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Biology > TOPIC 1 Biological Molecules > Flashcards

TOPIC 1 Biological Molecules Flashcards

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1
Q

Examples of monomers

A

Monosaccharides
Amino acids
nucleotides

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2
Q

Examples of polymers

A

Carbohydrates
Proteins
Nucleic acids

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3
Q

What type of sugar is glucose

A

Hexose

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4
Q

How many types of glucose are there

A

2

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5
Q

What are the different types of glucose

A
  1. Alpha Glucose
  2. Beta Glucose
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6
Q

Condensation reactions join which molecules?

A

Monosaccharides

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7
Q

What is a condensation reaction?

A

When 2 molecules join together with the formation of a new chemical bond, releasing a water molecule

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8
Q

What type of chemical bond forms between 2 monosaccharides?

A

Glycosidic

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9
Q

What is formed when 2 monosaccharides join together?

A

Disaccharide

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10
Q

What is Sucrose made from?

A

Alpha glucose and Fructose

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11
Q

What 2 molecules make lactose?

A

Alpha glucose and galactose

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12
Q

What is a hydrolysis reaction?

A

When 2 molecules are broken apart using a water molecule

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13
Q

What is broken down by hydrolysis to form monosaccharides?

A

Carbohydrates

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14
Q

Name 3 hexose monosaccharides

A
  1. Glucose
  2. Fructose
  3. Galactose
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15
Q

Describe the Benedict’s test for reducing sugars

A
  1. Add an equal volume of Benedict’s to a sample
  2. Heat the mixture in an electric water bath at 100°c for 5 minutes
  3. Positive result: colour change from blue to orange and Brick red precipitate forms
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16
Q

Describe the Benedict’s test for Non - reducing sugars

A
  1. Negative result: Benedict’s reagent remains blue
  2. Hydrolyse non- reducing sugars e.g sucrose into their monomers by adding 1cm^3 of HCl
  3. Heat in a water bath for 5 minutes
  4. Neutralise the mixture using sodium carbonate solution
  5. Proceed with Benedict’s test as usual
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17
Q

Describe the test for starch

A
  1. Add iodine solution
  2. Positive result = colour change from orange to blue / black
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18
Q

How would colorimetry be used to give qualitative results for the presence of sugars and starch ?

A
  1. Make standard solutions with known concentrations.
  2. record absorbance or % transmission values
  3. plot calibration curve (absorbance - y axis and concentration- x axis)
  4. record absorbance or % transmission values of unknown samples
  5. use calibration curve to read off concentration
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19
Q

How do you test for lipids ?

A
  1. dissolve solid samples in ethanol
  2. Add an equal volume of water and shake
  3. Positive result = milky white emulsion forms
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20
Q

How do triglycerides form?

A

Condensation reactions between 1 molecule of glycerol and 3 fatty acids forms ester bonds

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21
Q

What are 3 differences between saturated and unsaturated fatty acids?

A
  1. Saturated contain only single bonds
    whilst unsaturated contains C=C double bonds
  2. Saturated have higher melting points and are solids at room temperatures whilst unsaturated have lower melting point and are liquids at room temperature
  3. saturated are straight chain molecules that have many contact points
    whilst unsaturated are “kinked” molecules that have fewer contact points
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22
Q

Relate the structure of triglycerides to their functions

A
  • high energy : mass ratio = high calorific value from oxidation
  • insoluble hydrocarbon chain = no effect on water potential of cells and used for water proofing
  • slow conductor of heat = thermal insulation
  • less dense than water = buoyancy of aquatic animals
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23
Q

Describe the structure and functions of phospholipids

A

Amphipathic molecule: glycerol backbone attached to 2 hydrophobic fatty acid tails and 1 hydrophilic polar phosphate head

  • forms phospholipid bilayer in water = component of membranes
  • tails can splay outwards = waterproofing
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24
Q

Compare phospholipids and triglycerides

A

• both have glycerol backbone

• both formed by condensation reactions

• both contain the elements C, H , O

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25
Q

Contrast phospholipids and triglycerides

A

• phospholipids have 2 fatty acids and 1 phosphate group attached
triglycerides have 3 fatty acids attached

• phospholipids have a hydrophobic tail and a hydrophilic head
triglycerides are entirely hydrophobic

• phospholipids are used primarily in membrane formation
triglycerides are used primarily as a storage molecule

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26
Q

Are phospholipids and triglycerides polymers?

A

No - they are macromolecules

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27
Q

Why is water a polar molecule ?

A

O is more electronegative than H
so attracts the electron density in the covalent bond more strongly

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28
Q

what are 4 important properties of water?

A
  1. high specific heat capacity
  2. solvent / metabolite for chemical reactions in the body
  3. high latent heat of vaporisation
  4. cohesion between molecules
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29
Q

why is water significant to living organisms ?

A

• solvent for polar molecules during metabolic reactions

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30
Q

What are organic ions and where are they found in the body ?

A

• ions that do not contain carbon atoms

• found in cytoplasms and extracellular fluid

• May be in high or very low concentrations

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31
Q

Explain the role of hydrogen ions in the body

A

• High concentration of H+ = low acidic PH

• H+ ions interact with H - bonds and ionic bonds in tertiary structure of proteins, which can cause them to denature

32
Q

Explain the role of iron ions in the body

A
  • Fe2+ bonds to porphyrin ring to form haem group in haemoglobin
  • haem group has binding site to transport 1 molecule of O2 around body in bloodstream
  • 4 haem groups per haemoglobin molecule
33
Q

Explain the role of sodium ions in the body

A

• involved in co transport for absorption of glucose and amino acids in lumen of gut

• involved in propagation of action potentials in neurons

34
Q

Explain the role of phosphate ions in the body

A

Component of:
- DNA
- ATP
- NADP
- cAMP

35
Q

What is the general structure of an amino acid?

A
  • COOH (carboxyl group)
  • R variable
  • NH2 amine group
36
Q

How do you test for proteins in a sample?

A

Biuret’s tests :

  • confirms presence of peptide bonds
  • positive result = colour change from blue to purple
37
Q

How many amino acids are there?
How do they differ?

A

20

Differ only by their ‘R’ groups

38
Q

How do dipeptides and polypeptides form?

A

Condensation reaction forms peptide bond and eliminates molecule of water

• dipeptide : 2 amino acids

• polypeptide: 3 or more amino acids

39
Q

How many levels of protein structure are there?

A

4

40
Q

Define primary structure of a protein?

A

• sequence, number and type of amino acids in the polypeptide

• Determined by sequence of codons on mRNA

41
Q

Define secondary structure of a protein

A

• hydrogen bonds form between O- attached to C=O and H + attached to -NH

42
Q

Define the 2 types of of secondary protein structure

A

alpha helix -
• all N-H bonds on same side of protein chain
• spiral shape
• H-bonds parallel to helical axis

beta pleated sheet -
• N-H & C=O groups alternate from one side to the other

43
Q

Define tertiary structure of a protein.
Name the bonds present

A

3D structure formed by further folding of polypeptide

• disulphide bridges
• ionic bonds
• hydrogen bonds

44
Q

Describe each type of bond in the tertiary structure of proteins

A

• disulphide bridges :
strong covalent S-S bonds between molecules of the amino acid cysteine

• ionic bonds :
relatively strong bonds between charged R groups (pH changes cause these bonds to break)

• hydrogen bonds :
numerous and easily broken

45
Q

define quaternary structure of a protein

A

• functional proteins may consist of more than one polypeptide

• precise 3D structure held together by the same types of bond as tertiary structure

• may involve addition of prosthetic groups
e.g metal ions or phosphate groups

46
Q

Describe the structure and function of globular proteins

A

• spherical and compact

• hydrophilic R groups face outwards and hydrophobic R groups face inwards = usually water soluble

• involved in metabolic processes e.g enzymes and haemoglobin

47
Q

Describe the structure and function of fibrous proteins

A

• can form long chains or fibres

• insoluble in water

• useful for structure and support e.g collagen in skin

48
Q

What are enzymes?

A

• biological catalysts for intra and extracellular reactions

• specific tertiary structure determines shape of active site, complementary to a specific substrate

• formation of enzyme substrate complexes lowers activation energy of metabolic reactions

49
Q

Explain the induced fit model of enzyme action

A

• shape of active site is not directly complementary to substrate and is flexible

• conformational change enables enzyme substrate complexes to form

• this puts strain on substrate bonds, lowering activation energy

50
Q

How have models of enzyme action changed?

A

• initially lock and key model:
rigid shape of active site complementary to only 1 substrate

• currently induced fit:
also explains why binding all allosteric sites can change shape of active site

51
Q

what are 5 factors that affect the rate of enzyme-controlled reactions?

A
  • enzyme concentration
  • substrate concentration
  • concentration of inhibitors
  • pH
  • temperature
52
Q

Describe competitive inhibitors

A

• similar shape to substrate = bind to active site

• do not stop reaction: enzyme substrate complex forms when inhibitor is released

• increasing substrate concentration decreases their effect

53
Q

Describe non competitive inhibitors

A

• bind at allosteric binding site

• may permanently stop reaction: triggers active site to change shape

• increasing substrate concentration has no impact on their effect

54
Q

How do you calculate the rate of reaction from a graph?

A

• calculate the gradient of line or gradient of tangent to a point

• initial rate: draw tangent at t=0

55
Q

How do you calculate the rate of reaction from raw data?

A

change in concentration of product or reaction time

56
Q

why is it advantageous to calculate initial rate?

A

represents maximum rate of reaction before concentration of reactants decreased & ‘end product inhibition’

57
Q

what is the formula for pH?

A

pH = -log10 [H+]

58
Q

Name the pentose sugars in DNA and RNA

A

DNA: deoxyribose
RNA: ribose

59
Q

what is the role of DNA in living cells?

A

Base sequence of genes codes for functional RNA and amino acid sequence of polypeptides

genetic information: determines inherited characteristics = influences structure and function of organisms

60
Q

Define a condensation reaction

A

joining 2 molecules together creating a chemical bond, eliminating a water molecule

61
Q

Define a hydrolysis reaction

A

Breaking a chemical bond using water

62
Q

Name 3 monomers

A

Amino acids

Nucleotides

glucose

63
Q

Name 3 polymers

A

proteins

DNA

polysaccharides

64
Q

give 2 examples of a hydrolysis reaction

A

polypeptides into amino acids

lipids into fatty acids and glycerol

65
Q

give 2 examples of a condensation reaction

A

monosaccharides into polysaccharides

nucleotides into nucleic acid(DNA)

66
Q

What are monosaccharides?

A

monomers for carbohydrates

67
Q

what is the general formula for a monosaccharide

A

CH2On

68
Q

What are 3 examples of monosaccharides

A

glucose
galactose
fructose

69
Q

What is the formula for glucose

A

C6H12O6

70
Q

What makes
1. Maltose
2. sucrose
3. lactose

A
  1. maltose = glucose + glucose
  2. Sucrose = glucose + fructose
  3. lactose = glucose + galactose
71
Q

What are polysaccharides

A

long chains of monosaccharides joined by glycosidic bonds in condensation reactions

72
Q

what is starch

A
  • long chains of alpha glucose
  • chains can be coiled into an alpha helix —> compact
  • insoluble (no effect on osmosis) —> good for storage
  • branched to increase surface area so enzymes can hydrolyse the bonds quickly to provide glucose for respiration
73
Q

Define disaccharides

A

two monosaccharides joined together by glycosidic bonds

74
Q

what is starch made from and what do they allow regarding the structure?

A
  • amylase for coiling
  • amylopectin for branching
75
Q

Describe glycogen

A

long chains of alpha glucose

shorter and more branched than starch

found in animal cells (liver and muscle cells)

very highly branched so can be broken down quickly for use of alpha glucose in respiration

insoluble

76
Q

Describe cellulose

A

long chains of beta glucose

straight, unbranched chains that run parallel to each other and are cross linked by hydrogen bonds

in the cell walls of plants

77
Q

Why do we add extra steps when testing for non reducing sugars?

A

to break the glycosidic bonds and turn the disaccharides back into monomers so that we can carry out the benedicts test

Biology (6 decks)

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