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
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Hydrolysis
Addition of water to cause breakdown
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Hydrolysis Reactions
- Water is added to a disaccharide to break the glycosidic bond
- The constituent monosaccharides are released
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Sucrose Hydrolysis
Sucrose + Water --> Glucose + Fructose
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Lactose Hydrolysis
Lactose + Water --> Glucose + Galactose
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Maltose Hydrolysis
Maltose + Water -->
2 Glucose
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Test for Reducing Sugars
- 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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Test for Non-Reducing sugars
- Add dilute HCL acid to (sucrose) to hydrolyse it
- Boil the solution and neutralise it with sodium hydrocarbonate
- Repeat the Benedict's test
32
Types of Starch
- Amylopectin
- Amylose
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Amylopectin
- 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
Amylose
- 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
Glycogen
- 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
Cellulose
- 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
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Lipids
- Insoluble in water
- Soluble in other organic solvents (e.g. alcohol, acetone)
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2 Main Types of Lipids
- Triglycerides (fats and oils)
- Phospholipids
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Fats and Oils
- 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
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Role of Lipids
- In the cell membrane (phospholipids)
- Source of Energy
- Waterproofing
- Insulation
- Protect organs
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Triglycerides
- 3 fatty acids combined with a glycerol in a condensation reaction
- Form ester bonds
- The glycerol molecule in all triglycerides are the same
42
Phospholipids
- Have one less fatty acid which is replaced with a phosphate molecule
- Fatty acids are hydrophobic
- Phosphate molecules are hydrophilic
43
Cholesterol
- 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
Lipid Structure in Relation to Function
- 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
Saturated
No double bond between carbon atoms
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Mono-unsaturated
- One double bond between carbon atoms
- Causes hydrocarbon fatty acid tails to bend
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Poly-unsaturated
- More than one double bond between carbon atom
- Causes hydrocarbon fatty acid tails to bend
48
Test for Lipids
- 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
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Why does the solution turn cloudy in a positive lipids test?
- 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
Proteins
- 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
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Amino Acids
- 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
Dipeptides and Peptide Bonds
- 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
Primary Structure of Proteins
- 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
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Secondary Structure of Proteins
- Hydrogen bonds form between the amino acids
- Polypeptide isn't straight anymore (changes shape)
- Alpha helices and beta sheets created by folds
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Tertiary Structure of Proteins
- Chain is further folded
- Proteins formed as polypeptide chains form the 3D structure in this stage
- Ionic bonds and disulfide bridges are formed
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Quaternary Structure of Proteins
- Final 3D structure for proteins made of many polypeptides
- Held by hydrogen bonds and fold together
- E.g. insulin, haemoglobin, collagen
57
Test for Proteins/Enzymes
(Biurets Test)
- 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
Enzymes
- Biological catalysts of metabolic reactions
- Lower the activation energy of the reaction to speed it up
- Aren't used up in the reaction
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Lock and Key Theory
- 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
Induced Fit Model
- 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
Enzyme Activity at Low Temperature
- Low at low temperatures
- Enzyme and substrate have less kinetic energy
- Fewer collisions between the enzyme and substrate
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Enzyme Activity past Optimum Temperature
- 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
Enzyme Activity above/below Optimum pH
- 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
Inhibitor
Molecule that reduces the rate of an enzyme controlled reaction
65
Competitive Inhibitor
- 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
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Non-Competitive Inhibitor
- 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
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Allosteric Site
Site found elsewhere on the enzyme that isn't the active site
68
End Point Inhibition
- 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
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Properties and Uses of Water
- 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
ATP (Adenosine Triphosphate)
- 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
Uses of ATP Hydrolysis
- Muscle Contraction
- Metabolic Reactions
- Active Transport
- Secretion and Activation of Molecules
72
Inorganic Ions
- 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
Mechanical Digestion
Food is broken down into smaller pieces by structures like teeth and muscles like those in the walls of the stomach
74
Chemical Digestion
- Hydrolysis of larger, insoluble molecules into smaller, soluble ones
- Carried out by enzymes
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Peristalsis
Muscle contraction in the oesophagus pushes food towards the stomach
76
Starch Digestion In the Mouth
- 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
Starch Digestion in the Stomach
- 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
Starch Digestion whilst leaving the Stomach
- 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
Starch Digestion - Maltose Breakdown
- The epithelial lining of the ileum (small intestine) produces maltase
- Maltase breaks down maltose into alpha glucose
80
Lipid Digestion
- Hydrolysed by lipase which is produced in the pancreas - hydrolyses triglyceride ester bonds
- Produces monoglycerides (glycerol + single fatty acid
81
Emulsification
- 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
Endopeptidases
- Hydrolyse peptide bonds between amino acids in the central region of a protein molecule
- Form a series of peptide molecules
83
Exopeptidases
- Hydrolyse peptide bonds on the terminal amino acids of peptide molecules formed by endopeptidases
- Release dipeptides and amino acids
84
Dipeptidases
Hydrolyse the bond between the 2 amino acids of a dipeptide
85
Formula for pH
- pH=−log10[H+]
- [H+]is the concentration of hydrogen ions measured in moles per litre (M)
