BIOMOLECULES Flashcards
Colloid
A mixture where one substance is divided into colloidal particles (small particles) and dispersed throughout another substance. Not a true solution, but not a suspension as it doesn’t settle over time.
Example of colloidal solution
Globular proteins in water
How can interference in ATP production/breakdown affect body?
It’s fatal to the cell in question and ultimately destroys the whole organism
How does cyanide affect the body?
It blocks part of the cellular respiration process producing ATP - without ATP the cells stop working. Muscles go into spasm -> death.
What is a genome
Entire genetic material of an organism
How many base pairs on one twist of the helix
10
wHo produced the double helix model
watson and crick
codon
sequence of three bases on the DNA or RNA
gene
sequence of bases on a DNA molecule coding for a sequence of amino acids in a polypeptide chain, that affect a characteristic in the phenotype of the organism.
Differences between DNA and RNA
RNA contains ribose, not deoxyribose.
RNA has a different base, uracil not thymine.
RNA consists of a single helix and doesn’t form big complex molecules like DNA.
What are the 3 main functions in protein synthesis of RNA?
- carries instructions for a polypeptide from DNA in the nucleus to the ribosomes where proteins are made
- picks up specific amino acids from protoplasm and carries them to the surface of the ribosomes.
- makes up the bulk of the ribosomes themselves.
What is the antisense strand of the DNA
The template strand
Mutation
A permanent change in the DNA of an organism
When do mutations occur?
When gametes form, or during division of somatic (body) cells.
How does the “DNA repair system” help?
Specific enzymes cut out or repair any parts of the DNA strands that become broken or damaged, to reduce number of mutations
Point/gene mutation definition, and what this can include (examples)
One or a small number of nucleotides are miscopied during transcription. Eg deletions, substitutions, insertions
Gene deletion
A base is completely lost in the sequence
Insertion
Extra base is added to the sequence
Substitution
One base substitutes for another
Chromosomal mutation
Changes in the positions of the genes within the chromosomes
Whole-chromosome mutations
Entire chromosome is lost during meiosis, or duplicated in one cell by an error
Example of whole-chromosome mutation, describe mutation
Down’s syndrome. Three copies of chromosome 21 rather than 2.
What is a mutagen? Examples
Anything that increases rate of mutation. X-rays, ionising radiation, certain chemicals.
When do most mutations happen?
During copying of DNA for cell division.
Anabolic reactions
reactions that build up new chemicals
Catabolic reactions
Reactions that break substances down
What does metabolism refer to?
Combination of anabolic and catabolic reactions, a sequence of reactions.
Specificity
Characteristic of enzymes that means that as a result of v specific shapes resulting from tertiary and quaternary structures, each enzyme only catalyses a specific reaction/group of reactions.
What are intracellular enzymes? Examples.
Enzymes working inside the cells. DNA polymerase, DNA ligase.
Extracellular enzymes? Examples
Enzymes secreted by cells having an effect beyond boundaries of cell membrane. digestive enzymes, lysozyme.
What are the three scientific naming systems of enzymes?
1- short recommended name, often name of molecule the enzyme works on with -ase, OR substrate with an indication of what the enzyme does
2- systematic name describing type of reaction
3- classification number
What does a chromosome look like under a light microscope?
Only visible under light microscope when nucleus is dividing, otherwise looks like a diffuse network called chromatin.
What is in a chromosome?
Strands of DNA wrapped around histone core (core of nucleosome of eight histone molecules)
Do all eukaryotes have 1 nucleus
No, some lose it as they mature (RBCs) and some are multinucleate.
What do cristae (inner membrane folds) of mitochondria have?
Chemicals involved in ATP synthesis during aerobic respiration
What is the matrix of a mitochondrion?
Aqueous solution of metabolites and enzymes and small molecules of DNA.
What do the S units indicate in ribosomes?
Rate of sedimentation during centrifugation under standardised conditions
What is a vesicle?
A small sac of cytoplasm enclosed by membrane. Much smaller than vacuoles but no different.
What do ribosomes do?
Link amino acids together to form polypeptide chains
What is in the cytosol? What does it do?
Microtubules of tubulin forming a network of unbranched, hollow cylinders. They move organelles around in the cytoplasm.
What is the apoplast pathway?
Movement of water from cell wall to cell wall through gaps in cellulose bundles.
What is plasmodesmata?
Cytoplasmic connections between plant cells through gaps in their cell walls.
What does the symplast pathway allow?
Inorganic ions to pass from cell to cell without having to pass through cell walls or cell surface membranes.
What’s the process of building a cell wall when nucleus has divided?
The ER secretes vesicles of wall-forming enzymes, which collect then form cell wall layers. A boundary of calcium pectate, the middle lamella is laid down. Some of the ER of the parent cell gets trapped in the gaps of the middle lamella, and the cellulose wall is laid down, forming the primary wall, then more layers of cellulose are deposited, forming the secondary wall. the ER remains and forms the plasmodesmata. Sometimes lignin is added, which penetrates to all the layers and hardens them.
What is the tonoplast?
Membrane surrounding large, fluid-filled vacuole in plant cells.
What is the nucleoid?
Circular DNA molecule in prokaryotes
What’s the difference between a nucleoid and chromosome?
Chromosome has linear DNA surrounded by histones, nucleoid does not.
What is cyanobacteria?
Photosynthesis bacteria
Distinctive features of prokaryotes?
- very small
- no membrane-bound nucleus. Instead, a circular DNA molecule in their cytoplasm.
- some have plasmids with a few genes.
- 70S ribosomes instead of 80S
- no membrane-bound organelles
- all have a cell wall
- pili and flagella
What are the prokaryote cell walls made of?
Peptidoglycan
What are plasmids?
Small circular DNA molecules often with genes coding for resistance to antibiotics.
What do pili do?
Enable attachment to surfaces and to other bacteria. Prokaryotes.
What do flagella do?
Bring about movement of bacterium.
What does a cell wall do? (3)
Give a permanent shape to cell. Protect contents against rupture due to osmosis etc, protects some bacteria against harm.
What is gram positive bacteria like?
Thick walls made almost entirely of peptidoglycan.
What is gram negative bacteria like?
Thin walls of peptidoglycan with an additional outer membrane, with a high lipid content.
Why does gram negative bacteria not turn purple?
High lipid content in the outer membrane prevents crystal violet stain getting to the cell wall.
What is the gram staining process?
- Fix bacteria to slide with heat
- Add crystal violet to bacteria
- Apply iodine to bacteria - combines with crystal violet to form a complex
- wash with alcohol. Positive cell wall shrinks , outer capsule dissolves, trapping stain inside, negative cell wall is too thin and complex gets washed out.
- apply safranin to bacteria - taken up by colourless bacteria. Gram negative = red. Gram positive = purple.
What is peptidoglycan?
Polymer of amino acids and sugars
Is gram positive or negative easier to treat and why?
Gram positive as gram negative has another plasma membrane, lipid-rich and quite impermeable. Gram positive also have a cell wall with more peptidoglycan so there’s a target site with more receptors for the antibiotic.
What do the gram positive and negative have in common?
Outer capsule, peptidoglycan cell wall (but thickness varies).
Why aren’t viruses called living organisms?
They don’t have their own metabolism - their replication depends on the metabolism of the cells they infect.
What are the components of viruses?
Core of nucleic acid, with protein coat (capsid) around it. Some have envelope of membrane made of lipids and proteins.
How does virus control work?
Antivirals are developed which inhibit viral replication by the host cells.
If not, you just have to prevent spread of virus.
What are the different ways of copying the nucleic acid core in viruses?
If DNA -> transcribed to mRNA.
If RNA -> copied directly to form mRNA
If RNA -> reverse transcribed into DNA which is incorporated into the host cell’s DNA and later transcribed to form mRNA.
Explain the lytic cycle.
It’s absorbed onto the bacterium injects its own nucleic acid; the capsid remains outside the bacterial cell. The bacterium then produces more phage particles by replicating the phage nucleic acid and making new capsids causing the cell to burst and release the phage viruses
What is viral latency?
A period where, under the control of specific latency genes, a pathogenic virus remains dormant - it’s present in the cell but doesn’t control the cell’s activities.
What are the 2 types of viral latency? What condition do they have in common?
Episomal - the viral nucleic acid remains inactive but free in the cytoplasm of the infected cell
Proviral - the nucleic acid gets incorporated into the DNA of the host cell.
The nucleic acid can be reactivated at any time with both.
In what organ is glycogen stored in mammals?
Liver/muscles
How would you know if something that tested negative for a reducing sugar contained sucrose? (PP)
- mix equal vol of solution and dilute hydrochloric acid
- boil in water bath to hydrolyse sucrose to glucose and fructose
- mix with equal volumes of benedict’s
- if brick red precipitate then sucrose
How would you know if something contained protein? (PP)
Mix equal values of solution and dilute sodium hydroxide.
Run dilute copper sulphate solution into the solution.
A purple ring at the interface indicates protein. Dissolves to form purple solution on shaking.
Why is it important to have two types of glucose (alpha and beta)?
leads to greater chemical variety.
Alpha glucose is respiratory, whereas beta glucose is structural.
What is alpha glucose?
Starch
What is beta glucose?
Cellulose
What does saturated and unsaturated mean?
Sat. = molecule contains maximum number of hydrogen atoms Unsat. = molecule contains double bond
Why are lipids useful as storage molecules? (PP)
Don’t dissolve in water/body fluids, therefore don’t affect osmotic balance of cells.
Have higher calorific value than carbs.
Buoyancy
Can yield more energy per gram on oxidation
Insulation
How does a phospholipid differ structurally from a triglyceride?
One fatty acid molecule of the triglyceride would be replaced by phosphate.
Why are lipids useful other than for storage?
Waterproofing, cell membrane structure, buoyancy, insulation
How would you test for a lipid?
Take sample and add equal volume of ethanol and cold water. Mix and if positive a white emulsion forms.
What does the “R” mean?
Side chain
Give an example of an “R” group.
Hydrogen/methyl
What does “amino acids are amphoteric” mean?
Their molecules have both acidic and basic groups.
What gives a beta pleated sheet its high tensile strength?
Many H bonds between polypeptide chains.
What is tertiary structure?
Polypeptide chain folds extensively into a compact/globular structure.
What is tertiary structure?
Polypeptide chain folds extensively into a compact/globular structure.
What are complementary base pairs? (3)
Bases that will join together by hydrogen bonds. A to T and G to C.
Differences between RNA and DNA?
RNA has uracil, not thymine.
RNA has ribose sugar, not deoxyribose.
RNA is single-stranded, not double-stranded.
Examples of monosaccharides (2)
Ribose, glucose
Examples of disaccharides (2)
Maltose, lactose
Examples of polysaccharides (3)
Starch, glycogen, cellulose.
Differences between starch and cellulose? (3)
Starch has alpha glucose, cellulose has beta.
Starch linked by alpha glycosidic links, cellulose by beta glycosidic links.
Starch ay contain branched chains, cellulose is unbranched.
Two examples of pentose sugars
Deoxyribose, ribose
Bond between deoxyribose in DNA molecule?
Phosphate bond
What is ATP’s role in metabolism?
Supplies energy for all energy-requiring reactions.
What is the bond between two hexose units together? (disaccharides)
1,4 glycosidic bond
Function of hexose/disaccharides?
Respiration/energy substrate
How to detect presence of glucose in solution?
Mix together equal volumes of solutions and benedict’s, boil in waterbath. Presence of brick red precipitate indicates glucose
What happens during digestion of starch/protein/DNA?
Hydrolysed to smaller units
Function of glycoprotein in plasma membrane? (3)
Aids cell recognition
Aids cell adherence
Receptor sites for hormones/antibodies.
Name the polymers in starch and how they differ structurally.
Amylose (unbranched chain) and amylopectin (branched).
Out of phospholipids, potions, and carbs, which allow passage of water-soluble substances?
Protein
Out of phospholipids, potions, and carbs, which are involved in cell recognition?
Protein, carb.
Advantage for glycogen molecule to be branched? (2)
Many terminal glucose units, allows rapid release of glucose/rapid digestion of molecule.
Makes molecule compact so much can be stored in a small space.
Where in a prokaryote would you expect to find nucleic acid?
On the single chromosome strand/in a plasmid
What is the nucleolus like?
Extra dense area of almost pure DNA and protein, involved in ribosome production.
