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OCR BIOLOGY (MODULE 2) > BIOLOGICAL MOLECULES (2) > Flashcards

BIOLOGICAL MOLECULES (2) Flashcards

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1
Q

What do proteins do in organisms?

A
  • build cells (50%)
  • send chemical messages around the body (hormones)
  • carry oxygen in blood
  • fight bacteria and viruses=antibodies
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2
Q

What elements are proteins made up from?

A

Carbon, oxygen, hydrogen and nitrogen

-may contain sulphur

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3
Q

What do plants need from the soil to make all their amino acids?

A

Nitrates

-converted into the amino group, bonded to an organic group (product of photosynthesis)

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4
Q

In animals, how do they get the 15 essential amino acids that can’t be produced by the body?

A

Out of the 20, 15 of the amino acids are essential but can’t be built by other materials-so they have to be absorbed in the gut as they are found in food

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5
Q

How are amino acids broken down in the body?

A

In the liver by deamination

The amino groups are converted into urea, which is removed from the blood by the kidney and excreted in the urine

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6
Q

What bond is between multiple amino acids?

A

Peptide bond

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7
Q

What is the test for proteins?

A
  • mix 1cm*3 of suspension or solution with a equal volume of buret solution
  • swirl the tube and look for colour change (blue to lilac)
  • the chemicals in the biuret solution react with the peptide bonds in a protein
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8
Q

Why are some amino acids described as ‘non essential’?

A

Your body produces them-they can be made from other materials

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9
Q

Why would a solution or amino acids give a negative result for the biuret test?

A

Aren’t any peptide bonds for it to react with

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10
Q

What is the primary structure determined by?

A

The gene that codes for the polypeptide

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11
Q

Description of how to make the primary structure

A
  • condensation reaction occurs during protein synthesis (carried out by ribosomes)
  • the hydrolysis reaction is catalysed by enzymes (called protease), as covalent peptide bonds are too strong to fall apart by itself
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12
Q

In what processes does hydrolysis happen?

A

Digestion
Hormone regulation
Ageing

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13
Q

Description pf how to make the secondary structure

A

This is how the polypeptide FOLDS
Forms one or two structures (dependent on primary)
-Alpha helix (right handed helix)
-Beta pleated sheets
Stabilised by HYDROGEN BONDS (as small difference in charges between oxygen of carboxyl and hydrogen (=ve) of the amino group)
-weaker than peptide bonds but there are lots of them=major force holding together the shape of a polypeptide (hence sensitivity to pH and temperature)

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14
Q

Description of a beta pleated sheet

A

Flat sheet formed by a polypeptide that folds back on itself or links to adjacent polypeptides lying parallel to one another

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15
Q

What four bonds in the tertiary structure hold it together?

A

Disulfide (strongest)
Ionic
Hydrogen
Hydrophobic and hydrophilic interactions

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16
Q

Describe a hydrogen bond, its strength and what its broken by

A
  • formed between polar groups
  • very weak
  • pH and temp changes
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17
Q

Describe an ionic bond, its strength and what its broken by

A
  • forms between charged groups
  • weak
  • pH and temp changes
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18
Q

Describe a disulphide bond, its strength and what its broken by

A
  • forms between sulphur atoms and in R-group
  • strong
  • reducing agents
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19
Q

Description of hydrophobic and hydrophilic interactions, their strength and what breaks them

A

Hydrophobic- the R-group points inwards away from water
Hydrophilic- the R-group points outwards towards water
-both very weak
-changes to the overall 3D structure (distribution of other bonds)

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20
Q

What will a protein have if its made of two or more polypeptide chains?

A

Quarternary structure

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21
Q

What are the two main ‘shapes’ for a 3D structure of proteins?

A

Globular and fibrous

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22
Q

What is the 3D feature of a globular protein?

A

Roll up to form a ball

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23
Q

What is the 3D structure of a fibrous protein?

A

Forms fibres

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24
Q

What is the primary structure of a globular protein?

A

Usually a non-repeating amino acid sequence with chains of equal length

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25
Q

What is the primary structure of a fibrous protein?

A

Often a repeating amino acid sequence of varying chain length

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26
Q

What is the solubility of a globular protein in water?

A

Usually soluble:

-hydrophilic R-group on the outside

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27
Q

What is the solubility of a fibrous protein in water?

A

Usually insoluble

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28
Q

What is the role of a globular protein?

A

Usually metabolic

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29
Q

What is the role of a fibrous protein?

A

Usually structural

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30
Q

What is the structure of haemoglobin?

A
  • 4 polypeptides (2 alpha and 2 beta chains)

- haem prosthetic groups on each polypeptide (4 in total)

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31
Q

What is the function of haemoglobin?

A

-carry oxygen from the lungs to the tissue

32
Q

What is the structure of insulin?

A

-2 polypeptide chains
>A begins with an alpha helix
>B ends with a beta pleated sheet
-each forms own tertiary structure- joined by disulphide bods
-hydrophillic R-groups on the outside of the molecule (water soluble)

33
Q

What is the function of insulin?

A

Hormone:
Binds to glycoprotein receptors on muscle and fat cells to:
-increase rate of glucose uptake from blood
-increase rate of glucose consumption

34
Q

What is the structure of pepsin (enzyme)?

A

NO QUATERNARY STRUCTURE:

  • 1 polypeptide chain that folds into a symmetrical tertiary structure
  • of 327 amino acids, only 4 have basic R-groups0 gives stability in low pH environments
  • stabilised by H-bonds and 2 dis;fide bonds
35
Q

What is the function of pepsin?

A

Enzyme:

-digest proteins in the stomach (breaks peptide bonds)

36
Q

Why is haemoglobin a conjugated protein?

A

Contains non-protein prosthetic groups

37
Q

What are examples of fibrous proteins?

A

Collagen, keratin and elastin

38
Q

Where is collagen found?

A

Artery walls, tendons, bones and cartilage

39
Q

What properties and functions does collagen have?

A
  • strong and inelastic, providing mechanical strength

eg: prevents bursting, allows muscles to pull on bone

40
Q

What properties and functions does keratin have?

A
  • provide mechanical protection (hard and strong molecules)

- waterproof and impermeable barrier

41
Q

What properties and functions does elastin have?

A

Due to cross-linking and coiling it is strong and extensible properties allows things to stretch and apart to their shape

42
Q

What is the method of chromatography?

A
  1. Draw line whir pencils 1cm from bottom of paper, then. spot amino acids along line (and label)
  2. Add solvent to beaker and dip bottom of paper into it, then cover with lid
  3. When solvent reaches the top take it out and mark where solvent has reached
  4. Amino acids aren’t visible on paper so spray with ninhydrin solution to turn amino acid purple
43
Q

What is the name of the tube used to put amino acid sample onto the paper in chromatography?

A

Capillary tube

44
Q

Is collagen globular or fibrous?

A

Fibrous

45
Q

Is elastin globular or fibrous?

A

Fibrous

46
Q

Is keratin globular or fibrous?

A

Fibrous

47
Q

Is haemoglobin globular or fibrous?

A

Globular

48
Q

Is insulin globular or fibrous?

A

Globular

49
Q

What are nucleic acids?

A

Large molecules made from nucleotides

50
Q

What are the three subunits joined by in a nucleotide?

A

Covalent bonds

51
Q

What are the three subunits in a nucleotide?

A

Nitrogenous base- rectangle
Deoxyribose (sugar)- pentagon
Phosphate molecule- circle

52
Q

What doe DNA stand for?

A

Deoxyribonucleic acid

53
Q

What are the names for ATGC?

A

Adenine
Thymine
Guanine
Cytosine

54
Q

How many rings does purine have?

A

2

55
Q

How many rings does pyrimidines have?

A

1

56
Q

What does DNA exist as?

A

Double helix of two polynucleotide strands

57
Q

What are polynucleotide strands made from?

A

Sugar phosphate back bone attached to the bases (ATGC)

58
Q

How are nucleotide acids joined?

A

Condensation reactions between hydroxyl (OH) groups on the phosphate of one nucleotide and the sugar of the next
Creating a phosphodiester bond

59
Q

What bond forms between the bases of two polynucleotides?

A

Hydrogen bonds, stability

60
Q

Why is it important that the DNA molecule is stable?

A
  • need to have that structure to make proteins (throughout life)
  • pass onto offspring
61
Q

How many H bonds do A-T bases form?

A

2

62
Q

How many H bonds do G-C bases form?

A

3

63
Q

Explain how the structure of DNA is suited to its role

A

Base sequences code, the double helix= stability, double stranded= replication, H bonds made= copied easily

64
Q

How is DNA found in eukaryotes?

A
  • the majority of DNA found in the nucleus
  • DNA is wound around in histone proteins, making chromosomes
  • Loop of DNA, without histone, inside mitochondria and chloroplasts
65
Q

How is DNA found in prokaryotes?

A
  • DNA is a loop within cytoplasm- no nucleus
  • It is ‘naked’- not wound around histone proteins
  • Plasmids often present
66
Q

What is semi-conservative replication?

A

Making a new DNA molecule by keeping one half of the old molecule and making a new ‘other half’
Each molecule contains an old strand (parent) and a new strand (daughter)

67
Q

What are the stages of semi-conservative replication?

A
  1. Double helix untwisted a bit at a time- replication done in sections
  2. H bonds between nucleotides bases are broken
  3. DNA helicase ‘unzips’ the section, making two strands of DNA with exposed nucleotide bases
  4. Free nucleotides (in nucleus) associate with exposed bases following complementary base rules
  5. DNA polymerase catalysis the addition of new nucleotides bases in the 5’ to 3’ direction, the ‘unzipped’ single strands are used as templates
  6. Hydrolysis of activated nucleotides release an extra phosphate groups, supplies energy to make phosphodiester bonds between the deoxyribose and phosphate groups of adjacent nucleotides
  7. Leading strand is synthesised continuously and the lagging stand is synthesised in sections
68
Q

What does the enzyme DNA polymerase do?

A

Reforms polymers

69
Q

What does the enzyme DNA helicase do?

A

Unzips the the nucleotide bases

70
Q

What is a gene?

A
  • sequence of 3 nucleotide bases called a codon, corresponds for a specific amino acid
  • as codons are ‘read’, polypeptides are made and these form primary structure of all proteins
71
Q

How can you describe the genetic code?

A

UNIVERSAL- same triplet of bases codes for the amino acids in almost all organisms
TRIPLET- three bases code for one amino acid, called a triplet
DEGENERATE- for all amino acids except two there is more than one base triplet
NON-OVERLAPPING- code read from a fixed point (single codon marks the start of a gene sequence) ‘in frame’. ensures bases are read in the correct order within codons

72
Q

What is the structure of RNA?

A

Similar to DNA, polynucleotide strand with sugar-phosphate backbone, and nucleotides contain one of four bases

73
Q

How does RNA differ from DNA?

A
  1. ribose sugar
  2. single stranded polynucleotide model
  3. URACIL replace thymine
    > U-A
    > C-G
74
Q

What are the three forms of RNA?

A
  • mRNA (messenger- made as complementary strand to a section of DNA)
  • rRNA (ribosomal RNA is found in ribosomes)
  • tRNa (transfer RNA carries amino acts to ribosomes)
75
Q

Compare DNA and RNA

A

DNA:

  • double helix
  • deoxyribose
  • ATGC

RNA:

  • single stranded
  • ribose
  • AUGC

OCR BIOLOGY (MODULE 2) (6 decks)

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