Biology B4

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All cells have a nucleus except for bacteria. Bacteria simply have a cirular molecule of DNA floating around their cytoplasm. Also, unlike other cells, bacteria cells don't have a mitochondira. The mitochondria is where the aerobic enzyme reactions take place.

An animal cell has a nucleus, cytoplasm, cell membrane and mitochondria.

A plant cell has a nucleus, cytoplasm, cell membrane, mitochondria, cell wall, vacuole and chloroplasts.

A yeat cell has a nucleus, cytoplasm, cell membrane, mitochondria and a cell wall.

The nucleus contains the genetic informations (DNA), which codes for the proteins made e.g. enzymes for respiration or photosynthesis.

The cytoplasm is where proteins (e.g. enzymes) are made. Some anaerobic enzyme reactions take place here.

The cell membrane is what holds the cell together by allowing gases and water to diffuse in and out of the cell hile acting as a barrier to other chemicals.

The cell wall is made of cellulose; it supports the cell and makes it stronger.

The vacuole contains cell sap, which is a weak solution of sugar and salts.

The choloroplasts are where photosynthesis reactions take place. They contain chlorophyll and the enzymes needed for ophotosynthsis to take place.  


Enzymes are proteins that speed up chemical reactions. The 'lock and key model' is used to present the enzyme substrate reaction because the substrate must fit into the active site of the enzyme. If it doen't fit in (when it is meant to ), this menas that the enzyme is denatured. The enzyme can be denatured from certain temperatures, pH levels. They always have an optimum temperature and an optimum pH to work at. The substrate must be able to fit in the enzyme for the reaction to take place.


Aerobic respiration is respiration with plenty of (enough) oxygen. This takes place in animal and plant cells, and sometimes in micro-organisms.

Glucose + Oygen = Carbon Dioxide + Water (Energy released)

Anaerobic respiration is when there is a lack of…


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