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OCR AS/A Level Biology A > Module 2.2 Biological Molecules > Flashcards

Module 2.2 Biological Molecules Flashcards

1
Q

Calcium (Ca2+)

A
  • Increases rigidity of bones, teeth and cartilage
  • Component of the exoskeleton of crustaceans
  • Clotting blood and muscle contractions
  • Activator for enzymes e.g. lipase, ATPase and cholinesterase
  • Stimulates muscle contractions
  • Regulates transmission of nerve impulses
  • Regulates permeability of cell membranes
  • Important for cell wall development (in plants) and formation of middle lamellar between cell walls
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2
Q

Sodium (Na+)

A
  • Helps regulate osmotic pressure
  • Helps control water levels in body fluid
  • Helps maintaining pH
  • Affects absorption of carbohydrates in intestine
  • Affects absorption of water in the kidney
  • Contributes to nervous transmission and muscle contractions
  • Present in vacuole which helps maintain turgidity
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3
Q

Potassium (K+)

A
  • Helps control water levels in body fluid
  • Helps maintain pH
  • Assists active transport
  • Involved in synthesis of glycogen and protein, and breakdown of glucose
  • Helps keep leaves and flowers healthy
  • Involved w nervous transmission and muscle contraction
  • Present in vacuoles to help maintain turgidity
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4
Q

Hydrogen (H+)

A
  • Involved in photosynthesis
  • Involved in respiration
  • Involved in transport of oxygen and carbon dioxide in the blood
  • Involved in regulation of blood pH
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5
Q

Ammonium (NH4+)

A
  • Component of amino acids, proteins, vitamins and chlorophyll
  • Essential component of nuclei acids
  • Involved in maintaining pH in the body
  • Component in the nitrogen cycle
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6
Q

Nitrate (NO3-)

A
  • Component of amino acids, proteins, vitamins and chlorophyll
  • Essential component of nucleic acids
  • Some hormones are made out of proteins which contain nitrogen e.g. insulin
  • Component in nitrogen cycle
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7
Q

Hydrogencarbonate (HCO3-)

A
  • Regulates blood pH

- Involved in transport of carbon dioxide in and out of the blood

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8
Q

Hydroxide (OH-)

A

-Regulates blood pH

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9
Q

Chloride (Cl-)

A
  • Helps production of urine in the kidneys and maintaining water balance
  • Involved in transport of carbon dioxide in and out of the blood
  • Regulates affinity of haemoglobin to oxygen through allosteric effects on the haemoglobin molecule
  • Involved in blood pH regulation
  • Used to produce HCl in the stomach
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10
Q

Phosphate (PO4 3-)

A
  • Increases rigidity of bones, teeth and cartilage
  • Component of the exoskeleton of crustaceans
  • Component of phospholipids, ATP, nuclei acids + several important enzymes
  • Involved in blood pH regulation
  • Helps roots grow in plants
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11
Q

Phospholipids

A
  • Composed of glycerol and a phosphate head w 2 fatty acid tails
  • Soluble head and insoluble tail in water
  • Part hydrophilic, part hydrophobic
  • Make up cell surface membranes
  • Made up of C, H and O
  • Fatty acid chains joined to glycerol w ester bonds
  • Phosphate group + carbohydrate = glycolipid (used for cell signalling)
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12
Q

Triglycerides

A
  • Composed of a glycerol molecule and 3 fatty acid tails
  • Fatty acid chains joined to glycerol w ester bonds in a condensation reaction
  • The ester bonds form at 3 OH groups on glycerol - 3 water molecules released
  • Made up of C, H and O
  • Hydrophobic molecule (evenly distributed charge)
  • Insoluble in water (means doesn’t effect water potential of cells)
  • Used as energy stores by hydrolysing ester bonds breaking down CO2 and H2O to release energy
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13
Q

Cholesterol

A
  • Made up of C, H and O
  • Make up cell surface membranes
  • Hydrophobic molecule (evenly distributed charge)
  • Insoluble in water
  • Made up of a 4 carbon ring structure
  • Vital to organisms - made by many cells
  • Helps regulate fluidity
  • Can build up causing heart disease and can clog arteries etc. It can be deposited in blood vessels causing atherosclerosis
  • Produce steroid hormones e.g testosterone and oestrogen which can pass straight through membranes to target cells
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14
Q

Lipids

A
  • Solid lipid = fat
  • Liquid lipid = oil
  • Lipids dissolve in organic solvents e.g. alcohol but not in water
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15
Q

Roles of lipids in organisms

A
  • Energy source
  • Energy store (lipids stored in adipose cells)
  • Phospholipid bilayer
  • Insulation
  • Myelin sheath of neurones - electrical insulation
  • Steroid hormones
  • Waxy cuticle of leaves
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16
Q

Glycerol

A
  • C3H8O3
  • Glycerol and fatty acids are both found in 2 major groups of lipids - glycerolipids (energy store/source) and glycerophospholipids
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17
Q

Fatty acids

A
  • All have an acid group at one end joined to a hydrocarbon chain (2-20 carbons long)
  • Fatty acids are used to make up lipids
  • An essential fatty acid is one that we can’t assemble ourselves
  • 3 types - palmitic, stearic and oleic
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18
Q

Saturated fats

A
  • No double bonds in the hydrocarbon chain

- Raise cholesterol

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19
Q

Monounsaturated fats

A

One C=C bond

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20
Q

Polyunsaturated fats

A

2+ C=C bonds

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21
Q

Are unsaturated fats more or less permeable?

A

More permeable

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22
Q

What bond joins glycerol to a fatty acid?

A

An ester bond

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23
Q

Haemoglobin

A
  • Conjugated protein
  • 4 polypeptides
  • 2 alpha, 2 beta
  • Prosthetic haem groups have an affinity for oxygen (each one can attract 1 oxygen molecule)
  • Fe2+ ions
  • Function - to carry oxygen from the lungs to tissues for aerobic respiration
  • Globular - for metabolic reactions
  • Primary structure - amino acids
  • Secondary structure - mostly alpha helices
  • Tertiary structure - alpha chains and beta chains
  • Quaternary structure - 2 alpha and 2 beta chains
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24
Q

Collagen

A
  • Structural protein
  • Fibrous
  • Quaternary structure - 3 polypeptide chains tightly wound around each other
  • H bonds give strength
  • Every 3rd amino acid on each peptide chain is glycine - small - tiny R group - allows close packing
  • Covalent bonds across peptide chains (cross linkage) helps to form a collagen fibril - staggered cross linkage adds strength
  • Many fibrils make up a fibre
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25
Q

Functions of collagen (protein)

A
  • Lines arteriole walls - prevents bursting at high pressure
  • Tendons allow movement
  • Bones - collagen reinforced to make them hard
  • Cartilage and connective tissue
  • Used in cosmetic treatments
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26
Q

Properties of collagen (protein)

A
  • High tensile strength
  • NOT elastic
  • Flexible
  • Insoluble
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27
Q

Comparing collagen and haemoglobin (both proteins)

A

Collagen:

  • Fibrous
  • Insoluble
  • No prosthetic group
  • Structural

Haemoglobin:

  • Globular
  • Soluble
  • Prosthetic haem group
  • For transporting oxygen
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28
Q

Secondary structure of proteins

A
  • As polypeptides form, to stabilise them, they are coiled (a-helix) or pleated (ß-pleated sheets)
  • These are held in place by H bonds
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29
Q

Why is the secondary structure of proteins dependant on the primary structure?

A
  • Primary structure = unique sequence of amino acids in the protein
  • Different proteins have different combinations of amino acids which each have different R groups and different properties
  • Different proteins have H bonds formed in different places in the pleats/coils meaning some are more or less pleated/coiled than others
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30
Q

Tertiary structure

A
  • 3D shape
  • When coils/sheets are folded into their final shape
  • Tertiary structure is 🔑 to the protein’s function
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31
Q

Tertiary structure - disulfide bonds

A
  • The amino acid cysteine contains sulfur

- Where 2 cysteines are found close to each other, a covalent bond forms

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32
Q

Tertiary structure - ionic bonds

A
  • The strongest 💪🏻
  • R groups sometimes carry a charge (either +ve or -ve)
  • When oppositely charged amino acidsare found close to each other, an ionic bond forms
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33
Q

Tertiary structure - Hydrogen bonds

A

-Form when slightly positively charged groups are found close to slightly negatively charged groups

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34
Q

Tertiary structure - Hydrophilic and hydrophobic interactions

A
  • In a water-based environment, hydrophobic amino acids are most stable if they are held together w water excluded
  • Hydrophilic amino acids tend to be found on the outside in globular proteins w hydrophobic amino acids in the centre
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35
Q

Globular proteins

A
  • Ball shaped
  • Soluble - the hydrophobic groups are found in the centre of the ball w hydrophilic on the outside
  • For metabolic reactions
  • E.g. enzymes, plasma proteins, antibodies, haemoglobin
36
Q

Fibrous proteins

A
  • Looks like fibres
  • Insoluble
  • Structural
  • E.g. collagen and keratin
37
Q

Denaturation

A
  • Heat energy gives molecules KE
  • KE makes molecules vibrate and can break bonds
  • Heating proteins can break bonds in the tertiary structure
  • Once the tertiary structure is lost, the protein is no longer properly functional
38
Q

Which bond joins a glucose and a fructose unit to make sucrose?

A

1,4 glycosidic

39
Q

General formula for carbohydrates

A

Cx(H2O)y

40
Q

Elements that carbohydrates contain

A

C, H and O

41
Q

3 types of sugar

A
  • Hexose
  • Pentose (in DNA - ribose)
  • Triose
42
Q

Maltose

A

a + a

43
Q

Lactose

A

a + ß galactose

44
Q

Sucrose

A

a + fructose

45
Q

Cellubiose

A

ß + ß

46
Q

Amylose

A

a + a + a and so on…

47
Q

Cellulose

A

ß + ß + ß etc

48
Q

2 sugars are joined by a what bond?

A

Glycosidic bond

49
Q

Pentose

A

Ribose (in mRNA)

Deoxyribose (in DNA)

50
Q

Polysaccharides you need to know

A 
Amylose
Cellulose
Amylopectin 
Glycogen
Starch (amylose + amylopectin)
51
Q

Amylose

A

1,4 glycosidic bonds
No branches
a-glucose
Spiralled

52
Q

Amylopectin

A

1,4 glycosidic bonds and 1,6 glycosidic bonds

Branched

53
Q

Proteases

A
  • Enzymes that break down peptide bonds
  • E.g. pepsin in the stomach
  • Used in digestion and to break down hormones so that their effect isn’t constant
54
Q

Elastin

A
  • Protein
  • Coiled and cross linked for strength
  • Found in skin, the lungs, the bladder and blood vessels
55
Q

Pepsin

A
  • Single polypeptide chain
  • 327 amino acids
  • Symmetrical tertiary structure
  • Mainly acidic R groups (stable)
56
Q

Insulin

A
  • 2 polypeptide chains
  • a-chain begins w alpha helicies
  • b-chain ends w beta
  • Tertiary structure held together by disulphide links
57
Q

Transcription

A
  1. DNA helicase unwinds the double helix of DNA
  2. Free nucleotides attach by comp. base pairing (RNA polymerase joins the nucleotides together)
  3. mRNA moves away
  4. The 2 strands of DNA are zipped back together
  5. mRNA leaves via a nuclear pore and enters the cytoplasm
58
Q

Translation

A
  1. mRNA enters ribosome
  2. tRNA enters the ribosome and brings a specific amino acid that corresponds to the codon on the mRNA strand
  3. The tRNA anti-codon matches the mRNA codon (complimentary)
  4. The amino acids join by peptide bonds
  5. Polypeptide chain made
59
Q

Functions of proteins

A
  • Structural e.g. muscle or bones
  • Carrier/channel proteins
  • All enzymes
  • Many hormones
  • Antibodies
60
Q

Basic structure of amino acids

A
  • Amine group
  • Acid group
  • R group
61
Q

Explain why glycogen is referred to as an energy store

A
  • Can be hydrolysed to release a-glucose in aerobic respiration
  • Polysaccharide of glucose
  • Branched
62
Q

Name the 2 parts of starch

A

Amylose

Amylopectin

63
Q

Describe the structure of a cellulose microfibril

A
  • ß-glucose flipped 180*

- H bonds between chains

64
Q

What bonds hold polysaccharides together?

A

Glycosidic

65
Q

Formula of pentose sugars

A

C5H10O5

66
Q

a and ß glucose have different shapes but the same formula - what term is used to describe this?

A

Isomer

67
Q

3 things that happen in a condensation reaction

A

Larger molecules form
Covalent bonds form
Water used

68
Q

How do a glucose and b glucose differ?

A

a : OH below the plane of the ring

b : OH above the plane of the ring

69
Q

Peptidoglycan (murein)

A

Bacteria cell walls

70
Q

Chitin

A
  • Exoskeleton of insects

- Surgical thread (strong and flexible)

71
Q

Starch

A
  • Found in plants
  • Polysaccharide of a-glucose
  • Mix of unbranched, coiled amylose and branched amylopectin
  • Insoluble
  • Forms grains
  • Energy storage
72
Q

Glycogen

A
  • In animals e.g. liver and muscle cells
  • Polysaccharide of a-glucose
  • 1,4 and 1,6 glycosidic bonds
  • Insoluble
  • Forms granules
  • V branched
  • Shorter chains
  • Energy storage
73
Q

Cellulose

A
  • In plants - cell wall
  • ß-glucose
  • Insoluble
  • V strong
  • Unbranched, long, straight
  • 1,4 glycosidic bonds
  • Structural
  • Polysaccharide formed in condensation reactions
  • Every ß-glucose is flipped 180* from the last to form a glycosidic bond
74
Q

Cell walls

A
  • H bonds form between OH groups of neighbouring chains
  • Cellulose chains become cross linked to form a microfibril
  • Microfibrils are held together by H bonds to form macrofibrils
75
Q

Macrofibrils

A
  • Embedded in pectin (polysaccharide)
  • H bonds
  • Criss cross structure allows water through
  • Macrofibrils v strong = turgid when too much water
76
Q

Aerobic respiration

A

C6H12O6 + 6O2 –> 6CO2 + 6H2O

77
Q

Maltose and amylose

A
  • a-glucose + a-glucose = maltose
  • The same reaction thousands of times forms amylose - held together by 1,4 glycosidic bonds - spring shape - H bonds - unbranched - compact - insoluble
78
Q

Starch

A
  • Iodine gets caught in the spring like shape of amylose (orange –>blue/black)
  • Made up of amylose and amylopectin
  • Amylopectin - branches of a-glucose w 1,4 glycosidic bonds joined at the ends to another chain w 1,6 glycosidic bonds
  • Store of energy - broken down into a-glucose for resp in hydrolysis reactions
79
Q

Glycogen

A
  • Polysaccharide
  • a-glucose
  • Hydrolysis reactions are used to break it down to release glucose for respiration
80
Q

Comparing glycogen and starch

A
  • Glycogen - 1,4, shorter, more branched, more compact
  • Both insoluble
  • Both store glucose in chains
81
Q

Carbohydrates

A

C,H, O
Monomer- monosaccharides e.g. glucose
Polymer- polysaccharides e.g. starch

82
Q

Proteins

A

C, H, O, N and S
Monomer- amino acids
Polymer- polypeptides (proteins)

83
Q

Nucleic acids

A

C, H, O, N and P
Monomer- nucleotides
Polymer- DNA and RNA

84
Q

Condensation reactions

A
  • Link monomers
  • Covalent bond forms
  • Larger molecules formed
  • Water released
  • OH group needed
85
Q

Hydrolysis reactions

A
  • Covalent bonds broken
  • Smaller molecules formed
  • Water used
86
Q

H bonds

A
  • When a slightly positive and slightly negative charge come close
  • Weak
  • Easily broken
87
Q

Monosaccharides

A
  • Contain 3-6 carbons
  • Small
  • Soluble in water
  • Sweet tasting
  • Form crystals

OCR AS/A Level Biology A (14 decks)

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