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BIOLOGY A LEVEL AQA > BIOLOGICAL MOLECULES > Flashcards

BIOLOGICAL MOLECULES Flashcards

1
Q

The variety of life, both past and present is extensive, but the biochemical basis of life is similar for all living things. How?

A

All biological molecules contain:
- carbon
- hydrogen
- oxygen
Some also contain:
- sulfur
- nitrogen

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2
Q

What are monomers?

A

The smaller units from which larger molecules (polymers) are made

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3
Q

What are polymers?

A

Molecules made from a large number of monomers joined together

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4
Q

What are three examples of monomers?

A
  • amino acids
  • monosacharides
  • nucleotides
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5
Q

What is a condensation reaction?

A

Joins two molecules together with the formation of a chemical bond and involves the loss of one molecule of water

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6
Q

What is a hydrolysis reaction?

A

Breaks the chemical bond between two molecules and involves the use of one molecule of water

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7
Q

What are monosaccharides?

A

The monomers from which larger carbohydrates are made. Glucose, galactose and fructose are common monosaccharides.

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8
Q

What bond does a condensation reaction between two monosahcarides form?

A

1-4 glycosidic bond

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9
Q

What are three examples of disaccharides and the monosacharides they are made from?

A
  • maltose: 2 alpha glucose
  • sucrose: alpha glucose and fructose
  • lactose: alpha glucose and galactose
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10
Q

What are the two isomers of glucose and how are they different?

A
  • alpha and beta glucose
  • The hydroxyl and the oxygen are inverted on carbon 1 of beta glucose with the hydroxyl group on top
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11
Q

How is glycogen and starch formed?

A

polysacharides, formed by the condensation of many alpha glucose

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12
Q

How is cellulose formed?

A

A polysaccharide, formed by the condensation of many Beta glucose

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13
Q

What is the basic structure and function of glycogen ?

A
  • found in animals
  • energy store
  • Made of 1-4 and 1-6 glycosidic bonds to form a branched spiral
  • branched so that many alpha glucose can be released at a given time
  • spiral so it is compact and can store a large amount in a small space
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14
Q

What is the basic structure and function of starch?

A
  • found in plants
  • energy store
  • amylose: made of only 1-4 glycosidic bonds to form an unbranched spiral shape
  • less soluble than amylopectin and slower to break down
  • amylopectin: made of 1-4 and 1-6 glycosidic bonds to form a branched spiral structure
  • branched so that many alpha glucose can be released at a given time
  • spiral so it is compact and can store a large amount in a small space
  • insoluble so doesn’t affect water potential
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15
Q

What is the basic structure and function of cellulose?

A
  • found in plants
  • Made of 1-4 glycosidic bonds where every other Beta glucose is flipped 180 degrees to form a straight unbroken chain
  • The straight chains form together via hydrogen bonds to form microfribrils and eventually macrofibrils
  • It’s functions include: structural support, barrier to pathogens and water regulation
  • On mass the hydrgoen bonds creates a strong structure
  • Microfibrils provide strength for the upright growth of plants
  • cellulose forms cell walls
  • The straight unbroken chains of cellulose provide rigidity which helps regulate water movement in the plant
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16
Q

What is the bio-chemical test for reducing sugars?

A
  • add benedicts solution to crushed and filtered food sample
  • place in a hot water bath for 5 minutes
  • positive result: green, yellow and red
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17
Q

What is the biochemical test for non-reducing sugars?

A
  • Add hydrochloric acid to crushed and filtered food sample and then heat
  • Make the solution alkiline
  • add benedicts and heat solution again
  • positive result: green, yellow and red
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18
Q

What is the biochemical test for starch?

A
  • Add iodine to crushed and filtered food sample
  • positive result: blue/black
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19
Q

What is ATP?

A

A nucleotide derivative, formed from a molecule of ribose, a molecule of adenine and three phosphate groups

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20
Q

What is ATP hydrolysed into and what enzyme catalyses this reaction?

A
  • an inorganic phosphate group and ADP- one molecule of ribose, one molecule of adenine and two phosphate groups
  • ATP hydrolase
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21
Q

How can the hydrolysis of ATP be coupled to energy requiring reaction within cells?

A
  • Direct coupling
    The hydrolysis of ATP releases energy which can be used in energy requiring reactions
  • Phosphorylation
    Released inorganic phosphate bonds to a compound in order to make it more reactive
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22
Q

How is ATP resynthesised?

A
  • photophosphorylation- occurs in plants during photosynthesis
  • oxidative phosphorylation- occurs in animals during respiration
  • substrate level phosphorylation- occurs in plants and animals when phosphate groups are transferred from donor molecules to ADP
  • This reaction is catalysed by the enzyme ATP synthase
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23
Q

What are the 5 properties of water and their importance in biology?

A
  • High heat capacity, allowing it to buffer changes in temperature
  • Relatively high latent heat of vaporisation, giving it a cooling effect with little water lost to evaporation
  • it is a metabolite in many reactions such as condensation and hydrolysis reactions
  • it is an important solvent in which many metabollic processes occur
  • strong cohesion between water molecules, this supports columns of water in the tube like transport cells in plants, and produces surface tension where water meets air
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24
Q

Where are inorganic ions found?

A

In solution in the cytoplasm and body fluids of organisms, some in high concentrations and some in low.
Each ion has a specific role depending on its properties

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25
Q

What is the role of hydrogen ions?

A

Regulate pH levels, making it optimal for enzymatic reactions

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26
Q

What is the role of iron ions?

A

Iron ions are a component of haemoglobin, they are responsible for binding oxygen molecules to haemoglobin

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27
Q

What is the role of phosphate ions?

A

Components of ATP, DNA and the phospholipidbilayer

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28
Q

What is the role of sodium ions?

A

Co-transport of glucose and amino acids

29
Q

How does an enzyme increase the rate of reaction?

A

Lowers the activation energy

30
Q

What does the properties of an enzyme relate to?

A

The tertiary structure of its active site and its ability to combine with complimentary substrates to form an enzyme/substrate complex.

31
Q

What is the specificity of enzymes?

A

Specific enzymes catalyse specific reactions

32
Q

What is the affect of enzyme concentration on enzymatic reactions?

A
  • As the concentration of enzymes increase the rate of reaction will increase, until enzyme concentration and substrate concentration become equal, then the reaction plateaus as
  • the substrate is the limiting factor
33
Q

What is the affect of substrate concentration on enzymatic reactions?

A
  • As the substrate concentration increase so will the rate of reaction until it becomes equal with the enzyme concentration and rate plateaus
  • Enzyme concentration is the limiting factor
34
Q

What is the affect of non-competitive inhibitor concentration on enzymatic reactions?

A
  • inhibitor binds to a site on the enzyme away from the active site, causing the active sites tertiary structure to change shape, therefore it is harder for successful enzyme substrate complexes to form.
  • Rate will increase as concentration of enzyme concentration increases, but slower than if there wasn’t an inhibitor, rate will never reach its full maximum
35
Q

What is the affect of competitive inhibitor concentration on enzymatic reactions?

A
  • the inhibitor has a similar structure to the substrate so also is able to bind with the enzymes active site
  • The rate of reaction increase as enzyme concentration increases it will be faster than with a non-competitive inhibitor but slower than without an inhibitor
  • The rate will eventually reach its maximum
36
Q

What is the affect of pH on enzymatic reactions?

A
  • if too high or low enzyme denatures due to the breaking of hydrogen and ionic bonds
  • therefore active site is no longer a complimentary 3-D structure, so no enzyme/complexes are formed
37
Q

What is the affect of temperature on enzymatic reactions?

A
  • at low temperature, less kinetic energy in enzymes and substrates so less successful collisions. Often not enough activation energy.
  • at high temperatures enzyme denatures by the breaking of hydrogen ionic and disulphide bonds, so active site is no longer a complimentary 3-D structure
38
Q

What are the two groups of lipids?

A

Phospholipids and triglycerides

39
Q

How are triglycerides formed?

A

The condensation of one molecule of glycerol and three molecules of fatty acids the bonds formed are called ester bonds

40
Q

What is the structure of a fatty acid?

A
  • Every fatty acid has a carboxylic acid and a methyl end
  • The middle of the fatty acid is a hydrocarbon chain, they can be saturated where they have no carbon carbon double bonds or unsaturated where they have one C-C double bond or polysaturated when they have more than one
41
Q

What is the structure of a phospholipid?

A

One of the fatty acids of a triglyceride is substituted by a phosphate group

42
Q

How do you test for the presence of lipids?

A

Add ethanol shake and if cloudy suspension appears then lipids are present

43
Q

What are the different properties of triglycerides and phospholipids?

A
  • Phospholipids are hydrophobic and hydrophilic allowing it to form the cell membrane whereas triglycerides are hydrophobic making them an energy store
  • Phospholipids are fluid, saturated fatty acids found in animals aren’t fluid, unsaturated fatty acids found in plants are fluid
44
Q

What are amino acids?

A

The monomers that make up proteins

45
Q

What is the general structure of an amino acid?

A

On the left: NH3- amine group
On the right: COOH- carboxylic acid
On the bottom: hydrogen
On the top: R group, this differs for different amino acids

46
Q

How is a peptide bond formed?

A
  • Condensation reaction between two amino acids
47
Q

How are polypeptides formed?

A
  • The condensation reaction of many amino acids
48
Q

What is the primary structure of a protein?

A
  • The specif order of the amino acids in the polypeptide chain, this is coded by ribosomes
49
Q

What is the secondary structure of a protein?

A
  • The folding of the chain
  • This is controlled by hydrogen bonds between the H of the amine group and O of the carboxyllic acid
  • Folded in two ways: a-helix or B-plated sheet
50
Q

What is the tertiary structure of a protein?

A
  • Bonds are formed between the R groups of amino acids
  • ionic, hydrogen, polar/polar, non-polar/non-polar, disulphide
51
Q

What is the quartinary strucure of a protein? With an example.

A
  • Not all proteins have
  • The bonding of 2 or more polypeptide chains
  • Can have inorganic ions attached
  • Haemoglobin is a protein with a quartinary structure, made up of two a-helix and 2 B-plated sheet, with four iron ions attached
52
Q

What are some functions of proteins in organisms?

A
  • enzymes
  • transport - haemoglobin
  • cell recognition - antigens
  • channels - membrane proteins
  • protection - antibodies
  • hormones - insulin
53
Q

What is the test for the presence of proteins?

A
  • Bieuret
  • lilac for a positive result
54
Q

What are two ways of identifying different amino acids?

A
  • Two chromotography:
    Turning the paper 90 degrees and retesting to obtain a more accurate Rf value
  • Electrophesis:
    Placing the solution in a circuit, it separates based on charge
55
Q

What does DNA stand for?

A

deoxyribose nucleic acid

56
Q

What are the three comoponents of a nucleotide

A

nucleotides make up DNA
- nitrogenouse base
- phosphate
- deoxyribose sugar

57
Q

How is a dinucleotide formed?

A
  • condensation reaction
  • bond is formed between C3 and phosphate
  • phosphodiester bond
58
Q

What are the complimentary base pairings, number of hydrogen bonds and carbon rings?

A
  • A-T- 2 hydrogen bonds
  • G-C - 3 hydrogen bonds
  • On the left Purines (2 rings)
  • On the right pyrmadines (1 ring)
59
Q

Describe and explain the 4 adaptations of DNA?

A
  • Stability, maintains the sequence of genetic info, needs to last the lifetime of the cell
  • Hydrogen bonds- strength and stability on mass, allows strands to be seperated for protein synthesis or replication
  • Large molecule - stores all the genetic info
  • Base pairs are on the inside of the molecule- protects genetic code
60
Q

What are the uses of the two strands in DNA?

A
  • Coding strand - order of nitrogenous bases on the coding strand codes the order of amino acids in the primary structure of a protein
  • Non coding strand - provides two strands for DNA replication and protects the order of the bases
61
Q

Chromosome

A

23 pairs
structure where genes are stored

62
Q

chromatin

A

genetic material not during mitosis

63
Q

Histones

A

proteins that keep the DNA organised

64
Q

Give three ways in
which ATP is a suitable energy source for cells to use.

A
  • Phosphorykates other compounds making them more reactive
  • Immediate source of energy
  • can be rapidly resynthesied
  • is not lost from cells
65
Q

What are the components of RNA?

A
  • ribose
  • phosphate group
  • nitrogenous base- adenine, uracil (instead of thymine), guanine cyastine
66
Q

What are the three types of RNA?

A
  1. messenger RNA - carries genetic information from the DNA to the ribosomes
  2. transfer RNA - brings the amino acids to the ribosomes
  3. ribosomal RNA - produced in the nucleolis, forms a part of ribosomes
67
Q

What are the differences between DNA and RNA?

A
  • RNA is single stranded and DNA is double stranded
  • RNA uses uracil in place of thymine
  • RNA contains a ribose sugar and DNA contains a deoxyribose sugar
68
Q

What is the structure of mRNA?

A
  • Single stranded molecule
  • Contains unpaired bases
  • bases are arranged in codons (groups of three)
69
Q

What is the structure of tRNA?

A
  • single stranded molecule that folds into a specific shape
  • Secondary structure is a clover leaf shape
  • Tertiary structure is an L-shape
  • Has anticodon region complimentary to the codons on mRNA
  • attachment site for amino acids

BIOLOGY A LEVEL AQA (4 decks)

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