Biology mock (start of 2020) - topics to improve Flashcards
Describe features of eukaryotic DNA
- DNA in double membrane-bound nucleus
- DNA wound round histone proteins
- Normally multiple linear chromosomes
- No plasmids (but circular DNA does occur in mitochondria and chloroplasts, short and not associated with proteins similar to prokaryotic DNA)
Describe features of prokaryotic DNA
- DNA free in the cytoplasm
- Naked
- Single circular chromosome
- May contain smaller loops of DNA (plasmids)
Which two monosaccharides make up lactose?
Galactose and glucose
Which two monosaccharides make up maltose?
Two alpha glucose
Which two monosaccharides make up sucrose?
Fructose and glucose
Draw and label a DNA nucleotide
Deoxyribose (pentose sugar - 5 carbons)
Nitrogenous base - on 2nd C (right)
Phosphate group - on 5th carbon (left)
Give two features of DNA + explain how each one is important in the semi-conservative replication of DNA
- Hydrogen bonds are easily broken between the two strands
- There are two strands that make up DNA so both can act as templates
- DNA has complementary base pairs
What is the outer layer of a prokaryotic cell called?
A capsule (NOT capsid - capsid is a structure of a virus)
Describe the test for lipids
Emulsion test:
- Add ethanol AND water to your sample in a test tube
- Shake gently
- Positive test is that if white emulsion is formed
Which structure of a plant cell has stacked membranes arranged in parallel and contains DNA
Chloroplast
Which cell organelle is not surrounded by two membranes?
Golgi apparatus
Explain why two proteins have the same number and type of amino acids but different tertiary structures
- Amino acids may not be in the same order/sequence
- When the chain twists bonds can be formed in different places
Explain why you only use the first 5mm from the tip of the onion root
The very end of the root will undergo mitosis but the rest will not have any cells undergoing mitosis
Why should you press down firmly on the cover slip for the root tips experiment?
To squish cells/root tips so that the light is able to travel through. This will allow you to see the root tips more clearly
Describe + explain what the student should have done when counting cells to make sure that the mitotic index he obtained for this root tip was accurate
- Compare his value of mitotic index with his peers that also did the experiment
- Only counted whole cells
- Look at another area to count cells undergoing mitosis using the microscope
Why is C to D on the graph flattening? (graph axis - x is external conc. of molecule and y is rate of uptake by epithelial cells)
All carrier proteins have been used up/are limiting
Describe how the secondary structure of a polypeptide is produced by bonds between amino acids
- Hydrogen bonds form to keep the twisted polypeptide chain in place
- Forming a beta-pleated sheet/alpha helix
Name the different stages of mitosis in order
Interphase Prophase Metaphase Anaphase Telophase ( + cytokinesis)
Describe the interphase
- The cell grows and the DNA replicates itself
- The chromosomes are not visible
- Not strictly part of mitosis
Describe the prophase
- Chromosomes condense + become visible
- Centrioles move to opposite ends/poles of the cell
- Spindle apparatus form spindle fibres (part of the spindle apparatus) at the centrioles
Describe the metaphase
- The nuclear envelope breaks down
- Chromosomes align along the equator/centre of the cell pulled by spindle apparatus
Describe the anaphase
- Centromeres split, allowing chromatids to separate
- Chromatids move towards the poles, pulled by the spindle fibres
Describe the telophase
- Spindle fibres disperse
- Nuclear envelope reforms
- Chromosomes decondense
Describe cytokinesis
A ring of protein filaments form around the equator of the cell, which then tightens + splits the cell into two
