may 2012 mock test revision notes

1ai) mitosis - nuclear division that results in the formationof cells that are genetically identical   to the parent cell. 5 stages: interphase - cell prepares to divide, DNA is unravelled + replicated. prophase - chromosomes supercoil, centrioles start moving to opposite ends of cell forming network of protein fibres (spindles), nuclear envelope breaks down. Metaphase - chromosomes line up along the middle of the cell + become attached to the spindle by their centromere. Anaphase - centromere divide separating each pair of sister chromatids, spindles contract pulling chromatids to opposite ends of the cell, centromere first. Telophase - chromatids reach opposite poles on the spindle, uncoil and called chromosomes again. nuclear envelope forms around each group, 2 nuclei. cytoplasm divides, 2 daughter cells that are genetically identicle to the original cell and each other.

ii) The genetic material must be replicated so that the cells are genetically identical and so that they have the same DNA. Both of the daughter cells will recieve a full copy of the DNA.

b) Homoglous pair of chromosomes - the chromosomes that make up each pair are the same size and have the same genes, could have different versions of those genes (alleles). One maternal and one paternal. centromere in the same position, same banding pattern, they pair up in meiosis/ form bivalent.

ci) Tissue is a group of cells that are specialised to work together to carry out a particular function. can contain more than one type of cell.                    

ii) squamous - acts as surface, short diffusion pathway. Single layer of flat cells lining a surface. found in the alveoli, cheek lining and are in blood vessels.

ciliated - move mucus, secrete mucus. is a layer of cells covered in cilia, found on surfaces where things need to be moved. found in the bronchioles, bronchi, trachea and airways.

2ai) C = vesicle - small fluid filled sac in cytoplasm, surrounded by a membrane. They transport substances in and out of the cell and between organelles. some are formed by golgi apparatus or the endoplasmic reticulum, others are formed at the cell surface.

      D = plasma membrane/cell surface membrane - found on the surface of animal cells and just inside the cell wall of plant cells and prokaryotic cells. Made mainly of lipids and protein. regulates the movement of substances into and out of the cell. has receptor molecules on it, allow it to respond to chemicals like hormones.

      E = ribosome - very small organelle that either floats free in the cytoplasm of is attached to the rough endoplasmic reticulum. the function is the site where proteins are made/ make proteins.

ii) some types of extracellular protein secreted at B are enzyme, hormone or glycoprotein.

iii) stages during the secretion of a protein that requires energy is when vesicles are transported to the plasma/cell surface membrane or when fusing vesicles yo the membrane/exocytosis.

iv) the role of the golgi apparatus is to modify and package the proteins into vesicles do that…