Download this complete,fully solved and updated actual exam for CCEA AS Biology Unit One: KEY TERMS

Activation energy The activation energy required for a reaction is reduced by enzymes. Active site The area of the enzyme where the substrate fits. Can be denatured by pH and heat. Complementary to the substrate. Previous Play Next Rewind 10 seconds Move forward 10 seconds Unmute 0:00 / 0:15 Full screen Brainpower Read More Active transport Movement of molecules against the concentration gradient (low to high) and requires energy. Adenine One of the 4 bases in DNA. Airspace Air spaces in the spongy mesophyll allows gas exchange in the leaf. Amylase Makes up 20% of starch. Consists of -glucose and has 1-4 glycosidic bonds. Unbranched but spirals into a helix, held together by hydrogen bonds. Amylopectin Makes up 80% of starch. Consists of -glucose and has 1-6 glycosidic bonds which allow it to be easily hydrolysed. More branched than glycogen. Anaphase Chromosomes pulled to opposite poles of the cell. Aquaporin Allow water to move into and out of cells. Bacteriophage Type of virus that are commonly called phages, they are non-cellular, and attack bacterial cells. Bilayer The phospholipid bilayer makes up the cell membrane. The phosphate heads are hydrophilic and face towards the water, whereas the fatty acid tails are hydrophobic and face away from the water. Bivalents When the homologous chromosomes line up during Prophase 1 in meiosis. Calcium Needed for cell walls in plants and strong bones and teeth in animals. Cell cycle The sequence of events that occur within a cell, eg. G1, S, G2, Mitosis and Cytokinesis. Cell wall The cell wall is the outer layer of the cell in some organisms. Cellulose in plants and some protocista, Chitin in fungal cells and peptidoglycan in some bacteria. Cell plate How plant cells divide to form daughter cells, a cell plate grows across the equator of the cell from the centre outwards. Cellulose is laid down on the plate to form the cell wall. Cellulose Made up of -glucose. Molecules alternate 180 which makes it rigid. Role = structural. 1-4 glycosidic bonds and unbranched. Chiasmata Where the chromosomes have crossed over during prophase 1. Chloroplast Only found in plant cells, and is the site of phosynthesis. Cholesterol Cholesterol is a substance found in the blood. It is made in the liver and is needed for healthy cell membranes. However, too much cholesterol in the blood increases the risk of heart disease, and of diseased arteries. Cleavage furrow Formed in animal cells when cytokinesis occurs, Microfilaments pinch the cytoplasm, creating a furrow at the cell equator which deepens until 2 daughter cells are produced. Coenzyme Is a type of cofactor- it is organic and it is not bond to the enzyme. It helps the enzyme carry out its function. Cofactor A non-protein substance that helps an enzyme function.