SB1 - Key Concepts in Biology Flashcards
(32 cards)
What is magnification?
The magnification of an image is the number of times larger it appears than it’s actual size (e.g. something viewed under x30 magnification looks 30 times larger than it is in real life). Magnification = magnification of eyepiece lens x magnification of objective lens.
Actual size = image size / magnification
What is resolution?
Resolution is the smallest distance between two points that can still be seen as two points.
What are the main structures found in animal cells and what do they do?
Animal cells contain a cell membrane, a nucleus, cytoplasm, ribosomes and mitochondria.
Cell membrane - provides structure, selectively permeable (can control what gets in and out of the cell)
Nucleus - contains the cell’s DNA and controls the cell
Cytoplasm - a jelly-like substance in which most of the cell’s chemical reactions take place
Ribosomes - responsible for synthesising protein
Mitochondria - provides energy for the cell through aerobic respiration
What are the main structures in plant cells and what do they do?
Plant cells contain a cell wall, a cell membrane, a nucleus, a vacuole, cytoplasm, mitochondria, ribosomes and chloroplasts.
Cell wall - made of cellulose, supports and protects the cell
Cell membrane - selectively permeable (controls what gets in and out of the cell)
Nucleus - contains the cell’s DNA, controls the cell
Cytoplasm - where most of the cell’s chemical reactions occur
Vacuole - stores cell sap and helps the cell to stay firm and rigid
Mitochondria - provide energy for the cell by aerobic respiration
Ribosomes - responsible for protein synthesis
Chloroplasts - contain chlorophyll, which is needed for photosynthesis
What are the main differences between plant and animal cells?
Plant cells have chloroplasts, a vacuole and a cell wall, whereas animal cells do not.
What are specialised cells?
Specialised cells are cells which have differentiated to fit a particular purpose.
How are small intestinal cells specialised?
They have membranes with tiny folds (microvilli), which increase the surface area of the cell, and so speed up digestion.
How are cells in the pancreas specialised?
The pancreas produces many enzymes, which are a type of protein. Cells in the pancreas are therefore specialised to have many ribosomes.
How are human egg cells specialised for reproduction?
They have a haploid nucleus (contains half of the genetic material) so that when fertilised, the zygote has the full amount of chromosomes, very large to increase chances of fertilisation, jelly coat protects the egg cell and hardens after fertilisation to ensure that only one sperm cell enters the egg cell, cytoplasm is packed with nutrients to supply the fertilised egg with the energy and materials needed for growth and development of the embryo.
How are human sperm cells specialised for reproduction?
They have a haploid nucleus so that the embryo has the correct number of chromosomes, streamlined shape, tip of head has an acrosome which contains enzymes which break down the jelly coat of the egg cell, lots of mitochondria to produce lots of energy needed for the cell to travel long distances relative to its size, flagellum moves from side to side, allowing the sperm cell to swim.
How are cells in the oviduct and trachea specialised to their functions?
Ciliated epithelial cells are found in the oviduct and the trachea. They have hair-like structures called cilia on their surfaces, which wafts substances (in the trachea, the substance is mucus, in the oviduct, the substance is egg cells).
What are the structures in bacterial cells and what do they do?
Bacteria contain a cell wall, a cell membrane, cytoplasm, chromosomal DNA, plasmids (bacteria are prokaryotes so don’t have a nucleus), some have a slime coat, some have flagellum.
Cell wall - for support, made of peptidoglycan
Slime coat - for protection
Chromosomal DNA - contains most of the cell’s genetic material
Plasmids - contain the rest of the cell’s DNA
What are enzymes?
Enzymes are biological catalysts (they speed up reactions by lowering the activation energy) and can be used to break down or combine reactants into different products.
What does protease do?
Protease beaks down proteins into amino acids.
What does amylase do?
Amylase breaks down starch into sugars
What does lipase do?
Lipase breaks down lipids onto glycerol and fatty acids.
How do you test for reducing sugars?
Mix an equal volume of food solution with Benedict’s solution and place in a hot water bath for a few minutes. If it is blue, there is no reducing sugars, green means very little reducing sugars, orange means more reducing sugars, red means lots of reducing sugars.
How do you test for protein?
Biuret test - potassium hydroxide is mixed with a solution of food, two drops of copper sulphate solution are added. If the pale blue solution turns purple, there is protein in the food.
How do you test for lipids?
Ethanol emulsion test - the food is mixed with ethanol and shaken, this is poured into water and shaken again. If it goes cloudy, there are lipids in the food.
How do you test for starch?
Iodine solution changes colour from yellow-orange to blue-black when in contact with starch.
How do you test the calorie content of food?
Burn a known volume of food over a known volume of water. Record the temperature of the water before you start and after all the food has burned. The temperature change is used to calculate the calorie content of the food.
How do enzymes work?
The active site of the enzyme is complementary to the substrate, meaning that the substrate can fit into the enzyme’s active site, where it is broken down or formed. A large change in pH or temperature can affect the shape of the active site. If the shape changes too much, the substrate will no longer fit and the enzyme will not work anymore. It is said to be denatured.
How can the rate of a reaction be calculated?
Rate = amount of reactant used OR amount of product formed / time
Which factors affect the rate of enzyme activity?
Temperature - the higher the temperature, the more kinetic energy the enzymes have, the faster they move, so more collisions between enzyme and substrate occur. However, too high a temperature will cause the enzyme to be denatured
pH - the closer the pH value is to the enzyme’s optimum pH, the faster the reaction will go, too high or low a pH will cause the enzyme to denature.
Concentration of substrate - initially, a higher concentration of substrate will increase the rate of reaction, as more enzyme-substrate collisions will occur, however eventually the rate will plateau as all the active sites will be in use so the reaction cannot go any faster.
Concentration of enzymes - initially, a higher concentration of enzymes will increase the rate as more enzyme-substrate collisions occur, however eventually the rate will plateau as all of the substrate is being broken down, so adding more enzymes makes no difference.
