Things I Might Forget Flashcards
1
Q
Most common bond in the body?
A
Covalent
2
Q
Properties of water:
A
Excellent Solvent- Many substances can dissolve in water.
High Specific Heat Capacity- Takes a lot more energy to increase the temperature of water as compared to other substances.
High Latent Heat of Vaporisation- It loses a lot of heat to cool.
Cohesion- Water molecules stick together by hydrogen bonding.
Adhesion- Attraction between water molecules and other substances.
3
Q
Why can insects walk on water?
A
Water is polar - High surface tensions which results from cohesion between water molecules at the surface of water- therefore insects which are more dense than water can walk/ float on water.
4
Q
Carbohydrates and their functions
A
- C, H, O. Glycosidic bonding.
- Used as an energy source.
- Plants and Arthropods use it as structural elements.
5
Q
Glycogen
A
- Chains of alpha glucose, glycosidic bonding, formed by a condensation reaction.
- Short chains and highly branched.
- Insoluble and compact.
- Main energy storage in animals.
6
Q
Starch
A
- Chains of alpha glucose, glycosidic bonding, condensation reaction.
- Long chains of unbranched alpha glucose.
- Coiled structure held by hydrogen bonds.
- Compact- Good for storage.
- Main energy storage in plants.
7
Q
Cellulose
A
- Long, unbranched chains of beta glucose.
- Flip every other beta glucose upside down so glycosidic bonds can form.
- Straight cellulose chains linked by hydrogen bonds to form microfibrils which form fibres.
- Structural support and rigidity.
- Prevents the influx of water.
8
Q
Why can humans not digest cellulose?
A
Humans lack the enzyme specific to cellulose.
9
Q
What are lipids used by cells for?
A
- Energy storage.
- Insulation.
- Membranes.
Lipids are non-polar (hydrophobic) cannot dissolve in water.
10
Q
Bonding in lipids and difference between saturated and unsaturated.
A
- Bonding= Ester Bonds.
- Saturated- No C=C double bonds within fatty acid chains.
- Unsaturated- At least one C=C double bond.
11
Q
Name the different lipid groups
A
- Phospholipids.
- Waxes.
- Steroids.
- Fats and Oils.
12
Q
How to check for unsaturated fat content?
A
Analyse the fat content of hydrogens.
13
Q
2 examples of proteins or why they are used?
A
- Enzymes= Catalyst that speed up the rate of chemical reactions.
- Structural- Shape and Movement.
14
Q
Structures of Proteins
A
- Primary= Sequence and order of amino acids.
- Secondary= Hydrogen bonding of peptide backbone causes amino acids to fold into repeating patterns (alpha helix and beta pleated sheets).
- Tertiary- 3D folding of protein due to side chain interactions.
- Quaternary- 1 or more polypeptide chains.
If the shape of proteins change, then the function changes.
15
Q
Fibrous Proteins:
A
- Secondary structure is important (alpha helixes and beta pleated sheets).
- Insoluble.
- Structural function= Keratin and Collagen.
16
Q
Globular Proteins:
A
- Tertiary Structure is important, bend and fold into spherical shapes).
- Soluble in water.
- Enzymes, antibody, hormones: Amylase, Insulin and Globulin.
17
Q
What do nucleic acids serve as?
A
- Information Storage.
- Transfer Molecules.
- Energy Transducers.
18
Q
Each cell is?
A
A living functional and structural unit enclosed by a membrane.
19
Q
Cells can be divided into 3 parts?
A
Nucleus.
Cytoplasm.
Plasma membrane.
20
Q
Light microscope?
A
- Uses light.
- *1000 magnification.
- Observe living cells by staining.
21
Q
Electron microscope?
A
- *500,000 magnification.
- Uses beam of electrons.
- SEM- Sees 3D structure of cell.
- TEM- Sees structures inside of a cell.
22
Q
Prokaryotic Cell?
A
- Much smaller than eukaryotic cells.
- Cytoplasm that lacks membrane-bound organelles.
- Smaller ribosomes.
- No nucleus, single circular DNA free in cytoplasm, not associated with proteins.
23
Q
Bacterial Cell?
A
- Extra DNA carried as plasmids.
- No membrane bound nucleus.
- Transcription and translation occur in the same place.
24
Q
Some extra info on eukaryotic?
A
- Nuclear membrane separates protein synthesis.
- Each animal cell has a centrosome and lysosome but plant cell does not.
25
What is an endomembrane system?
Work together to modify, package and transport proteins.
26
Lysosome?
Membrane enclosed vesicles contain digestive enzymes.
Breakdown large biomolecules and worn out organelles.
27
Peroxisome?
Small rounded organelles enclosed by single membrane.
Reactions to break down fatty acids and amino acids occur here.
Contain oxidases, which are enzymes that oxidise various organic substances.
Detoxification- Reduces toxicity.
28
Proteasome?
Continuously destroy unneeded, damaged or faulty proteins.
29
SER ( smooth endoplasmic reticulum)?
- Few/ No ribosomes.
- Lipids are made here.
- Detoxification of poisons.
30
RER (rough endoplasmic reticulum)?
- Ribosomes.
- Proteins made.
31
Golgi?
- Lipids/ Proteins within transport vesicles need to be packaged and processed and tagged to get to the right place.
- Contents emptied into lumen of Golgi.
32
Nucleus?
- Co ordinates cells activities.
- Stores hereditary material and DNA.
33
Ribosome?
- Made of rRNA and proteins.
- Smaller in prokaryotes.
- 2 subunits.
Ribosomes assemble amino acids into proteins.
34
Mitochondria?
- Most ATP production occurs here.
- Cristae and matrix.
35
A cytoskeleton is?
Network of protein fibers with several functions.
36
Functions of cytoskeleton?
- Maintains shape of cell.
- Hold organelles in specific positions.
- Allows movement of cytoplasm and vesicles within cell.
- Enables cells within multicellular organisms to move.
37
Order the cytoskeleton small to large?
1. Micro filament.
2. Intermediate filament.
3. Microtubule.
38
What is a micro filament?
- Double helix of actin monomers.
- Involved in movement and determine+stabilise shape.
39
What is an intermediate filament?
- Strong fibre composed of intermediate filament proteins.
- Defects result in skin for less resistant to physical stress.
- Not involved in intracellular movement.
40
What is microtubule?
Hollow tube formed from tubulin dimers. E.g. Cilia and Flagella.
41
Intracellular junctions provide?
- Provides direct channels of communication between cells.
- Plants and animals do this differently.
42
Plasmosdesmata?
Channels that pass between cell walls in plants to connect the cytoplasms and allow materials to move from one cell to another.
43
Tight Junction?
Watertight seals between animals cells that prevents material from leaking between cells.
44
Desmosome?
Anchors cell to its surroundings.
Key components of a desmosome are cadherins and intermediate filaments.
45
Gap Junctions?
Allows movement of ions and nutrients between cells.
46
What does cytoplasm have that cytosol does not?
Organelles.
47
Cell membranes are composed of?
Lipids.
Carbohydrates.
Proteins.
48
A plasma membrane is?
A selective barrier that controls the movement of molecules in and out of the cell.
49
Phospholipids arrange themselves in a?
Bilayer.
50
Cholesterol?
- Amphipathic structure of cholesterol allows it to pack tightly with phospholipids.
- Increase/ Decrease membrane fluidity depending on temperature.
- At normal temperatures, interaction of cholesterol with phospholipid fatty acids reduces mobility of phospholipids and fluidity of membrane.
- At lower temperatures, cholesterol prevents phospholipids from packing tightly and increases membrane fluidity.
51
Membrane is affected by?
- Cholesterol.
- Phospholipid type: Saturated fatty acids pack closer together than unsaturated fatty acids= more rigid (increased fluidity).
- Temperature- Cold= Rigid.
52
2 different types of proteins?
- Integral- Nestled into phospholipid bilayer, helpful for transporting larger molecules like glucose.
- Peripheral- Help with transport and communication. Can be attached to end of integral proteins.
53
3rd major component of membrane is?
Carbohydrates.
Function is cell to cell recognition.
Components of glycolipids and glycoproteins.
54
Transport is either?
- Passive- No energy required.
- Active- Energy is required (ATP).
55
Describe diffusion?
- Simplest.
- High to low concentration.
- Only small non- polar molecules and lipid hormones pass through.
56
Facilitated Diffusion?
- High to low concentration.
- Through membrane via integral proteins.
- Ions and small polar molecules can pass through.
- Channel and carrier proteins= transport proteins.
57
A channel protein is?
- Some are open all the time.
- Others are gated, only opening when a signal is received.
- E.g. Aquaporins, specific to H2O.
58
A carrier protein is?
- They are specific to single substances.
- Large molecule like glucose and amino acids cannot diffuse across the phospholipid bilayer so they move across here.
59
Describe osmosis?
- High to low water potential.
- Across a partially permeable membrane.
- More solute= More negative water potential.
60
What does tonicity mean?
Capability of a solution to modify the volume of cells by altering the water content.
61
What does osmolarity mean?
Total solute concentration of a solution.
62
Different osmolarities?
- Hypertonic: Water leaves the cell (shrivels).
- Isotonic: Same osmolarity.
- Hypotonic: Water enters the cell (lysed/ bursts).
63
Active transport?
- Low to high concentration.
- For example glucose.
- Energy is always required.
64
2 types of active transport?
- Primary: ATP from hydrolysis provides energy.
- Secondary: Electrochemical gradient provides energy.
65
Active transport occurs through?
Carrier proteins:
-Uniporter: 1 molecules/ions in the same direction.
-Symporter: 2 different molecules/ions in the same direction.
-Antiporter: 2 different molecules/ions in different directions.
66
Bulk transport is?
A type of active transport where large molecules takes place across cell membrane with help of cellular energy.
Energy is required.
67
Bulk transport divided into?
Endocytosis:
- Phagocytosis- Large particles (cells/cell debris) transported into the cell.
- Pinocytosis- Cell takes small amount of extracellular fluid ( held in small vesicles which are smaller than the large vacuoles in phagocytosis).
- Receptor mediated- Receptor proteins on cell surface membrane are used to capture a specific target molecule.
Exocytosis:
- Vesicles containing substances fuse with the plasma membrane and the contents are then released into the exterior of the cell.
Golgi relies on exocytosis to complete its function.
68
Metabolism is?
A set of biochemical reactions that transports biomolecules and transfers energy.
69
Bioenergetics is?
The study of energy flow through a living system.
70
Anabolic is?
Small molecules assembled into larger ones.
Energy is required (ATP).
71
Catabolic is?
Larger molecules are broken into smaller ones.
Energy is released.
72
Phototroph is?
Energy from the sun.
73
Chemotroph is?
Energy from chemicals.
74
Autotroph is?
Energy from Carbon.
75
Heterotroph is?
Organisms that eat other organisms or molecules.
76
Energy is?
Ability to do work.
77
Energy can be classified into?
- Kinetic: Objects in motion.
- Potential: Objects that have the potential to move.
78
Gibbs free energy is?
Amount of energy available to do work.
79
All chemical reactions affect G:
- Anabolic: +H and -S and +G= Endergonic therefore energy is required. E.g. ADP+P to ATP+H2O.
- Catabolic: -H and +S and -G= Exergonic therefore energy is released.
Spontaneous.
E.g. ATP+H2O to ADP+P.
80
Activation energy is?
The energy required for a reaction to proceed.
81
1st Law of Thermodynamics?
Energy cannot be created or destroyed.
82
2nd Law of Thermodynamics?
Transfer of energy is not completely efficient.
83
What is ATP composed of?
Ribose sugar, nitrogenous base and 3 phosphates.
84
Functions of ATP?
Gluconeogenesis (making glucose from non-carbohydrate sources).
Active transport.
Cellular signalling.
Protein synthesis.
DNA synthesis.
Muscle contraction.
Phagocytosis.
Neurotransmitters.
85
Enzymes are?
Biological catalysts.
Increase rate of metabolic reactions.
Active site.
Substrate is turned into a product.
Protein catalysts that speed up rate of reaction by lowering activation energy.
86
Enzyme regulation?
- Temperature increases- Rate of reaction increases but too big of an increase will lead to denaturing enzymes.
- pH- Enzymes have an optimal range.
- Substrate concentration increases- Rate of reaction increases.
- Inhibitors.
87
Penicillin works by?
Inhibiting (stops) a bacterial enzyme that is responsible form cross links in bacteria cell walls.
88
Examples of different enzymes?
-Lactase
-Catalase- Breaks Hydrogen peroxide down.
-Glycogen synthase- Catalyses the formation of glycosidic bonds between glucose molecules.
-ATP ase- Breaks down ATP into ADP+Pi.
89
How many ATPs are generated per glucose?
38.
90
90% of ATP is produced by?
Chemiosmosis.
91
When there is no oxygen, fermentation regenerates NAD. The two types are?
- Lactic Acid fermentation- Occurs is muscles cells, lactate dehydrogenase catalyses this reaction.
- Alcohol Fermentation- Anaerobic yeast species, involves 2 reactions, catalysed by pyruvate decarboxylase and then by alcohol dehydrogenase.
92
Cellular respiration is regulated by?
Hormonal control of glucose entry into the cell.
Enzyme reversibility.
Enzyme sensitivity to pH changes due to lactic acid build up.
Feedback controls.
93
When ATP levels are high?
Cell does not need to make ATP so pathways are slowed.
PFK-1 inhibited so glycolysis slows.
94
When ATP levels are low?
Cell activated pathways that lead to ATP synthesis.
PFK-1 is activated so glycolysis can continue.
95
High NAD levels?
Cellular respiration stimulated.
96
High NADH levels?
Cellular respiration rate is lowered (downregulated).
97
Signalling molecules are often called?
Ligands (term for molecules that bind specifically to other molecules).
98
Message carried by a ligand often relayed through a chain of chemical messengers inside a cell, leads to change in the cell. Process or order is?
Intercellular- Between cells.
Intracellular- Within the cell.
Triggers a response.
99
Essential elements for cell signalling?
Signalling cell.
Signalling molecule (ligand).
Receptor molecule (protein).
Receptor cell (target cell).
100
Paracrine Signalling?
Involves 2 cells close to each other.
Allows cells to locally co ordinate activities with their neighbours over a short distance for example synaptic signals and neurotransmitters.
101
Endocrine signalling?
Signals are produced by specialised cells, they are released into the bloodstream to get to the target cell over a long distance for example hormones.
102
Autocrine?
Cell signals itself, released a ligand that binds to its own receptors (cell death signalling).
103
Direct contact?
- Requires cells to be in direct membrane to membrane contact.
- Gap junctions in animals and plasmosdesmata in plants.
104
2 types of ligands?
- Small hydrophobic ligands: steroid hormones, diffuse directly across the membrane. Nitrogen Oxide activates the signalling pathway in muscle.
- Hydrophilic ligands: Polar/Charged so cannot pass through the membrane so they bind to extracellular domains of the cell surface receptors.
105
2 types of receptors?
- Intracellular: Found within the cell (cytoplasm/nucleus). Many are transcription factors and regulate gene expression.
- Transmembrane: Found in the plasma membrane. Signal does not enter the cell, it is transmitted by the receptor.
106
What is an enzyme coupled transmembrane receptor?
Signal activated enzyme activity of itself.
A kinase transfers a phosphate group to a protein or other target.
A tyrosine kinase receptor transfers a phosphate group specifically to the amino acid tyrosine.
107
What is a G-Protein coupled?
Signal activates a G protein that activates the downstream of enzymes- second messengers.
108
Ion channel coupled?
Signal activates an ion channel.
When the signalling molecules bind, pores in plasma membrane open and let ions in or out of the cell.
109
What does signal transduction mean?
Ligand binds to receptor.
Signal transmitted through membrane to cytoplasm continuing the signal.
Message can remain in cytosol or go to nucleus.
110
Dimerisation is?
2 receptors bind together to form a stable complex.
111
Signalling pathway?
Chain of events including second messengers, enzymes and activated proteins that follow a ligand binding to a receptor.
112
Signal integration?
Signal from 2 or more different cells surface receptors merge to activate the same response in the cell.
113
What is apoptosis?
When a cell is damaged, not needed or potentially dangerous, it may undergo programmed cell death or apoptosis.
114
Signalling in single celled organisms?
- Budding yeast use mating factors.
- Signalling bacteria occurs to maintain extracellular conditions, bacterial signalling is named quorum sensing.
Quorum sensing uses autoinducers.
115
What is an autoinducer?
A signalling molecule that is secreted by bacteria to communicate with other bacteria.
Autoinducers enter the target cell, bind to transcription factors and with gene expression on or off.
116
Cell division has 2 functions?
- Multicellular organisms use it for growth, maintenance and repair of cells and tissues.
- Single celled organisms use cell division to reproduce.
- Mitosis produces 2 diploid identical cells.
117
Functions of DNA?
- Needed to build proteins, essential for proper functioning of cells.
- Important information carrying molecule.
- Hold or store genetic material.
- Contains instructions for the growth and development of all organisms.
118
Physical nature of DNA?
- A-T bind together. 2H bonds.
- C-G bind together. 3H bonds.
A and G are purines and C and T are pyrimidines.
- Watson and Crick proposed structure of DNA molecule.
- 2 strands join together to form a double helix.
119
How is DNA packaged for cell division?
1. Short stretches of DNA wrap around a core of 8 histone proteins- like a string of beads.
2. The histone-DNA complex (bead) is called a nucleosome. The string is called the linker DNA.
3. This structure coils to form a chromatic fiber.
4. Fibrous proteins further pack each chromosome.
5. Each linear chromosome is packed into a chromatin (combination of DNA and proteins).
120
A checkpoint for regulation of DNA is, near the end of G1. Explain this.
External influences and no DNA damage are favourable conditions. If the cell does not meet these conditions it cannot move on to S phase.
2 options if conditions are not met:
- Stop cycle and fix the problem.
- Return to G0 and wait for signs that conditions are better.
121
A checkpoint for regulation is G2 to mitosis transition. Explain this.
Cell size and protein reserves are checked again. Most important role of this checkpoint is to make sure chromosomes have replicated and DNA is not damaged.
122
A checkpoint for regulation is in metaphase of mitosis. Explain this.
This is known as the spindle checkpoint.
Cell examines whether the sister chromatids are correctly attached to the spindle micro tubules.
123
Formation of cancer?
- p53 is a protein found in the nucleus.
- Damaged DNA activates protein kinases that phosphorylate p53.
- Phosphorylated p53 acts as a transcription factor that turns on genes that inhibit the cell cycle.
- Inhibiting the cell cycle gives DNA time to treat the damaged DNA.
124
Prokaryotic cell division?
- DNA replication.
- Cell elongates and DNA separates.
- A new membrane and cell wall are synthesised at the site of constriction.
- Daughter cells are separated.
125
Meiosis creates?
4 genetically different daughter cells.
4 haploid cells.
126
Meiosis begins with?
A diploid parent cell.
127
Meiosis 1?
- DNA replication occurs before meiosis.
- Crossing over occurs during prophase 1 and separation of chromosomes during anaphase 1.
- End of meiosis 1, 2 daughter cells are haploid but still contain copies.
- Independent Assortment- During metaphase.
128
Meiosis 2?
- No interphase but sometimes there is a rest phase (interkinesis).
- Meiosis 2 starts with 2 haploid cells.
- Crossing over does not occur but separation of sister chromatids occurs in anaphase 2.
- Four haploid cells are produced which can go on to being gametes.
129
Aneuploidy?
Variation in the number of chromosomes.
130
3 main categories of life cycles in multicellular organisms?
- Diploid dominant.
- Haploid dominant.
- Alternations of generations.
131
Diploid dominant life cycle?
Most animals have this strategy.
Only haploid cells produced are the gametes.
Germ cells produced by testes and ovaries to produce gametes.
132
Haploid dominant life cycle?
Fungi and bacteria, specialised haploid cells from two individuals join to form a diploid zygote.
133
Alternation of generations?
Seen in some algae and all plants.
Haploid multicellular plants are called gametophytes because they produce gametes from a specialised cell.
Zygotes give rise to a multicellular plant called a sporophyte.
134
During prophase1:
Recombination between non sister chromatids of homologous chromosomes.
135
Gregor Mendel made a discovery that?
Blending inheritance was not the right model.
It is not traits that are transmitted in inheritance, it is genes.
136
Mendels experiment?
Mendel interbreeded 2 different varieties of the pea plant.
So he crossed the peas. And saw that one trait disappeared.
137
Law of segregation?
Individuals inhibit 2 copies of each gene.
2 copies separated equally in gametes.
138
Independent assortment?
States that segregation of one set of alleles of a gene is independent of the segregation of another set of allele on another pair.
139
X Linked genes?
X linked disorders are more common in males than females.
140
Epistasis?
Effect of one gene is dependent on the presence of one or more modifier genes.
141
Describe the experiments that confirmed DNA as the hereditary material?
142
Describe the structure and sequencing of DNA?
- DNA is a double helix.
- Found in nucleus.
- Made up of a nucleotide.
- Nitrogenous base binds on the 1’ carbon.
- If there are 2 OH’s at the bottom of sugar it is a ribose.
- Triphosphate group.
- Percentage of A=T and C=G.
-5’ to 3’ on left and 3’ to 5’ on right.
- DNA bases are read in 5’ to 3’ direction.
143
Describe how the structure of DNA relates to its replication?
-DNA replication is semi conservative- 1 new strand and 1 old.
- Conservative- Both new strands.
- Dispersion- In one strand half new and half old.
- Parental strands acts as template.
- Meselson and Stahl’s experiment demonstrated that replication was semi- conservative.
144
DNA replication in eukaryotes?
New strands are added in a 5-3 direction.
1. DNA replications starts at ORIGINS OF REPLICATION.
2. Two strands open forming replication forks.
3. New strands grow at the fork.
4. Replication bubbles grow as replication begins, each bubble has two forks either end moving opposite directions.
5. At each replication fork, the new strand with the free 5’ end is the lagging strand and the free 3’ end is the leading strand.
6. Helicase- Unwinds and separates strands by breaking hydrogen bonds.
7. Single strand binding proteins- Attach and keep strands untwisted and separated.
8. Topoisomerase attaches to fork of bubble to relieve stress on molecule as it separates.
9. Before new strands can form, RNA primers need to be present to start the addition of new nucleotides.
10. Primase is an enzyme which synthesises RNA primer.
11. Polymerase can then add the new nucleotides. It also checks for errors one DNA subunit at a time.
12. At a replication fork, the leading strand is elongated continuously.
13. The lagging strand is formed from discontinuous Okazaki fragments (series of short segments on the lagging strand must be joined together by an enzyme ligase).
145
DNA replication in prokaryotes?
1. Replication of circular DNA, replication starts at the origin and moves around the circular chromosome in both directions.
The rest is basically the same.
There is RNA primer.
146
DNA mutations?
- Substitution- One base is exchanged for another. E.g switch A to G.
- Insertion/Addition- Extra base pairs are inserted into a new place in the DNA.
- Deletion- A section of DNA is lost or deleted.
147
DNA repair mechanisms?
- Proofreading- DNA polymerases check their work with each base they add so if there is an incorrect pair DNA polymerase removed the nucleotide and replaced.
- Mismatch repair- Remove and replace mis paired bases straight after new DNA is synthesised if the problem was not fixed during proofreading.
- If DNA is damaged it can be repaired by various mechanisms e.g. chemical reversal.
148
Central drogma?
- DNA to RNA to protein.
- DNA to RNA= Transcription. (DNA and RNA use the same language).
- RNA to protein= Translation. (A change in the language of nucleic acids to that of amino acids).
149
Flow of genetic information?
- DNA is transcribed to form mRNA.
- Ribosomes decode the genetic information inscribed on a strand of mRNA.
- They use this information to string amino acids together into a protein.
150
How is RNA different to DNA?
- Single stranded.
- Ribose pentose sugar.
- Uracil instead of thymine.
151
Different types of RNA?
- mRNA- Carries information from DNA to nucleus to ribosomes.
- rRNA- Structural component of ribosomes.
- tRNA- Carries amino acids to the ribosome during translation to help build amino acid chain.
152
Why Uracil rather than thymine?
- Energetically less expensive to produce.
- RNA is comparatively short lived molecule.
153
Characteristics of the genetic code?
- 64 combinations.
- Only 20 amino acids.
- Triplets are codons.
154
Genetic code is degenerate?
- More than one triplet (codon) coded for an amino acid.
155
Genetic code is non overlapping?
Same base is not read more than once one letter does not overlap to next triplet.
156
Genetic code is comma less?
No signal to indicate end of one codon and start of next codon.
157
Genetic code is non ambiguity?
One codon cannot code for more than one amino acid.
158
Genetic code is universal?
Same 3 bases sequence codes for same amino acid in all living organisms.
159
Genetic code is polarity?
Code is always read in 5-3 direction.
160
Chain initiation codon?
- AUG.
- GUG.
161
Chain termination (STOP codons)?
-UAA.
-UGA.
-UAG.
Don’t correspond to an amino acid.
162
Transcription is?
The process where a gene’s DNA sequence is copied into an RNA molecule.
163
The first RNA nucleotide transcribed is called the +1 nucleotide, or the start site (the initiation site).
164
RNA polymerase which makes a new RNA from a DNA template must?
Attach to the DNA of the gene at a place called the promoter. In bacteria RNA polymerase attaches to the right to the DNA of the promoter.
165
What is needed in transcription?
1. DNA template.
2. rNTPs: ribonucleoside trophosphates are the building blocks of RNA synthesis as well as synthesis of primers in DNA replication.
3. RNA polymerase, catalyse production of RNA based on a DNA sequence.
166
RNA polymerase has 4 major subunits:
- Alpha, beta and beta’- These ensure RNA polymerase is bound to DNA.
- Sigma factor or s is only involved in initiation of transcription. Ensures that polymerase begins to synthesise mRNA from an appropriate initiation site.
167
Eukaryotic transcription takes place in?
Nucleus.
168
Prokaryotic transcription and translation takes place in?
Cytoplasm.
169
Eukaryotic translation takes place in the?
Cytoplasm.
170
Prokaryotic transcription process:
- Initiation: RNA polymerase breaks hydrogen bonds, unwinds double helix structure. After addition of around 10 nucleotides, the s factor is released from the RNA polymerase.
- Elongation:
- Termination: RNA polymerase will keep transcribing until it gets signals to stop (stop codons). Rho independent termination is where the show forms a hairpin.
- In prokaryotes, transcription and translation are coupled, translation begins even before transcription is completed.
171
Eukaryotic transcription:
- Transcription is initiated at a promoter sequence (TATA box) and ends at a terminator sequence. The transcript is synthesised in a 5’ to 3’ direction.
- Transcriptional activator proteins, mediator complex and RNA polymers II and general transcription factors brought close together into close proximity, allowing transcription to proceed.
172
Main enzyme involved in transcription is?
RNA polymerase II.
173
Transcription factors?
- Activators: Increase transcription.
- Repressors: Decrease transcription.
Enhancers and silencers can turn a gene on or off.
In eukaryotes, RNA polymerase can attach to promoter only with help of proteins called basal (general) transcription factors. Transcription factor makes it easier or harder for RNA polymerase to bind to the promoter of the gene.
174
General transcription factors non to promoter.
Transcriptional activator proteins bind to enhancers.
175
RNA processing in eukaryotes:
176
Translation:
- mRNA code is used in protein synthesis is called translation.
- Base pair converted into an amino acid sequence.
- mRNA attaches to the smaller subunit of mRNA and then AUG is the start codon, anticodons on tRNA attaches to codons. Larger subunit comes in and then the sequence moves into the large ribosome.
- At A-
- At P-
- At E-
Amino acid users peptidyl transferase.
Stop codon is reached. Amino acid chain then processed.
177
If lactose is present?
Lac operon is present, transcription is on.
178
If there is no lactose?
Repressor (off) binds to operator so transcription cannot continue.
179
Expressed means?
Gene is on.
180
Repressed means?
Gene is off.
181
Gene expression is used to save?
Energy.
Space.
Time.
182
Inducers?
Increase and stop transcription.
183
Operons?
Cluster of genes that are transcribed together to give a single mRNA therefore code for multiple proteins. Only in prokaryotes.
