Unit 1 - Biological Molecules and Digestion Flashcards
1
Q
Molecule
A
Two or more atoms held together by chemical bonds
2
Q
Biological Molecule
A
A molecule that is produced inside a living organism
3
Q
4 main biological molecules
A
- Proteins
- Lipids
- Carbohydrates
- Nucleic Acids
4
Q
Proteins Examples
A
- Form cell structures
- Used for growth and repair
- Enzymes (catalysts)
- Haemoglobin (binds to oxygen)
- Collagen (provides structural support)
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
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)
7
Q
Nucleic Acids Examples
A
- DNA
- RNA
- Used to produce and transfer genetic material
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
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
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
11
Q
Polymerisation
A
When monomers join together to form a long chain polymer
12
Q
Macromolecules
A
Large molecules
13
Q
Carbohydrates
A
- Carbon molecules combined with water
- Can be large or small
- Any molecule with carbon is an organic molecule
14
Q
Monosaccharides
A
Single sugar molecules
15
Q
Isomer
A
- Compounds with the same chemical formula but different arrangements of atoms
- E.g. alpha and beta glucose
16
Q
Disaccharide
A
2 monosaccharides joined together by a glycosidic bond formed by a condensation reaction
17
Q
Polysaccharide
A
Many monosaccharides joined together by glycosidic bonds joined together in a condensation reaction
18
Q
3 main monosaccharides
A
- Glucose
- Fructose
- Galactose
19
Q
Monomer
A
A singe unit that forms a chain of polymers when many join together
20
Q
3 main disaccharides
A
- Maltose
- Sucrose
- Lactose
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
22
Q
Maltose Formation
A
Glucose + Glucose –> Maltose + Water
23
Q
Lactose Formation
A
Glucose + Galactose –> Lactose + Water
24
Q
Sucrose Formation
A
Glucose + Fructose –> Sucrose + Water
25
Q
Hydrolysis
A
Addition of water to cause breakdown
26
Q
Hydrolysis Reactions
A
- Water is added to a disaccharide to break the glycosidic bond
- The constituent monosaccharides are released
27
Q
Sucrose Hydrolysis
A
Sucrose + Water –> Glucose + Fructose
28
Q
Lactose Hydrolysis
A
Lactose + Water –> Glucose + Galactose
29
Q
Maltose Hydrolysis
A
Maltose + Water –>
2 Glucose
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
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
32
Q
Types of Starch
A
- Amylopectin
- Amylose
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
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
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)
