Essay paragraphs Flashcards
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3.1.4 Proteins
-The primary structure is a polypeptide chain of amino acids joined by peptide bonds, formed in a condensation reaction
-The secondary structure is formed by hydrogen bonding, which folds the polypeptide to be either an alpha helix or beta pleated sheet
-The tertiary structure is formed by a combination of ionic and hydrogen bonds, or disulfide bridges between two cysteine molecules-amino acids that contain sulfur
-The quaternary structure is formed from two or more tertiary proteins
-Proteins are important, an example of a tertiary protein is an enzyme. These are essential in many reactions as they lower the activation energy. Enzymes can be used in both photosynthesis and respiration. Proteins can also be present in cell membranes as channels or carriers, allowing for processes such as facilitated diffusion, active transport and co-transport
3.2.2 Mitosis
-Interphase-DNA replication occurs and the cell prepares for osmosis
-Prophase-chromosomes condense becoming visible, protein spindles form, centrioles form on the opposite poles and the nuclear membrane breaks down
-Metaphase-chromosomes align along the equator and attach to the spindle fibres
-Anaphase-centromeres divide, separating sister chromatids, the spindle fibres contract to pull them to opposite poles of the cell
-Telophase-chromosomes uncoil, the nuclear membrane forms around the two groups of chromosomes, cytokinesis
-Mitosis is important in the secondary immune response, where B cells are stimulated to divide by mitosis, forming plasma cells identical to the B cells that can secrete antibodies specific to the infection
3.3.4.1 Haemoglobin and the Bohr effect
-Haemoglobin is a quaternary protein, containing four proteins, which each have a haem group, which includes an Fe2+, which binds to the oxygen to form Fe3+
-The oxygen dissociation curve is when oxygen associates with Hb at a high partial pressure, such as in the lungs, but unloads at a low partial pressure, such as at respiring tissues
-Co-operative binding references the fact that after one O molecule has loaded, it alters the tertiary structure of the protein to allow more O to load, this can then be applied in reverse to the unloading of haemoglobin
-The Bohr effect occurs during exercise, when the rate of respiration is increased in the body, more CO2 is present as a waste product. This decreases the blood pH, which alters the protein structure of the Hb, decreasing its affinity for O, so the O can unload more easily at respiring tissues
-Haemoglobin is an important transport molecule in the body, as it allows O to be taken up efficiently at gas exchange surfaces, and can be rapidly unloaded to tissues in response to the cells respiratory requirements
