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A level Biology > Biological Molecules > Flashcards

Biological Molecules Flashcards

1
Q

What elements are the most abundant in living organisms?

A

Carbon (C) Hydrogen (H) Oxygen (O) Nitrogen (N) Phosphorus (P) and Sulfur (S)

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2
Q

When does a covalent bond occur?

A

When two or more atoms share a pair of electrons. The electrons are unpaired and present in the outer shell orbitals of the atoms.

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3
Q

How many bonds can carbon form with other atoms?

A

4 e.g. methane

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4
Q

How many bonds can nitrogen form with other atoms?

A

3 e.g. nitrogen

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5
Q

How many bonds can oxygen form with other atoms?

A

2 e.g. oxygen

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6
Q

How many bonds can hydrogen form with other atoms?

A

1 e.g. water

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7
Q

What is life often referred to as?

A

‘Carbon-based’ as most biological molecules have the backbone of carbon.

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8
Q

What is an ion?

A

An electrically charged particle formed from the loss or gain of one or more electron from an atom ot group of atoms.

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9
Q

What are ions in solution known as?

A

Electrolytes

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10
Q

What are calcium ions used for?

A

Nerve impulse transmissions, and muscle contraction.

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11
Q

What are sodium ions use for?

A

Nerve impulse transmissions and kidney function.

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12
Q

What are potassium ions used for?

A

Nerve impulse transmissions and stomatal opening.

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13
Q

What are hydrogen ions used for?

A

Catalyst of reactions and pH deteremination.

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14
Q

What are ammonium ions used for?

A

Production of nitrate ions by bacteria.

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15
Q

What are nitrate ions used for?

A

Nitrogen supply to plants for amino acid and protein formation.

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16
Q

What are hydrogen carbonate ions used for?

A

Maintain blood pH.

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17
Q

What are chloride ions used for?

A

Balance positive charge of sodium and potassium ions in cells.

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18
Q

What are phosphate ions used for?

A

Plasma membrane formation, nucleic acid and ATP formation and bone formation.

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19
Q

What are hydroxide ions used for?

A

Catalyst of reactions and pH determination.

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20
Q

What makes up carbohydrates?

A

Carbon, hydrogen and oxygen. Usually in the ratio Cx(H2O)x.

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21
Q

What makes up lipids?

A

Carbon, hydrogen and oxygen.

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22
Q

What are proteins made of?

A

Carbon, hydrogen, oxygen, nitrogen and sulfur.

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23
Q

What are nucleic acids made of?

A

Carbon, hydrogen, oxygen, nitrogen and phosphorous.

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24
Q

What are polymers?

A

Long-chain molecules made up by linking up sub-units called monomers, in a repeating pattern.

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25
Q

What are the monomers in carbohydrates called?

A

Saccharides

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26
Q

What are the monomers in proteins called?

A

Amino acids

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27
Q

Define the term ‘polar’

A

Molecules have regions of negativity and positivity. A molecule is polar if one atom in the covalent bond attracts more electrons, so is said to be more electronegative.

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28
Q

Give an example of elements that are polar

A

Oxygen and hydrogen. Oxygen is more electronegative than hydrogen, so attracts the electrons in the pair more strongly.

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29
Q

What are the O-H bonds known as? Give an example of a molecules with this

A

Hydroxyl group. Water has 2 of these groups, so is polar.

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30
Q

What are the characteristics of hydrogen bonds with water?

A

Hydrogen are weak interactions. Due to the high number they occur in, hydrogen bonds give water a high boiling point, as lots of energy is needed to break the many bonds.

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31
Q

Why is water liquid at room temperature?

A

Due to the hydrogen bonding. It takes a lot of energy to increase the temperature of water and convert it into a gaseous state.

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32
Q

What is different about the formation of ice to water?

A

Ice is less dense than water. Most substances are more dense in a solid form. The hydrogen bonds in the water molecule fix at lower temperatures, causing the polar molecules to move further apart than in the liquid state to form a lattice structure. This produces a giant covalent structure, which oxygen atoms at the centre of a tetrahedral structure.

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33
Q

What does ice being less dense mean?

A

Ice can float.

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34
Q

What other properties does water have?

A

Water is cohesive, so molecules are attracted to each other.
Water is adhesive, so molecules are attracted to other molecules strongly.
Water being so cohesive, allows surface tension to happen.

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35
Q

How does being a solvent make water critical to life?

A

Many solutes in organism are dissolved in water. The cytosol of prokaryotes and eukaryotes is mainly water. Many solutes are also polar molecules, amino acids, proteins and nucleic acids. Water is a medium for these reactions to take place in and helps transport dissolved compounds in and out of cells.

36
Q

How is water an effective transport medium?

A

Cohesion between water molecules means that water transported through the body is able to stick together. Adhesion allows other substances to be transported through the body, by sticking to water.

37
Q

What is capillary action?

A

The effects of adhesion and cohesion result in water exhibiting capillary action. This is the process by which water can move up a narrow tube against the force of gravity.

38
Q

How does water act as a coolant?

A

Due to large amounts of energy being required to overcome hydrogen bonding. This helps to buffer temperature changes during chemical reactions. This maintains a constant environmental temperature, which helps enzymes to maintain chemical reactions, and work at their optimum in the required temperature range.

39
Q

What are the benefits of ice being able to float?

A

An insulating layer forms, because it forms on the top of water, due to being less dense. Aquatic organism can therefore survive beneath the ice.

40
Q

What is the general formula of carbohydrates?

A

Cx(H2O)y

41
Q

What is a single sugar unit known as?

A

Monosaccharide e.g. glucose, fructose and ribose.

42
Q

What are two bonded monosaccharides known as?

A

Disaccharide e.g. lactose and sucrose.

43
Q

What are multiple monosaccharides bonded known as?

A

Polysaccharide e.g. glycogen, cellulose and starch.

44
Q

What is the formula of glucose?

A

General formula of C6H1206, so is a hexose monosaccharide.

45
Q

How are carbons numbered in diagrams?

A

Clockwise, with the carbon on the right of the oxygen.

46
Q

What are the two structural variations of glucose?

A

Alpha and beta. The -OH group is on different sides of carbon 1.

47
Q

Which side is the -OH group on for alpha and beta

A 
Alpha = bottom
Beta = top
48
Q

Are glucose molecules soluble?

A

Yes, because of the hydrogen bonds that form between the -OH groups and water. This means that glucose can be dissolved in the cytosol of cells.

49
Q

What happens in condensation reactions?

A

A water molecule is removed. With glucose, maltose is formed (disaccharide). A bond forms between carbon 1 and carbon 4 on the separate glucose monomers.

50
Q

What is the bond called, which is formed in a condensation recation?

A

1,4-glycosicdic bond, with an oxygen molecule in the centre.

51
Q

What sugar is formed from (alpha) glucose and fructose?

A

Sucrose

52
Q

What sugar is formed from galactose and (beta) glucose?

A

Lactose

53
Q

What are pentose monosaccharides?

A

Sugars than contain 5 carbon atoms. Ribose is the sugar in RNA nucleotides and deoxyribose in DNA nucleotides.

54
Q

What is starch?

A

Many alpha glucose molecules bonded by glyosidic bonds to form the polysaccharide.

55
Q

What are the two types of starch?

A

Amylose and amylopectin.

56
Q

How is amylose formed?

A

Alpha glucose molecules bonded by only 1,4 -glycosidic bonds. The chain forms a helix, stabilised by hydrogen bonding.

57
Q

How does the structure of amylose affect its function?

A

More compact and less soluble than the glucose molecules used to make it. Unbranched within the -OH groups. Being more compact, more can be stored. There are only 2 accessible ends as a result of the helix shape, for amylase to bind.

58
Q

How is amylopectin formed?

A

Alpha 1,4-glycosidic bonds but with 1,6-glycosidic bonds occurring every 25 glucose subunits.

59
Q

How does the structure of amylopectin affect its function?

A

The molecule is branched between chains so is more compact, and ideal for storage. More accessible ends for amylase to bind to.

60
Q

What is the difference between amylopectin and glycogen?

A

Found in animals and fungi, and stored in muscle and liver cells. Has even more branching than amylopectin, so has even more accessible ends. This make it ideal for high metabolic demands. Both are insoluble.

61
Q

How do carbohydrates make themselves more stable?

A

The aldehyde ring forms a pyranose ring.

62
Q

What is the opposite reaction to condensation?

A

Hydrolysis. Water is added, breaking the glycosidic bond, and forming monosaccharides.

63
Q

What is formed from 2 (alpha) glucose molecules?

A

Maltose

64
Q

Is amylose broken down slowly or quickly?

A

Slowly due to only 2 accessible ends for amylase to bind to.

65
Q

Is amylopectin broken down slowly or quickly?

A

Quickly, due to multiple accessible ends.

66
Q

How is cellulose formed?

A

(Beta) glucose molecules form a chain of 1,4 -glycosidic bonds, which are inverted (by 180) to allow the bonding. This an unbranched chain. Hydrogen bonds exist between the chain.

67
Q

How is the structure of cellulose suited to its role?

A

Resistant to enzyme hydrolysis, as water cannot enter. Cellulase is the only enzyme found in herbivores which cam digest the cell wall. The unbranched, fibrous structure gives mechanical strength.

68
Q

How are microfibrils formed?

A

Hydrogen bonding between cellulose molecules. these then join together to form macrofibrils. These macrofibrils combine to form cellulose fibres.

69
Q

What are cellulose fibres like?

A

Insoluble and strong to make cell walls. Hard to break down into monomers. Provides the fibre for a healthy digestive system.

70
Q

Name some reducing sugars

A

Glucose, galactose, fructose, maltose and lactose.

71
Q

Name non-reducing sugars

A

Sucrose

72
Q

Describe reducing sugars

A

Can donate electrons
Have a free ketone (CO) and aldehyde (CHO) group.
Functional groups allow these sugars to be reducing .

73
Q

Describe non-reducing sugars

A

Cannot donate electrons.

Glycosidic bonds from between the free aldehyde group of glucose and free ketone group of fructose.

74
Q

How can you test for a reducing sugar?

A

Use Benedict’s reagent. Made of copper(II) sulfate (Cu2+). If a reducing sugar is present, this reduces into copper oxide, as reducing sugars can donate an electron. A coloured precipitate forms as copper oxide is insoluble in water.

75
Q

How can you test for a non-reducing sugar?

A

With a Benedict’s test, there will be no colour change. To ensure that the solution is definitely a non-reducing sugar, add HCl to hydrolyse the glycosidic bond between glucose and fructose. Repeat the Benedict’s test, and a colour change should be observed, as the sugars have separated into monomer form.

76
Q

How can the concentration of glucose be measured?

A

A colorimeter is used to measure the absorbance, transmission or wavelength of light by a coloured solution. A colorimeter is calibrated by adding distilled water in a cuvette and using a red filter for the light. The solutions being tested are filtered to remove the filtrate. The absorbance is then measure by the colorimeter.

77
Q

How will solutions differ in colour when the filtrate (precipitate) is removed?

A

Colourless for a high glucose concentration. Blue for a low concentration of glucose.

78
Q

Which concentrations of glucose will absorb more light?

A

Low concentrations (more blue) because less light is able to pass through.

79
Q

What must be done for every calibration of the colorimeter?

A

The colorimeter must be reset to zero. This prevents results being inaccurate.

80
Q

Are lipids polar or non-polar?

A

Non-polar, because the electrons in the outer orbitals that form the bonds are more evenly distributed. There is no differences in electronegativity, so lipids are not soluble in water.

81
Q

What are lipids known as?

A

Macromolecules, because they do not form from repeating units or monomers.

82
Q

What is a triglyceride?

A

Combination of 1 glycerol molecule with 3 fatty acids.

83
Q

What is glycerol? What are fatty acids?

A

Glycerol = alcohol.

Fatty acids = carboxylic acids with a hydrocarbon chain.

84
Q

What bonds form between the fatty acids and glycerol?

A

Ester bonds. Water is removed. This is esterification (a type of condensation reaction). Hydrolysis is the action.

85
Q

What are saturated lipids?

A

The fatty acid chains have no double bonds between the carbon atoms. All the carbon atoms form the maximum number of bonds with hydrogen atoms.

86
Q

What are unsaturated lipids?

A

Double bonds exist between some of the carbon atoms. Just one double bond is a monounsaturated lipid. More than one double bond is a polyunsaturated lipid.

87
Q

What do the double bonds in a lipid do to the molecules?

A

Causes the lipid to bend, meaning the molecules cannot pack as closely. This makes the lipid liquid at room temperature, rather than solid without.

A level Biology (10 decks)

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