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Biology M3 Flashcards

1
Q

What does DNA helicase do?

A

Breaks the hydrogen bonds between complimentary base pairs to split the DNA strand, exposing bases on both strands

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2
Q

What happens when DNA base pairs have been exposed?

A

Free nucleotides in the nucleus are attracted to the complementary bases forming hydrogen bonds

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3
Q

DNA replication steps

A

1) DNA helicase breaks the hydrogen bonds between complementary base pairs
2) free nucleotides in the nucleus are attracted to the exposed bases and form new hydrogen bonds between complementary bases
Each DNA strand acts as a template
3) DNA polymerase attatches to the nucleotides and joins them together using a condensation reaction forming phosphodiester bonds, 2 new strands are beginning to form
2 new DNA molecules are formed which coil to form 2 helixes

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4
Q

Which features make DNA ideal for semi conservative replication

A

There are 2 strands, DNA has bases that form complementary pairings, strands held together by hydrogen bonds

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5
Q

What does mRNA do

A

Carries DNA from the nucleus to the ribosomes where it is used for protein synthesis

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6
Q

Transcription (eukaryotes)

A

1) break down complementary base pairs hydrogen bonds using RNA polymerase - it binds to DNA and runs along it breaking the hydrogen bonds leaving 2 exposed strands
2) then RNA polymerase adds RNA nucleotides to complementary bases on one strand
3) then is joins the nucleotides together using a condensation reaction forming a phosphodiester bonds
4) as RNA polymerase moves along the DNA, it re attatches the DNA helix behind it
5) the RNA polymerase moves along the strand until it is complete, once its complete the RNA strand and RNA polymerase detach from the DNA leaving a DNA strand and RNA strand which is pre-mRNA
6) then the pre-mRNA is spliced which removes the introns in the strand

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7
Q

How is mRNA produced in transcription

A

By splicing out introns which are non coding regions, however this is only done in eukaryotes

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8
Q

Transcription in prokaryotes

A

The same as eukaryotes however no splicing takes place because prokaryotic DNA doesn’t contain introns

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9
Q

What are introns

A

Regions which don’t code for proteins in DNA

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10
Q

What’s are exons

A

Regions which code for proteins in DNA

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11
Q

Translation steps

A

1) ribosome attaches to the mRNA strand start codon
2) a tRNA molecule with a complementary anticodon to the start codon binds to the mRNA, it has a specific amino acid attatches
3) the ribosome joine the amino acids together using a condensation reaction forming a peptide bond
4) the ribosome moves along the strand causing the tRNA molecule to detach from the ribosome and the amino acid it was carrying, it can now go pick up another amino acid
5) ribosome continues moving along the mRNA molecule, attaching mor amino acids to the polypeptide chain, once complete everything detaches

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12
Q

What is a gene mutation

A

A change in the base sequence of a chromosome which can occur spontaneously during DNA replication, or by mutagenic agents

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13
Q

What are mutagenic agents

A

Outside factors which increase the rate of mutations

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14
Q

What is a base deletion mutation

A

When a nucleotide is removed from a DNA sequence casing a frame shift

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15
Q

What is a frame shift

A

A change to the sequence of triplets which changes the sequence of amino acids that are coded for and a large change in resulting protein

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16
Q

Base substitution

A

When a base is swapped out for a different one , only affects a single triplet in thr DNA sequence which can result in a different amino acid changing the primary structure, r in the same amino acid which doesn’t change the primary structure because DNA code is degenerate

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17
Q

What does it mean that the DNA code is degenerate

A

It means that many triplets code for the same AA

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18
Q

What happens when mutations cause a change to the primary protein structure

A

Alter the bonds within the tertiary structure (disulphide bridges, ionic bonds, hydrogen bonds) which can result in a non functional protein

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19
Q

Why is the bonding of G-C more stable than A-T

A

Because there are 3 hydrogen bonds within G-C and only 2 between A-T

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20
Q

How many different triplet bases are there

A

64

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21
Q

Which triplet starts the DNAn sequence

A

ATG (methionine)

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22
Q

How id DNA diffferent to RNA

A

DNA contains deoxyribose sugar instead of ribose, RNA is single stranded while DNA is double, DNA contains thymine which is replace by uracil in RNA

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23
Q

Function of stop codon

A

Mark the end of the polypeptide chain, don’t code for amino acids

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24
Q

What are histones

A

Proteins that DNA wraps around

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25
What is an allele
A variant of a gene
26
What is a diploid cell
A cell with. Sets of chromosomes
27
What is a haploid cell
A cell which contains one set of chromosomes
28
What are homologous chromosomes
A pair of chromosomes with the same genes
29
How does mRNA leave the nucleus
Via nuclear pores
30
What is transcription
Making pre-mRNA using DNA as a template
31
What is splicing
Removing introns and joining exons together
32
Where does a ribosome attach onto on mRNA
At the start codon
33
What do tRNA do once their amino acid joins the polypeptide chain
Leav the ribosome to collect another amino acid
34
What is a codon
A set of 3 bases on DNA or mRNA that codes for a single amino acid
35
What is a genome
The complete set of genes in a cell
36
What is a proteome
All the proteins produced in a given cell or organisms at a given time under specific conditions
37
What is a proteome
All the proteins produced in a given cell or organisms at a given time under specific conditions
38
What is an anticodon
Three tRNA bases complementary to the mRNA codon
39
2 parts of tRNA
Anticodon and amino acid binding site
40
What is an active site
The region on the enzyme where a substrate fits to catalyse a reaction
41
Induced fit model of enzyme
Substrate begins to bind to the active site, then the shape of the active site slightly changes to fit around the substrate making them complementary. This puts stress of the bonds and makes them easier to break lowering activation energy
42
How does increased enzyme concentration affect the rate of reaction
Increases the rate of reaction because there are more active sites available which increases probability of ES complexes forming
43
What’s happens if the enzyme is limiting in a reaction
All the active sites will eventually become occupied (saturated) causing the reaction to plateau
44
What is a competitive inhibitor
An inhibitor with a similar shape to the substrate and so binds to the active site of the enzyme
45
What is a non competitive inhibitor
Have a different shape to the substrate so aren’t competing, they bind to the allosteric site which changes shape of active site meaning that ES complex can no longer form
46
Conditions for enzyme action
Collision with substrate, active site with shape complementary to substrate
47
Components of ATP
Adenine, ribose, 3 phosphates
48
How is energy release from ATP
A hydrolysis reaction - ATP+H2O -> ADP + Pi
49
How is ATP synthesised
Condensation reaction - ADP + Pi (+energy) -> ATP+H2O
50
In what situations does ATP synthesis occur
Photosynthesis, respiration, transfer of phosphates from donors to ADP
51
ATP has unstable bonds and releases little energy. Why does this suit its function
provides immediate energy and small quantities are more manageable
52
Uses for ATP
Metabolic u=processes, active transport, movement, secretion, activation of molecules
53
Glucose takes longer to break down and releases lots of energy, why is it a poor energy donor
Takes longer to break down so can’t be used for immediate energy, ;archer quantities are less manageable and more is wasted
54
What is the Pi (inorganic phosphate) used for when ATP is hydrolysed
Used to phosphorylate other compounds making them more reactive
55
Nucleotides structure
phosphate group, Deoxyribose/ribose sugar (depending if its RNA or DNA), and nitrogen base (organic) °—⬠—▭
56
What is metabolic rate
Amount of energy expended by that organism in a given time period
57
What is metabolic demand
How much oxygen and nutrients required to respire enough to maintain metabolic rate
58
Plant adaptations
Many small pores called stomata, meaning no cell is far from a stomata making diffusion distance short Numerous interconnecting airspaces occurring throughout spongy mesophyll so gases can readily come into contact with it, reduced diffusion pathway Large SA of mesophyll cells for rapid diffusion
59
Xylem adaptations
Elongated tubes formed of dead cells (don’t require energy) No end walls between cells - continuous column Thick walls made of lignin - withstand lots of tension, waterproof to prevent water adhering to surface Gaps in cell wall - allows water to move out by osmosis
60
Transpiration
Xylem is a hollow tube which allows water to be drawn up easily, it is a passive process. Water evaporates from leaves which reduces water potential in the cells.water from the mesophyll moves in by osmosis reducing the water potential. Cohesive water molecules are drawn up a continuous column under tension, adhering to walls pulling them inward. Reduces water potential in the xylem so water is pulled up the roots which moves in by osmosis.
61
Translocation
Sucrose solution moves from source to sink. In the source sucrose solution is co-transported (requiring active transport) into phloem via companion cells. Lowers water potential of STE and so water from xylem moves in by osmosis. Increases volume and hydrostatic pressure. Pressure pushes sucrose to sink. It is cotransported into companion cells (using active transport) and into sink.
62
Structure of phloem
Long sieve tube elements with holes in end walls called sieve tube plates
63
What are xerophytes
Plants adapted to live in extreme dry conditions
64
Adaptations of xerophytes
No leaves/ leaves reduced to spikes - reduce SA so less stomata so less water loss Sunken stomata - trap moist air around stomata which reduces water potential between inside and outside stomata reducing transpiration rate Rolled up leaves - traps layer of air which becomes saturated with water vapour Hairy leaves - traps layer of moist air (both work by water potential being decreased between outside and inside) Thick waxy cuticle - minimise water loss
65
Function of nucleus
Contains genetic material and controls cell
66
Function of cell surface membrane
Controls movement of substances in and out of cell
67
Function of mitochondria
Site of aerobic respiration
68
Functions of Golgi apparatus
Modify proteins into glycoproteins, produce enzymes and carbs, modify and store lipids, form lysosomes
69
Function of Golgi vesicle
Transport modified lipids and proteins
70
What are criteria in Golgi apparatus
Flattened stacks of membranes
71
What 3 things do lysosomes break down
Old organelles, dead cells, material from phagocytes
72
What are monomers
The smaller subunits from which larger molecules are made
73
What’s a polymer
Long chains of subunits
74
What 2 things happen in a condensation reaction
Bonds form between monomers, water molecule produces
75
What 2 things happen in a hydrolysis reaction
Bonds between monomers break, water molecule used
76
Monomer in carbohydrate
Monosaccharide
77
What is a disaccharide
A molecule made by the condensation of 2 monosaccharides
78
How does beta and alpha glucose differ
Beta glucose has OH on first carbon on same side as oxygen
79
3 stages for reducing sugar
Add sample in reduced form, add same volume of Benedict’s reagent, boil for 5 mins and observe precipitate
80
Maltose monosaccharides
Glucose and glucose
81
Sucrose monosaccharides
Fructose and glucose
82
Lactose monosaccharides
Glucose and galactose
83
What organisms store alpha glucose as starch
Plants
84
What animals store alpha glucose as glycogen
Animals
85
2 chains in starch
Amylose and amylopectin
86
Amylose and amylopectin differences
Amylose unbranched whilst amylopectin is, amylose contains 1-4 glycosidic bonds only, amylopectin contains 1-4 and 1-6
87
Difference between search and glycogen
Glycogen is more branched
88
4 parts of an amino acid
Amino group (NH2), variable group (R), carboxylate group (COOH), hydrogen group
89
Primary protein structure
Sequence of amino acids in a polypeptide, polypeptide bonds only
90
Secondary protein structure
Alpha helixes and beta pleated sheets, contains hydrogen bonds
91
Tertiary protein structure
3D shape of polypeptide chain, contains hydrogen bonds, ionic and disulphide bridges
92
Quarternary structure protein
Polypeptide chains joined together, or a non protein group
93
Biurets test
Ad sodium hydroxide to sample, mix in copper (II) sulphate, purple positive result
94
What are grana
Stacks of thylakoid discs in chloroplasts
95
What is stroma
Fluid where sugars are synthesised during photosynthesis
96
Things found in stroma
Enzymes ribosomes DNA
97
Why does RER have large SA
For protein synthesis and material transpot
98
Functions of SER
Synthesis store and transport lipids and carbs
99
What is made in the nucleoulous
Ribosomes
100
3 parts of virus
Attachment proteins, capsid, nucleic acid
101
Mitosis
Prophase - chromosomes become condensed (shorter thicker and visible under microscope), nuclear envelope disintegrates, centrioles move to poles and produce spindle fibres Metaphase - chromosomes align in equator, spindle fibres attach to centromeres Anaphase - spindle fibres contract and pull a chromatid from each pair to opposite poles Telophase - chromosomes uncondense (become longer and thinner), nuclear envelope reforms
102
Virus replication
Attachment protein attach to host cell receptors Inject nucleic acid into cell Host produces proteins with the nucleic acid Virus particles assemble Cell lyses and viruses are released
103
Binary fission
Cell contents replicate Cell elongates and DNA moves to poles of cell Cytoplasm divides Cell wall reforms 2 genetically identical daughter cells

Biology Y12 (2 decks)

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