Biology Model answers

Enzymes

An enzyme is a biological catalyst that speeds up the rate of reaction without being used up.
Enzymes have an active site with a specific shape that fits with a complementary substrate to form an enzyme substrate complex. 

Enzymes (Temperature)

Enzymes and substrates gain kinetic energy, so there are more frequent collisions between enzymes and substrates, so more enzyme substrate complexes are formed.
Above the optimum temperature the enzyme starts to denature this causes the active site to change shape; the substrate no longer fits, and the enzyme substrate complex can’t be formed. 

Diffusion

The net movement of particles from an area of high concentration to an area of low concentration. 

Osmosis

The movement of water from an area of high-water potential to an area of low water potential through a partially permeable membrane.  

Active transport

The movement of particles from an area of low to high concentration using energy. 

Testing for respiration

We can investigate the production of carbon dioxide by using two different tests.
Limewater turns colourless to cloudy and hydrogen carbonate indicators which turn red to yellow.

Adaptations of alveoli

One cell thick walls for a short diffusion distance.
Large surface area with lots of space for oxygen and carbon dioxide to diffuse.
Lots of capillaries this allows for a rich blood supply so a high concentration gradient.
Moist walls help the gases to dissolve.
Constant movement of both blood and air maintains the steep concentration gradient. 

Eukaryotic vs Prokaryotic

Eukaryotic organisms have a nucleus, and other membranes bound organelles such as mitochondria.
Prokaryotic organisms have no membrane bound organelles.
Instead of a nucleus, their DNA is free in the cell, and they will have plasmids. 

Saprotrophic nutrition

They secrete enzymes to digest large molecules outside the cells into small molecules that can be absorbed by the hyphae. (fungi have no chloroplasts and have cell walls made of chitin).

Fermenter controls

Aseptic – sterilizes to kill unwanted microorganisms. Nutrients – glucose added.
Temperature – using a thermometer and controlled with a cooling jacket.

Immune response

Pathogen enters bloodstream through a cut or ingestion.
A lymphocyte detects pathogens and produces antibodies until one matches the pathogen’s antigens.
It will bind onto the antigens and mark them for phagocytosis.
A phagocyte detects marked pathogens and will engulf them.
They are then digested by enzymes inside the phagocyte, then they will be released. 

Vaccinations

Dead or weakened pathogens are put into the body.
The antigens on the pathogen are detected by white blood cells; lymphocytes are stimulated to secret antibodies.
Some of these lymphocytes remain as memory cells.
If the body is then exposed to the same pathogen again, the memory cells can produce antibodies sooner and faster, making the phagocytosis quicker.