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Biology A Level Content > 2.1.2 Biological Molecules > Flashcards

2.1.2 Biological Molecules Flashcards

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1
Q

What is the importance of water?

A
  • Reactant in lots of chemical reactions (incl. hydrolysis)
  • Solvent as some substances dissolve in it
  • Transports substances like glucose and oxygen around plants and animals
  • Temperature control (thermoregulation)
  • Habitat for organisms to survive and reproduce in
  • Ice floats which forms an insulating layer
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2
Q

How is water polar?

A
  • It is polar due to the unevenly distributed charge
  • The oxygen end acts negative
  • The hydrogen end acts positive
  • Water is polar as it has both positive and negative charge
  • Overall, water is neutral
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3
Q

How do hydrogen bonds form?

A
  • Formed between a highly electro-negative atom of a polar molecule and a hydrogen
  • One hydrogen bond is weak but many bonds are strong
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4
Q

What is cohesion?

A
  • It produces a surface film on the water (e.g. allowing insects to walk on water surface)
  • Attraction between molecules of the same type due to polarity of the molecule
  • Results in surface tension
  • Water has a greater surface tension than most liquids because hydrogen bonds resist stretching or breaking of the surface
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5
Q

What is adhesion?

A
  • Attraction between two different substances
  • Water will make hydrogen bonds with other surfaces (e.g. transpiration process which plants remove water from soil)
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6
Q

What is the specific heat capacity of water?

A
  • Water has a high specific heat capacity
  • Water can absorb and release large amounts of heat energy with little change in the actual temperature due to the hydrogen bonds
  • Water prevents temperature fluctuations and provides a stable thermal environment
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7
Q

What is the latent heat of vaporisation of water?

A
  • Water has a high latent heat of vaporisation (amount of energy to convert 1kg of water from a liquid to a gas)
  • For water to evaporate, hydrogen bonds must be broken
  • As water evaporates, it removes a lot of heat with it (cooling effect)
  • This moderates Earth’s climate and prevents organisms from overheating
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8
Q

What is the density of water?

A
  • Ice is less dense as a solid than as a liquid
  • Liquid water has hydrogen bonds that are constantly being broken and reformed
  • Frozen water forms a crystal like lattice where molecules are set at fixed distances
  • Prevents water from freezing from the bottom up
  • Ice forms on surface first as freezing of water releases heat to the water below, creating insulation
  • Makes transition between season less abrupt
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9
Q

How is water a good solvent?

A
  • Water is polar so the positive and negative parts are attracted to the negative and positive parts of a solute
  • Water molecules cluster around the the charged parts of the solute molecules and keep them apart so they can dissolve
  • As water is a good solvent, molecules and ions can be transported around living things whilst dissolved and reactions can occur
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10
Q

What is a monomer and a polymer?

A

A monomer is a single unit and a polymer is when many of the same monomers have been joined together

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11
Q

What is a condensation reaction?

A

A condensation reaction occurs when 2 molecules are joined together with the removal of water

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12
Q

What is a hydrolysis reaction?

A

A hydrolysis reaction uses water to split molecules apart

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13
Q

What elements, monomers and polymers are in carbohydrates?

A

Elements - C, H and O
Monomers - monosaccharides (e.g. glucose)
Polymers - polysaccharides (e.g. starch)

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14
Q

What elements, monomers and polymers are in proteins?

A

Elements - C, H, O, N and S
Monomers - amino acids
Polymers - polypeptides and proteins

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15
Q

What elements, monomers and polymers are in nucleic acids?

A

Elements - C, H, O, N and P
Monomers - nucleotides
Polymers - DNA and RNA

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16
Q

What elements are in lipids?

A

C, H and O

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17
Q

What are the uses of carbohydrates?

A
  • Substrate for respiration
  • Energy store (starch and glycogen)
  • Recognition of molecules outside a cell
  • Structure (cellulose and chitin)
  • Hereditary information
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18
Q

What is the structure of an alpha and beta glucose ring?

A
  • In an alpha glucose ring, the H is on top of the OH on the first carbon
  • In a beta glucose ring, the H is below the OH on the first carbon
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19
Q

What is a disaccharide?

A

Formed from two monosaccharides joined by a glycosidic bond during a condensation reaction

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20
Q

What are the monomers in different disaccharides?

A

Glucose + glucose = maltose
Glucose + galactose = lactose
Glucose + fructose = sucrose

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21
Q

What is starch?

A
  • Energy store in plants
  • Excess glucose is stored as starch
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22
Q

What is the structure of starch?

A
  • Mixture of amylose and amylopectin
  • Amylose is a long unbranched chain of α glucose and has a compact coiled structure
  • It is good for storage and has 1-4 glycosidic bonds
  • Amylopectin is a long branched chain of α glucose
  • It has 1-4 and 1-6 glycosidic bonds
  • Glucose can be released quickly as it is easier for enzymes to get to branches (more easily hydrolysed)
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23
Q

What is glycogen?

A
  • Energy store in animals
  • Excess glucose is stored as glycogen
  • Found in the liver and muscles
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24
Q

What is the structure of glycogen?

A
  • It is a polysaccharide of α glucose
  • Lots of side branches for fast release of energy (easily hydrolysed)
  • 1-4 and 1-6 glycosidic bonds
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25
Q

What is cellulose?

A
  • Structural support for cells (in cell wall) in plants
26
Q

What is the structure of cellulose?

A
  • Long straight unbranched chains of β glucose
  • Hydrogen bonds between chains forming microfibrils
  • 1-4 glycosidic bonds
  • Each alternate glucose molecule rotates 180° to allow bonding of hydroxyl groups
  • Chains run parallel to each other (microfibrils) and are strengthened with cross-linkages (hydrogen bonds)
  • Stability makes it difficult to digest
27
Q

What are lipids?

A

Macromolecules (not polymers) as they are made of different components
Insoluble as they aren’t polar

28
Q

What are triglycerides?

A
  • Macromolecules
  • Contain one molecule of glycerol and three fatty acid tails
29
Q

What are the functions of triglycerides?

A
  • Energy source (secondary respiratory substrate)
  • Energy store
  • Insulation
  • Buoyancy
  • Protection
30
Q

What is the structure of glycerol?

A
  • Made of 3 carbon atoms
  • Each has a hydroxyl group attached to it on the right
  • Hydrogen atoms occupy remaining positions
31
Q

What is the structure of fatty acids?

A
  • Contains an acid group (COOH) attached to a hydrocarbon chain
32
Q

What are the types of fatty acids?

A

Saturated = every carbon atom is joined by a single C-C bond
Monounsaturated = contains one C=C bond
Polyunsaturated = many double bonds
- Double bonds make the molecule more fluid due to the kink in its structure

33
Q

What is the process of creating triglyceride molecules?

A

Esterification as an ester link/bond is formed

34
Q

What is the structure of phospholipids?

A
  • Contains a diglyceride, a phosphate group and a simple organic molecule (choline)
  • One fatty acid tail is substituted
  • Most commonly has 1 saturated and 1 unsaturated hydrocarbon chain
35
Q

What do phospholipids do in water?

A
  • The phosphate group has a negative charge, attracted by water (hydrophillic)
  • The fatty acid tails are non polar, repelled by water (hydrophobic)
36
Q

What is the structure of an amino acid?

A

It has a central carbon atom with 4 different chemical groups
- Amino group
- Carboxyl group
- H group
- R side chain

37
Q

How many different amino acids are there?

A
  • 20 as there are 20 different R groups
  • Glycine is the basic amino acid structure
38
Q

How is a peptide bond formed?

A

Condensation reaction

39
Q

What is the primary structure of a protein?

A
  • The order and sequence of amino acids in a polypeptide chain
  • Amino acids are joined together to make a polypeptide in a process called polymerisation
  • Primary structure of a protein determines its ultimate shape and function
  • Changing the amino acid can lead to changes in the shape of the protein
40
Q

What is the secondary structure of a protein?

A
  • POlypeptide has -NH+ and -C=O- groups on either side
  • These two groups form a weak hydrogen bond
  • This causes the chain to twisted into an α-Helix or a β-pleated sheet
41
Q

What is the tertiary structure of a protein?

A
  • The α-Helix can be twisted and folded even further to give the complex 3D structure of a protein
  • Maintained by disulfide bonds (fairly strong), ionic bonds (formed between carboxyl and amino groups but easily broken) and hydrogen bonds (numerous but easily broken)
  • The tertiary structure is what can be denatured by heat
  • Heat increases the kinetic energy of the molecule and makes parts vibrate faster
  • Bonds that hold the protein in the globular shape are broken and complex shape will unravel
  • Tertiary shape is what defines the active site on an enzyme
42
Q

What is the quaternary structure of a protein?

A
  • Protein structure that consists of more than one polypeptide chain that are linked in various ways
  • There may be a non protein (prosthetic group)
43
Q

What are the functions of proteins and an example of each?

A
  • Enzymes e.g. amylase
  • Transport e.g. haemoglobin
  • Movement e.g. actin and myosin
  • Cell recognition e.g. antigens
  • Channels e.g. membrane proteins
  • Structure e.g. collagen and keratin
  • Hormones e.g. insulin
  • Protection e.g. antibodies
44
Q

What are globular proteins?

A
  • Almost spherical in shape
  • Soluble in water
  • 3D shapes
  • α-Helix

E.g. enzymes

45
Q

What are fibrous proteins?

A
  • Repetitive sequence of amino acids
  • Insoluble in water
  • Structural
  • β-pleated sheet (straight)

E.g. collagen

46
Q

What is the structure of haemoglobin?

A
  • It is made of 2 α-globin and 2 β-globin polypeptide chains (each with its own tertiary structure)
  • Haem area is called a prosthetic group
  • A molecule of oxygen can bind to each haem group as it contains
  • Conjugated protein as it has a non-protein group attached
47
Q

What is the structure of insulin?

A
  • Made of two polypeptide chains
  • A chain begins with a section of α-helix
  • B chain ends with a section of β-pleat
  • Both chain are joined by disulfide links
  • Hydrophilic R groups are on the outside which makes it soluble in water
48
Q

What is the structure of amylase?

A
  • Catalyses the breakdown of starch to maltose
  • A single chain of amino acids with both α-helix and β-pleated sheet sections
49
Q

What is the structure of collagen?

A
  • Repeating sequence of amino acids
  • Each 3rd amino acid is glycine so it can wind up tightly
  • Helix shape
  • Made of 3 polypeptide chains wound together like rope
  • Hydrogen bonds hold the chain together
  • Structural protein
  • Found in artery walls, tendons and bones
50
Q

What is the structure of keratin?

A
  • Rich in cysteine so lots of disulfide bridges between its polypeptide chains
  • Alongside hydrogen bonds so the molecule is very strong
  • Provides mechanical structure and is waterproof
  • Found in fingernails, hair, fur, horns, scales and feathers
51
Q

What is the structure of elastin?

A
  • Cross-linking and coiling makes the structure strong and flexible
  • When subjected to a stretching force, the elastin proteins elongate but remain attached to each other
  • Found in lungs, bladder, skin and lining blood vessels
52
Q

What is the role of calcium?

A
  • Muscle contraction
  • Bone formation
53
Q

What is the role of sodium ions?

A
  • Nerve impulse
  • Affects absorption of carbohydrates in the intestine
54
Q

What is the role of potassium ions?

A
  • Nerve impulse
  • Stomatal opening
55
Q

What is the role of hydrogen ions?

A
  • Production of ATP
  • pH determination
56
Q

What is the role of ammonium ions?

A
  • Production of nitrate ions by bacteria
57
Q

What is the role of nitrate ions?

A
  • Component of nucleic acid
  • Component of the nitrogen cycle
58
Q

What is the role of hydrogencarbonate ions?

A
  • Involved in the transport of carbon dioxide
59
Q

What is the role of chloride ions?

A
  • Involved in the transport of carbon dioxide
  • Regulates affinity of haemoglobin to oxygen
60
Q

What is the role of phosphate ions?

A
  • Component of phospholipids, ATP and nucleic acids
  • Helps root growth
61
Q

What is the role of hydroxide ions?

A
  • Involved in regulation of blood pH

Biology A Level Content (6 decks)

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