Module 2

• Observations that you would see when the cell has stopped dividing at the G2 checkpoint is larger organelles, more DNA, and the nuclear membrane present.
• Climax community is when the habitat has reached its final state. For example, in a pond if there is insects, plants, fish and other producers then ecologists would call it a climax community.
• The process for a nitrogenous compound to be converted to nitrate so that plants can uptake is through the bacteria nitrosomonas which breaks the compound into nitrite. Then the nitrobacter bacteria breaks it to form nitrate.
• To improve diagram drawings, there should be no shading, includes a title and a magnification (scale).
• Scanning electron microscopes and laser scanning confocal microscopes can both produce 3D images.
• An image produced by a LSCM can differ from an electron microscope is that they can see living things and have a lower resolution power.
• Leaves are supported as there is air inside the leaf which creates buoyancy and is supported by water in between the layers.
• To measure the diameter of an organelle using a light microscope can be done through a eyepiece graticule. Start by calibrating the graticule using the stage micrometer. Align the two scales and then measure the diameter of the organelle. Take repeated measures and draw out a mean to get accurate results.
• The benefits of using stains when making slides for light microscopy is that it improves contrast between organelles making organelles more visible.
• Methylene blue is a dye that is used to bind to the phosphate group of DNA to make chromosomes more visible when using light microscope.
• It is important to use a differential stain when examining a blood smear under a microscope so that you can differentiate between the different organelles. The stains also produce contrast which makes white cells more visible.
• A non-specific immune response can be seen if the nucleus is lobed
• The role of the membrane in the rough endoplasmic reticulum is to compartmentalise the cell from organelles separating. It also holds the organelles in place and keeps the cell from breaking.
• Goblet cells have large numbers of mitochondria to provide lots of energy.
• Golgi apparatus is used to process and modify the protein. It is then packaged and then secreted by the vesicle by exocytosis.
• After translation, the molecule is transported by a vesicle from the RER. The vesicle enters the golgi apparatus for modifying and processing. It is then packaged into a secretory vesicle which moves along the cytoskeleton. The vesicle then fuses with the cell surface membrane where the protein is released by exocytosis.
• The genetic code requires three bases to code for one amino acid. The sequence determines the primary structure of the amino acid.
• Cytoskeleton provides mechanical strength to maintain the shape of the cell. It also allows movement of organelles within the cell.
• Peroxisomes can be moved around inside the cell when attached to cytoskeleton moved by protein motors.
• Epithelial cells act as a defence against pathogens as they include goblet cells that secrete mucus. The mucus traps the pathogens from entering the lungs. As the pathogens are trapped, the phagocytes engulf the pathogens. Once engulfed the ciliated cells waft the mucus away.
• Bonds that hold sucrose is alpha glycosidic.
• Carbohydrates have many properties to help them perform their roles as energy storage in plants and animals. For example, they are polymers of glucose. This allows glucose to be used for respiration. They are formed from 1,4 glycosidic bonds which are easy to break and form.
• Lipids act as an energy storage molecule for animals. For example, fats are energy rich therefore more energy can be stored in less space. They are insoluble therefore does not affect the water potential.
• Mammals store glycogen instead of glucose because glycogen is metabolically inactive therefore will not be used up. Glucose is needed for respiration whereas glycogen is not required for anything. Glycogen is insoluble therefore will not affect the water potential. Glycogen is a highly branched molecule which means lots of energy can be released and stored simultaneously.
• Properties that make cellulose suitable for cell walls are insoluble, flexible and unreactive.
• Glycogen is more suitable than amylopectin as an energy store because it is more branched than amylopectin. Therefore, you can add or release energy.
• Alpha glucose is different to beta glucose as the hydroxyl groups are flipped.
• Amylose is insoluble, unbranched and formed from condensation reaction.
• The hydrophilic nature of heads of phospholipids allows them to form membranes. Glycolipids also contain fatty acids and form part of the membrane.
• Lipids cab be used for energy storage in the form of triglycerides. Some hormones are also lipids and they are similar in structure to cholesterol molecules. 
• Human pancreatic lipase breaks the bonds between fatty acids and glycerol through hydrolysis.
• Cholesterol binds to phospholipid fatty-acid tails, increasing the packing of the membrane, therefore reducing the fluidity of the membrane.
• Examples of unsaturated fatty acids are: palmitoleic acid, oleic acid, myristeroleic acid, linoleic acid and arachidonic acid.
• Examples of saturated fatty acids are: stearic acid and palmitic acid.
• If there is a higher ratio of hydrogen to oxygen then the molecule is more likely to be a triglyceride.
• The structure of phospholipids allows them to form the bilayer of a plasma membrane as they include hydrophilic heads and hydrophobic tails. The tails repel from water whilst the heads bonds with water. The hydrophobic nature of tails results in the facing towards each other.
• Ester bonds are formed between a glycerol and a fatty acid
• When ester bonds are formed, water is formed.
• The molecule that forms a more dense liquid in a triglyceride is glycerol as fatty acids tend to float on top when reacted with methanol.
• Functions of triglycerides in living organisms are: energy storage, thermal insulation and protection.