LONG EXAM QUESTIONS Flashcards

Question

What are the properties of water?

Answer 1

Strong cohesion = H₂O has strong cohesion between water molecules due to H bonding - produces surface tension when air meets water. Strong cohesion also supports columns of water in the transport cells of plants. Metabolite = H₂O is a metabolite in many metabolic reactions, including condensation & hydrolysis. Solvent = So metabolic reactions occur AND allows transport of substances. High specific heat capacity = So good at buffering changes in temperature. High latent heat of vaporisation = Provides a cooling effect through evaporation.

Answer 2

1) Pipette a drop of WATER onto a slide. 2) Use tweezers/FORCEPS to separate epidermis tissue from onion, and place the tissue onto the slide. 3) Pipette a drop of a STAIN (E.G. iodine dissolved in potassium iodide) 4) Lower cover slip gently on top using a MOUNTED NEEDLE. 5) Place slip onto stage of microscope and clip it.

Answer 3

> ICE-COLD = stops enzyme activity - prevents breakdown of organelles. > BUFFERED = maintains pH so enzymes/proteins aren’t denatured. > ISOTONIC = concentration is kept the same inside & outside the cell to prevent osmosis. Prevents osmosis so organelles don’t burst or shrink from gain/loss of water.

Answer 4

1) Homogenise plant cell walls/membrane with blender/pestle & mortar and add a cold, buffered, isotonic solution. 2) Filter sample to remove debris & collect organelle-rich solution. 3) Centrifuge sample at low speed to separate the dense organelle first (nucleus). 4) Ultracentrifuge by repeating spinning at higher speeds. Chloroplast forms a pellet. 5) Syringe supernatant liquid out of tube to separate from pellet.

Answer 5

MOST DENSE > nucleus chloroplasts mitochondria lysosomes membranes / RER / SER ribosomes LEAST DENSE

Answer 6

1# Plasmids and circular DNA makes copies of itself. 2# The 2 copies of DNA move to polar sides of cell and the cell ELONGATES. 3# The plasmids divide RANDOMLY between the 2 sides, and the organelles grow. 4# Cytoplasm SPLITS and membrane folds in. 5# 2 new cells produced with different number of plasmids.

Answer 7

1# Virus ATTACHES to the protein markers on a host cell using attachment proteins. 2# Virus INJECTS its genetic material into the HOST cell. 3# Host cell transcribes / translates the viral genes. 4# Protein forms NEW virus particles. 5# Virus particles BURST out of host cells and the host cell is destroyed.

Answer 8

A virus consists of… Genetic material = ALL viruses contain DNA / RNA. Capsid = Protein structure which contains the genetic material. Attachment proteins = Allow virus particles to attach and enter host cell. Lipid envelope = SOME viruses are surrounded by a lipid envelope formed from the host cell membrane.

Answer 9

1) Pathogen releases chemicals called chemoattractants which attract phagocytes which moves along the concentration gradient 2) The pathogen is ENGULFED in a vesicle called a PHAGOSOME 3) The phagosome membrane FUSES with the membrane of the lysosomes in the phagocyte 4) Lysosome contains hydrolytic enzymes, lysozymes which are released into phagosome 5) Lysozymes hydrolyse the molecules the pathogen is made of 6) Soluble products of breakdown are absorbed into cytoplasm (e.g. glucose, amino acids, antigens) 7) Non-soluble products expelled out of the cell

Answer 10

1) Phagocyte engulfs pathogen 2) Phagocyte presents antigens on its cell surface membrane = APC 3) Specific Helper T-cells with RECEPTORS complementary to the specific antigen BIND to the APC. The TH cells become ACTIVATED 4) The activated TH cells divide by mitosis (clonal selection) > They also secrete chemicals which activate other T-cells and B-cells which have the same receptors. 5) > Killer T cells - `Cytotoxic T-Cells (TC) are stimulated –> Produces chemicals which make the APC’s membrane permeable which can kill the cell. The holes also allow toxins to get in, which kills the cell and everything in it (e.g. viruses that invaded) > B-cells are stimulated > Stimulate phagocytosis by phagocytes > Form T-memory cells

Answer 11

1) Cytotoxic T-Cells are stimulated –> Produces chemicals which make the APC’s membrane permeable which can kill the cell. The holes also allow toxins to get in, which kills the cell and everything in it (e.g. viruses that invaded) 2) B-cells are stimulated 3) Stimulate phagocytosis by phagocytes 4) Form T-memory cells

Answer 12

1) Pathogens 2) Abnormal cells - (cancer) 3) Foreign cells from other organisms of the same species - transplants 4) Toxins (released by pathogens)

Answer 13

1) Antibodies are proteins with a quaternary structure 2) Made of 4 polypeptide chains… > 2 heavy chains (large polypeptide chain) > 2 light chains (small polypeptide chain) 3) The heavy and light polypeptide chains are held by DISULPHIDE bonds 4) Contains VARIABLE regions which form antigen binding sites 5) The rest of the antibody is CONSTANT. http://www.biology.arizona.edu/immunology/tutorials/antibody/structure.html

Answer 14

1) Divide by mitosis / forms clones 2) To produce plasma cells 3) The plasma cells make antibodies 4) The plasma cells produce memory cells

Answer 15

1) Virus contains antigen 2) Virus is engulfed by phagocyte and presents the antigens on its surface 3) T cells with a specific complementary receptor bind to the antigen and are activated. 4) T cells undergo mitosis/differentiation (stimulate macrophages, become cytotoxic T cells/form memory T cells (Store memory of that antigen) 5) Remain T helper cells can also activate B cells 6) B cells divide by mitosis and undergo clonal selection 7) …(and) form plasma cells which produce antibodies (monoclonal)

Answer 16

Bacteria (with 14N) are grown in a broth containing the heavy (15N) isotope A sample of DNA from the 15N culture of bacteria was extracted and spun in a centrifuge The bacteria containing only 15N DNA was then taken out of the 15N broth and added to a broth containing only the lighter 14N nitrogen. The bacteria were left for enough time for one round of DNA replication to occur before their DNA was extracted and spun in a centrifuge The DNA molecules would now contain both the heavy 15N and light 14N nitrogen and would therefore settle in the middle of the tube (one strand of each DNA molecule would be from the original DNA containing the heavier nitrogen and the other (new) strand would be made using only the lighter nitrogen)