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Biology > 3.1 Biological Molecules > Flashcards

3.1 Biological Molecules Flashcards

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1
Q

What are monomers? + e.g

A

Monomers are smaller units from which larger molecules form (polymers)
E.g monosaccharides, amino acids, nucleotides

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2
Q

What is a condensation reaction?

A

1) joins 2 molecules together
2) forms chemical bond
3) elimination of water molecule

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3
Q

What is a hydrolysis reaction?

A

1) breaks chemical bond
2) between 2 molecules
3) involves use of water molecules

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4
Q

What is a monosaccharides? + e.g

A

Monomers from which larger carbohydrates are made
E.g glucose, fructose and galactose

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5
Q

What is/forms when 2 monosaccharides join?

A

Condensation reaction is which forms a glycosidic bond

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6
Q

What are the examples of disaccharides?

A

• 2 glucose= maltose + water
• glucose + fructose = sucrose + water
• glucose + galactose = lactose + water

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7
Q

What is the definition of isomers (e.g)?

A

Same molecular formula but different structure. Glucose has 2 isomers= alpha and beta glucose

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8
Q

How are polysaccharides formed? (E.g)

A

Condensation reaction of many glucose units
•Glycogen + starch = alpha glucose
•cellulose= beta glucose

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9
Q

Describe starch (polysaccharide)

A

1) store of glucose in plants

2)2 polymers=
•amylose-unbranched helix
•amylopectin-branched molecule

3) •helix-compact to fit +glucose in small space
•branched- +SA for rapid hydrolysis back to glucose
•insoluble-no affect water potential

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10
Q

Describe cellulose (polysaccharide)

A

1) structure strength for cell wall

2)•long straight chains
•chains held in parallel by +H2 bonds to form fibrils

3)• +H2 bonds- give collective strength
•insoluble- no affect water potential

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11
Q

Describe glycogen (polysaccharide)

A

1) store of glucose for animals

2) •highly branched molecule
•very compact: lots stored

3)•branched- +SA for rapid hydrolysis back to glucose
•insoluble-no affect water potential

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12
Q

What is the difference between the alpha and beta glucose isomers?

A

Hydroxyl group in c1 is in a different position

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13
Q

What are all monosaccharides and some disaccharides (e.g maltose)?

A

Reducing sugars except sucrose

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14
Q

How are reducing sugars tested? +results

A

1) liquid form or grind in test tube
2) add equal vol Benedict’s reagent
3) heat mix in gently boiling water bath for 5 mins

+ result= blue to red

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15
Q

Why does a reducing sugar turn Benedict’s solution into red?

A

Reduces the chemical (donates e-) which forms the Cu(II)SO4 into an insoluble red precipitate of Cu(I)O

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16
Q

How are triglycerides formed and what is their bond called?

A

3 Condensation reaction between 3 fatty acids and glycerol. Forming 3 ester bonds

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17
Q

What is the general formula of fatty acids and what can they be?

A

RCOOH
•saturated
•unsaturated

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18
Q

What are saturated fatty acids?

A

Only single bonds between Carbon atoms within HC chain

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19
Q

What are unsaturated fatty acids?

A

Have one or more double bonds between carbon atoms in HC chain

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20
Q

What is the structure and function of triglycerides?

A

•energy store: high ratio of energy storing C-H bonds
•metabolic water source: high ratio of H2:O2. Water forms when oxidised
•insoluble: no affect on water potential as large + hydrophobic
•low mass: lots stored, less mass

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21
Q

How are phospholipids made?

A

Condensation reaction between 2 fatty acids and glycerol. Forming 2 ester bonds

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22
Q

How are phospholipids different to triglycerides?

A

They have a negatively charged phosphate group (hydrophilic) instead of a 3rd fatty acid.

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23
Q

What happens when phospholipids are placed in water?

A

•polar Hydrophilic phosphate ‘head’ faces water (attracted). Hydrophobic fatty acid ‘tails’ so move inwards (repel).

•This forms a bilayer where centre acts as a barrier to water soluble substances.

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24
Q

What are cell membranes composed of?

A

Phospholipid bilayer

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25
Q

How is the emulsion test carried out?

A

1) shake lipids in ethanol = dissolved
2) add distilled water
3) white emulsion formed

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26
Q

How is starch tested for?

A

Add iodine solution to 2cm3 sample. Iodine in potassium iodide solution turns orange to blue-black

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27
Q

How do you test for non-reducing sugars?

A

•Benedict’s test: negative (blue)
•boil in HCl to hydrolyse to monosaccharides
•cool and neutralise with sodium hydrogen carbonate
•redo Benedict’s test = brick red

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28
Q

Why do you add Sodium hydrogen carbonate during non reducing sugar test?

A

As Benedict’s solution doesn’t work in acidic conditions

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29
Q

How can the quantity of reducing sugar in a solution be tested?

A

•colorimeter: light absorbance
•filter and dry to find weight

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30
Q

Why does using a colorimeter improve repeatability?

A

•quantitative
•standardised method
•colour change is subjective

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31
Q

How is a dipeptide and polypeptide chain formed? (+name of bond)

A

Di:condensation reaction between 2 amino acids
Poly: condensation reaction between many amino acids

Peptide bond

32
Q

What is an amino acid composed of?

A

•Amino group (NH2)
•Carboxylic group (COOH)
•R group

33
Q

What is the ‘R’ group in an amino acid?

A

Variable group for 20 different amino acids

34
Q

How is a peptide bond formed between amino acids?

A

Condensation reaction between OH of Carboxylic group and H of amine group. Forming a molecule of H20

35
Q

What is the primary structure of a protein and what will happen if it is changed?

A

1) sequence of amino acids joined by peptide bonds in a polypeptide chain

2) change in aa sequence causes bonds to form at different locations so change in 3D shape

36
Q

What is the secondary structure of proteins?

A

Hydrogen bonds form between amino acids in the chain so coil to alpha helix or fold to a beta pleated sheets.

37
Q

Where do hydrogen bonds form in the secondary structure of proteins?

A

Form between C=O groups of Carboxyl group and N-H in the amine group

38
Q

What is the tertiary structure of proteins?

A

The chains are coiled and folded more, so more bonds form between different parts of polypeptide e.g ionic, hydrogen and disulphide bridges.
This forms the unique 3D shape

39
Q

Where do ionic and disulphide bonds form between in the tertiary protein structure?

A

Between R groups
Where disulphide bonds: only 2 R’s with S

40
Q

What is the quaternary structure of protein?

A

Several different polypeptide chains held by bonds to from unique 3D structure

41
Q

What happens to the protein structure when they denature?

A

The bonds between the 2nd and 3rd structure will break and 3D shape is lost. No longer complementary

42
Q

How is protein tested for?

A

Biuret test:
1) add drops of NaOH solution (alkali)
2) add Cu(II)SO4 solution
3) + test= blue to purple

43
Q

What is a conjugated protein?

A

Proteins combined with non-protein substances (prosthetic groups)

44
Q

What is a fibrous protein?

A

e.g collagen + keratin
•insoluble
•structural

45
Q

What is a globular protein?

A

e.g enzymes + haemoglobin
•soluble
•3D shape

46
Q

What is an enzyme?

A

Biological catalyst with a tertiary structure active site that is complementary to the substrate and will lower its activation energy

47
Q

What is the lock and key theory?

A

Specific substrate bonds to a complementary active site, that has a fixed shape

48
Q

What is the accepted model of the enzyme catalyst?

A

Induced fit model:
•active site will mould around the substrate (complementary)= enzyme substrate complex
•puts strain in the bonds, lowering activation energy
•returns to original shape + reused

49
Q

How does temperature effect rate of reaction of an enzyme?

A

•below optimum: low KE so less successful collisions with substrate
•above optimum: denatures, active site changes shape so no more enzyme substrate complexes

50
Q

How does ph effect rate of reaction of an enzyme?

A

Too low or too high Ph:
•interferes with charges in amino acids
•breaks (ionic) bonds holding tertiary structure, active site shape changes
•denatures = no more enzyme substrate complexes

Optimum:
Active site is most complimentary to substrate

51
Q

What happens when an enzyme is denatured?

A

The bonds holding the tertiary structure will break which will change its unique and specific 3D shape. Changing active site’s complimentary shape so less E-S complexes

52
Q

Why does a graph plateau when enzyme concentration continues to increase?

A

There are empty active sites but insufficient substrates to catalyse.

53
Q

Why does a graph plateau when substrate concentration continues to increase?

A

Enzyme active sites are all saturated

54
Q

How do competitive inhibitors affect enzyme reactions and what happens when you add more substrate?

A

•similar shape to substrate so will bind to active site, preventing enzyme substrate complexes
• more substrate= flood and out compete inhibits so they are knocked out of active site

55
Q

How do non-competitive inhibitors affect enzyme-substrate reactions?

A

•binds to allosteric site, away from active site
•causes active site to change shape so it is no longer complementary to substrates
•less E-S complexes

56
Q

What does DNA do?

A

•codes for sequence of ‘AA’ in primary protein structure and determines the final 3D structure and function
•holds genetic info
•polymer made up of nucleotides

57
Q

What is a nucleotide made up of for DNA?

A

•Phosphate group
•pentose sugar: deoxyribose
•organic bases: adenine+thymine, cytosine+guanine

58
Q

How is a polynucleotide and double helix in DNA formed?

A

polynucleotide: condensation reaction between nucleotides forming phosphodiester bonds = sugar phosphate backbone

double helix: 2 polynucleotides bind by H-bonds between complimentary base pairs. This coils and twists

59
Q

How does the structure of DNA link to its function?

A

•stable + strong : sugar phosphate backbone with covalent bonds
•double stranded:replication using a strand as a template
•weak h-bonds: easy to unzip for replication
•long tightly coiled molecule: carries lots of info
•complimentary base pairing: allows identical copies to be made
•sequence of bases: allows info to be stored
•double helix: protects weak H-bonds, prevents damage to code

60
Q

What is RNA and what is it composed of?

A

Short polynucleotide which transfers genetic info from DNA to ribosomes

•phosphate group
•ribose sugar
•uracil+adenine and cytosine+guanine

61
Q

What is MRNA and why is it useful?

A

Messenger: carries the genetic code of one gene from nucleus to the ribosome
•much shorter than DNA so can leave nucleus
•short lived: broken down by the time it has carried out function
•single stranded, every 3 bases (codon)= AA

62
Q

What is the function of TRNA?

A

•attaches to one of the 20 different AA and transfers this AA to ribosome = polypeptide chain
•specific AA attach to TRNA based on the complimentary codons on the MRNA = anticodon

63
Q

What is Rrna?

A

Subunit of ribosomes
Protein+RRNA = ribosomes

64
Q

Why is RNA different to DNA?

A

•much shorter
•single stranded
•contains uracil not thymine
•contains ribose not deoxyribose as pentose sugar

65
Q

What is the process of semi conservative replication?

A
  1. DNA helicase breaks H-bonds between complimentary base pairs in polynucleotide strands= double helix unwinds
    *each strand acts as a template
  2. Free floating nucleotides are attracted to exposed base pairs on template strands
  3. DNA polymerase joins the adjacent nucleotides together by condensation reaction, forming phosphodiester bonds

= 2 daughter DNA with parental strand and synthesised strand

66
Q

How was semi conservative replication proved correct?

A

•bacteria grown in medium of nitrogen isotopes (14N light and 15N heavy)
•DNA spun in centrifuge and separated due to density (top:14 bottom:15)
•when 14N added to 15N DNA, centrifuge will show 100% 14N-15N in middle

67
Q

What is ATP?

A

•Nucleotide derivative
•immediate source of energy
•ribose, adenine and 3 inorganic phosphate groups

68
Q

How does ATP release energy?

A

Hydrolysis of ATP is catalysed by ATP hydrolase into ADP + Pi (+energy)

69
Q

How is ATP made?

A

Made in respiration by a condensation reaction between ADP +Pi, catalysed by ATP synthase

70
Q

What is phosphorylation?

A

When inorganic Pi released from the hydrolysis of ATP makes other compounds more reactive

71
Q

Why is ATP more useful than glucose?

A

•small, manageable amounts of energy so less wasted = less heat
•both: small + soluble so easily transported around the cell
•only one bond hydrolysed so faster
•phosphorylation
•ATP can’t pass out of cell, so all cells have constant ATP supply

72
Q

What is the structure and function of water that make it useful?

A

1) metabolite-metabolic reactions e.g hydrolysis

2)polar so universal solvent-transport of substances / reactions can occur

3)high heat capacity-buffers changes in temperature e.g for enzymes

4) large latent heat of vaporisation-cooling effect with little water lost by evaporation

5) strong cohesion between H20 molecules-continuous column of water (xylem) + surface tension= habitat

73
Q

What are some important inorganic ions in the body?

A

•iron: Fe2+ in haemoglobin will bind + transport oxygen
•H+: maintain Ph, important for ATP synthase
•sodium: communication between neurones, co-transport of aa/glucose
•phosphate: groups in DNA, ATP and RNA, phosphorylation, hydrophilic phospholipid area, joins nucleotides

(Both Na and phosphate affect osmosis/ water potential)

74
Q

What is end product inhibition and what happens when it is high/low?

A

•regulate metabolic pathways
High: binds non-competitively to enzyme, blocking more production
Low: inhibition ends and pathway restarts

75
Q

Why is the direction in which new DNA strand made different for the 2 strands?

A

•DNA has anti parallel strands
•shape of nucleotides is different/aligned differently
•DNA polymerase have specific active sites
•only substrates with complementary shape bind
•only complementary with phosphate end of developing strand

76
Q

Which bases are purines and which are pyramidines?

A

AG: purine
TCU: pyramidines

77
Q

How can a colorimetry be used to give qualitative results for unknown samples?

A

1.make standard solutions of known conc. and record its % absorbance or transmission (a/t)
2.plot calibration curve: % a/t in y-axis and conc. in x-axis
3.find % a/t of unknown values and use graph to read off conc.

Biology (8 decks)

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