because fats are hydrophobic and repel water.

85
Q

Saturated fatty acids

A

They can also be saturated, with only single bonds between carbon atoms. They contain the maximum number of hydrogen atoms.

Lipids containing only saturated fatty acids generally form fats at room temperature. This is because the fatty acid tails are straight and can pack closely together. Stronger forces of attraction can form which means more energy is needed to break the bonds and melt the fat – the melting point is higher.

86
Q

Unsaturated fatty acids

A

Fatty acids can also be unsaturated, with one or more double bonds between carbon atoms.

They do not contain the maximum number of hydrogen atoms. For each carbon-carbon double bond, the fatty acid will contain two fewer hydrogen atoms.

Lipids containing unsaturated fatty acids are usually oils at room temperature.

The double bonds make the fatty acid tails less straight (they kink) so they cannot pack as closely together.

The forces of attraction between the fatty acids are weaker, so less energy is needed to break the bonds and melt the fat – they have a lower melting point.

87
Q
A

1. Biology A-level (9 decks)

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