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UACE Biology > Chemicals Of Life > Flashcards

Chemicals Of Life Flashcards

1
Q

Describe the molecular structure of water

A
  • The water molecule comprises two hydrogen atoms and one oxygen atom
  • The molecule itself is polar (specifically dipolar) as there is an uneven distribution of charges in it
  • The oxygen atom is slightly negative and that of the hydrogen is slightly positive thus making it polar
  • Water molecules have weak forces of attraction to each other with opposite charges coming together
  • The hydrogen bonds are constantly being formed and broken and although individually weak, their collective effect give water its unusual properties
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2
Q

State functions of water

A

It is a component of cells
➢ It is a solvent and a medium of transport
➢ It is a reagent in hydrolysis
➢ It enables fertilization by swimming gametes
➢ It enables dispersal of seeds, fruits, gametes and larvae stages in aquatic organisms.
➢ It is important in transpiration in plants.
➢ It is important in translocation in plants.
➢ It enables germination to proceed by activating enzymes, transporting hydrolyzed stored food, swelling and
breaking open the testa.
➢ It is involved in Osmo-regulation in animals
➢ It enables cooling by evaporation as a result of sweating and panting.
➢ It is a component of lubricants at joints e.g. the synovial fluid.
➢ It offers support in hydrostatic skeleton.
➢ It offers protection as a component of mucus and tears.
➢ It enables migration to occur as a result of river flow or ocean currents.

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3
Q

How do the properties of water relate to its biological role in organisms?

A

1) Water is transparent and this allows light penetration in aquatic habitats to enable photosynthesis of aquatic
autotrophs and visibility of aquatic animals.
2) Water has a low viscosity and this allows for smooth flow of water and other dissolved substances in an aquatic medium for easy transport.
3) It has a high surface tension providing support to aquatic organisms and allowing movement of living organisms on water surface.
4) Has a high latent heat of vaporization hence a cooling effect on the body surface since evaporation of water from the body of an organism draws out excess heat.
5) It has a high boiling point thus provides a stable habitat and medium since a lot of heat which is not normally provided in the natural environment is needed to boil the water.
6) It has a high latent heat of fusion and hence a low freezing point thus providing a wide range of temperature for survival of aquatic organisms since it prevents freezing of cells and cellular components.
7) It has a high specific heat capacity which minimizes drastic temperature changes in biological systems and provides a constant external environment for many plant cells and aquatic organisms.
8) It has a maximum density at 4o C hence ice floats on top of water insulating the water below hence increasing the chances of survival of aquatic organisms below the ice.
9) Water is liquid at room temperature providing a liquid medium for living organisms and metabolic reactions and a medium of transport.
10) It has high adhesive and cohesive forces creating enough capillarity forces for transport in narrow tubes of biological systems.
11) It is a universal solvent hence providing a medium for biochemical reactions.
12) Water is a polar molecule allowing solubility of polar substances, ionization or dissociation of biochemical
substances.
13) Water is incompressible thus providing support in hydrostatic skeleton and herbaceous stems.
14) Water is neutral hence does not alter the pH of cellular components on their environme

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4
Q

State the properties of water

A

i) It is liquid at room temperature.

ii) It has a high heat capacity therefore much energy is used to raise its temperature because it is used to break the hydrogen bonds which restrict the mobility of the molecules. As a result water is relatively slow to heat up or to cool down thus a high heat capacity.

iii) Water expands as it freezes unlike other liquids which contract on cooling.
iv) Water reaches its maximum density above its freezing point at 4oC hence when water freezes, the ice formed is
less dense than the water and hence floats on top of the surface. In this way, ice insulates water below making it
less dense and able to float hence the water will be warmer than the air above.

v) Water has a high surface tension. Surface tension is the force that causes the surface of a liquid to contract so
that it occupies the least area. It is high due to the fact that molecules are oriented so that most hydrogen bonds
point inwards towards other water molecules.

vi) It has a high latent heat of fusion i.e. much heat must be removed before freezing occurs.

vii) It has high adhesive and cohesive properties preventing it from breaking under tension.

viii) It is colourless and transparent.

ix) It has a low viscosity i.e. water molecules slide over each other very easily.

x) It dissolves more substances than any other liquid i.e. it is a universal solvent.

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5
Q

What is an enzyme?

A

A biological catalyst protein in nature that catalyzes (speeds up) the rate of a biochemical reaction and itself remains unchanged by the end of it

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6
Q

What is a substrate?

A

This is the chemical worked upon by the enzyme.

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7
Q

What is a product?

A

The final result of a chemical reaction

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8
Q

What pH is considered neutral?

A

pH 7

Below 7-acidity

Above 7- alkalinity/basis

(pH 6.9 is slightly acidic, and 7.1 is slightly basic)

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9
Q

What is an acid?

A

A compound which when dissolved in water ionizes to produce hydrogen ions as the only positive charged ions e.g. hydrochloric acid, nitric acid, Sulphuric acids e.t.c.

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10
Q

What is a base?

A

A base is a compound, which can react with acids to produce a salt and water only.

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11
Q

What is an alkali?

A

A substance which when dissolved in a solvent produces hydroxyl ions as the only charged ions.

-Alkalis are bases but not all bases are alkaline.
-Strong alkalis completely ionize e.g. sodium hydroxide
-Weak alkalis don’t ionize completely e.g. ammonium hydroxide

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12
Q

Give functions of acids

A

-They provide a suitable pH for the proper functioning of enzymes e.g. pepsin
-Acids like hydrochloric acids activate organic substances like pepsinogen
-Acids kill bacteria, which may be ingested together with food

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13
Q

Give functions of bases

A

-Provide an optimum pH range for enzyme activity e.g.in the duodenum
-They are buffers in the body

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14
Q

What is a buffer?

A

A buffer is a substance that minimizes/ resists changes in pH of a solution when small amounts of acids or bases are added.

-Most buffers are acid base pairs

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15
Q

What is the importance of buffers in the body?

A

To maintain the narrow range of pH in which enzymes function

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16
Q

Give examples of acids in the body

A
  • Nucleic acids
  • Hydrochloric acids
    -Amino acids
    -Lactic acids
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17
Q

What is a salt?

A

A compound which is formed when the hydrogen ions in an acid are either partially or fully replaced by a metal ion or ammonium ion

HCL ———> NaCl, KCl etc

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18
Q

Give the functions of mineral salts

A
  1. They form body structures
    e.g. the bones, the teeth, etc
  2. They form body pigments
    e.g. Haemoglobin contains Iron, chlorophyll contains magnesium.
  3. They form chemicals in the body
    e.g. Sulphur and Nitrogen form proteins, nucleic acids, ATP etc.
  4. They are metabolic activators. Certain ions activate enzymes
    e.g. magnesium activates enzymes that are
    involved in phosphorylation of glucose.
  5. They are constituents of enzymes
    e.g. nitrogen in proteins.
  6. Constituents of various chemicals
    e.g. ATP contains phosphorous while thyroxin contains iodine.
  7. They are determinants of osmotic pressure. Mineral salts and other solutes determine the osmotic pressure
    of cells and body fluid.
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19
Q

Which are the four most common elements in living organisms and why?

A
  • Hydrogen
  • Carbon
  • Oxygen
  • Nitrogen
    (In that order)

Due to their ability to form more stable covalent bonds than any other elements with their valencies

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20
Q

What is the name of this chemical group?
-S-H

A

Sulphydryl group

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21
Q

What is the -COOH group responsible for in compounds containing it?

A

Acidic nature
eg fatty acids, amino acids

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22
Q

What is the difference between a saturated and unsaturated compound?

A

Saturated compounds contain single carbon-carbon bonds while unsaturated compounds contain double or triple carbon-carbon bonds

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23
Q

What characteristics of the carbon atom make possible the building of a variety of biological molecules

A
  • It is a relatively small atom with a low mass
  • The ability to form four strong, stable covalent bonds
  • The ability to form carbon-carbon bonds thus building up large carbon skeletons
  • The ability to form multiple covalent bonds with other carbon atoms, nitrogen and oxygen
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24
Q

What is the general formula for carbohydrates?

A

CnH2nOm
(n and m may be either the same or vary)

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25
Q

What is the formula of glucose?

A

C6H12O6

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26
Q

What is the general formula of sucrose?

A

C12H22O11

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27
Q

What are the three main groups of carbohydrates?

A

-Monosaccharides
-Disaccharides
-Polysaccharides

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28
Q

Give differences between sugars and polysaccharides

A

Sugars:
-Small molecules
-Sweet
-Readily soluble in water
-Crystalline

Polysaccharides:
-Marcomolecules
-Not sweet
-Insoluble or slightly soluble in water
-Non-crystalline

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29
Q

What are aldoses/ aldose sugars?

A

These are sugars containing an aldehyde group (-CHO).

Their functional group is at the terminal end of the chain.

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30
Q

What are ketoses /keto sugars?

A

These are monosaccharides containing a ketone group (C=O)

Their functional group is anywhere in the middle of the chain.

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31
Q

Give examples of aldoses

A

-Glyceraldehyde
(triose sugar)
-Ribose, Xylose ,Arabinose
(pentoses)
-Glucose, Galactose, Mannose
( hexoses)

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32
Q

Give examples of ketoses

A

-Dihydroxyacetone
(Triose)
-Ribulose,Xylulose
(Pentoses)
-Fructose, Sorbose
(Hexoses)

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33
Q

What is the difference between the alpha glucose ring and the beta glucose ring structure?

A

The -OH group on carbon atom 1 is “down” in alpha glucose and “up” in beta glucose

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34
Q

What are isomers?

A

Compounds with the same molecular formula but different structural formulae

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35
Q

By what chemical reaction do monosaccharides combine to form disaccharides?

A

Condensation reaction

(Removal of water)

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36
Q

By what chemical reaction do disaccharides break down to form their component monosaccharides?

A

Hydrolysis reaction

(Break down with addition of a water molecule)

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37
Q

What is the resultant bond of a condensation reaction?

A

Glycosidic bond

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38
Q

Glucose + Glucose = ?

A

Maltose

Mainly a breakdown product during digestion of starch by amylase enzymes.

Common in animals and germinating seeds

Applied in brewing beer when barley grain is used as the source of starch. The process is called malting.

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39
Q

Glucose + Galactose = ?

A

Lactose
(Milk sugar)

Exclusively in milk

Energy source for young mammals

Digested slowly thus a steady release of energy

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40
Q

Glucose + Fructose = ?

A

Sucrose

(Cane sugar)

Commonly found in plants

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41
Q

Which of the following is not a reducing sugar?
a) Lactose
b) Maltose
c) Sucrose
d) Glucose

A

c) Sucrose

Sucrose is the only non- reducing disaccharide
All monosaccharides are reducing sugars

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42
Q

True or false?
“Polysaccharides are reducing sugars”

A

False

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43
Q

What do reducing sugars do to Benedict’s solution?

A

Reduce copper (ii) ions in Benedict’s solution to copper (I) oxide giving an orange precipitate.

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44
Q

Give importances of monosaccharides

A

-Trioses are intermediates in respiration, photosynthesis and other branches of carbohydrate metabolism

-Pentoses are used in synthesis of nucleic acids, ATP etc

-Hexoses are a source of energy when oxidized in respiration

-Hexoses combine to form disaccharides and polysaccharides

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45
Q

What specific monomer makes up the polymer of starch?

A

Alpha glucose

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46
Q

Which of the following are most abundant in plants?
a) Starch
b) Starch and cellulose
c) Cellulose and glycogen
d) Starch and glycogen

A

b) Starch (storage) and cellulose (structure i.e the cell wall)

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47
Q

What are the two major components of starch?

A

-Amylose (20%)
-Amylopectin (79%)

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48
Q

What is the use of starch in plants?

A

It is made from excess glucose as a food reserve (storage polysaccharide)

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49
Q

Give differences between amylose and amylopectin

A

Amylose;
-Has 1,4-glycosidic bonds only
-Made up of unbranched helical chains
-Made up of fewer glucose units (300)
-Smaller molecular mass

Amylopectin;
-Has both 1,4 and 1,6 glycosidic bonds
-Made up of branched helical chains
-Made up of more glucose units(1300)
-Larger molecular mass

50
Q

Give similarities between amylose and amylopectin

A

-Both amylose and amylopectin are made up of alpha glucose molecules

-Both amylose and amylopectin have 1,4 glycosidic bonds

51
Q

What are the adaptations of starch to its storage function in plants?

A
  • It is insoluble thus it has no osmotic effect within cells
  • It is insoluble thus cannot be lost in solution form
  • It is a compact polymer hence takes up little space in the cell
  • Made up of glucose thus it can be hydrolyzed by enzymes to provide energy in form of ATP when needed
52
Q

What is the animal equivalent of starch?

A

Glycogen

(Also present in fungi)

53
Q

What monomer makes up the glycogen polymer?

A

Alpha glucose

54
Q

Where is glycogen mainly stored in animals?

A

Liver and muscles

(Centers of high metabolic activity as it is an energy reserve)

55
Q

Which bonds are present in glycogen?

A

1,6 glycosidic bonds
( making it highly branched)

56
Q

Which is more soluble, starch or glycogen?

A

Glycogen
(Is more branched)

57
Q

Give adaptations of glycogen to its storage functions.

A
  • It is high branched thus can be broken down into glucose easily to release energy
  • It is insoluble thus it has no osmotic effect within cells
  • It is insoluble thus cannot be lost in solution form
  • It is a compact polymer hence takes up little space in the cell
58
Q

What is the monomer of cellulose?

A

Beta glucose

59
Q

Which bonds are present in cellulose?

A

1,4-glycosidic bonds
(Unbranched parallel chains)

60
Q

Where is cellulose mainly found?

A

Cell walls of plant cells

61
Q

Many chains of cellulose form?

A

Microfibrils

(Which form macrofibrils)

62
Q

Give commercial uses of cellulose

A

-Used in the manufacture of paper

-Cellulose in cotton is used to make fabrics

63
Q

Give differences between glycogen and starch

A

Glycogen:
-More soluble in water
-More branched
-Hydrolyzed more easily than starch
-Found in animals

Starch:
-Less soluble in water
-Less branched
-Hydrolyzed less easily than starch
-Found in plants

64
Q

What is the biological significance of iced water being less dense than liquid?

A

During the winter, the ice floats thus providing an insulating barrier for aquatic life forms below whose enzymes would otherwise be inactivated leading to death

65
Q

Describe the sequence of events of the action of enzymes

A
  • The enzyme works on a substrate to which it is specific and combines with it forming a short-lived enzyme substrate complex
  • The proximity of the enzyme to the substrate in the complex greatly increases chances of a reaction occurring
  • Once the reaction has taken place, the complex breaks up into products and enzyme.
  • The enzyme remains unchanged by the end of the reaction and is free to interact with more substrate

E + S <=> ES (complex) <=> EP (complex) <=> E + P

66
Q

Explain the importance of water as a solvent

A
  • Transport
    The solvent properties of water mean that it is a transport medium, as it is in blood plasma, tissue fluid, lymph, in mammals and Xylem and Phloem in plants. They are all made up of water and dissolve a number of substances which can then be easily transported.
  • Excretion
    Metabolic wastes like ammonia, urea, excess salts require water to be removed from the body in solution form.
  • Secretion
    They are transported from their place of secretion in solution form (aqueous form) e.g. most digestive juices have enzymes in solution, tears mainly consist of water, snake venoms have toxins in suspension composed of water.
67
Q

How does a nucleoside differ from a nucleotide?

A

A nucleoside is a compound formed when sugar joins a nitrogeneous base with the loss of a water molecule (condensation reaction) while a nucleotide the compound formed when a nucleoside joins a phosphate group by loss of another water molecule

68
Q

State the fat soluble vitamins

A

Vitamin A
Vitamin D
Vitamin E
Vitamin K

69
Q

How do enzymes speed up the rate of a chemical reaction?

A

They lower the amount of activation energy required to initiate a reaction.

70
Q

Give similarities between glycogen and starch

A
  • Both exist in form of granules
  • Both are made up of alpha glucose molecules
  • Both are storage polysaccharides
  • Both have glycosidic bonds
71
Q

Give differences between cellulose and starch

A

Cellulose
-Made up of beta glucose molecules
-Structural polysaccharide
-Not easily hydrolyzed
-Parallel chains

Starch:
-Made up of alpha glucose molecules
-Storage polysaccharide
-Easily hydrolyzed
-Folded helical chains

72
Q

Explain the importance of water as a solvent

A

i. Transport
The solvent properties of water mean that it is a transport medium, as it is in blood plasma, tissue fluid, lymph, in mammals and Xylem and Phloem in plants.
They are all made up of water and dissolve a number of substances which can then be easily transported.

ii. Excretion
Metabolic wastes like ammonia, urea, excess salts require water to be removed from the body in solution form.

iii. Secretion
They are transported from their place of secretion in solution form (aqueous form) e.g. most digestive juices have enzymes in solution, tears mainly consist of water, snake venoms have toxins in suspension composed of water.

73
Q

Give differences between cellulose and glycogen

A

CELLULOSE
- Structural polysaccharide
- Made up of beta glucose molecules
- Present in plants

GLYCOGEN
- Storage polysaccharide
- Made up of alpha glucose molecules
- Present in animals

74
Q

Give adaptations of polysaccharides to their role in food storage

A
  • easily hydrolyzed
  • Folded into compact shapes
  • No osmotic effect on the cell
75
Q

True or false
Oils exist as liquids and fats exist as solids at room temperature

A

True

76
Q

What is the determining factor of the chemical and physical properties of a lipid?

A

The fatty acid

77
Q

Give examples of saturated and unsaturated fatty acids

A

SATURATED
- Stearic acid
- Palmitic acid
- Cerotic acid

UNSATURATED
- Oleic acid
- Linoleic acid

78
Q

Why can’t triglycerides (lipids) dissolve in water?

A

They are non-polar thus do not form hydrogen bonds with water molecules and cannot dissolve in water.

79
Q

What type of reaction yields a lipid?

A

Condensation reaction
(Loss of water molecules)

80
Q

What type of bond is present in a triglyceride that joins the fatty acid to the glycerol?

A

Ester bonds

81
Q

Why are lipids better storage materials in animals than carbohydrates?

A
  • They are lighter than carbohydrates
  • Lipids are more compact
  • Insoluble in water
  • Higher calorific value
  • Serve secondary functions
  • Shock absorbers
  • Buoyancy
  • Insulation
  • No osmotic effect
82
Q

Give the structural functions of lipids

A
  • act as shock absorbers
  • Component of the myelin sheath
  • Subcutaneous, fat layer in the dermis of the skin
  • Buoyancy in aquatic organisms
  • Component of the cell membrane
  • Component of the waxy cuticle in the exoskeleton of arthropods
  • Waxy, cuticle in plants
83
Q

Give the physiological functions of lipids

A
  • they are respired to yield a lot of energy
  • Yield metabolic water on oxidation
  • Stores, fat, or lipid soluble vitamins ADEK
  • Synthesis of steroid hormones
  • Component of brown adipose tissue
84
Q

What is the difference between essential and non-essential amino acids?

A

Essential amino acids cannot be synthesized by the body, but must be provided in the diet while non-essential amino acids can be synthesized by the body

85
Q

Describe the structure of amino acids

A
  • amino acids have an amino group/ basic group, an alpha carbon atom, a carbonyl group/ acidic group, a hydrogen atom and an R group
  • The amino group is responsible for the basic properties. Well, the carbonyl is responsible for the acidic properties.
  • Therefore, the amino acid has both acidic and basic properties. Thus it is known as an amphoteric compound.
  • The R group is responsible for the uniqueness of each amino acid as it varies from one to another
86
Q

What is a Zwitterion?

A

A molecule or ion having separate positively and negatively charged groups

87
Q

What happens to an amino acid in basic conditions?

A
  • The carboxyl group dissociates, and the hydrogen atom is lost, which combines with hydroxide ions in the medium, forming water with a neutral pH
88
Q

What happens to an amino acid in neutral conditions?

A
  • The Carbonyl group dissociates, losing a proton and remains negatively charged
  • The proton is attracted to the basic amino group which becomes positively charged
  • The amino acid becomes dipolar
89
Q

What happens to an amino acid in acidic conditions?

A
  • hydrogen ions in the medium, are attracted to the amino group that has a higher affinity will hydrogen ions and this neutralizes the solution
90
Q

What is a buffer?

A

Chemical substances which resist pH changes when small amounts of an acid or base are added to it

91
Q

What type of reaction leads to the formation of a protein?

A

Condensation reaction
(loss of a water molecule)

92
Q

Describe the process of formation of a polypeptide

A
  • First, a dipeptide is formed through
  • when two amino acids are combined together
  • A peptide bond joins the two amino acids and a water molecule is lost
  • A carbonyl group is exposed on one end of the dipeptide and an amino group on the other thus more amino acids may be added to the dipeptide
  • Addition of more amino acids to the dipeptide forms, a polypeptide chain
93
Q

Describe the bonds that stabilize the protein structure

A

HYDROGEN BONDS
- this form the alpha helix structure
- Hydrogen in OH or NH groups becomes slightly positively charged, attracted to a neighboring, O, or N atoms that can occur along the polypeptide chain
- Hydrogen bonds are weak, but they provide a strong force because of increased numbers in proteins

IONIC BONDS
- acidic R groups are negatively charged well basic R groups are positively charged
- Thus they can be attracted to each other forming ionic bonds
- However, in an aqueous environment ionic bonds are weaker than covalent as they can be broken by changing the pH of the medium

DISULPHIDE BONDS/ BRIDGES
- these may be intrachain or interchain
- They are strong bonds
- Neighboring sulphydryl R groups may be oxidized (hydrogen removed) to form a sulphydryl bond

HYDROPHOBIC INTERACTIONS
- hydrophobic groups come close to exclude water, thus folding
- The hydrophobic groups point inwards while the hydrophilic ones point outwards, making the protein soluble
- This is how globular proteins are formed

94
Q

Describe the fibrous structure of proteins

A
  • The secondary structure is most conspicuous
  • Insoluble in water
  • Physically tough
  • Long parallel, polypeptide chains, cross-linked at intervals, forming long fibers or sheets
95
Q

Give examples of functions performed by fibrous proteins

A
  • Structural functions; such as collagen, myosin in muscle, silk in spiderwebs and keratin in hair, horns and nails
96
Q

Describe the globular structure of proteins

A
  • The tertiary structure is most conspicuous
  • Easily soluble in water
  • Polypeptide chains are tightly folded, to form the spherical shape
97
Q

Give examples of functions performed by globular proteins

A
  • Form enzymes, antibodies and some hormones
98
Q

Give the differences between fibrous and globular proteins

A

FIBROUS
- insoluble
- Repetitive regular sequence of amino acids
- Polypeptide chains form long, parallel strands
- Stable structure
- Support and structural functions, for example, collagen and keratin
- Sheet like

GLOBULAR
- Soluble
- Irregular sequence of amino acids
- Polypeptide chains fold into a spherical shape
- Relatively unstable structure
- Metabolic functions, for example, enzymes and hormones
- Spherical

99
Q

Describe the primary structure of proteins

A
  • this is the linear sequence of amino acids in a polypeptide
  • It is stabilized by peptide bonds
  • It is determined by the sequence of bases in the DNA
100
Q

Describe the secondary structure of proteins

A

ALPHA HELIX
- It’s structure is an alpha helix
- It is stabilize by hydrogen bonds between the CO and NH2 groups
- Examples include keratin which is in hair, horns and hooves

BETA PLEATED SHEETS
- this is in the form of a beta pleated sheet
- The amino acids run, anti-parallel to each other
- It is stabilized by hydrogen bonds
- Examples include spiderwebs

101
Q

Describe the tertiary structure of proteins

A
  • this is a result of extensive coiling and folding of the polypeptide chain into a compact globular shape
  • In addition to the hydrogen bond, more bonds, such as Ionic, disulfide, and hydrophobic bonds, stabilize the tertiary structure
    describe the quaternary structure of proteins
  • More than one polypeptide chain associate to create a quaternary structure for example, hemoglobin (which has two alpha polypeptide chains and two beta polypeptide chains)
  • It is stabilized by hydrogen, ionic and hydrophobic interactions
102
Q

What is an enzyme?

A

A biological catalyst protein in nature, which speeds up the rate of a metabolic reaction without itself undergoing a permanent change

103
Q

State the properties of enzymes

A
  • specific in action
  • Remain chemically unchanged at the end of a reaction
  • Protein in nature
  • Possess active sites
  • Required in small amounts
  • Activity affected by pH and temperature
104
Q

What is the role of enzymes in chemical reactions?

A

They provide an alternative pathway of low activation energy required to initiate a chemical reaction

105
Q

Describe the lock and key hypothesis

A
  • The substrate is imagine to be like a key, whose shape is complementary to the enzyme, which is the lock
  • The site where the substrate binds is the active site and it has a specific configuration
  • The substrate fits in to the active site, and forms the enzyme substrate complex
  • The enzyme product complex once formed the products no longer fit into the active site and escape into the surrounding medium, leaving the active site free to receive further substrate molecules

(It is based on the fact that enzymes are not used up, but used over and over again)

106
Q

Describe the induced fit hypothesis

A
  • enzymes have active sites which are flexible structures, and can be modified
  • The active site is modified as the substrate interacts with the enzymes
  • The amino acids, which make up the active site are molded into a precise shape, which enables the enzyme to perform its catalytic function effectively

(It is based on the fact that enzymes are not static, but rather dynamic molecules)

107
Q

Explain the factors affecting enzyme activity

A
  • enzyme concentration
  • Substrate concentration
  • Temperature
  • pH
108
Q

Define enzyme inhibition

A

This is the slowing down or stopping of enzyme-controlled reactions by inhibitors

109
Q

What is an enzyme inhibitor?

A

These are substances that reduce the activity of enzymes

110
Q

What is an antidote?

A

This is a chemical substance that counteracts the effect of an inhibitor or a poison

111
Q

Explain competitive inhibition

A
  • this occurs when a compound, which has a structure similar to that of the normal substrate, prevents it from entering the active site
  • The inhibitor occupies the active site and prevent the true substrate from entering
  • Therefore the inhibitor and the substrate to compete for the active site
  • If the substrate concentration is increased, the rate of reaction increases
112
Q

Explain non-competitive reversible inhibition

A
  • The inhibitor has no structural similarity to the substrate and combines with the enzyme at a point other than its active site
  • It does not affect the ability of the substrate to bind to the enzyme, but makes it impossible for catalysis to take place
  • The enzyme loses its three-dimensional structure
  • The rate of reaction decreases with increasing inhibitor concentration
  • Once the inhibitor is removed the enzyme, may regain its three-dimensional structure and normal catalysis resumes
113
Q

Describe non-competitive irreversible inhibition

A
  • The inhibitor permanently attaches to the enzyme, their attachment is irreversible
  • This causes the enzyme to lose its three-dimensional shape. Thus the shape of the active site is completely altered, and the substrate no longer fits into the active site.
  • The proteins of the enzyme molecule precipitates
114
Q

Give the importance of enzyme inhibitors

A
  • regulate enzyme controlled reactions
  • have important medical and agricultural uses for example in drugs and pesticides
  • Enable biochemists to reconstruct metabolic pathways
  • Provide information about the shapes and properties of active sites
115
Q

Give the categories of enzymes according to the reactions they catalyze

A
  • Oxidoreductases
  • Transferases
  • Hydrolases
  • Lyases
  • Isomerases
  • Ligases
116
Q

Explain how end-product inhibition in an enzyme controlled reaction is negative feedback

A

For biochemical reactions that occur in series, accumulation of the final product acts as an allosteric inhibitor for the first enzyme controlling the first step of the reaction pathway. This temporarily stops its formation.
However, if the final product reduces, the inhibition is reduced or removed, and more end-products are formed

117
Q

Why are enzyme controlled reactions carried out in a step-by-step mechanism?

A

The body can control the amount of energy produced by the body’s requirement

118
Q

What are enzyme cofactors?

A

These are non-Protein compounds required for efficient activities of enzymes

119
Q

Define inorganic ions as enzyme activators

A

These mould the enzyme or substrate into a shape that allows the enzyme-substrate complex to be formed.

For example, salivary amylase activity is increased in the presence of chloride ions.

120
Q

Define prosthetic groups

A

These are organic molecules tightly bound to the enzyme on a permanent basis that assist the catalytic function of the enzyme

eg Haem

121
Q

Define coenzymes

A

These are organic non-protein molecules not bonded to the enzyme. They do not remain attached to the enzyme between reactions.

eg NAD, CoA, ATP

(They are organic)

UACE Biology (20 decks)

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