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A - Level Biology AQA > Topic 1 - Biological Molecules > Flashcards

Topic 1 - Biological Molecules Flashcards

1
Q

What are Monomers?

A

Monomers are small units which are the components for larger molecules

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2
Q

Give an example of a monomer

A

Monosaccharides such as glucose, amino acids and nucleotides

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3
Q

Define Hydrolysis

A

When water is added to break a chemical bond between two molecules.
It is the opposite of a condensation reaction

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3
Q

How are monomers joined?

A

By a chemical bond in a condensation reaction whereby a water molecule is eliminated

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4
Q

What are Carbohydrates?

A

Carbohydrates are molecules which consist only of carbon, hydrogen and oxygen and they are long chains of sugar units called saccharides

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5
Q

What is a single monomer called?

A

A monosaccharide

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6
Q

What are a pair of monomers called?

A

A disaccharide

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7
Q

What happens when many monosaccharides are combined?

A

The formation of a polysaccharide. These are all joined together with a glycosidic bond formed in a condensation reaction

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8
Q

What is glucose?

A

Glucose is a monosaccharide containing 6 carbon atoms in each molecule, and is the main substrate for respiration and therefore of great importance

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9
Q

What are the two isomers of glucose?

A

Alpha and beta glucose

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10
Q

Give a list of common monosaccharides

A

Glucose, galactose and fructose. They are typically sweet tasting and soluble

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11
Q

What is a disaccharide?

A

When two monosaccharides join together in a condensation reaction. In this process a molecule of water is produced

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12
Q

Give examples of some common disaccharides

A

Maltose, sucrose and lactose

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13
Q

How is maltose formed?

A

By condensation of two glucose molecules

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14
Q

How is sucrose formed?

A

By condensation of glucose & fructose

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15
Q

How is lactose formed?

A

By condensation of glucose & galactose

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16
Q

How are glycogen and starch formed?

A

By the condensation of alpha glucose

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17
Q

How is cellulose formed?

A

By the condensation of beta glucose

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18
Q

What is glycogen?

A

The main energy storage molecule in animals and is formed from many molecules of alpha glucose. It is a relatively large but compact molecule thus maximising the amount of energy it can store. Being insoluble means it cannot diffuse out of cells

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19
Q

What is starch?

A

Starch stores energy in plants and is a mixture of two polysaccharides called amylose and amylopectin

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20
Q

What is amylose?

A

Amylose is an unbranched chain of glucose molecules joined by 1, 4 glycosidic bonds, and as a result amylose is coiled and thus a very compact molecule storing a lot of energy

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21
Q

What is amylopectin?

A

Amylopectin is branched and is made up of glucose molecules joined by 1, 4 and 1, 6 glycosidic bonds. Due to the presence of many side branches these can be acted upon simultaneously by many enzymes and thus broken down to release its energy

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22
Q

Give some of the key properties of starch

A

Its insoluble so will not affect cell water potential
It’s compact so a lot of energy can be stored in a small space and when it is hyrdrolysed the released alpha glucose can be transported easily

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23
Q

What is cellulose?

A

Component of cells walls in plants and is composed of long, unbranched chains of beta glucose which are joined by glycosidic bonds

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24
Q

What are lipids?

A

Lipids are biological molecules made of carbon, hydrogen and oxygen which are soluble in organic solvents such as alcohols. The main lipid types are TRIGLYCERIDES and PHOSPHOLIPIDS

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25
Q

What are triglycerides?

A

Triglycerides are lipids made up of one molecule of glycerol and three fatty acids joined by ester bonds formed in condensation reactions.

26
Q

How many different types of fatty acid are there?

A

Over 70 different types

27
Q

What are saturated lipids?

A

Found in animal fats - saturated lipids do not contain any carbon-carbon double bonds

28
Q

What are unsaturated lipids?

A

Can be found in plants - unsaturated lipids contain carbon-carbon double bonds. The presence of a double bond means that the molecule is able to bend. As a result unsaturated fats cannot pack together as tightly and are therefore liquid at room temperature

29
Q

What are the properties of triglycerides as a result of their structure?

A

High ratio of energy storing carbon-hydrogen bonds to carbon atoms and therefore they are an excellent energy store.
A low mass to energy ratio meaning that they are a good storage molecule, with a lot of energy being stored in a small volume. This is beneficial for animals as it is less mass to move around.

30
Q

What are phospholipids? (discuss structure)

A

In phospholipids, one of the fatty acids of a triglyceride is substituted by a phosphate-containing group.
Phosphate heads are hydrophilic (loves water) and the tails are hydrophobic (hates water) and as a result phospholipids form micelles when they are in contact with water. This molecule is therefore known as polar.

31
Q

Give the properties of phospholipids as a result of their structure

A

In an aqueous environment being polar means a bilayer can be formed

The hydrophilic heads of the phospholipids can be used to hold at the surface of the cell surface membrane

Their structure allows them to form glycolipids with carbohydrates which are important on the cell surface membrane for cell recognition

32
Q

Describe what proteins are

A

Amino acids are the monomers from which proteins are made. Amino acids contain an amino group (NH2), carboxylic acid group (-COOH) and a variable R group which is a carbon containing chain

33
Q

How many different types of Amino Acid are there?

A

20 different amino acids, each determined by their different R groups

34
Q

State how amino acids are joined

A

By peptide bonds formed in condensation reaction

35
Q

How is the structure of proteins determined?

A

By the order and number of amino acids, bonding present and the shape of the protein

36
Q

What is the primary structure of a protein?

A

The order and number of amino acids in a protein. This primary structure contains the initial sequence of amino acids and will therefore determine the proteins function in the end

37
Q

What is the secondary structure of a protein?

A

The shape that the chain of amino acids makes - either alpha helix or beta pleated sheet. The hydrogen in the -NH has a slight positive charge whilst the oxygen in the -C=O has a slight negative charge. As a result weak hydrogen bonds can form leading to alpha helices or beta pleated sheets

38
Q

What is the tertiary structure of a protein?

A

The 3D shape of the protein and is formed from further twisting and folding. a number of different bonds maintain the structure.

39
Q

Give the first stage of the Biuret Test

A

Place the sample to be tested in a test tube and add an equal volume of sodium hydroxide at room temperature

40
Q

Give the second stage of the Biuret Test

A

Add a few drops of very dilute (0.05%) copper sulphate solution and mix gently

41
Q

Give the third and final stage of the Biuret Test

A

A purple colouration indicates the presence of a peptide bond and hence a protein. A negative result would mean the solution remains blue

42
Q

What does both DNA and RNA do?

A

Carry information

43
Q

What does DNA do?

A

Holds genetic information

44
Q

What does RNA do?

A

Transfers genetic information from DNA to ribosomes for protein synthesis

45
Q

Give the components of a DNA nucleotide

A

Deoxyribose sugar
A phosphate group
One of the nitrogen containing organic bases: A, C, G, T

46
Q

Give the components of a RNA nucleotide

A

Ribose sugar
A phosphate group
One of the nitrogen containing organic bases: A, C, G, U

47
Q

How do nucleotides join together and what is formed?

A

Phosphodiester bonds formed in condensation reactions
The result is a dinucleotide, which join to form polynucleotides

48
Q

Where do Phosphodiester bonds form?

A

Between the deoxyribose sugar of one nucleotide and the phosphate group of another

49
Q

Give one reason why a DNA molecule is stable

A

The phosphodiester backbone protects the more chemically reactive nitrogen containing organic bases inside the double helix

50
Q

Give the first stage of DNA replication

A

An enzyme, DNA helicase, causes the two strands of DNA to separate breaking the hydrogen bonds between the complementary bases

51
Q

Give the second stage of DNA replication

A

One of the strands is used as the template and complementary base pairing occurs between the template strand and free nucleotides

52
Q

Give the third stage of DNA replication

A

Once activated nucleotides are bound the enzyme DNA polymerase joins them together by forming phosphodiester bonds
The result is that two identical strands of DNA are formed

53
Q

What is ATP?

A

Adenosine triphosphate is a nucleotide derivative and consists of ribose, adenine and three phosphate groups

54
Q

What happens when ATP is hydrolysed?

A

Energy is released to form ADP and a phosphate molecule

55
Q

Give two properties of ATP

A

It is an immediate source of energy and is more desirable to use than glucose as ATP can be broken down in a single step to release a manageable quantity of energy

ATP is used in a variety of different ways, these include, metabolic processes, movement, active transport, secretion and activation of molecules

56
Q

Why is water a metabolite?

A

To aid reactions such as condensation and hydrolysis which are used in forming and breaking of chemical bonds

57
Q

Why is water a solvent?

A

To allow gases to readily diffuse as well as enzymes and waste products e.g. ammonia and urea

58
Q

Why does water have a high specific heat capacity?

A

Because water molecules stick together with hydrogen bonds meaning that a lot of energy is required to break these bonds
This helps to minimise temperature fluctuations in living things therefore it acts as a buffer

59
Q

What are Inorganic ions?

A

Occur in solution in the cytoplasm and body fluid of organisms, some in high concentrations and others in very low concentrations

60
Q

Give the function of hydrogen ions

A

Determine the pH of substances such as blood - the higher the concentrations of hydrogen ions, the lower the pH

61
Q

Give the function of iron ions

A

A component of haemoglobin which is an oxygen carrying molecule in red blood cells

62
Q

Give the function of sodium ions

A

Involved in co-transport of glucose and amino acids

63
Q

Give the function of Phosphate ions

A

Component of DNA and ATP

A - Level Biology AQA (3 decks)

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