AQA GCSE Biology B2 Higher

B2.1.1 Cells and cell structure

In human and animal cells the following structures can be found:

A nucleus to control the cell

Cytoplasm in which most chemical reactions occur

A cell membrane to control movement of substances in and out of the cell

Mitochondria to release energy in respiration

Ribosomes to synthesise proteins

Cells in plants and algae also have a cellulose cell wall to strengthen the cell. They also have chloroplasts for photosynthesis, turning light energy into food, and a vacuole filled with cell sap.

Bacterial cells contain cytoplasm and a membrane, surrounded by a cell wall. The genes are kept in the cytoplasm, not the nucleus.

Yeast, a single-celled organism, has a nucleus, cytoplasm and a membrane, surrounded by a cell wall.

Cells can be specialised. This means they will perform a particular function.

B2.1.2 Dissolved substances

Dissolved substances, such as oxygen for respiration and carbon dioxide, can move in and out of cells via diffusion.

Diffusion is the spreading of particles to result in a net movement down a concentration gradient. The greater the difference in concentration the faster the diffusion.

B2.2.1 Animal organs and the stomach

Large organisms have developed organ systems to help the exchange of materials. When they grow the cells differentiate so they can perform they can perform a specific function.

A tissue if a group of cells that all have a similar structure and function. For example, there is muscular tissue which can contract, glandular tissue which can secrete enzymes and hormones.

Organs are made of tissues. The stomach, an organ, has muscular tissue to churn the contents, glandular tissue to product digestive tissues, and epithelial tissue to line its inside and outside.

B2.2.1 The digestive system

Humans and other mammals use the digestive system to exchange substances with the environment.

Glands such as the pancreas and salivary glands produce digestive juices.

The stomach and small intestine digest food.

The liver produces bile.

The small intestine absorbs soluble food.

The large intestine absorbs water leaving faeces.

B2.2.2 Plant organs

Stems, roots and leaves are all organs found in plants. Plant organs contain plant tissues.

Epidermal tissue covers plants.

Mesophyll tissue conducts photosynthesis.

The xylem and phloem transport substances around the organism.

B2.3.1 Photosynthesis

The word equation for photosynthesis is:

I think there's a character limit on this. Hmmm.

(slow clap)

Could you please make a second part to this,

PLEEEEEEEASEEE!