BIOSCI 101 Short Answers Flashcards
What are the 3 Parameters of Magnification?
Magnification, Resolution, Contrast.
What is a Light Microscope used for?
To visualise cells and large subnuclear organelles.
What is an Electron Microscope used for?
Electron beam sees through specimen or onto its surface.
What are the 3 Differences between SEM and TEM?
SEM - 10nm res, onto surface, 3D images.
TEM - 2nm res, internal structure, through specimen
What do Plant Cells have that Animal Cells don’t?
Cellulose cell wall, central vacuole, chloroplasts.
What are the 2 Key Features of a Mitochondria?
Respiratory enzymes in inner membrane/matrix, contain own DNA/ribosomes.
What are the 2 Key Features of a Chloroplast?
Bound by outer and inner membrane, has thylakoids.
What are the 3 Functions of the Cytoskeleton?
Maintains cell shape, facilitates cell movement and movement of cell components.
What are the 3 Types of Cytoskeletal Filaments?
Microtubules, microfilaments, intermediate filaments.
Describe the Process that takes place in the ER.
Vesicle fuses with golgi to empty proteins, proteins are modified, budding off into vesicles.
What is the Function of Intermediate Filaments?
Anchors.
What is the Function of Microtubules?
Road network for organelles.
What is the order of Cell Fractionation?
Tissue cells, homogenisation, homogenate, centrifugation.
What is the Purpose of Cell Fractionation?
Isolates cell components based on size and density.
How is Centrifuge Speed related to Visible Components?
Slow speeds = Larger organelles.
How are Polymers Assembled and Degraded?
Assembly (dehydration) and degradation (hydrolysis).
Why are Lipids Insoluble?
Non-polar hydrocarbon chains.
What is the Difference between Saturated and Unsaturated Fats?
Saturated - solid at room temp.
Unsaturated - liquid at room temp.
What are the 3 Functions of Polysaccharides?
Energy/fuel, structural support, carbs can be added to improve other functions.
What are the Major Cell Characteristics?
Arise from preexisting cells, genetic info as DNA, proteins are synthesised on ribosomes, membrane encloses every cell.
What are Mitochondria?
Site of cellular respiration where oxygen and food are combined to make energy (ATP).
What is the Chemical Composition of Cells?
50%C, 10%N, 15%H, 20%O, 5% other.
What are the 3 Types of Polysaccharides?
Mono (1), Di (2), Poly (many).
How are Saccharides Stored in Plants?
Starch: granules in plastids, glucose released by hydrolysis.
How are Saccharides Stored in Animals?
Glycogen: in liver/muscle cells, glucose released by hydrolysis.
How can Lipids be Identified?
Long hydrocarbon chain, glycerol group, only contain H,C,O.
How can Proteins be Identified?
Contains C,H,O,N, contains NH2 group and an acid group.
How can Saccharides be Identified?
Only contains H,C,O, 1C:2H:1O ratio, arranged as a ring.
Describe the Phospholipid Bilayer.
7-8nm thick, made of hydrophilic head and hydrophobic tail.
How Fluid are Phospholipids?
Lateral movement happens 10 million times a second.
Which Experiment proved Cell Fusion was Viable?
Mouse cell + human cell, hybrid cell, mixed proteins in 1 hour.
What are the 6 Functions of Membrane Proteins?
Enzymatic activity, signal transduction, cell-cell recognition, attachment to cytoskeleton and ECM, intercellular joining, transport.
What are some Examples of Active and Passive Transport?
Passive - Diffusion, facilitated
Active - Na/K Pump
Describe the Main Components of Active Transport?
Molecules move across membrane against concentration gradient, requires energy.
What are the Functions of Transport Proteins?
Provide selectivity, can increase of transport, continuously recycled, rate of transport limited.
What are the 3 Types if Endocytosis?
Phagocytosis, pinocytosis, receptor mediated endocytosis.
What are Nucleotides Composed?
Phosphate group, sugar/pentose, nitrogenous base.
How is Fluidity Impacted?
By saturation - unsaturated = greater fluidity.
How is Fluidity Maintained?
By squeezing of cholesterol at v. cold temperatures.
What are Integral Proteins?
Inserted into cell membrane associating with hydrophobic region.
What are Peripheral Proteins?
Outside of membrane.
What are the Functions of a Protein Extension?
Cell communication with outside environment, anchoring.
How many Connexins form a Gap Junction?
6.
What is the Function of Plasmodesmata?
Allow RNA/small proteins to move between cells.
When is Facilitated Diffusion required?
Hydrophylic can’t pass hydrophobic layer.
What is Selectivity?
Only select proteins can pass through.
What is ‘Cell Eating’?
Pseudopodium sent out to engulf food particle.
What is ‘Cell Drinking’?
Gulps of outside molecules.
What does ‘Receptor Mediated’ mean?
Bind to specific molecules.
Which Amino Acids are Hydrophobic and Hydrophilic?
Non-polar: Hydrophobic
Polar: Hydrophilic
Electrically: Hydrophilic
What is the Function of Peptide Bonds?
Link carboxyl group of one amino acid to amino group of the next.
What is RNA Responsible for?
Information in RNA determines amino acid sequence.
Where is the Alpha Helix Found?
In the regions of transmembrane proteins that cross the bilayer.
Where are Beta Pleated Sheets Found?
In the core of many globular proteins.
What are the 2 Functions of Chaperonins?
Assists the folding of proteins, check correct folding has occurred.
How does Heat Denature Structures?
Breaks weak bonds.
How does pH Denature Structures?
Changes ionisation patterns of R groups.
How do Reducing Agents Denature Structures?
Reduce S=S bonds to SH.
How do Organic Solvents Denature Structures?
Disturb hydrophobic and hydrophilic interactions.
How do Detergents Denature Structures?
Disrupt hydrophobic interactions.
What is an Anabolic Reaction?
Energy enters reaction and is stored in molecular products. Large molecules synthesised from small molecules.
What is a Catabolic Reaction?
Energy exits reaction and is available for cellular work. Breakdown of large molecules into energy + small molecules.
What is Transport Work?
ATP phosphorylates transport proteins.
What is Mechanical Work?
ATP binds non-covalently to motor proteins and then is hydrolysed.
What is the Function of an Enzyme?
Act as catalysts, lowering Ea and increasing rate of reaction.
Are Enzymes ever ‘Used Up’?
No - they are not consumed by the reaction.
What are Co-Factors?
Non-proteins that help with catalytic activity.
How do Temperature and pH impact Enzyme Activity?
They influence secondary, tertiary and quaternary structure.
How do Enzymes Regulate Activity?
By controlling when and where certain enzymes are active.
How do Enzymes Dance?
They oscillate between active and inactive forms.
What is Feedback Inhibition?
Metabolic pathway is switched off by the end product, binding to/inhibiting an enzyme that acts early in the pathway.
How does ATP Release Energy?
Hydrolysing ATP cleaves away a P, energy is released and used to drive cellular processes.
How is ATP involved in Transport Work?
ATP donates a P group, providing energy for carrier protein to change shape.
How is ATP involved in Mechanical Work?
ATP binds to motor protein, energy released stimulates shape change so protein can take ‘steps’.
What are the 3 Basic Components of Enzymes?
Majority are made of protein and highly selective/specific, catalyse reactions.
How does Substrate amount impact ROR?
Increased substrate = increased ROR (dwindling impact until saturation point reached).
What are Prosthetic Groups?
Organic or inorganic molecules tightly bound to the protein.
What are Coenzymes?
Small organic molecules non-covalently bound to protein.
What were Franklin and Williams Responsible for?
1st to generate X-ray diffraction image of DNA (2 strands).
Who came up with the Double Helix Structure?
Watson and Crick.
What does each Nucleotide consist of?
Nitrogenous base, sugar, phosphate group.
What is a Chromosome?
DNA packed together with proteins.
What are RNA Molecules?
Single polynucleotide chains.
What is the Function of mRNA?
Conveys info from DNA in nucleus to the ribosome.
What is the Function of tRNA?
Translator: nucleotide sequence from mRNA into amino acids.
What is each tRNA made of?
4 base-paired regions, 3 loops including anticodon, amino acid attachment site.
What is the Function of Single-Strand Binding Proteins?
Prevent single-strand binding DNA from re-pairing.
What is the Function of Topoisomerase?
Breaks, swivels and rejoins parental DNA ahead of replication fork (removes strain caused by DNA unwinding).
What is the Function of Primase?
Synthesises short RNA primers using the parental DNA as template.
What is the Function of Telomeres?
Protect ends of chromosomes, prevent loss of genes near ends.
What are the Functions of 5’ Cap and 3’ Poly-A Tail?
May promote export of mRNA from nucleus, protects mRNA from degradation, 5’ cap facilitates ribosome attachment.
What happens during Splicing?
Introns are cut out and the exons are ligated together to form the mature mRNA molecule.
What is a Codon?
Sequence of 3 nucleotides which can be translated into a particular amino acid.
What are tRNA Molecules made up of?
Amino acid attachment site, anticodon loop to pair with the mRNA codon.
What is Responsible for Attaching the Correct Amino Acid to each tRNA Molecule?
Aminoacyl tRNA synthetase.
Where do Ribosomes Bind?
The 5’ end of newly transcribed mRNA at the mRNA binding site.
What is the Signal Mechanism?
Signal peptides on the newly generated polypeptides can target them to the ER.
What is the Genetic Code?
Set of rules which determines how mRNA info is translated into amino acid sequence.
What is the Problem associated with the Genetic Code?
There are only 4 nucleotide bases to specify 20 amino acids.
What is Wobble?
Where some tRNA molecules only require accurate pairing for first 2 positions, so 3rd can be mismatched.
What is a Start Codon?
Initiates translation but also codes for methionine.
What are Point Mutations?
Change in a single base pair.
What is a Silent Mutation?
Where there is no effect on amino acid sequence.
What is a Missense Mutation?
Where an amino acid is changed.
What is a Nonsense Mutation?
Creation of a termination codon or premature stop codon.
How can DNA be Damaged?
Incorrectly paired or altered nucleotides, chemical changes of DNA bases.
How does Gene Expression Differ in Prokaryotes and Eukaryotes?
Prokaryotes involve response to changes in available nutrients, eukaryotes regulate cell differentiation.
What is a Mutation?
Can a permanent, inheritable alteration in the DNA sequence.
What is a Mammary Cell?
Totipotent - capable of giving rise to any cell type.
What is Alt. RNA Splicing?
Different mRNA molecules are produced from the same pre-mRNA.
What is Protein Processing?
Many protein functions require a mutation, proteins can be marked for destruction.
What happens during Tryptophan Synthesis?
As tryptophan increases, enzyme 1 can be shut down rapidly. Full repression is less rapid.
What happens during Negative Gene Regulation?
Repressor protein binds to operator to prevent gene being expressed.
What happens to cAMP when Glucose Decreases?
Decrease in glucose = increase in cyclic AMP.
What is DNA Methylation?
Condensation of chromatin and reduced transcription.
What are Transcription Factors?
Proteins that can initiate and regulate transcription in eukaryotic cells.
How long does mRNA take to Degrade?
Typically minutes.
Describe Protein Processing?
Protein modification and trafficking is regulated, as well as the length of time a protein functions.
How can Non-Coding RNAs Control Gene Expression?
Influencing: chromatin packing, translation, mRNA degradation.
Which 2 Levels does Metabolic Control occur at?
- Adjust the catalytic activities of the enzymes already made
- Adjust the production of enzyme molecules by regulating expression of the genes encoding enzymes.
How do E.Coli adapt to Lactose?
As a new food source by regulating transcription.
How do the Numbers of B-Gal increase so quickly?
Bacterial mRNA only lasts a few minutes, so bacteria can rapidly change pattern of protein synthesis in response to a change in food source.
What are the 3 Structural Genes in the Lac Operon?
Lac Z, Lac Y, Lac A.
What happens during Negative Regulation?
A repressor protein binds to the operator to prevent the gene being expressed.
What happens during Positive Regulation?
A transcription factor or a transcription activator binds to the promoter and enables RNA polymerase to initiate transcription.
What does the Lac Repressor do?
Binds to the operator and obstructs the promoter.
What does Lactose do when Present?
It acts as an inducer, binds to lac repressor so it changes shape and cannot bind to the operator.
Does Bacteria prefer Lactose or Glucose?
Glucose.
What happens when Glucose is Low and Lactose is Present?
E.Coli will generate enzymes for lactose breakdown and use lactose as an energy source.
How do our Bodies detect Low Glucose Levels?
Without glucose, the signalling molecule (cAMP) accumulates, binding to/activating the activator protein (CAP).
What is Positive Gene Regulation?
Where active CAP binds to promoter and facilitates binding of RNA polymerase to promoter, resulting in transcription of the Lac Operon genes.
What happens to the Repressor when Lactose is Present?
Repressor is unable to bind to operon.
What happens to cAMP when Glucose Increases?
cAMP will fall, so it cannot activate CAP.
What happens to the Lac Operon if Glucose is Present?
CAP detaches, RNA polymerase binds less efficiently to promoter, so transcription occurs at a low level.
What happens when there is a Mutation in the Structural Genes of the Lac Operon?
A non-functional protein may be produced.
What happens when there is a mutation in Lac I?
Transcription is abolished, RNA polymerase binding site may be destroyed, transcription may be permanently turned on.
What is Recombinant DNA Technology?
Genes or DNA from 2 different sources are combined in vitro into the same molecule.
What are the Two Sections of a Typical Gene?
Promoter and coding region.
What is Biotechnology?
The manipulation of organisms or their components to make useful products.
What is Genetic Engineering?
The in vitro alteration or recombination of genetic material and the reintroduction of the altered genetic material into a living organism.
What do Restriction Enzymes do?
Cut DNA at specific sequences 4-8 bp in length.
What are Cloning Vectors?
DNA molecule that can carry foreign DNA.
When is a Cell Competent?
Once the cell is ready to take up DNA.
What are the 2 types of Selectable Marker?
- A marker to make sure the bacterium has taken up the plasmid.
- A marker to make sure that the plasmid has an insert or foreign gene.
What is DNA Ligase?
The sticky or blunt ends of DNA.
What does DNA Ligase do?
Catalyses the formation of covalent bonds that close up the sugar-phosphate backbone.
What is Transformation used for?
Introducing plasmid DNA into bacterial cells.
What is PCR?
A 3 step process that produces millions of copies of a targeted region of DNA.
How long do the D,A,E Cycles take?
D - 10 secs
A - 30 secs
E - 1 min per kilo based pair
What does Gel Electrophoresis do?
Separates macromolecules on the basis of their rate of movement though a gel in an electrical field - molecular sieve.
What does Rate of Movement in Gel Electrophoresis depend on?
Size, electrical charge, other physical properties.
What is the Genome?
The total compliment of DNA that makes up the inherited genetic material of an organism.
What is the Function of DNA Sequencing?
Reveals the order of nucleotides along a strand of DNA.
How do we Identify Bases?
There is a distinct fluorescent tag for each type of nucleotide.
What is Next-Gen Sequencing?
The ability to sequence multiple DNA strands simultaneously.
What is Reproduction?
When an entity undergoes division that results in the production of two entities of the same kind.
What is the Difference between the Mitotic Phase and Interphase?
Mitotic Phase - division
Interphase - non-dividing
How does Random Fertilisation impact Variation?
Adds to the variation arising from meiosis.
What is Complete Dominance?
An allele is dominant when the phenotypic effect is the same in both the heterozygous and homozygous conditions.
What is Incomplete/Partial Dominance?
The dominant allele is not fully expressed in heterozygotes. The heterozygote has an intermediate phenotype.
What is Co-Dominance?
Full expression of both alleles in the heterozygote. In humans that have the AB blood group both proteins are present and detected by immunological tests.
What is an example of Multiple Alleles?
The gene encoding the ABO blood group.
