Topic 1 - Key concepts in biology

It contains DNA which codes for enzymes and other proteins and coordinates cell activity This is in eukaryotic cells (plant + animal)

-A jelly-like substance which chemical reactions occur in This is in all eukaryotic cells (plant + animal)

-It controls what exits and enters the cell This is in prokaryotic and eukaryotic cells (bacteria + plant + animal)

-It contains the enzymes for respiration, providing energy for the cell This is in all eukaryotic cells (plant + animal)

-Where protein synthesis occurs (proteins are made) This is in prokaryotic and eukaryotic cells (bacteria + plant + animal)

-It contains the green pigment, chlorophyll, which absorbs light energy for photosynthesis -It contains the enzymes needed for photosynthesis This is only in plant cells

-It contains cell sap -Supports the cell/improves its rigidity This is only in plant cells

-Made of cellulose -Provides structure This is in plant cells, some bacteria have them

Small loops of DNA which control a few of the cell’s activities

It is one singular loose loop of DNA which controls most of the cell’s activities

Propels the bacteria to allow movement

Their function as a gamete is to carry the male’s DNA to the egg cell for successful reproduction -Contain an acrosome, which contains enzymes which, when released, breaks down the outer layers of the egg cell’s membrane -Has a haploid nucleus, has 23 chromosomes as an egg cell has the other 23 -Has a streamlined head to aid swimming -Has a tail for swimming -Contains many spiralled mitochondria, because it needs to respire to move, this supplies the energy and the spiral is more compact

-Has a haploid nucleus, has 23 chromosomes as a sperm cell has the other 23 -Has a special cell membrane which becomes impermeable after accepting one cell -Cytoplasm contains nutrients for the growth of the early embryo

-It has a thin layer of long hair-like projections called cilia that waft mucus that contains trapped microbes from one place to another, eventually to be transported to the stomach and killed by stomach acid.

Electron microscopes have a greater magnification and resolution than light microscopes. They can have a magnification of up to 2,000,000x and resolving power of 10nm. This means they can view things such as organelles, viruses or proteins more clearly and in more detail, especially very small structures. These can be identified more easily

magnification of the eyepiece lens x magnification of the objective lens

size of image/magnification = size of object

milli (10⎺³) 0.001 mm micro (10⎺⁶) 0.000001 µ nano (10⎺⁹) 0.000000001 n pico (10⎺¹²) 0.000000000001 p

-Take a thin layer of cells from your sample by peeling them off or using a cotton bud -Add a small amount of chemical stain, this makes the specimen more visible through the microscope -Apply the cells to your glass slide by placing them on it/wiping the bud against it -Lower a coverslip onto your slide, taking care to avoid air bubbles

-Place the slide on the stage and clip with stage clips -Look through the eyepiece lens -Turn the focus wheel to obtain a clear image -Start with the lowest objective lens magnification -Increase the magnification of the objective lens and refocus using the fine focus adjustment

In the Lock and Key Hypothesis the shape of the substrate is complementary to the shape of the active site, so when they bond it forms an enzyme-substrate complex

The rate of reaction increase with an increase in temperature up to the optimum, but above this temperature it rapidly decreases and eventually the reaction stops. When the temperature becomes too hot the bonds that hold the enzyme together will begin to break. This changes the shape of the active site, so the substrate can no longer fit the enzyme, which is now denatured and cannot work.

As the substrate concentration increases, the rate at which enzyme-substrate complexes can be formed increases. This only occurs up to a point, however - this is called the saturation point, and increasing the substrate concentration above this will have no effect on the rate of reaction. The saturation point is different for every enzyme.

Enzyme activity and the rate of reaction is highest at the optimum pH. If the pH is too high or too low, the forces that hold the amino acid chains that make up the protein will be affected. This will change the shape of the active site so the substrate can no longer fit in: the enzyme is denatured and can no longer work.