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Biology Year 12 > 3 - Biological molecules > Flashcards

3 - Biological molecules Flashcards

1
Q

what kind of bonding occurs between water molecules, and what feature does this give?

A
  • hydrogen bonds

- cohesion and adhesion

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2
Q

What are the features of water and give an example of how it is useful.

A
  • high specific heat capacity: provides a stable environment for aquatic organisms.
  • high latent heat of evaporation: sweating cools down organisms.
  • cohesion/adhesion: useful property in the transpiration stream in plants.
  • good solvent: internal transport medium, medium for reactions.
  • transparent: allows underwater photosynthesis.
  • ice is less dense than water: provides a habitat for polar bears, it is an insulating layer for water underneath so aquatic organisms do not freeze.
  • surface tension: habitat for pond skaters.
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3
Q

What elements make up carbohydrates?

A

C, H, O

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4
Q

What elements make up lipids?

A

C, H, O

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5
Q

What elements make up proteins?

A

C, H, O, N, S

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6
Q

what elements make up nucleic acids (DNA, RNA)?

A

C, H, O, N, P

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7
Q

α - glucose

A

OH groups: down down up down

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8
Q

β - glucose

A

OH groups: up down up down

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9
Q

What is a hexose monosaccharide?

A

A monosaccharide with six carbon atoms.

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10
Q

What is a pentose monosaccharide?

A

A monosaccharide with five carbon atoms.

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11
Q

function of glucose?

A
  • good energy source in animals and plants.

- soluble: easy to transport.

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12
Q

what type of monosaccharide is glucose?

A

hexose

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13
Q

What is an example of a pentose sugar?

A

ribose

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14
Q

What bond is formed between monosaccharides, what type of reaction is this, and how does it form?

A
  • glycosidic bonds
  • condensation reaction
  • H atom from one monosaccharide and OH group from another bond to form a water molecule.
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15
Q

How are bonds between monosaccharides?

A
  • hydrolysis reaction

- addition of a water molecule to break the glycosidic bond.

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16
Q

Reactions of α-glucose with other monosaccharides to produce disaccharides?

A

glucose + glucose -> maltose

glucose + fructose -> sucrose

glucose + galactose -> lactose

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17
Q

What two polysaccharides make up starch?

A
  • amylose

- amylopectin

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18
Q

amylose

A
  • α-glucose
  • 1,4 glycosidic bonds only
  • helix structure
  • hydrogen bonding further stabilises the molecule
  • coiled structure: compact, good for storage
  • insoluble
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19
Q

amylopectin

A
  • α-glucose
  • 1,4 and 1,6 glycosidic bonds.
  • branched structure
  • compact, good for storage
  • branched structure allows enzymes to easily access the glycosidic bonds: glucose can be released quickly.
  • insoluble
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20
Q

glycogen

A
  • α-glucose
  • energy store in animals.
  • 1,4 and 1,6 glycosidic bonds.
  • branched structure, more branching than amylopectin
  • compact, good for storage (more compact than amylopectin)
  • branched structure allows enzymes to easily access the glycosidic bonds: glucose can be released quickly. (faster than amylopectin).
  • insoluble: (does not affect water potential of cell)
  • can be broken down quickly
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21
Q

cellulose

A
  • β - glucose
  • 1, 4 glycosidic bonds only
  • forms straight chains
  • adjacent glucose units in alternate orientation.
  • cellulose chains make hydrogen bonds with each other, forming macrofibrils.
  • macrofibrils combine to form fibres.
  • cellulose provides structural support in plant cells.
  • insoluble.
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22
Q

test for reducing sugars

A
  • bendict’s solution
  • sample in test tube
  • add equal vol of benedict’s solution
  • water bath 5 mins
  • blue to brick red if reducing sugar is present.
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23
Q

test for non-reducing sugars

A
  • remains blue after benedict’s solution added.
  • add dilute HCl
  • add benedict’s solution
  • blue to red.
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24
Q

Example of reducing sugars?

A

monosaccharides

  • glucose
  • fructose
  • galactose
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25
Q

Example of non-reducing sugars

A

disaccharides

  • sucrose
  • maltose
  • lactose
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26
Q

Why is dilute HCl added to non-reducing sugars before benedicts?

A
  • hydrolyses the disaccharide into monosaccharides which are reducing sugars (positive result with benedict’s).
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27
Q

Test for starch?

A
  • iodine test
  • iodine dissolved in potassium iodide solution mixed with sample
  • brown to purple/black (positive result)
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28
Q

what else can be used for the test for reducing sugars?

A
  • reagent strips.
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29
Q

do lipids have polarity? what does this mean?

A
  • they are non-polar molecules

- insoluble in water

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30
Q

What kind of molecules are lipids?

A
  • macromolecules
  • built from repeating units/monomers.
  • complex molecules with a relatively large molecular mass.
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31
Q

What is triglyceride composed of? What bonds are between these?

A
  • one glycerol
  • 3 fatty acids
  • ester bonds between them.
  • insoluble, non polar
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32
Q

What group are fatty acids in?

A
  • carboxylic acids
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33
Q

How do triglycerides form?

A
  • 3 ester bonds form between the 1 glycerol molecule and 3 fatty acids.
  • when they combine, 3 water molecules are produced (condensation reaction) since 3 ester bonds are formed
  • the reaction that leads to the formation of the ester bonds is called esterification (condensation reaction).
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34
Q

saturated and unsaturated fatty acids?

A

saturated: only contain single C-C bonds
unsaturated: contain C=C double bonds.

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35
Q

How do unsaturated fatty acids affect tryglycerides?

A
  • kink/bend in fatty acid
  • fatty acids cannot pack as closely together.
  • liquid at room temp.
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36
Q

How are triglycerides broken down into glycerol and fatty acids?

A
  • 3 water molecules are supplied to break the 3 ester bonds between the glycerol and fatty acids.
  • hydrolysis reaction.
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37
Q

phospholipid structure?

A
  • modified triglycerides.
  • 1 glycerol molecule
  • 2 fatty acids
  • 1 phosphate group.
  • phosphate (group) head is hydrophilic (polar)
  • fatty acid tails are hydrophobic (non-polar)
  • this occurs due to length of molecule.
38
Q

functions of triglycerides?

A

good long term energy storage because:

  • long hydrocarbon fatty acid tails means that they contain a lot of chemical energy. A lot of energy is released when they are broken down.
  • insoluble, doesn’t affect cell water potential.
39
Q

function of phospholipids?

A
  • found in cell membranes of all organisms (eukaryotes and prokaryotes).
  • form a phospholipid bilayer due to hydrophilic phosphate heads, and hydrophobic fatty acids.
  • centre of phospholipid bilayer is hydrophobic therefore water soluble substances cannot easily pass through (acts as a barrier to these type of substances).
40
Q

function of cholesterol?

A
  • They are positioned in between the phospholipids by binding to the hydrophobic tails.
  • they add stability to cell surface membranes.
  • they regulate the fluidity of cell surface membranes.
  • more fluid at low temps, more rigid at high temps.
41
Q

roles of lipids as a whole?

A
  • membrane formation, hydrophobic barriers.
  • hormone production
  • waterproofing (e.g bird feathers).
  • thermal insulation
  • protects vital organs (cushioning)
  • provides buoyancy for aquatic animals.
42
Q

test for lipids?

A
  • emulsion test
  • mix sample with ethanol
  • mix with water and shake
  • white emulsion layer forms on top of solution (insoluble in water).
  • indicates that a lipid is present.
  • remains clear if test is negative.
43
Q

Structure of an amino acid?

A
  • attached to a carbon atom,
  • amine group
  • carboxyl group
  • R group
44
Q

What type of bonds form between amino acids, how are they formed, and what is formed when amino acids join together?

A
  • peptide bond
  • by a condensation reaction. A water molecule is formed for every peptide bond formed.
  • OH from carboxyl group of one amino acid and H from amine group of another amino acid combine to form a water molecule. The C and N atom join together to form a peptide bond.
  • polypeptides are formed (multiple amino acids).
  • dipeptide formed (2 amino acids).
45
Q

How are peptide bonds broken?

A
  • water molecule is added to break the peptide bond.
  • hydrolysis reaction
  • amine and carboxyl groups are reformed.
46
Q

What is the primary structure?

A
  • The sequence of the amino acids in a polypeptide chain.

- different proteins have different amino acid sequences.

47
Q

What is secondary structure? What bonds are present?

A
  • oxygen, nitrogen, hydrogen of the amino acids in the chain interact.
  • hydrogen bonds form within the amino acid chain.
  • coil into alpha helix
  • fold into beta pleated sheet.
48
Q

What is tertiary structure? What bonds are present?

A
  • the 3D folding of a protein into its final shape.
  • R groups of amino acids get closer together.
  • the 3D folding gives specialised characteristics and functions.
  • hydrophobic and hydrophilic interaction
  • hydrogen bonds
  • ionic bonds
  • disulfide bridges
49
Q

What is quaternary structure? What bonds are present?

A
  • found in proteins containing more than one polypeptide chain (subunits) (can be identical or different).
  • same interactions occur as in tertiary structure, but the interactions are between the subunits.
  • hydrophobic and hydrophilic interactions
  • hydrogen bonds
  • ionic bonds
  • disulfide bridges.
50
Q

Example of a protein with a quaternary structure?

A
  • haemoglobin
  • 4 subunits: 2 sets of 2 identical subunits.
  • 2 alpha chains, 2 beta chains
  • has haem groups containing iron.
51
Q

test for proteins?

A

biuret test

  • add 3cm^3 liquid sample into test tube.
  • add equal volume of KOH solution and stir
  • and few drops of copper sulfate solution and stir until blue
  • turns blue to purple if protein is present.
  • remains blue for negative test.
52
Q

What are globular proteins?

A
  • compact
  • soluble in water
  • they are proteins which are compact and soluble in water, due to the hydrophobic and hydrophilic interactions formed in the tertiary structure.
  • roughly spherical in shape
53
Q

How are globular proteins formed?

A
  • when proteins fold in their tertiary structure.
  • hydrophobic R groups kept away from aqueous environment.
  • hydrophilic R group on outside of protein.
  • hydrophobic and hydrophilic interactions make the proteins soluble in water.
54
Q

What are conjugated proteins?

A
  • they are globular proteins that contain a non-protein component (prosthetic group).
  • opposite is called simple proteins.
55
Q

Example of a conjugated protein?

A

haemoglobin

  • quaternary protein (4 subunits, 2 alpha, 2 beta)
  • each subunit contains a prosthetic haem group.
  • haem groups contain iron II ions, which oxygen binds to and are released from.
56
Q

Example of an enzyme conjugated protein?

A
  • catalase
  • quaternary protein
  • contains 4 prosthetic haem groups.
  • iron II ions in the haem groups allows catalase to interact with hydrogen peroxide and speed up its breakdown.
  • catalase prevents the accumulation of hydrogen peroxide (damaging to cells if accumulate).
57
Q

Example of a globular protein?

A
  • insulin
  • hormone involved in regulation of blood glucose concentration.
  • solubility is important as hormones are transported in the bloodstream.
  • precise shape (to match specific receptors on cell surface membranes).
  • 2 polypeptide chains held by disulfide bridges.
58
Q

What are fibrous proteins?

A
  • long, insoluble proteins.
  • insoluble due to high proportion of amino acids with hydrophobic R-groups in the primary structure.
  • fibrous proteins tend to make long, strong molecules which are not folded into 3D shapes like globular proteins.
59
Q

Keratin

A
  • fibrous protein
  • found in hair, skin, nails.
  • can be flexible like in skin. or hard and tough like in nails.
60
Q

Elastin

A
  • fibrous protein
  • found in elastic fibres (in walls of blood vessels and alveoli of lungs).
  • gives flexibility to expand, and return to normal size.
61
Q

Collagen

A
  • fibrous protein
  • connective tissue found in skin, bone, muscle.
  • very strong molecule
  • minerals can bind to the protein to increase rigidity.
62
Q

Examples of inorganic CATIONS involved in biological processes

A 
Ca2+
Na+
K+
H+
NH4+
63
Q

Examples of inorganic ANIONS involved in biological processes

A 
NO3-
HCO3-
Cl-
PO43-
OH-
64
Q

formula for retention value?

A

Rf = distance moved by solute / distance moved by solvent.

65
Q

What does a nucleotide consist of?

A
  • pentose sugar
  • phosphate group
  • nitrogenous base
66
Q

What bonds are between nucleotides and how are they formed? What is a bunch of nucleotides joined together called?

How are these bonds broken?

A
  • phosphodiester bonds
  • condensation reaction
  • polynucleotide
  • bonds are broken by hydrolysis (water molecule is used to break the bonds) and release individual nucleotides.
67
Q

What are the 4 bases and which ones pair up? Also, which ones are purines and which ones are pyrimidines?

A

A - T, G - C

A and G are purines (bigger bases)
T and C are pyrimidines (smaller bases)

between A and T, 2 hydrogen bonds form

between G and C, 3 hydrogen bonds form.

68
Q

what is the pentose sugar in DNA nucleotides?

A

deoxyribose

69
Q

what is the pentose sugar in RNA nucleotides?

A

ribose

70
Q

What bonds are formed between the bases?

A

hydrogen bonds.

71
Q

Differences in DNA nucleotides and RNA nucleotides?

A

in RNA nucleotides:

  • ribose (pentose sugar) instead of deoxyribose
  • Uracil (U) instead of thymine (T). U replaces T base.
72
Q

Characteristics of DNA strands?

A
  • antiparallel strands
  • two strands are coiled into a DNA double helix
  • Hydrogen bonds occur between complementary bases on two antiparallel polynucleotides, leading to the formation of a DNA molecule.
  • complementary base pairing.
73
Q

What are DNA backbones composed of?

A

deoxyribose-phosphate molecules.

74
Q

DNA extraction steps?

A
  • grind sample (break down cell walls)
  • mix with detergent (breaks down cell membrane)
  • add salt (breaks hydrogen bonds between DNA and water molecules)
  • add protease enzyme
  • add layer of alcohol (causes DNA to precipitate out of solution)
  • DNA can be seen as white strands between sample and alcohol layer.
75
Q

steps of semi-conservative replication?

A
  • DNA helicase unzips the DNA double strand by breaking the H bonds between complementary bases.
  • Free nucleotides are attracted to exposed complementary bases and form H bonds.
  • DNA polymerase joins the new lines of nucleotides together.
  • Nucleotides are joined together by phosphodiester bonds.
  • Two identical DNA molecules are formed.
  • Each molecule is semi-conservative: composed of one old and one new strand.
76
Q

Which direction does DNA polymerase travel?

A

3’ to 5’

77
Q

mutation?

A
  • sequences of bases are not always matched correctly.
  • incorrect sequence in the newly copied strand
  • these errors happen randomly and spontaneously and are known as mutations.
78
Q

Nature of genetic code?

A
  • triplet code
  • degenerate
  • non-overlapping
  • universal
79
Q

triplet nature of genetic code?

A
  • the code in the base sequences is a triplet code
  • sequence of three bases, codon.
  • each codon codes for an amino acid.
80
Q

degenerate nature of genetic code?

A
  • there are several different codons that can code for the same amino acid.
  • 64 different codons possible.
  • reduces effects of mutations to base sequence.
81
Q

non-overlapping nature of genetic code?

A

each base can only be part of one codon.

82
Q

universal nature of genetic code?

A

the same sequences of 3 bases (codons) code for the same amino acid in all organisms.

83
Q

how does a gene determine protein primary structure?

A
  • the gene determines the sequence of amino acids produced to form a polypeptide chain, which is the primary structure of a protein.
84
Q

What are the stages of protein synthesis?

A
  • transcription

- translation

85
Q

stages of transcription:

A
  • DNA helicase unzips the DNA double strand and exposes the nucleotide bases.
  • one strand acts as a template strand.
  • free RNA nucleotides pair up with complementary bases on the template strand.
  • RNA polymerase join the RNA nucleotides together to form mRNA.
  • the mRNA formed is almost identical to the sense strand of the DNA.
86
Q

stages of translation:

A
  • mRNA leaves the nucleus via nuclear pores and travels to the ribosomes.
  • the ribosome attaches to the start codon of mRNA.
  • bases are read in triplets (codons).
  • a specific tRNA with complementary anticodons to the mRNA codons pair pair with the mRNA.
  • The tRNA molecule has a specific amino acid attached.
  • The ribosome moves along the mRNA and the process is repeated.
  • Amino acids are joined together by an enzyme, forming peptide bonds. A chain of amino acids is produced.
87
Q

Structure of ATP?

A
  • 3 phosphate groups
  • pentose sugar (ribose)
  • nitrogenous base (adenine)
  • phosphorylated nucleotide
88
Q

How does ATP release energy?

A

ATP + H2O -> ADP + Pi + energy

Pi is inorganic phosphate

  • Adenosine triphosphate
  • Adenosine diphosphate
  • hydrolysis reaction
89
Q

Structure of ADP?

A
  • 2 phosphate groups
  • pentose sugar (ribose)
  • nitrogenous base (adenine)
  • phosphorylated nucleotide
90
Q

Why is ATP such a good source of energy?

A
  • single step reaction.
  • measurable quantities of energy released.
  • not stored in large quantities therefore ADP is easily reformed.

Biology Year 12 (11 decks)

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