PROGRESS TEST Flashcards
How can you tell if a cell is undergoing mitosis when observing it under a microscope?
Chromosomes are condensed and therefore visible
Double the amount of DNA
Contrast how an optical microscope and a
transmission electron microscope work
and contrast the limitations of their use when studying cells.
- TEM use electrons and optical use light;
- TEM allows a greater resolution;
- So with TEM smaller organelles can be seen and in greater detail
- TEM view only dead specimens and optical can view live specimens;
- TEM does not show colour and optical can;
- TEM requires thinner specimens;
- TEM requires a more complex and time consuming preparation;
- TEM focuses using magnets and optical uses (glass) lenses;
Define the mitotic index.
The ratio of the number of cells undergoing mitosis to the total number of cells in a specimen
Name the stages of mitosis in order
Prophase
Metaphase
Anaphase
Telophase
Why does glycogen need to be more highly branched than starch?
- Animals are more active than plants
- higher respiratory rate
- need to access glucose more rapidly, so more branches means more glucose can by hydrolysed at once.
Describe and explain how cell fractionation and ultracentrifugation can be used to isolate mitochondria from a suspension of animal cells
- Cell homogenisation to break open cells
- Filter to remove large debris;
- Use isotonic solution to prevent damage to organelles;
- Keep cold to reduce damage by enzymes /
- Use buffer to prevent protein / enzyme denaturation;
- Centrifuge at lower speed to separate heavy organelles;
- Re-spin supernatant at higher speed to get organelle at bottom
What is the name of the reaction that breaks bonds between monomers?
Hydrolysis
What do we call a molecule that consists of many monosaccharides bonded together?
Polysaccharide.
Draw the structure of alpha and beta glucose.
alpha - hydogen at top
beta - hydrogen at bottom
What type of bond joins the components of a triglyceride?
Ester bonds
Compare and contrast the structure and properties of triglycerides and phospholipids
BOTH
1. contain ester bonds between glycerol and fatty acid;
- contain glycerol;
- have saturated or unsaturated Fatty acids ;
- insoluble in water;
- contain C, H and O but phospholipids also contain P;
DIFF
6. Triglyceride has three fatty acids and phospholipid has two fatty acids plus phosphate group;
- Triglycerides are hydrophobic/non-polar and phospholipids have hydrophilic and hydrophobic region;
- Phospholipids form monolayer in water but triglycerides don’t;
Give the equation for calculating magnification from size of object and image.
Magnification = Size of image / Size of Object
What does secondary structure mean?
- Folding, due to hydrogen bonds, of the polypeptide chain into alpha helix or beta pleated sheet.
What does the RER do?
Synthesises proteins
What does the SER do?
Synthesises lipids
Describe the DNA in a prokaryote
- Short
- Circular not linear
- Plasmids
- Not associated with histones
- no introns
Contrast the structure of a bacterial cell and the structure of a human cell.
- Bacterial cell is much smaller than a human cell;
- Bacterial cell has a cell wall but human cell does not;
- Bacterial cell lacks a nucleus but human cell has a nucleus;
- Bacterial cell lacks membrane-bound organelles but human cell has membrane-bound organelles;
- Bacterial ribosomes smaller than human ribosomes
- Bacterial DNA is circular but human DNA is linear;
- Bacterial DNA is ‘naked’ whereas human DNA is bound to histones / proteins
What does the golgi body do?
- Modifies proteins (eg forms glycoproteins)
- forms vesicles to transport modified proteins to cell membrane
What organelle is used by phagocytes to digest pathogens?
lysosomes
What type of biological molecule are triglycerides?
lipids
What organelles are in the first two pellets when centrifuging cell organelles?
nucleus then mitochondria
Describe the structure of proteins.
- Polymer of amino acids;
- Joined by peptide bonds;
- Formed by condensation;
- Primary structure is order of amino acids;
- Secondary structure is folding in alpha helix and or beta pleated sheets of polypeptide chain due to hydrogen bonding;
- Tertiary structure is 3-D folding due to hydrogen bonding and ionic / disulfide bonds;
- Quaternary structure is two or more polypeptide chains.
What would you call many amino acids bonded together?
Polypeptide
Draw a sketch of the structure of an amino acid
Explain why an enzyme can only catalyse one particular reaction.
Each enzyme has a unique tertiary structure
Active site complimentary to one substrate
What type of carbohydrate are glucose, galactose and fructose?
Monosaccharides
a. What monomers make up sucrose
glucose and fructose
b. What monomers make up lactose
glucose and galactose
c. What monomers make up maltose
glucose and glucose
What type of bond joins the monomers on carbohydrates?
Glycosidic bonds.
What is the difference between a triglyceride and a phospholipid?
Triglyceride is made of glycerol attached to 3 fatty acids
In phospholipids one of the fatty acids is substituted by a phosphate group
What is the name of the reaction that joins two monomers together?
Condensation
Explain six properties that make water important for organisms.
- A metabolite in photosynthesis/respiration;
- A solvent so allowing transport of substances;
- High heat capacity so buffers changes in temperature;
- Large latent heat of vaporisation so provides a cooling effect (through evaporation);
- Cohesion (between water molecules) so supports columns of water (in plants);
- Cohesion (between water molecules) so produces surface tension supporting (small) organisms;
Describe how the structures of starch and cellulose molecules are related to their functions
Starch
1. Helical/ spiral shape so compact;
- Large and insoluble so osmotically inactive;
- Branched so glucose is easily released for respiration;
- Large molecule so cannot leave cell
Cellulose
5. Long, straight, unbranched chains of β glucose;
- Joined by hydrogen bonding;
- To form microfibrils;
- Provides rigidity and strength;
What is the role of DNA helicase and DNA polymerase?
DNA helicase breaks hydrogen bonds
DNA polymerase joins adjacent nucleotides together
Explain what a non-competitive inhibitor does?
- Not a similar shape to active site
- attaches allosteric site of enzyme
- causes active site to change
- fewer ES complexes formed.
