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IB Biology > molecular biology - part one > Flashcards

molecular biology - part one Flashcards

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1
Q

What is molecular biology?

A
  • A branch of biology that explains living processes in terms of the chemical substances involved
  • Considers the various biochemical processes of a living organism and breaking it down into its component parts
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2
Q

What is vitalism?

A
  • The theory that the origin and phenomena of life are due to a vital principle, which is different from purely chemical or physical forces
  • Belief that organic compounds in plants/animals could only be made with the help of the “vital principle”
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3
Q

What is the significance of the synthesis of urea?

A
  • urea is a compound that is produced by living organisms
  • when urea was synthesized artifically, it disproved vitalism (it was believed that organic compounds produced by living organisms relied on a “vital principle” and thus could not be synthesized outside of the body)
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4
Q

How many bonds can carbon form? Why is this signifcant?

A
  • four bonds

- allows a diversity of compounds to exist

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5
Q

State four important carbon compounds for life

A
  1. Carbohydrates
  2. Lipids
  3. Proteins
  4. Nucleic acids
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6
Q

Carbohydrates

A
  • composed of carbon, hydrogen and oxygen in the ratio of two hydrogen atoms to one oxygen
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7
Q

Lipids

A
  • broad class of molecules that are insoluable in water
  • includes steroids, waxes, fatty acids and trigylcerides
  • trigylcerides are fats if they are solid at room temperature or oils if they are liquid at room temperature
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8
Q

Proteins

A
  • composed of one or more chains of amino acids
  • all amino acids in these chains contain the elements carbon, hydrogen, oxygen and nitrogen
  • two of the twenty amino acids also contain sulphur
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9
Q

Nucleic acids

A
  • chains of subunits called nucleotides which consist of carbon, hydrogen, oxygen, nitrogen and phosphorus
  • two types of nucleic acid: ribonucleic acid (RNA) and deoxyribonucleic acid (DNA)
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10
Q

Define anabolism

A

the synthesis of complex molecules from simpler molecules including the formation of macromolecules from monomers by condensation reactions

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11
Q

List some examples of anabolism

A
  • protein synthesis using ribosomes
  • DNA synthesis during replication
  • photosynthesis, including production of glucose from carbon dioxide and water
  • synthesis of complex carbohydrates including starch, cellulose, and glycogen
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12
Q

Define catabolism

A

the breakdown of complex molecules into simpler molecules including the hyrdrolysis of macromolecules into monomers

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13
Q

List some examples of catabolism

A
  • digestion of food in the mouth, stomach and small intestine
  • cellular respiration in which glucose or lipids are oxidized to carbon dioxide and water
  • digestion of complex carbon compounds in dead matter by decomposers
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14
Q

Define metabolism

A

The web of all the enzyme catalysed reactions in a cell or organism

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15
Q

Define metabolic pathway

A

a sequence of chemical reactions undergone by a compound or class of compounds in a living organism.

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16
Q

What are common patterns in metabolism

A
  1. Most chemical changes happen not in one large jump, but in a sequence of small steps, together forming what is called a metabolic pathway
  2. Most metabolic pathways involve a chain of reactions.
  3. Some metabolic pathways form a cycle rather than a chain. In this type of pathway, the end product of one reaction is the reactant that starts the rest of the pathway.
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17
Q

What is the role of enzymes in metabolism?

A
  • enzymes lower the activation energy of the chemical reactions that they catalyse
  • in other words, they act as catalysts to speed up chemical reactions
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18
Q

Define substrate

A

the substance on which an enzyme acts

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19
Q

Enzyme-subtrate specificity

A
  • the active site of an enzyme is very specific to its substrates as it has a very precise shape.
  • this results in enzymes being able to catalyze only certain reactions as only a small number of substrates fit in the active site.
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20
Q

Active site

A
  • The active site is the region on the surface of the enzyme which binds to the substrate molecule
  • The active site and the substrate complement each other in terms of both shape and chemical properties
  • Hence only a specific substrate is capable of binding to a particular enzyme’s active site
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21
Q

Explain enzyme catalysis

A
  • involves molecular motion and the collision of substrates with the active site
    1. The substrate binds to the active site of the enzyme
  • some enzymes have two substrates that bind to different parts of the active stie
  • a substrate molecule can only bind to the active site if it moves very close to it; movement of both the substrate and the enzyme are random, so collisions occur because of random movements
  • successful collisions are ones in which the substrate and active site are correctly alligned to allow binding to take place
    2. While the substrates are bound to the active site, they change into different chemical substances, which are the products of the reaction
    3. The products separate from the active site, leaving it vacant for substrates to bind again
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22
Q

List three factors that affect enzyme activity

A
  1. temperature
  2. pH
  3. substrate concentration
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23
Q

Define denaturation

A
  • the irreversible alteration of a protein/biological molecule’s structure (ie. primary/secondary/tertiary/quaternary) due to certain conditions such as temperature or pH
  • since the biological activity of a protein is related to its primary, secondary, tertiary and quaternary structure, alterations to the structure disrupts its biological activity
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24
Q

What are the causes and consequences of denaturation in enzymes?

A

Note: Enzymes are proteins

Causes:

  • high temperatures
  • high/low pH

Consequences:

  • the active site is altered, meaning that the substrate may no longer be able to bind
  • if the subtrate can still bind, the reaction which the enzyme normally catalyses does not occur
  • in many cases, denaturation causes enzymes that were dissolved in water to become insoluable and form a precipitate
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25
Q

What is meant by immobilized enzyme?

A
  • the attachment of enzymes to another material or into aggregations so that the mvoement of the enzyme is restricted
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26
Q

What are the practical applications and advantages of immobilized enzymes?

A

Application:
- widely used in industries (ie. biotechnology, medical, food, agriculture, etc.)

Advantages

  • enzyme can easily be separated from the products of the reaction, stopping the reaction at the ideal time and preventing contamination of the products
  • enzymes can be recycled which savves money (some enzymes are very expensive)
  • immoblization increases the stabiltiy of enzymes to changes such as temperature and pH, reducing the rate at which they are degraded and have to be replaced
  • substrates can be exposd to higher enzyme concentrations than with dissolved enzymes, speeding up reaction rates
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27
Q

How and why is lactose-free milk produced?

A
  • Lactose is a disaccharide of glucose and galactose which can be broken down by the enzyme lactase

How: Lactose-free milk can be produced by treating the milk with the enzyme lactase

  • The lactase is purified from yeast or bacteria and then bound to an inert substance (such as alginate beads)
  • Milk is then repeatedly passed over this immobilised enzyme, becoming lactose-free

Why:

  • some poeple are lactose-intolerant
  • galactose/glucose are sweeter than lactose, so less sugar needs to be added to sweet foods such as milk shakes or fruit yoghurt
  • lactose tends to crystallize during the production of ice cream giving a gritty texture; galactose/glucose are more soluable and give a smoother texture
  • bacteria ferment glucose and galactose more quickly than lactose, so the production of yoghurt and cottage cheese is faster
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28
Q

What is an enzyme inhibitor?

A

Chemical substances that bind to enzymes and reduce the activity of the enzyme

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29
Q

List the two types of enzyme inhibitors

A
  1. Competitive

2. Non-competitive

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30
Q

Explain competitive inhibition

A
  • Competitive inhibition involves a molecule, other than the substrate, binding to the enzyme’s active site
  • The molecule (inhibitor) is structurally and chemically similar to the substrate (hence able to bind to the active site)
  • The competitive inhibitor blocks the active site and thus prevents substrate binding
  • As the inhibitor is in competition with the substrate, its effects can be reduced by increasing substrate concentration
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31
Q

Give an example of a competitive inhibitor

A
  • Relenza is a synthetic drug designed by Australian scientists to treat individuals infected with the influenza virus
  • Virions are released from infected cells when the viral enzyme neuraminidase cleaves a docking protein (haemagglutinin)
  • Relenza competitively binds to the neuraminidase active site and prevents the cleavage of the docking protein
  • Consequently, virions are not released from infected cells, preventing the spread of the influenza virus
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32
Q

Define allosteric site

A
  • a special site on the enzyme away from the active site
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33
Q

Explain non-competitive inhibition

A
  • Non-competitive inhibition involves a molecule binding to a site other than the active site (an allosteric site)
  • The binding of the inhibitor to the allosteric site causes a conformational change to the enzyme’s active site
  • As a result of this change, the active site and substrate no longer share specificity, meaning the substrate cannot bind
  • As the inhibitor is not in direct competition with the substrate, increasing substrate levels cannot mitigate the inhibitor’s effect-
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34
Q

Give an example of a non-competitive inhibitor

A
  • Cyanide is a poison which prevents ATP production via aerobic respiration, leading to eventual death
  • It binds to an allosteric site on cytochrome oxidase – a carrier molecule that forms part of the electron transport chain
  • By changing the shape of the active site, cytochrome oxidase can no longer pass electrons to the final acceptor (oxygen)
  • Consequently, the electron transport chain cannot continue to function and ATP is not produced via aerobic respiration
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35
Q

Explain how databases can be used to identify new anti-malarial drugs

A
  • chloroquine is an anti-malarial drug, but the malarial parasite is becoming increasingly resistant to it; therefore, scientists are in search of new anti-malarial drugs
  • the genome of a strain of the malarial parasite is sequenced in a database
  • 310,000 chemicals are screened against the chloroquine-sensitive strain of the parasite and the chloroquine-resistant strain to see if these chemicals inhibit metaboism
  • in this way, 19 chemicals that inhibit the enzymes normally targeted by anti-malarial drugs were found; 15 chemicals that bind to a total of 61 different malarial proteins were found
  • provides scientists with possible lines of investigation in the search of new drugs
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36
Q

How can the rate of an enzyme-controlled reaction be measured?

A
  • measure the rate of disappearance of a substrate OR measure the rate of appearane of a product
  • convert the units to a rate unit if applicable (should be “per second”)
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37
Q

Explain the molecular structure of water with reference to its chemical bonds

A
  • a water molecule is formed by covalent bonds between an oxygen atom and two hydrogen atoms
  • the bond involves unequal sharing of electrons; it is a polar covalent bond
  • the nucleus of the oxygen atom is more attractive to electrons than the nuclei of the hydrogen atoms
  • the oxygen atom has a partial negative charge and the hydrogen atoms have a partial positive charge
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38
Q

List four properties of water that result from hydrogen bonding and dipolarity

A
  1. Cohesive property
  2. Adhesive property
  3. Thermal property
  4. Solvent property
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39
Q

Explain the cohesive property of water

A
  • Cohesion is the ability of like molecules to stick together
  • Water is strongly cohesive (it will form hydrogen bonds) due to the polar nature of water molecules
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40
Q

Give an example of the benefit of the cohesive property of water to living organisms

A
  • Useful for water transport in plants
  • Transpiration stream; the cohesive property of water allows water molecules to pull up other water molecules against gravity
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41
Q

Explain the adhesive property of water

A
  • Adhesion is the ability of dissimilar molecules to stick together
  • Water will form intermolecular associations with polar and charged molecules
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42
Q

Give an example of the benefit of the adhesive property of water to living organisms

A
  • Useful in leaves, where water adheres to cellulose molecules in cell walls
  • When water evaporates from the cell walls, adhesive forces cause water to be drawn out of the nearest xylem vessel
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43
Q

List the thermal properties of water

A
  1. High specific heat capacity

2. High latent heat of vaporization

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44
Q

Explain the high specific heat capacity of water

A
  • hydrogen bonds restrict the motion of water molecules
  • increases in the temperature of water require hydrogen bonds to be broken
  • brekaing hydrogen bonds requires energy
  • therefore, the amount of energy required to raise the temperature of water is relatively large
  • to cool down, water must lose relatively large amounts of energy
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45
Q

Give an example of the benefit of the high specific heat capacity of water to living organisms

A
  • water’s temperature stays relatively stable in comparison to air/land, so it is a thermally stable habitat for aquatic organisms
46
Q

Explain the high latent heat of vaporization of water

A
  • when a molecule evaporates, it separates from other molecules in a liquid and becomes a vapour molecule
  • the heat required to evaporate is known as the latent heat of vaporization
  • considerable amounts of heat are needed to evaporate water due to the hydrogen bonds
47
Q

Give an example of the benefit of the high latent heat of vaporization of water to living organisms

A
  • since lots of heat is needed to evaporate water, evaporation has a cooling effect (ie. uses up heat)
  • this makes it a good evaporative coolant (ie. sweating)
48
Q

Explain the high boiling point of water

A
  • the boiling point of a substance is the highest temperature that it can reach in a liquid state
  • considerable amounts of heat are required to boil water due to hydrogen bonds
49
Q

Give an example of the benefit of the high boiling point of water to living organisms

A
  • water is liquid over a broad range of temperatures (from 0 degrees Celcius to 100 degress Celcius)
  • this is the temperature range found in most habitats on Earth
  • therefore, water is available in the form of liquid in most habitats
50
Q

Explain the solvent properties of water

A
  • the polar nature of water molecule means that it forms shells around charged and polar molecules, preventing them from clumping together and keeping them in solution
  • water forms hydrogen bonds with polar molecules
  • partially negative oxygen pole is attracted to postiively charged ions
  • partially positive hydrogen poles are attracted to negatively charged ions
  • therefore, both positive and negative ions will dissolve
51
Q

Give an example of the benefit of the solvent properties of water to living organisms

A
  • cytoplasm is a complex mixture of dissolved substances in which the chemical reactions of metabolism occur
52
Q

Explain hydrophobic interactions

A
  • forces that cause nonpolar molecules to join together into groups in water
  • since water molecules are polar, they have a cohesive property; thus, water molecules are attracted to other water molecules
  • water molecules are more attracted to each other than to the nonpolar molecules, so nonpolar molecules tend to join together in water to form larger and larger groups
53
Q

Explain the differences in the thermal properties of water and methane

A

Methane (CH4) provides a good basis for comparison with water due to the many similarities between their structures:

  • Comparable size and weight (H2O = 18 dalton ; CH4 = 16 dalton)
  • Comparable valence structures (both have tetrahedral orbital formations, but water is bent due to unbonded electron pairs)

The differences in thermal properties between water and methane arise from differences in polarity between the molecules:

  • Water is polar and can form intermolecular hydrogen bonds (due to high electronegativity of oxygen atom)
  • Methane is non-polar and can only form weak dispersion forces between its molecules (carbon has a lower electronegativity)

This means water absorbs more heat before changing state (each H-bond has an average energy of 20 kJ/mol)

  • Water has a significantly higher melting and boiling point
  • Water has a higher specific heat capacity (energy required to raise the temperature of 1 g of substance by 1ºC)
  • Water has a higher heat of vaporisation (energy absorbed per gram as it changes from a liquid to a gas / vapour)
  • Water as a higher heat of fusion (energy required to be lost to change 1 g of liquid to 1 g of solid at 0ºC)
54
Q

Explain why water is an effective coolant in sweat

A
  • The evaporation of water as sweat is a fundamental mechanism employed by humans as a means of cooling down
  • The change of water from liquid to vapour (evaporation) requires an input of energy
  • This energy comes from the surface of the skin when it is hot, therefore when the sweat evaporates the skin is cooled
  • Because water has a high specific heat capacity, it absorbs a lot of thermal energy before it evaporates
  • Thus water functions as a highly effective coolant, making it the principal component of sweat
55
Q

Explain the method of transport of glucose in blood in relation to their solubilty in water

A

A polar molecule that is freely soluble in water and is carried dissolved in blood plasma

56
Q

Explain the method of transport of amino acids in blood in relation to their solubilty in water

A

Amino acids have both negative and positive charges and are thus soluble in water. Howveer, their solubiltiy varies depending on the R group, some of which are hydrophilic whie others are hydrophobic. All amino acids are soluble enough to be carried dissolved in blood plasma

57
Q

Explain the method of transport of cholesterol in blood in relation to their solubilty in water

A

Hydrophobic, apart from a small hydrophilic region at one end. It is transported with fats in lipoprotein complexes; positioned in the phospholipid monolayers, with the hydrophilic region facing outwards in the region with the phosphate heads.

58
Q

Explain the method of transport of fats in blood in relation to their solubilty in water

A

Entirely nonpolar and are relatively large, making them insoluble in watr. They are carried in blood inside lipoprotein complexes which are groups of molecules with a single layer of phospholipid on the outside and fats and proteins inside. It is arranged so that the hydrophilic phosphate heads face outwards, in contact with water, while the hydrophobic tails/lipids/proteins are inside to avoid contact with water.

59
Q

Explain the method of transport of oxygen in blood in relation to their solubilty in water

A

A nonpolar molecule; it can dissolve in water due to its small size, but only sparingly and in low concentrations. Thus, there are hemoglobin in red blood cells, which have binding sites for oxygen to increase the capacity of the blood for oxygen transport

60
Q

Explain the method of transport of sodium chloride in blood in relation to their solubilty in water

A

Sodium chloride (NaCl) is an ionic compound that is freely soluble in water, and its components (Na+ and Cl–) may be freely transported within the blood

61
Q

Define monosaccharide

A

single sugar units

62
Q

Define disaccharide

A

consist of two monosaccharides linked together

63
Q

Define polysaccharide

A

consist of many monosaccharides linked together

64
Q

How are disaccharides/polysaccharide polymers formed?

A

monosaccharides monomers are linked together by condensation reactions to form disaccharides and polysaccharide polymers

65
Q

Glycosidic bond

A

a type of covalent bond that joins a carbohydrate (sugar) molecule to another group, which may or may not be another carbohydrate.

66
Q

List 4 examples of monosaccharides

A
  1. glucose
  2. fructose
  3. ribose
  4. galactose
67
Q

List 3 examples of disaccharides

A
  1. sucrose
  2. lactose
  3. maltose
68
Q

List 3 examples of polysaccharides

A
  1. starch
  2. glycogen
  3. cellulose
69
Q

Differentiate between the structure of Alpha-D glucose and Beta-D glucose

A
  • glucose has 5 -OH groups
  • glucose can have the -OH group on the carbon atom 1 pointing either upwards or downwards
  • in Alpha-D glucose, the -OH group points downwards, whilst it points upwards in Beta-D glucose
70
Q

How is cellulose formed?

A
  • made by linking together Beta-D glucose molecules (bound in a 1-4 arrangement)
  • cellulose molecules are unbranched chains of Beta-D glucose, allowing them to form bundles (called cellulose microfibrils) with hydrogen bonds linking the cellulose molecules
71
Q

What are the functions of cellulose?

A
  • the cellulose microfibrils have very high tensile strength

- used in plant cell walls to prevent plant cells from bursting, even when high pressures have developed

72
Q

How is starch formed?

A
  • made by linking together Alpha-D glucose molecules (bound in 1-4 arrangement)
  • exists in two forms: amylose and amylopectin
73
Q

Differentiate between amylose and amylopectin

A
  • Both are types of starch
  • Amylose is a linear (helical) molecule while amylopectin is branched (contains additional 1-6 linkages)
  • Amylose is harder to digest and less soluble, however, as it takes up less space, is the preferred storage form in plants
74
Q

What are the functions of starch?

A
  • an energy storage polysaccharide found in plants
  • only made by plant cells
  • hydrophilic but are too large to be soluble in water, so they are useful in cells where large amounts of glucose need to be stored without causing too much water to enter by osmosis
75
Q

How is glycogen formed?

A
  • similar to starch; formed by linking together Alpha-D glucose molecules
  • there is more branching in glycogen than starch
  • glycogen is made by animals and some fungi
76
Q

What are the functions of glycogen?

A
  • similar to starch, it acts as a storage for energy in the form of glucose, in cells where large stores of dissovled glucose would cause osmotic problems
  • unlike starch, it is found in animals/some fungi rather than plants
77
Q

How are triglycerides formed?

A
  • triglycerides are formed by condensation from three fatty acids and one glycerol
  • eat of the fatty acids is linked to the gylcerol by a condensation reaction, so three water molecules are produced
  • the linkage formed between each fatty acid the glycerol is an ester bond
78
Q

Ester bond

A
  • a type of bond that is formed when an acid reacts with the -OH group in an alcohol
79
Q

Compare/contrast lipids and carbohydrates as energy storages

A
  • lipids and carbohydrates are both used for energy storage in humans
  • lipids (adipose tissue) are usually used for long-term energy storage

Advantage of lipids:

  • the amount of energy released in cellular respiration per gram of liids is double that of carbohydrates
  • fats form pure droplets in cells with no water associated while each gram of glycogen is associated with about two grams of water
  • lipids are 6x more efficient in the amount of energy that can be stored per gram of body mass for the above two reasons, which is important because we have to carry around these energy stores wherever we go (it is especially important in birds which have to fly)
  • lipids have secondaty roles such as heat insulators and shock absorbers

Advantages of glycogen (carbohydrate)

  • used in short-term storage
  • can be broken down to glucose rapidly and then transported by the blood to where it is needed whereas fats cannot be mobilized rapidly
  • can be used in oth anaerobic and aerobic cellular respiration whereas fats can only be used in aerobic respiration
80
Q

What is the formula to calculate BMI?

A

mass in kg divided by the square of the height in metres

kg / m^2

81
Q

List the BMI categories and their ranges

A

below 18.5: underweight
18.5-24.9: normal weight
25.0-29.9: overweight
over 30.0: obese

82
Q

List the types of fatty acids

A
  • saturated

- unsaturated (monounsaturated, polyunsaturated)

83
Q

Saturated fatty acid

A
  • a fatty acid with single bonds betwen all of its carbon atoms
  • contains as much hydrogen as it possibly could
84
Q

Unsaturated fatty acid

A
  • fatty acids that have one or more double bonds

- contain less hydrogen that it could

85
Q

Monounsaturated fatty acid

A
  • a type of unsaturated fatty acid that only has one double bond
86
Q

Polyunsaturated fatty acid

A
  • a type of unsaturated fatty acid that has more than one double bond
87
Q

Differentiate between cis- and trans- fatty acids

A

cis-fatty acids

  • have the hydrogen aroms on the same side of the two carbon atoms that are double bonded
  • are much more common
  • there is a bend in the hydrocarbon chain at the double bond
  • do not pack well together in regular arrays; therefore have lower melting point and are usually liquid at room temperature (oil)

trans-fatty acids

  • have the hydrogen atoms on opposite sides of the two carbon atoms that are double bonded
  • less common; produced artifically
  • do not have a bend in the hydrocarbon chain
  • pack together; therefore have a higher melting point and are usually solid at room temperature
88
Q

What is CDH?

A
  • coronary heart disease

- the coronary arteries become partially blocked by fatty deposits, leading to blood clot formation and heartt attacks

89
Q

Evaluate the statement: Consumption of saturated fats causes CDH

A
  • a positive correlation has been found between saturated fatty acids intake and rates of CHD in many research programs
  • however correlation does not equal causation
  • another factor correlated with saturated fat intake, such as low amounts of dietary fibre, could be the actual cause of CHD
  • there are populations that do not fit the correlation (ie. Maasai of Kenya) which have a diet rich in meat/fat/blood/milk and thus have a hgih consumption of saturated fats but very low CHD rates
90
Q

Evaluate the statement: Consumption of monounsaturated fats prevents CHD

A
  • populations whose diets are rich in olive oil, which contains cis-monounsaturated fatty acids, have low rates of CHD
  • it is claimed that the low rate of CHD is caused by the intake of cis-monounsaturated fatty acids
  • however, once again, correlation does not equal causation
  • it could be genetic factors or other aspects in the diet that explain the CHD rates
91
Q

Evaluate the statement: Consumption of trans-fats causes CDH

A
  • there is a positive correlation between trans-fats consumed and rates of CHD
  • other risk factors have been tested to see if they can account for the correlation, but none did
  • in patients who died from CHD, fatty deposits in the diseased arteries have been found to contain high concentrations of transfats
  • thus, it is likely that trans-fats do cause CHD
92
Q

What are some limitations that must be considered when evaluating health claims made about lipids?

A
  1. How large was the sample size?
    - larger sample size = more accurate
  2. How even was the sample in sex/age/state of health/life style?
    - a more even sample = less likely that other factors affect the results
  3. If the sample was uneven, were the results adjusted to eliminate other factors?
  4. Were the measurements of lipid instake and disease rates reliable?
    - surveys may be inaccurate as people may report incorrectly
93
Q

What are some implications that must be considered when evaluating health claims made about lipids?

A
  1. Is there a correlation between instake of the lipid being investigated and the rate of the disease or the health benefit?
    - could be positive or negative
  2. How large is the difference between mean rates of the disease with different levels of lipid intake?
    - small differences may not be significant
  3. How widely spread is the data?
    - more widely spread = less likely for the differences to be significant
  4. If statistical tests have been done on the data, do they show significant differences?
94
Q

How are polypeptides formed?

A
  • formed by linking together amino acids by condensation reactions; results in the formation of water
  • happens on ribosomes by a process called translation
95
Q

Carboyl group

A

-COOH

96
Q

Amino group

A

-NH2

97
Q

Peptide bond

A

the bond that is formed between two amino acids during the condensation reaction in the formation of polypeptides

98
Q

How many types of amino acids are there? What is the significance of this?

A
  • 20
  • because of the R groups, the 20 amino acids are chemically very diverse
  • allow for a huge range of possible polypeptides (effecitvely infinite)
99
Q

What limits the amount of polypeptides that can be synthesized by a living organism?

A
  • while practically infinite possibly polypeptides can be created, the amount that is actually created by a living organism is limited
  • amino acid sequence of polypeptides is coded for by genes
  • thus, genes limit the amount of polypeptides that can be synthesized by a living organism
100
Q

How many polypeptides does a protein contain?

A

A protein may consist of a single polypeptide or more than one polypeptide linked together

101
Q

Differentiate between fibrous and globular proteins

A

Fibrous

  • usually elongated, with a reepating structure
  • amino acid sequence prevents folding up and ensures that the chain of amino acids remians in an elongated form

Globular

  • intricate shape that often includes parts that are helical or sheet-like
  • polypeptides gradually fold up as they are made to develop the final conformation
  • this is stabilized by bonds between the R groups of the amino acids
  • in water-soluble globular proteins, the hydrophilic R groups are on the outside of the molecule and usually hydrophobic R groups inside
102
Q

Outline the causes of the denaturation of proteins

A
  1. Heat
    - causes vibrations within the molecule that can break intermolecular bonds or intereactions
    - 3D structure of the protein is altered
    - proteins vary in their heat tolerance
  2. pH
    - extremes of pH, both acidic and alkaline, can cause denaturation
    - charges on R groups are changed, breaking ionic bonds within the protein or causing new ionic bonds to form
    - 3D structure of the protein is altered
103
Q

List 12 functions of proteins

A
  1. Catalysis
  2. Muscle contraction
  3. Cytoskeletons
  4. Tensile strengthening
  5. Blood clotting
  6. Transport of nutrients and gases
  7. Cell adhesion
  8. Membrane transport
    9, Hormones
  9. Receptors
  10. Packing of DNA
  11. Immunity
104
Q

What is the function of the protein rubisco?

A
  • An enzyme involved in the light independent stage of photosynthesis
  • Catalyses the reaction that fixes carbon dioxide from the atmosphere
  • Present at high concentrations in leaves; probably the most abundant of all proteins on Earth
105
Q

What is the function of the protein insulin?

A
  • Produced as a signal to many cells in teh body to absorb glucose and help reduce the glucose concentration of the blood
  • Cells in the body have a receptor for insulin in their cell membrane to which the hormone binds reversibly
  • The shape and chemical properties of the insulin molecule correspond precisely to the binding site on the receptor, so insulin binds to it, but not other molecules
  • Secreted by beta cells in the pancreas and is transported by the blood
106
Q

What is the function of the protein immunoglobulin?

A
  • AKA antibodies
  • have sites at the tips of their two arms that bind to antigens on bacteria or other pathogens
  • the other parts of the immunoglobulin cause a response, such as actng as a marker on phagocytes that can engulf the pathogen
  • the binding sites are hypervariable; the body can produce a huge range of immunoglobulins, each with a different type of binding site; this is the basis of specific immunity to disease
107
Q

What is the function of the protein rhodospin?

A
  • one of the pigments that absorb light
  • a membrane protein of the rod cells of the retina
  • consists of lgiht sensitive retinal molecule, not made of amino acids, surrounding by an opsin polypeptide
  • when the retinal molecule absorbs a single photon of light, it changes shape, causing a change to the opsin, in turn leading to the rod cell sending a nerve impulse to the brain
  • even very low light intensities can be detected
108
Q

What is the function of the protein collagen?

A
  • rope-like proteins made of three polypeptides wound together
  • about a quarter of all protein in the human body is collagen (more abundant than any other protein)
  • forms a mesh of fibres in skin and in blood vessel walls that resist tearing
  • bundles of parallel collagen molecules give ligaments and blood vessel walls their immense strength
  • forms part of the structure of teeth and bones, helping to prevent cracks and fractures
109
Q

What is the function of the protein spider silk?

A
  • different types of silk with different functions are produced by spiders
  • it is used to make the spokes of spiders’ webs and the lifelines on which spiders suspend themselves
  • when first made, it contains regions where the polypeptide forms parallel arrays; other regions seem like a disordered tangle, but when the silk is stretched, they gradually extend, making the silk extensible and very resistant to breaking
110
Q

Proteome

A
  • proteome is all the proteins produced by a cell, a tissue, or an organism
  • the proteome is variable because different cells in an organism make different proteins; even in a singl ecell, the proteins that are made vary over time depending on the cell’s activities
  • proteome thus reveals what is actually happening within an organism, not what potentially could happen
  • within a species, there are strong similarities in the proteome of all indiviudals, but also differences; every individual has a unique proteome

IB Biology (17 decks)

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