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Biology A LEVEL > Carbs, Lipids and Proteins > Flashcards

Carbs, Lipids and Proteins Flashcards

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1
Q

What 5 main biological molecules are all living organisms made from?

A

carbohydrates
lipids
protein
DNA/RNA
water

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2
Q

What is a monomer?

A

an individual unit that makes a polymer

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3
Q

What is a polymer?

A

many repeating units of monomers

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4
Q

What are 4 types of monosaccharides?

A

alpha glucose

beta glucose

galactose

fructose

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5
Q

What are all 4 monosaccharides an example of?

A

reducing sugars (act as reducing agents in chemical reactions)

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6
Q

What are 3 types of disaccharides?

A

maltose

lactose

sucrose

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7
Q

What is sucrose an example
of?

A

a non reducing sugar

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8
Q

What are 3 types of polysaccharides and which glucose isomer are they formed by?

A

starch (alpha glucose)

glycogen (alpha glucose)

cellulose (beta glucose)

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9
Q

What is starch?

A

-polysaccharide of alpha glucose joined via condensation reaction
-energy store found in plant cells in the form of grains

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10
Q

What kind of bonds form starch?

A

1,4 and 1,6 glycosidic bonds

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11
Q

Describe 4 structural features of starch:

A

-large
-insoluble
-helix shape
-branched

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12
Q

How does starch being large aid its function?

A

it won’t diffuse out of cells

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13
Q

How does starch being insoluble aid its function?

A

won’t affect water potential so it is osmotically inactive

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14
Q

How does starch being in a helix shape aid its function?

A

it makes it a compact energy store

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15
Q

How does starch being branched aid its function?

A

increases the surface area so glucose can rapidly be released when needed for aerobic respiration

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16
Q

What is glycogen?

A

-polysaccharide of many alpha glucose joined via condensation reaction to form glycosidic bonds
-energy store in the form of granules in the cytoplasm

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17
Q

What bonds form glycogen?

A

1,4 glycosidic bonds and many more 1,6 glycosidic bonds compared to starch

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18
Q

Describe the structure of glycogen and explain how this aids its function:

A

SEE STARCH

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19
Q

What is cellulose?

A

-polysaccharide of many beta glucose molecules joined through condensation reactions
-used to make cell walls

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20
Q

How is cellulose formed?

A

1,4 glycosidic bonds

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21
Q

How is cellulose joined together?

A

joined together by hydrogen bonds in long straight/ unbranched chains that forms fibrils

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22
Q

Describe the structure of cellulose:

A

-Made from beta glucose
-Parallel chains can form hydrogen bond ‘cross links’
-Can form microfibrils which join to form fibres

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23
Q

How does cellulose being made from beta glucose aid its function?

A

Allows long straight chains to form

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24
Q

How does cellulose being in parallel chains that can form hydrogen bonds aid its function?

A

adds strength to cell walls

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25
Q

How does cellulose being able to form microfibrils aid its function?

A

adds strength to cells walls

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26
Q

What is reduction?

A

the gain of electrons

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27
Q

What is a reducing sugar able to do and how do we test for this ?

A

-able to lose an election and give it to another
-by giving them something to reduce

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28
Q

What does Benedict’s raegent contain?

A

cu2+ ions in the form of copper II sulfate
(blue colouring)

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29
Q

When does copper sulfate become red copper oxide ?

A

When the cu2+ ions gain an electron from a reducing sugar they become cu+ ions in the form of red copper I oxide

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30
Q

How do you do the test for reducing sugars?

A

-Add Benedict’s solution
-Heat
-Colour change from blue to green , yellow, orange and red if positive

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31
Q

What are the possible colour results for a benedict’s test?

A

blue- negative
green- very low
yellow- low
orange- moderate
red- high

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32
Q

What type of results are the benedict’s test and what does this mean?

A

-Semi- quantitative
- They give an idea of concentration but not fully quantitatively as numbers would

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33
Q

How do you do the test for a non-reducing sugar?

A
  • Get a negative Benedict’s test
  • Boil with HCL to hydrolyse the non-reducing sugar
  • Neutralise HCL using NaOH
  • Add Benedict’s
  • Heat
  • Colour change from blue to red
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34
Q

Why does the colour change at the top of the solution first in a reducing sugars test?

A

The hotter particles in the bottom of the solution are rising because they are being heated and so the hottest point in the solution is at the top. Molecules have more kinetic energy at the top so more successful collisions (convection currents)

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35
Q

What is a colorimeter?

A

A light-sensing device that is used to measure the absorbance and transmittance of light as it moves through a sample of liquid.

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36
Q

What must be done before using a colorimeter?

A

Filter off the red precipitate leaving just the blue Benedict’s solution

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37
Q

What type of testing is a colorimeter?

A

Quantitative testing

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38
Q

How does a colorimeter work?

A

-Test tube of solution into colorimeter
-Light inside of unit in colorimeter shines into solution
-Solution absorbs light
-This is picked up by a light receptor which is connected to the screen giving an absorbance reading

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39
Q

What are the steps for identifying an unknown glucose solution?

A

Step 1- make known concentrations of glucose (0, 12.5, 25, 50, 100)

Step 2- Perfom a benedict’s test

Step 3- Perform colorimetry to identify absorbance (0, 0.125, 0.25, 0.5, 1)

Step 4- Produce a calibration curve with concentration on x and absorbance on y

Step 5- Perfom benedict’s and colorimetry on unknown sample to identify absorbance

Step 6- Read off graph to identify concentration of unknown solution

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40
Q

What does an absorbance and concentration graph look like?

A
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41
Q

What does the absorbance reading read if the concentration of the solution is 100 and why?

A

1 because the solution is absorbing all the light and no light makes it to the sensor (maximum concentration)

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42
Q

What does a transmission value show?

A

The higher the number, the more light can pass through. 0= max concentration 1= dilute

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43
Q

What are lipids used for?

A
  • Energy store
  • Insulation (thermal, electrical)
  • Water proofing (waxy cuticle)
  • Protection (heart, kidneys)
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44
Q

What are the two types of lipids?

A

Triglycerides and Phospholipids

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45
Q

What do triglycerides consist of?

A

They consist of fats (solid at room temp) and oils (liquid at room temp)

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46
Q

What is the general structure of triglycerides?

A
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47
Q

Do fatty acid molecules join together?

A

NO. They are individual molecules that don’t join together. Lipids are neither polymers nor are they monomers.

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48
Q

What does this chemical structure show?

A

Glycerol

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49
Q

What does this chemical structure show?

A

Fatty acids

50
Q

What is the bond of carbon, oxygen and hydroxide called?

A

Carboxylic acid group

51
Q

How are fatty acids and glycerol joined together?

A

OH from carboxylic acid group and H from glycerol form H20 via a condensation reaction

52
Q

When does an ester bond form?

A

when a hydroxyl (-OH) group from the glycerol bonds with the carboxyl (-COOH) group of the fatty acid. The formation of an ester bond is a condensation reaction. For each ester bond formed a water molecule is released.

53
Q

Describe 4 structures of Lipids:

A
  • Insoluble
  • Low mass to energy ratio
  • High ratio of H atoms to O atoms
  • High ratio of energy storing C-H bonds
54
Q

How does a lipid being insoluble aid its function?

A

osmotically inactive

55
Q

How does a lipid having a low mass to energy ratio aid its function?

A

don’t have to carry heavy energy store

56
Q

How does a lipid having a high ratio of H atoms to O atoms aid its function?

A

water can be released during breakdown

57
Q

How does a lipid having a high ratio of energy storing C-H bonds aid its function?

A

energy dense molecule

58
Q

What are saturated fatty acids?

A

the hydrocarbon chain has only single bonds between carbons

59
Q

What are unsaturated fatty acids?

A

the hydrocarbon chain consists of at least one double bond between carbons

60
Q

What are phospholipids?

A

major component of cell membranes

61
Q

What is the general structure for a phospholipid?

A
62
Q

What can be said about the fatty acid ‘tails’ and their electrons?

A

The fatty acid tails are ‘non polar’ and so the electrons are evenly spread. They are hydrophobic.

63
Q

What can be said about the ‘polar head’ of a phospholipid?

A

Delta positive and delta negative regions. There is an uneven distribution of electrons. It is hydrophilic.

64
Q

What is an amphipathic?

A

A molecule with polar and non-polar regions. This property is essential to form a phospholipid bilayer.

65
Q

What is the chemical structure of a phospholipid?

A
66
Q

Describe the structure of phospholipids:

A

-Hydrophobic/ hydrophilic regions
-Glycolipids can form

67
Q

How do phospholipids having hydrophobic/ hydrophilic regions aid its function?

A

Allows phospholipid bilayer formation (barrier around cells formed by thin polar membrane made of two layers of lipid molecules)

68
Q

How is a phospholipid bilayer created?

A

-Have two charged regions, so they are polar.
-In water they are positioned so that the heads are exposed to water and the tails are not.
-This forms a phospholipid bilayer membrane structure which makes up the plasma membrane around cells.

69
Q

How do glycolipids being able to form from phospholipids aid its function ?

A

Allows for cell recognition

70
Q

What is the emulsion test for lipids?

A

-Add ethanol
-Add distilled water
-Shake
-White emulsion layer if positive

71
Q

What are the 4 functions of proteins?

A

Structural- collagen, keratin

Signalling- hormones

Catalysts- enzymes that speed up reactions

Transport- haemoglobin transports oxygen

72
Q

What is the specific name for protein monomers?

A

Amino acids

73
Q

What is the specific name for protein diamers?

A

Dipeptides

74
Q

What is the specific name for protein polymers?

A

Polypeptides (peptide is a short polypeptide)

75
Q

Draw and label the structure of an amino acid:

A
76
Q

How many different amino acids are there?

A

20 which all have the same general structure only the variable group changes

77
Q

Draw and label the formation of a dipeptide:

A
78
Q

How are amino acids joined together to form a dipeptide?

A

-Condensation reaction
-Water is removed
-Peptide bond forms between OH of carboxyl and H or amine group

79
Q

What are the 4 levels of protein structure?

A
  1. Primary structure
  2. Secondary structure
  3. Tertiary structure
  4. Quaternary structure
80
Q

What is the sequence of amino acids determined by?

A

Your genes

81
Q

What can the secondary structure of protein formation be described as?

A

The initial folding of a polypeptide into an alpha helix or beta pleated sheet due to hydrogen bonding.

82
Q

Where do hydrogen bonds form during protein formation?

A

between the C=O groups of the carboxyl group of one amino acid and the H in the amine group of another amino acid

83
Q

What can the tertiary structure of protein formation be described as?

A

-The further folding of the secondary structure
-To form a unique 3D shape.
- Held in place by ionic, hydrogen and disulphide bonds.

84
Q

Where do the ionic and disulphide bonds form during protein formation?

A

-The ionic and disulphide bonds form between the R groups of different amino acids.
-Disulphide bonds only sometimes occur, as there must be a sulfur in the R groups for this bond to occur

85
Q

What can the quaternary structure of protein formation be described as?

A

A protein made up of more than one polypeptide chain e.g haemoglobin formed from 4 polypeptide chains

86
Q

Why is the primary structure of a protein so important?

A

If even one amino acid in the sequence is different then it will cause the ionic/hydrogen/disulphide bonds to form in a different location and make a diff 3d shape.

87
Q

What is the impact of even one amino acid changing in the sequence?

A

-Enzymes will have a different shaped active site (will be non-functioning)
-Carrier proteins will have a different shaped binding site

88
Q

What are enzymes?

A

Biological catalysts that increase the rate of reaction by lowering the activation energy

89
Q

What is the activation energy?

A

The energy required to cause molecules to collide hard enough to react (to break and form new bonds)

90
Q

What is the active site of an enzyme?

A

the region where a complementary substrate can bind to form an enzyme-substrate complex

91
Q

What is a metabolic pathway?

A

a series of enzyme catalysed reactions where the product of a reaction is the reactant in the next reaction eg. respiration

92
Q

What is the lock and key model for enzymes?

A
  1. The shape of the active site is fixed and does not change shape
  2. Active site is complementary to substrate before during and after forming an enzyme-substrate complex
93
Q

What is the induced model of enzyme action?

A
  1. Before the reaction, the active site is NOT complementary to substrate
  2. Shape of active site changes as enzyme-substrate complex forms
  3. This stresses bonds or brings substrates closer together
  4. Lowers the activation energy
94
Q

What type of structure do enzymes have?

A

A complex tertiary structure

95
Q

What do enzymes control?

A

All intracellular and extracellular reactions in organisms

96
Q

Why would a molecule not get broken down by a specific enzyme?

A

The specific structure of the active site is complementary to the shape of one substrate, forming an enzyme-substrate complex

97
Q

What are the two types of non-functional proteins?

A
  1. Mutations
  2. Denatured
98
Q

How do you know if a protein has mutated?

A
  • Changes to the base sequence of DNA
  • Change to the base sequence of mRNA
  • Change to the primary structure of protein which leads to change to tertiary structure
99
Q

How do you know if a protein has denatured?

A
  • Increase in kinetic energy
  • breaks the hydrogen + ionic bonds between variable groups
  • change to the tertiary structure of the protein
100
Q

What is the result of a protein mutating or denaturing?

A
  • changes the shape of the active site
  • substrate is no longer complementary
  • no enzyme-substrate complex forms
101
Q

What are the 5 factors that affect the rate of enzyme-catalysed reactions?

A
  1. Temperature
  2. PH
  3. Enzyme concentration
  4. Substrate concentration
  5. Inhibitors
102
Q

Describe and explain the graph for enzyme rate of reaction against temperature:

A
  • At 0 degrees enzymes are frozen and catalyse no reactions
  • The peak of the curve shows the optimum temperature for enzyme activity is 37 degrees
  • When the graph hits the x axis again it shows that enzymes have denatured
103
Q

Explain the effect of temperature on enzyme catalysed reactions:

A
  • As temperature increases, the rate of reaction increases due to molecules gaining more kinetic energy.
  • Most enzyme-substrate complexes form at optimum temperature
  • As temp increases past 37 degrees, the rate of reaction decreases due to enzymes denaturing until it stops
104
Q

Describe what the graph for time against volume of product for the effect of temp on an enzyme catalysed reaction looks like:

A
105
Q

What is hydrogen peroxide?

A

toxic cellular waste product that must be broken down

106
Q

What is the equation for the breakdown of hydrogen peroxide?

A

Hydrogen peroxide ———> water + oxygen

catalase enzyme breaks down

107
Q

What does the first part of the graph for the progress of an enzyme reaction graph mean?

A

-initially lots of substrate and empty active sites
-many E-S complexes can form
-reaction starts off fast

108
Q

What does the graph for the progress of an enzyme reaction look like?

A
109
Q

What does the second part of the enzyme progress reaction graph mean?

A

-less substrate, more product
-more difficult for E-S complex to form
-reaction slows

110
Q

What does the third part of the enzyme progress reaction graph mean?

A

-no more substrate
-no E-S complexes
-reaction stopped

111
Q

How do you calculate the mean rate of reaction?

A

amount of product formed/ time taken to form product

112
Q

Describe the graph for enzyme rate of reaction against PH:

A
  • Enzyme activity increases until it reaches optimum PH
  • Enzyme activity begins to decrease as enzyme is being denatured due to acidic conditions
113
Q

Explain the effect of PH on enzyme catalysed reactions:

A
  • Enzymes have an optimum temp
  • Increasing or decreasing PH away from optimum causes enzyme activity to decrease
  • The H+ or OH- will interact with hydrogen or ionic bonds
  • Changes tertiary structure and active site shape so less e-s complexes form
114
Q

What happens at PH 2 during an enzyme catalysed reaction and what does this graph look like?

A

-increased H+ attracted to amino acids of enzymes
-hydrogen/ ionic bonds of 3 degrees disrupted
-active site denatures
-fewer e-s complexes form

115
Q

Describe the graph for enzyme rate of reaction against enzyme concentration:

A
116
Q

Explain the effect of enzyme concentration on enzyme catalysed reactions:

A
  • Rate increases with enzyme conc in positive correlation
    -because there are more e-s complexes forming (more successful collisions)
    -if substrate runs out, adding more enzymes will make no diff to rate of reaction
117
Q

Describe the graph for enzyme rate of reaction against substrate concentration:

A
  • Rate increases with substrate conc in positive correlation
    -because there are more e-s complexes forming (more successful collisions) until all active sites are occupied
    -enzyme conc is now the limiting factor and adding more substrate will not change rate
118
Q

What do enzyme inhibitors do?

A

Slow down enzyme catalysed reactions

119
Q

What are the two types of inhibitors that affect the rate of enzyme-catalysed reactions?

A
  1. Competitive
  2. Non-competitive
120
Q

What does the graph for effect of competitive and non-competitive inhibitors on enzyme activity look like?

A
121
Q

Explain the effect of competitive inhibitors on enzyme activity:

A
  • Competitive inhibitors have a similar shape to substrate
    -They can also bind to active site
  • This stops e-s complexes from forming
    -The proportion of substate to competitive inhibitor will affect how much the rate of reaction changes
122
Q

Explain the effect of non-competitive inhibitors on enzyme activity:

A

-Non-competitive inhibitors bind to the enzyme but not at the active site
-Changes the tertiary structure of the active site permanently
-No more e-s complexes form as no longer complementary
-Changing conc of substrate won’t make any difference

Biology A LEVEL (5 decks)

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