B4

• enzymes are proteins that speed up chemical reactions.
• living things produce enzymes
• every enzyme molecule has a active site
• enzymes work by the 'lock and key' model 
• enzymes usually only speed up one chemical reaction
• for an enzyme to work; a substrate has to be the coorect to fit into the active site
• PH is a measure of how acidic or alkaine a solution is
• enzymes need the right temperature and PH
• optimum - when they're most active (usually 37 degrees)
• changing the temperature changes the rate of an enzyme - cointrolled reaction
• If the temperature gets too hot for an enzyme, some of the bonds holding the enzyme together break, this changes the shape of an enzyme active site so the substrate wont fit and it doesnt work. this mean the enzyme is denatured - this is the same with PH
• cells make enzymes according to instructions in the genes
• the reactions require energy they do this by using the energy released by the cells doing respiration

maintenance of a constant internal environment                                                                                              what we must keep constant?

• heart rateblood pressure
• temperature
• blood * sugar levels
• water levels

what happens if;                                                                                                                                                            we're too hot: dehydrate, lose of breath, sweat, redness                                                                             we're too cold: shiver, teeth chattering, goose bumps, go blue                                                                        an automatic response does require consicous thought, homeostatus is acheived by automatic responses  

 average human temperature - 37.4 degrees

core body temperature is slightly different to the temperature elsewhere in the human body, this is because the core is kept at 2 more constant temperature because it is more inportant to keep organs at a good temperature rather than less important parts of the ody. Ther body maintains the temperature through negative feedback this is when apposes the change it does 

Photosynthesis is a series of chemical reactions that use energy sunlight to produce food, the 'food' it produces is glucose - a sugar. Photosyntheisis happens in the cells in green parts of plants (leaves) this is because chlorophyll is need for photosyntheisis to happen and is found in leaves.

factors that effect rate of photosynthesis:

• amount of light
• amount of carbon dioxide (CO²)
• temperature

uses of glucose:

respiration - releases energy from glucose - produces CO² and releases O²

make chemicals for growth - converted into cellulose for making cell walls combined with nitrogen to make amino acids = proteins helps make chlorophyll and is stored as starch in roots

word and symbol equations:

cardbon dioxide + water --> glucose = oxygen

6CO² = 6H²O --> C6H1206 = 6O²    (pink indicates smaller numbers)

• diffusion is the passive overall movement of particles from a region of their higher concentration to a region of thier lower concentration
• osmosis is the overall movement of water from a dilute oto a more concentrated solution through a semi-permable membrane
• active transport is the overal movement of chemicals across a cell membrane from a region of loer concentration to a region of hiher concentration using energy released by respiration - some cells can be moved by active transport

diffusion is important to our plants because to have the right amount of carbon dioxide in and around the cells during photosynthesis to produce oxygen and glucose

root cell functions:

• collects minerals and water
• anchor the plant

Anarobic respiration is respiration without oxygen = glucose > lactic acid (toxic, buils up in cells = PAINFUL) + (ENERGY)

lactic acid can only be removed by reacting it with oxygen

Aerobic: produces CO² & H²0, with oxygen, produces MORE energy, releases energy slowly, takes place in animal & plants & soem microbes

Anarobic: produces lactic acid, without oxygen, produces LESS energy, releases energy quickly, takes place in plant roots & water logged soil, bacteria in puncture wound, human cells during vigarous exercise

• every living thing is made up of the same basic cells (building blocks) 
• lots of important chemical reactions happens in cells
• yeast are single celled microrginisms
• yeast are used to make bread and wine

BACTERIA CELL CONTAINS:

• circular DNA molecule
• cell membrane
• cytopasm

They dont have mitchondria but they can still respire aerobically

bacetria cells have a circular molecule of DNA instead of a nucleus (floatsarouns in the cytoplasm) 

Bactria have a simple cell sructure

bacteria cells are a bit different to plant animal and yeast cells

• Nucleus - contains DNA whoch contains the instructions for making proteins e.g. the enzymes used in the chemical reactions of respiration and photosynthesis
• cytoplasm - gel like substance where proteins like enzymes are made some enzyme controlled reactions take place in the cytoplasm e.g. th reacions of anearobic respiration
• cell membrane - holds cell together and controls what goes in and out (body gaurd) it lets gases and water pass freely while acting as a barrier to other chemicals
• mitochondria - these are where the enzymes needed for aerobic respiraion are found and where the reactions take place

PLANT CELLS HAVE A FEW EXTRA THINGS ANIMAL CELLS DONT HAVE:

RIGID CELL WALL - MADE O CELLULOE SUPPORTS CELL AND STRENGTHENS IT

VACUOLE - CONTAINS CELL SAP (A WEAK SOLUTION OF SUGAR AND SALTS)

CHLOROPLATS - WHERE REACTION FOR PHOTOSYNTHESIS TAKE PLACE THEY CONTAIN A GREEN SUSTANCE CALLED CHOLOROPHYLL AND THE THE ENZYMES NEEDED FOR PHOTOSYNTHESIS