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Biological molecules Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Define a monomer

A

Smaller units that join together to form larger molecules

Monosaccharides (glucose, fructose and galactose)

Amino acids

Nucleotides

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2
Q

Define a polymer

A

Molecules formed when many monomers join together

Polysaccharides
Proteins
DNA/RNA

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3
Q

What happens in a condensation reaction?

A

A chemical bond forms between 2 molecules and a molecule of water is produced

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4
Q

What happens in a hydrolysis reaction?

A

A water molecule is used to break a chemical bond between 2 molecules

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5
Q

Name the 3 hexose monosaccharides

A

Glucose
Fructose
Galactose

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6
Q

Name the type of bond formed when monosaccharides react

A

1,4 or 1,6 glycosidic bonds

2 monomers = 1 chemical bond = disaccharide

Multiple monomers = many chemical bonds = polysaccharide

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7
Q

Name 3 disaccharides and describe how they form

A

Condensation reaction forms glycosidic bond between 2 monosaccharides

Maltose = glucose + glucose
Sucrose= glucose + fructose
Lactose= glucose + galactose
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8
Q

Describe the structure and functions of starch

A

Storage polymer of a-glucose in plant cells

insoluble = no osmotic effect on cells
large = does not diffuse out of cells
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9
Q

Describe the structure and functions of glycogen

A

Main storage polymer of a-glucose in animal cells

1,4 and 1,6 glycosidic bonds

Branched = many terminal ends for hydrolysis

Insoluble = no osmotic effect and does not diffuse out of cells

Compact

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10
Q

Describe the structure and functions of cellulose

A

Polymer of b-glucose, gives rigidity to plant cell walls

1,4 glycosidic bonds

Straight chain, unbranched

Alternate glucose molecules rotated at 180 degrees

H-bond crosslinks between parallel strands form microfibrils = high tensile strength

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11
Q

Describe the Benedict’s test for reducing sugars

A
  1. Add an equal volume of Benedict’s reagent to a sample
  2. Heat the mixture in a water bath at 100 degrees for 5 minutes
  3. Positive result = colour change from blue to orange/ brick red
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12
Q

Describe the Benedict’s test for non reducing sugars

A
  1. Negative result = Benedicts reagent remains blue
  2. Hydrolyse non reducing sugars e.g sucrose into their monomers by adding 1cm3 of HCL. Heat in a water bath for 5 minutes
  3. Neutralise the mixture using sodium carbonate solution
  4. Proceed with the Benedicts test as usual
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13
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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14
Q

Describe how to 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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15
Q

How do triglycerides form?

A

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

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16
Q

What is a saturated fatty acid?

A

Contain only single bonds

Straight chain molecules have many contact points

Higher melting point = solid at room temperature

Found in animal fats

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17
Q

What is an unsaturated fatty acid?

A

Contain c=c doubl bonds

Kinked molecules have fewer contact points

Lower melting point = liquid at room temperature

Found in plant oils

18
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 waterproofing

Slow conductor of heat = thermal insulation

Less dense than water = buoyancy of aquatic animals

19
Q

Describe the structure and function of phospholipids

A

Glycerol backbone attached to 2 hydrophobic fatty acid tails and 1 hydrophobic polar phosphate head

Forms phospholipid bilayer in water = component of membranes

Tails can splay outwards = waterproofing

20
Q

Compare phospholipids and triglycerides

A

Both have a glycerol backbone

Both may be attached to a mixture of saturated, monounsaturated and polyunsaturated fatty acids

Both contain the elements C, H, O

Both formed by condensation reactions

21
Q

What are the differences between phospholipids and triglycerides?

A

Phospholipids:

2 fatty acids and 1 phosphate group

Hydrophilic head and hydrophobic tail

Used in membrane function

Triglycerides:

3 fatty acids attached

Entire molecule is hydrophobic

Used as a storage molecule

22
Q

Are phospholipids and triglycerides polymers?

A

No; they are not made from a small repeating unit. They are macromolecules

23
Q

What is the general structure of an amino acid?

A
  • COOH carboxyl/ carboxylic acid group
  • R variable side group consists of carbon chain and may include other functional groups
  • NH2 amino group
24
Q

Describe how to test for proteins in a sample

A

Biuret test- presence of peptide bond

  1. Add equal volume of sodium hydroxide to sample at room temperature
  2. Add 2 drops of dilute copper sulfate solution
  3. Positive result: color changes from blue to purple

Negative result: solution remains blue

25
Q

How many amino acids are there and how do they differ from one another?

A

20

26
Q

How do dipeptides and polypeptides form?

A

Condensation reaction forms peptide bond and eliminates a molecule of water

Dipeptide: 2 amino acids
Polypeptide: 3 or more amino acids

27
Q

How many levels of protein structure are there

A

4

28
Q

Define a primary structure of a protein

A

The sequence of amino acids

Determined by sequence of codons on mRNA

29
Q

Define a secondary structure of a protein

A

Alpha helix or Beta pleated sheet

30
Q

Define the tertiary structure of a protein

A

3D structure formed by further folding of the polypeptide

Disulfide bridges
Ionic bonds
Hydrogen bonds

31
Q

Define the quaternary structure of a protein

A

Functional proteins may consist of more than one polypeptide

Precise 3D structure held together by the same bonds as the tertiary structure

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

32
Q

Describe the structure and function of globular proteins

A

Spherical and compact

Hydrophilic R groups face outwards and hydrophobic R groups face inwards

Involved in metabolic processes e.g enzymes and haemoglobin

33
Q

Describe the structure and function of fibrous proteins

A

Can form long chains or fibres

Insoluble in water

Useful for structure and support

34
Q

What are enzymes?

A

Biological catalysts for 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

35
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 ES complexes to form

This puts strain on substrate bonds, lowering activation energy

36
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 model: also explains why binding at allosteric sites can change shape of active site

37
Q

What are 5 factors that affect the rate of enzyme controlled reactions

A 
Enzyme concentration
Substrate concentration
Concentration of inhibitors
pH 
Temperature
38
Q

How does substrate concentration affect rate of reaction?

A

Enzymes concentration is fixed so rate increases proportionally to the substrate level

Rate levels off when maximum number of ES complexes form at any given time

39
Q

How does enzyme concentration affect rate of reaction?

A

Substrates are in excess so the rate increases proportionally to enzyme concentration

Rate levels off when maximum number of ES complexes form at any given time

40
Q

How does temperature affect rate of reaction?

A

Rate increases as kinetic energy increases and peaks at optimum temperature

Above optimum, ionic and H bonds break so the active site is no longer complementary to the substrate

41
Q

How does pH affect rate of reaction?

A

Enzymes have a narrow optimum pH range

Outside the range they denature

42
Q

What are the differences between competitive and non competitve inhibitors?

A

Competitive inhibitors:

Similar shape to substrate = bond to active site

Do not stop reaction; ES complex forms when inhibitor is released

Increasing substrate concentration decreases their effect

Non-competitive inhibitors:

Bind to anywhere other than the active site

May permanently stop reaction; triggers active site to change shape

Increasing substrate concentration has no impact on their effect

Biology (20 decks)

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