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A-Level Biology > Biological Molecules and Digestion > Flashcards

Biological Molecules and Digestion Flashcards

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1
Q

Molecule

A

Two or more atoms held together by chemical bonds

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2
Q

Biological Molecule

A

A molecule that is produced inside a living organism

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3
Q

4 main biological molecules

A
  • Proteins
  • Lipids
  • Carbohydrates
  • Nucleic Acids
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4
Q

Proteins Examples

A
  • Form cell structures
  • Used for growth and repair
  • Enzymes (catalysts)
  • Haemoglobin (binds to oxygen)
  • Collagen (provides structural support)
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5
Q

Lipids Examples

A
  • Triglycerides (Energy store)
  • Phospholipids (forms a phospholipid bilayer used to form membranes in and around cells)
  • Cholesterol
  • Also used as certain hormones
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6
Q

Carbohydrates Examples

A
  • Starch (Energy store that breaks down into glucose and is used for respiration, found in plants)
  • Glycogen (Energy store that breaks down into glucose and is used for respiration)
  • Cellulose (structural molecule used to strengthen cell walls)
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7
Q

Nucleic Acids Examples

A
  • DNA
  • RNA
  • Used to produce and transfer genetic material
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8
Q

Polarisation

A
  • When atoms covalently bond, the electrons shared aren’t evenly distributed
  • One region is more negatively charged
  • This uneven distribution means the molecule is polarised
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9
Q

Hydrogen Bonding

A
  • When atoms covalently bond, the electrons shared aren’t evenly distributed
  • One region is more negatively charged this uneven distribution is polarised
  • These polar molecules form hydrogen bonds
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10
Q

Hydrogen Bonding with water

A
  • Uneven distribution of charge between the oxygen atom and the hydrogen atoms as the oxygen atom is bigger
  • The hydrogens become more positively charged and the oxygen becomes more negatively charged
  • As water is made up of many water molecules, a negative oxygen is weakly attracted to a positively charged hydrogen from another water molecule
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11
Q

Polymerisation

A

When monomers join together to form a long chain polymer

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12
Q

Macromolecules

A

Large molecules

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13
Q

Carbohydrates

A
  • Carbon molecules combined with water
  • Can be large or small
  • Any molecule with carbon is an organic molecule
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14
Q

Monosaccharides

A

Single sugar molecules

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15
Q

Isomer

A
  • Compounds with the same chemical formula but different arrangements of atoms
  • E.g. alpha and beta glucose
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16
Q

Disaccharide

A

2 monosaccharides joined together by a glycosidic bond formed by a condensation reaction

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17
Q

Polysaccharide

A

Many monosaccharides joined together by glycosidic bonds joined together in a condensation reaction

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18
Q

3 main monosaccharides

A
  • Glucose
  • Fructose
  • Galactose
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19
Q

Monomer

A

A singe unit that forms a chain of polymers when many join together

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20
Q

3 main disaccharides

A
  • Maltose
  • Sucrose
  • Lactose
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21
Q

How do disaccharides form?

A
  • Monosaccharides join and a molecule of water is removed (condensation reaction)
  • A glycosidic bond forms between the 2 monosaccharides
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22
Q

Maltose Formation

A

Glucose + Glucose –> Maltose + Water

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23
Q

Lactose Formation

A

Glucose + Galactose –> Lactose + Water

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24
Q

Sucrose Formation

A

Glucose + Fructose –> Sucrose + Water

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25
Q

Hydrolysis

A

Addition of water to cause breakdown

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26
Q

Hydrolysis Reactions

A
  • Water is added to a disaccharide to break the glycosidic bond
  • The constituent monosaccharides are released
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27
Q

Sucrose Hydrolysis

A

Sucrose + Water –> Glucose + Fructose

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28
Q

Lactose Hydrolysis

A

Lactose + Water –> Glucose + Galactose

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29
Q

Maltose Hydrolysis

A

Maltose + Water –>
2 Glucose

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30
Q

Test for Reducing Sugars

A
  • Heat Benedict’s Solution in a water bath for 5 minutes
  • Add the food being tested to the solution
  • If reducing sugars are present the the solution should change colour from blue to brick red
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31
Q

Test for Non-Reducing sugars

A
  • Add dilute HCL acid to (sucrose) to hydrolyse it
  • Boil the solution and neutralise it with sodium hydrocarbonate
  • Repeat the Benedict’s test
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32
Q

Types of Starch

A
  • Amylopectin
  • Amylose
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33
Q

Amylopectin

A
  • Branched (branches are longer than glycogen but less)
  • Forms 1-4 and1-6 glycosidic bonds
  • Highly branched so many enzymes can act on it simultaneously
  • Forms alpha glucose when hydrolysed
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34
Q

Amylose

A
  • Unbranched (forms coils which are compact)
  • Forms 1-4 glycosidic bonds
  • Forms alpha glucose when hydrolysed
  • Insoluble in water so it doesn’t impact water potential
  • Compact so more of it can be stored in a small space
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35
Q

Glycogen

A
  • Branched (shorter but more chains than amylopectin)
  • Forms 1-4 and 1-6 glycosidic bonds
  • Forms alpha glucose when hydrolysed
  • Highly branched so many enzymes can act on it simultaneously
  • This is so more glucose is readily available for respiration as humans have a higher metabolic/respiratory rate
36
Q

Cellulose

A
  • Unbranched
  • Chains run parallel to one another and are joined by hydrogen bonds, forming cross linkages (microfibrils)
  • Forms B-glucose when hydrolysed
  • Controls osmotic pressure by exerting inward pressure
  • Strengthens cell wall which helps maximise plant surface area for photosynthesis
37
Q

Lipids

A
  • Insoluble in water
  • Soluble in other organic solvents (e.g. alcohol, acetone)
38
Q

2 Main Types of Lipids

A
  • Triglycerides (fats and oils)
  • Phospholipids
39
Q

Fats and Oils

A
  • Fats are solid at room temperature
  • Oils are liquid at room temperature as double bonds cause molecules to bend so they can’t pack together closely
40
Q

Role of Lipids

A
  • In the cell membrane (phospholipids)
  • Source of Energy
  • Waterproofing
  • Insulation
  • Protect organs
41
Q

Triglycerides

A
  • 3 fatty acids combined with a glycerol in a condensation reaction
  • Form ester bonds
  • The glycerol molecule in all triglycerides are the same
42
Q

Phospholipids

A
  • Have one less fatty acid which is replaced with a phosphate molecule
  • Fatty acids are hydrophobic
  • Phosphate molecules are hydrophilic
43
Q

Cholesterol

A
  • Lipid that slots in between the phospholipid tails in the membrane
  • They push the tails together
  • Regulates the fluidity and stability of the membrane
44
Q

Lipid Structure in Relation to Function

A
  • Triglycerides have a high ratio of energy storing carbon-hydrogen bonds to carbon atoms, making them a good energy source
  • Low mass to energy ratio so they can store lots of energy in a small volume
  • Insoluble in water so they don’t impact water potential (osmosis)
  • High ratio of hydrogen and oxygen atoms so they release water when oxidised
45
Q

Saturated

A

No double bond between carbon atoms

46
Q

Mono-unsaturated

A
  • One double bond between carbon atoms
  • Causes hydrocarbon fatty acid tails to bend
47
Q

Poly-unsaturated

A
  • More than one double bond between carbon atom
  • Causes hydrocarbon fatty acid tails to bend
48
Q

Test for Lipids

A
  • Use a completely dry and grease free test tube
  • Add 5cm3 ethanol to 2cm3 of the sample
  • Shake the tube thoroughly to dissolve any lipid in the sample
  • Add 5cm3 of water and shake again
  • If the ethanol turns white/milky, lipids are present
49
Q

Why does the solution turn cloudy in a positive lipids test?

A
  • The lipid is finely dispersed in the solution which forms an emulsion
  • Light is refracted as it passes through the oil droplets to the water droplets
50
Q

Proteins

A
  • Macronutrients used for growth and repair
  • Made up of amino acids
  • Essential amino acids are obtained from food
  • Non-essential amino acids are obtained during protein synthesis
51
Q

Amino Acids

A
  • Made up of an R group, a carboxyl group and an amine group
  • The amine group is the variable part of the amino acid
  • The R group gives the amino acid its specific properties
52
Q

Dipeptides and Peptide Bonds

A
  • 2 amino acid monomers bond from a dipeptide
  • Forms a peptide bond (condensation reaction)
  • OH from carboxyl group and H from amine group
  • Bond is broken by hydrolysis
53
Q

Primary Structure of Proteins

A
  • Sequence of amino acids joined by peptide bonds
  • Bond created by a condensation reaction of the carboxyl and amine groups of the adjacent amino acids
54
Q

Secondary Structure of Proteins

A
  • Hydrogen bonds form between the amino acids
  • Polypeptide isn’t straight anymore (changes shape)
  • Alpha helices and beta sheets created by folds
55
Q

Tertiary Structure of Proteins

A
  • Chain is further folded
  • Proteins formed as polypeptide chains form the 3D structure in this stage
  • Ionic bonds and disulfide bridges are formed
56
Q

Quaternary Structure of Proteins

A
  • Final 3D structure for proteins made of many polypeptides
  • Held by hydrogen bonds and fold together
  • E.g. insulin, haemoglobin, collagen
57
Q

Test for Proteins/Enzymes
(Biurets Test)

A
  • Add 5cm3 of the sample into a test tube
  • Add 5cm3 of biurets solution to the sample
  • If proteins are present the solution changes from blue to lilac
58
Q

Enzymes

A
  • Biological catalysts of metabolic reactions
  • Lower the activation energy of the reaction to speed it up
  • Aren’t used up in the reaction
59
Q

Lock and Key Theory

A
  • Enzymes are complementary to substrates
  • Substrate collides with active site of enzyme and attaches to it
  • Enzyme catalyses breakdown of substrate
  • Products released from active site
  • Enzyme molecule is unchanged
60
Q

Induced Fit Model

A
  • Enzymes aren’t complementary to substrates
  • When the enzyme is attached to the substrate it alters its shape to fit the substrate
  • The enzyme puts a strain on the substrate to catalyse it
61
Q

Enzyme Activity at Low Temperature

A
  • Low at low temperatures
  • Enzyme and substrate have less kinetic energy
  • Fewer collisions between the enzyme and substrate
62
Q

Enzyme Activity past Optimum Temperature

A
  • The active site of the enzyme changes shape
  • Substrate isn’t complementary anymore and can’t attach to active site
  • Enzyme is denatures
  • Rate of enzyme activity decreases till it’s 0
63
Q

Enzyme Activity above/below Optimum pH

A
  • Enzyme activity decreases
  • Extra H+ ions (too acidic) or OH- ions (too alkaline) alter the chemical structure of the amino acids
  • This shifts the ionic bonds and disulfide bridges making up the enzyme
64
Q

Inhibitor

A

Molecule that reduces the rate of an enzyme controlled reaction

65
Q

Competitive Inhibitor

A
  • Binds at the active site of the enzyme
  • Prevents the substrate from attaching to the active site as it is occupied by the inhibitor
  • Remedied by adding extra substrate to increase the chance of enzyme substrate collisions
66
Q

Non-Competitive Inhibitor

A
  • Inhibitor binds to allosteric site and changes the shape of the active site
  • Substrate can’t properly bind to the active site as the tertiary structure of the enzyme is altered
  • Adding more substrate makes no difference
67
Q

Allosteric Site

A

Site found elsewhere on the enzyme that isn’t the active site

68
Q

End Point Inhibition

A
  • The final product inhibits an enzyme involved in the initial reaction
  • Way of controlling the amount of product produced
  • Product acts as a non-competitive inhibitor to an enzyme
69
Q

Properties and Uses of Water

A
  • Polar Molecule: Cohesive so creates surface tension allowing support for small organisms (e.g. water skimmers)
  • High Specific Heat Capacity: Acts as a buffer for temperature
  • Large Specific Latent Heat of Vapourisation: Water easily evaporates which allows animals to cool down via sweating
  • Metabolite: Used/Produced in condensation and hydrolysis reactions
  • Solvent: Allows for transport of dissolved substances
70
Q

ATP (Adenosine Triphosphate)

A
  • Made up of adenine, a ribose sugar and 3 phosphate molecules
  • ATP hydrolase hydrolyses ATP and forms ADP and P(i)
  • The P(i) can phosphorylate other compounds to make them more reactive
  • The energy comes from the bonds between the phosphate molecules that are unstable, have a low activation energy and release a sizeable amount of energy when broken
  • ATP Synthase reforms ATP from ADP and P(i) in a condensation reaction during respiration
71
Q

Uses of ATP Hydrolysis

A
  • Muscle Contraction
  • Metabolic Reactions
  • Active Transport
  • Secretion and Activation of Molecules
72
Q

Inorganic Ions

A
  • Fe+ ions: Component of haemoglobin
  • H+ ions: Determine pH of substances, e.g. blood (higher H+ concentration means lower pH, more acidic)
  • Na+ ions: Involved in co-transport of glucose and amino acids
  • P³+ ions: Component of DNA and ATP
73
Q

Mechanical Digestion

A

Food is broken down into smaller pieces by structures like teeth and muscles like those in the walls of the stomach

74
Q

Chemical Digestion

A
  • Hydrolysis of larger, insoluble molecules into smaller, soluble ones
  • Carried out by enzymes
75
Q

Peristalsis

A

Muscle contraction in the oesophagus pushes food towards the stomach

76
Q

Starch Digestion In the Mouth

A
  • Food is chewed in the mouth
  • Pieces are coated with saliva containing amylase that hydrolyses starch into maltose
  • Salts in the saliva maintain the correct pH
77
Q

Starch Digestion in the Stomach

A
  • Stomach acid denatures the salivary amylase
  • Digestion of starch is halted until the food enters the small intestine as the amylase has been denatured
78
Q

Starch Digestion whilst leaving the Stomach

A
  • Stomach acid is neutralised in the small intestine
  • Secretions from the pancreas (pancreatic juice) contain pancreatic amylase which continues starch hydrolysis
  • Alkaline salts from the pancreas and intestinal wall maintain pH
79
Q

Starch Digestion - Maltose Breakdown

A
  • The epithelial lining of the ileum (small intestine) produces maltase
  • Maltase breaks down maltose into alpha glucose
80
Q

Lipid Digestion

A
  • Hydrolysed by lipase which is produced in the pancreas - hydrolyses triglyceride ester bonds
  • Produces monoglycerides (glycerol + single fatty acid
81
Q

Emulsification

A
  • Lipids split into micelles by bile
  • Bile is produced in the liver
  • Emulsification increases surface area of the lipids to speed up lipase action
82
Q

Endopeptidases

A
  • Hydrolyse peptide bonds between amino acids in the central region of a protein molecule
  • Form a series of peptide molecules
83
Q

Exopeptidases

A
  • Hydrolyse peptide bonds on the terminal amino acids of peptide molecules formed by endopeptidases
  • Release dipeptides and amino acids
84
Q

Dipeptidases

A

Hydrolyse the bond between the 2 amino acids of a dipeptide

85
Q

Formula for pH

A
  • pH=−log10[H+]
  • [H+]is the concentration of hydrogen ions measured in moles per litre (M)

A-Level Biology (9 decks)

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