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IBDP Biologie > 2. Molecular Biology > Flashcards

2. Molecular Biology Flashcards

1
Q

Why is molecular biology useful in living processes?

A
  • explains living processes in terms of chemical substances and reactions
  • makes it possible to solve problems associated with living processes by balancing the chemical substances and reactions involved
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2
Q

List the organic compounds in organic chemistry and non-organic carbon compounds.

A

Organic compounds: the chemical substances containing carbon compounds in living organisms
Eg. glucose, fats, proteins

Non- organic carbon compounds: carbon dioxide, carbon monoxide, carbonates and hydrogent carbonates.

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3
Q

What are 4 carbon based compounds in living organisms?

A

Lipids
Carbohydrates
Nucleic acids
Proteins

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4
Q

Define macromolecules.

A

Organic compounds that make up living organisms, building blocks that join together to form larger structures called polymers.

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5
Q

List the functions and names of 4 carbohydrates macromolecules.

A

Alpha-D-glucose
Used in the production of ATP in cells.

Beta-D-glucose
Used to build cell walls in plants.

Starch
Used as long-term storage in plants.

Ribose
Used as a component of DNA and RNA.

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6
Q

List the functions and names of 3 lipids macromolecules.

A

Triglycerides
Used as long-term storage in adipose tissue in animals.

Steroids
Used as chemical messengers in the body, have a distinctive ring shape.

Phospholipids
Major component of plasma membranes.

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7
Q

List the functions and names of 3 proteins macromolecules.

A

Structural proteins
Form the structural framework of many parts of the body.

Enzymes
Metabolic proteins that speed up chemical reactions in the body.

Polypeptides
A sequence of amino acids that may make up a protein, or a series of polypeptides can also make up a protein.

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8
Q

List the functions and names of 2 nucleic acids macromolecules.

A

DNA
Used to store genetic information.

RNA
Used to create proteins at ribosomes using the information stored in DNA

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9
Q

How can you test the presence of carbohydrates?

A
  • using benedict’s solution
  • called reducing sugars
  • blue to orange when heated
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10
Q

Define metabolism, anabolism, and catabolsim.

A

Metabolism:
all the enzymatic reactions that take place inside a living organism

Anabolism:
synthesis of complex molecules from simple molecules

Catabolism:
breakdown of complex molecules into simpler molecules

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11
Q

Explain the process of anabolism.

A

Process that requires input of energy
Includes the formation of macromolecules from monomers by condensation reactions
Eg. protein and starch made from amino acids and glucose units

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12
Q

Explain the process of catabolism.

A

Energy is released
Includes the hydrolysis of macromolecules into monomers
Eg. The breakdown of sugars or fats to release energy

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13
Q

Differentiate between hydrolysis and condensation reactions.

A

Hydrolysis reaction: the breaking of chemical bonds by the addition of water molecules

Condensation reaction: the reaction in which two smaller molecules combine to form a larger molecule with the accompanied formation of water or some simple molecule

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14
Q

What is the theory of vitalism?

A

It explains that organic compounds could only be synthesised by living organisms as they possessed an element that non-living organisms did not have.

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15
Q

Why do hydrogen bonds between water molecules form?

A

Due to the presence of both positive and negative charges

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16
Q

Why is the polarity of water molecules important?

A

The polarity of water molecules allows them to attract other polar and charged compounds and form hydrogen bonds with them. This means that most polar or charged compounds can be dissolved in water.

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17
Q

What happens in the cohesion of water?

A
  • water molecules stick together due to hydrogen bonding between them
  • each water molecule can form four hydrogen bonds with other water molecules in a tetrahedral agreement
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18
Q

What is surface tension?

A

The presence of a large number of hydrogen bonds in water gives cohesive forces great strength.
- due to hydrogen bonding water surface behave like strong elastic membrane

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19
Q

What is adhesion?

A

Interaction of water molecules with other different molecules

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20
Q

What is capillary action?

A

The movement of water molecules and all things that dissolve in it withing thin spaces without relying on gravity

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21
Q

What is the high specific heat capacity and why is it necessary?

A

The high specific heat capacity is the amount of heat that must be absorbed or released for 1g of a substance to change its temperature by 1 degree celsius. It is necessary to break the hydrogen bonds in water.

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22
Q

How does the high specific heat capacity of water help in aquatic ecosystems?

A

The high specific heat capacity of water means that the temperature in aquatic ecosystems, for example ponds, lakes and seas, does not change rapidly, making these ecosystems stable.

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23
Q

Why is water a great coolant?

A

Water is used as a coolent because of its high specific heat capacity,water can absorb large amounts of excess heat without much increase in temperature.

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24
Q

What are solvents?

A

All reactions in cells occur in liquid medium and are dependent on water to dissolve the reactants for reactions to proceed (e.g. hydrolysis).

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25
Q

How does cohesive properties benefit living organisms?

A
  • allows water to be pulled up from roots to leaves

- permits insects to float on surface water

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26
Q

How does adhesive properties benefit living organisms?

A
  • movement of water in xylem vessles

- capillary action in blood vessels

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27
Q

How does thermal properties benefit living organisms?

A
  • evaporation - helps cool sweat

- high specific heat capacity - aquatic ecosystems

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28
Q

How does solvent properties benefit living organisms?

A
  • water dissolves minerals and transports it in xylem vessels
  • water in blood dissolve nutrients and gases
  • universal solvent
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29
Q

How do the insoluble substances travel in the human body?

A

The water-insoluble substances will be absorbed and transported via lymph vessels

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30
Q

List the biological molecules found in blood.

A 
Glucose 
Amino acids
Fats 
Cholesterol 
Sodium chloride 
Oxygen
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31
Q

Explain the solubility and polarity of glucose in blood.

A
  • hydrophilic
  • polar
  • soluble
  • blood glucose levels need to be maintained due to effect on osmotic potential
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32
Q

Explain the solubility and polarity of amino acids in blood.

A
  • hydrophilic
  • solubility depends on size and R group
  • amino acids with hydrophilic R group will dissolve in blood
  • but hydrophobic R group will not dissolve
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33
Q

Explain the solubility and polarity of fats in blood.

A
  • hydrophobic
  • non polar
  • transported in structures called lipoproteins
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34
Q

What are lipoproteins?

A

A single layer of phospholipids with proteins embedded among the molecules surrounding the fat

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35
Q

Explain the solubility and polarity of cholesterol in blood.

A
  • hydrophobic
  • require lipoproteins to help with transport because it is hydrophobic
  • required of synthesis of many biological molecules and component of membranes
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36
Q

Explain the solubility and polarity of oxygen in blood.

A
  • soluble

- transported in blood called hemoglobin

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37
Q

Explain the solubility and polarity of sodium chloride in blood.

A
  • ionic compound
  • dissolved in water
  • transported in blood in form of Na+ and Cl-
38
Q

List some differences and similarities of water and methane.

A

Both small in size
Similar molecular mass
Both covalent compounds

But different properties

  • physical state
  • polarity
  • solvent
  • boiling temperature
  • melting point
  • specific heat capacity
  • latent heat of vaporisation
39
Q

What are monosaccharides?

A
  • sugar that dissolves in water

- act as monomers to make larger complex carbohydrate molecules

40
Q

How is a polysaccharide formed?

A
  • two monosaccharides monomers are linked together by a condensation reaction
  • this forms a glycosidic bond producing a disaccharide releasing one water molecule
  • several monomers linked together forms polysaccharides
41
Q

What is the shape of glucose?

A
  • two forms: Dglucose and L glucose
  • have isomers
  • two forms of Dglucose : alpha and beta
  • differ in place of the OH group on carbon 1
42
Q

What are polysaccharides?

A
  • large molecules composed of cellulose
  • glycogen: storage substance in animals and fungi
  • starch: plants store starch in roots and stems
43
Q

What monomers form sucrose, maltose, lactose, starch, glucose and cellulose?

A
  • glucose and fructose
  • glucose 2 units
  • glucose and galactose
  • glucose
  • glucose
  • glucose
44
Q

How are glucose monomers orientated in starch molecules and in cellulose molecules?

A

Starch:
- same direction

Cellulose:
- rotate 180 degrees around the backbone change

45
Q

What are the roles of monosaccharides? Give examples of sources.

A
  • polar and soluble in water
  • glucose, ribose and fructose, galactose
  • Fructose: a sugar found in fruits and honey
  • galactose is a sugar in milk
46
Q

What are the roles of disaccharides? Give examples of sources.

A
  • polar and soluble in water
  • maltose, lactose and sucrose
  • maltose: is found in grains
  • Sucrose: found in sugar cane and sugar beets
  • Lactose: is found in mammalian milk
47
Q

What are the roles of polysaccharides? Give examples of sources.

A
  • not all are polar and soluble
  • glycogen, cellulose, starch
  • cellulose: structural component of plant cell walls
  • starch: forms energy stores in plants
  • glycogen: storage form of carbohydrate found in animals in liver and muscles
48
Q

List some utilisation of starch in industry.

A
  • starch is made of glucose monomers
  • glucose monomers form a branched amylopectin or unbranched chain called amylose
  • amylopectin gives starch its characteristics stickness, useful in food, paper and chemical industries and potatoes
49
Q

Differentiate between a saturated and unsaturated fatty acid.

A

Saturated:
no double bonds between carbon atoms

Unsaturated:
Monosaturated and polysaturated

50
Q

Differentiate between Cis and Trans isomers unsaturated fatty acids

A

Cis-isomers:

  • occur in nature
  • two hydrogen atoms are attached to the same side of the two carbon atoms
  • healthier because they have low melting points

Trans-isomers:

  • produced artificially when lipids formed by polyunsaturated fatty acids from plants are partially hydrogenated chemically. this process makes plant fatty acids more solid, like saturated fats
  • Hydrogen atoms are on the opposite side of the two carbon atoms
  • higher melting point and solid at room temperature
51
Q

Why are cis isomers unsaturated fatty acids healthy but why isnt trans isomers not healthy?

A

Cis:
have lower melting points and are liquid at room temperature
- healthier and promote good cholesterol

Trans:
have higher melting points and are solid at room temperature
- dangerous for cardiovascular system
- bad cholesterol

52
Q

Give an example of good lipids; unsaturated fatty acids of the cis type.

A

Fish oil are good for you as they are made up of unsaturated omega-3 fatty acids. The theory is that omega-3 fatty acids, found in some fish oils and flax seeds, protect you against certain types of heart disease.

53
Q

Why are lipids useful in whales?

A

Whales make use of both of these properties of lipids. Humpback whales gorge themselves on krill during the summer months in Antarctica, increasing their blubber (fat) layer to a thickness of more than 30 cm. In the cold waters of the southern oceans, where water temperatures can be as low as 1 ºC, the blubber helps to insulate the whales against the colder temperatures. When it is time to give birth, the females migrate to warmer waters and rely on their fat reserves to nurse their offspring

54
Q

Why are lipids better for long-term storage than carbohydrates?

A

A gram of lipid gives more energy than a gram of glycogen

Each gram of glycogen stored is usually associated with 2g of water while lipids are stored in pure form

55
Q

Even though lipids are better storage than carbohydrates, why do animals use cabohydrates?

A
  • energy storage in animals
  • stored in liver and muscles
  • can be broken down to glucose used to transport rapidly around the body for cellular respiration
  • easier to access
56
Q

List and explain the key properties of lipids.

A

Energy content: more energy per gram than other

Density: less dense than water

Solubility: non polar so will dissolve other non-polar substances

Insulation: heat insulation

Waterproof: water-insoluble

57
Q

What are trans fats?

A

Formed by hydrogenation of vegetable oils under pressure. Why vegetable oils can be spread and extend life

58
Q

Evaluate the evidence for health claims made about lipids.

A
  • The hypothesis that trans fat and saturated fats contribute to the formation of atherosclerotic plaque in arteries which could lead to heart attacks
    Evidence: patience who have died
    But no causal relationship have been proved
    The populations of people in maasai of kenya has a diet rich in saturated fats but low incidence of CHD.
59
Q

What does a high BMI show and does not show?

A
  • high body fatness

- but does not show a diagnosis of body fatness or health

60
Q

What is the basic unit of a polypeptide?

A

Amino acid. A carbon based compound with a carboxyl and an amino group. Order of amino acids determine the shape and function of the protein.

61
Q

What are genes?

A

Sections of DNA that contain the instruction for all the polypeptides of an organism. Code for one polypeptide.

62
Q

Define conformation.

A

The process where the polypetide chain or chains fold up in the protein and so directly affect it three-dimensional structure

63
Q

Explain the primary, secondary, tertiary and quaternary structures.

A

Primary structures:
- sequence of amino acids in a protein

Secondary :
- the folding of the chains to form pleated sheets or alpha helixes

Tertiary:
- formed when the polypeptide forms and coils

Quaternary:

  • only occurs in proteins that are made up of two or more polypeptide chain
  • refers to the way multiple subunits are held together in a multi-subunit complex
64
Q

What are proteins?

A
  • very diverse group of macromolecules
  • can be divided into different groups depending on their chemical structures and functions
  • dissolve in water
65
Q

What are globular proteins?

A
  • consist of complex polypeptide chains that can be linked to other chains to form large complex proteins
  • soluble in water because of their hydrophobic R groups folded into core of molecule
66
Q

What are fibrous proteins?

A
  • fibre, long , thread-like
  • made of long polypeptide chains where the hydrophobic R groups are exposed
  • insoluble
67
Q

How to determine the solubility of proteins through the position of the R group?

A

If the hydrophobic R group is folded inside the core of the molecule (away from the surrounding water molecules) = soluble

If the hydrophobic R group is exposed to the water molecules = insoluble

68
Q

List 6 types of proteins and its shapes and function.

A

Rubisco:

  • globular
  • fixation of CO2 in chloroplasts

Insulin:

  • globular
  • produced in pancreas by beta cells
  • involved in glucose uptake from blood

Immunoglobulin:

  • globular
  • antibodies
  • fights infections by recognising and binding to antigen molecules

Rhodopsin:

  • globular
  • found on the membrane of rod cells of retina
  • allows very low light intensities to be detected

Collagen:

  • fibrous
  • found in muscles, tendons and ligaments
  • gives tensile strength
  • occurs in skin and bones where it prevents tearing and fractures
69
Q

What happens in denaturation of proteins?

A

Denaturation: process in which proteins lose their secondary and tertiary structures
The hydrogen bonds formed between R-groups of amino acids and amino groups of different amino acids are disrupted. Active sites lose their shape. As a result, the whole enzyme loses its enzymatic properties.

70
Q

What are two ways to denature proteins?

A
  1. Exposing the protein to higher temperatures

2. Changing the pH of a surrounding solution

71
Q

What happens when the proteins in the egg white lose their conformation?

A

The interaction between certain amino acids will be changed so that the tertiary and quaternary structures are changed permanently
Results in the denatured proteins losing their form and function

72
Q

Why are high fevers dangerous to humans?

A

At 40 degrees celsius and above, the proteins start to denature and enzymes no longer function properly.

But certain enzymes that break down RNA and proteins are stable and require long periods of high temperature before they denature properly

73
Q

How does pH play a role in the denaturation of proteins?

A

Strong alkaline or acidic solutions can break the bonds between the non-adjacent amino acids or between the polypeptide chains of quaternary proteins

74
Q

How do enzymes help with reactions to be completed faster?

A
  • the complex proteins lower the minimum energy or activation energy that reactants need to react
75
Q

Why do enzyme and substrate reactions usually take place in a watery environment?

A

Where the enzymes and substrate mix and bump into each other. These collisions allow the substrate to bind to the active site on the enzyme so that the reaction can proceed

76
Q

What happens at the active site of enzymes?

A

A special area on the molecule where the actual catalytic reaction takes place.

  • interaction between substrate and active site is highly specific
  • only one type of substrate can fit
  • one enzyme can catalyses one type of reaction
77
Q

What is the structure of the active site?

A
  • folding of the polypeptide chains

- the resulting of the folding forms the active site where the substrate interact with the enzyme

78
Q

What is the induced fit model?

A

When the substrate enters the active site, it triggers a change in the three-dimensional shape of the enzyme that allows a tighter fit. This is called an induced fit and is possible because of the flexibility of the protein molecules that make up the enzyme

79
Q

What does the induced fit model suggest?

A

That a substrate is capable of inducing a change of the active site that will enable the enzyme to perform its catalytic function. The active site can slightly change its shape to fit a substrate

80
Q

Explain the steps when a substrate enters an active site.

A
  1. Substrate enters the active site, the shape of the enzyme changes for a tighter fit
  2. When the substrate and enzyme fit together tightly, the enzyme induces the weakening of bonds of the molecules of the substrate, this reduces the activation energy needed
  3. When the enzyme-catalysed reaction is completed, the products are released from the enzyme
81
Q

Define activation energy.

A

The minimum energy that reacting particles should possess in order for a reaction to occur

82
Q

What affects the rate of enzyme activity?

A

Temperature
pH
Substrate concentration
Enzyme concentration

83
Q

How does temperature affect the rate of enzyme activity?

A
  • low temp = slower movement of molecules = lower collision
  • if the temperature is higher than the optimal, the enzyme can be denatured

This increases the rate of enzymatic reaction.

84
Q

How does substrate concentration affect the rate of enzyme activity?

A

low substrate concentration = more enzyme molecules = lower rate

Increasing the substrate concentration causes more changes of collision.
This increases the rate.

85
Q

What happens when all the active sites are occupied by substrates?

A
  • the increase in substrate concentration stops

- the substrate have to wait for active sites to be available before binding

86
Q

How does pH affect the rate of enzyme activity?

A
  • different types of enzymes for different environments
  • high pH = denature an enzyme by altering the 3D structure of active site
  • low pH = rate of reaction decrease
87
Q

What happens during denaturation of enzymes?

A
  • destroys the tertiary or quaternary conformation of a protein
  • When there is a minor temperature increase or change in pH, the reaction is still reversible and the protein can fold back to its original and functional conformation
88
Q

What is immobilisation?

A

A process of attaching an enzyme to a material so that its movements are restricted

89
Q

What are advantages of immobilisation?

A

Permits higher concentrations of enzymes to be used, allowing a faster rate of reaction

Allows immediate separation of the enzymes from the reaction mixture which allows them to be recycled, reducing production costs

90
Q

Why are people lactose-intolerant?

A

Because they lack lactase and unable to break down lactose in dairy products

Lack of lactase causes lactose to build up and remain in the digestive system, where it is fermented by the bacteria. 
This causes: 
Gas
Diarrhea 
Constipation
91
Q

Give 3 advantages of producing lactose-free products.

A
  1. No effects after consumption
  2. Quicker fermentation
  3. Sweeter tasting milk
92
Q

How are lactose-free products produced?

A

By adding the enzyme lactase to milk

Enzyme lactase: usually made up of fungus aspergillus niger

Lactase can be immobilised in alginate beads and milk flows through, making it easier to make lactose-free milk and the lactase doesn’t go into the product as well

IBDP Biologie (15 decks)

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