GCSE AQA Biology 2 Cells & Diffusion

1. Nucleus

   Anotações:

   • Contains genetic material that conrols activities of cell
2. Cytoplasm

   Anotações:

   • Gel-like substance where most chemical reactions happen - contains enzymes
3. Cell membrane

   Anotações:

   • Hold cell together & controls what goes in/out
4. Mitochondria

   Anotações:

   • Where reactions for respiration take place - releases energy
5. Ribosomes

   Anotações:

   • Where proteins are made - protein synthesis

1. Cell wall

   Anotações:

   • Rigid, made of cellulose - supports & strengthens cell
2. Permanent vacuole

   Anotações:

   • Contains cell sap - weak solution of sugars & salts
3. Chloroplasts

   Anotações:

   • Where photosynthesis happens (makes food for the plant) - contain green substance (chlorophyll)

Anotações:

• The spreading out of particles from an area of high concentration to an area of low concentartion

1. Allow small molecules through (e.g. oxygen, glucose, amino acids, & water)
2. Don't allow big molecules through (e.g. starch & proteins)
3. Particles move randomly but net movement from high to low concentration

1. Packed with chloroplasts - for photosynthesis
2. Tall shape - large surface area exposed down side for absorbing carbon dioxide
3. Thin shape - can pack lots at top of leaf

1. Open & close stomata in leaf
2. When plant has lots of water...

   Anotações:

   • Guards cells fill with water & become turgid, making stomata open - gases can be exchanged for photosynthesis
3. When plant is short of water...

   Anotações:

   • Guard cells lose water & become flaccid, making stomata close - stops too much water vapour escaping
4. Thin outer walls & thick inner walls
5. Sensitive to light & close at night

   Anotações:

   • To save water - adapted to function of allowing gas exchange & controlling water loss within leaf

1. Concave shape

   Anotações:

   • Big SA for absorbing oxygen & helps them move smoothly through capillaries
2. Packed with haemoglobin

   Anotações:

   • Pigment that absorbs oxygen
3. No nucleus

   Anotações:

   • More room for haemoglobin

1. Sperm cells
   1. Long tail & streamlined head

      Anotações:

      • Help it swim to egg
   2. Lots of mitochondria

      Anotações:

      • Energy needed to swim
   3. Carry enzymes

      Anotações:

      • In head - to digest egg cell membrane
2. Egg cells
   1. Huge food reserves

      Anotações:

      • To feed embryo
   2. Membrane can change structure

      Anotações:

      • To stop more sperm getting in - offspring ends up with right amount of DNA

Anotações:

• Process by which cells become specialised for a particular job

1. Occurs during development

Anotações:

• That work together to carry out a particular function

1. Examples of tissues
   1. Muscular tissue - contracts to move
   2. Glandular tissue - makes & secretes chemicals e.g. enzymes & hormones
   3. Epithelial tissue - covers parts of the body

Anotações:

• That work together to perform a certain function

1. e.g. Stomach is made of...
   1. Muscular tissue - moves stomach wall to churn food
   2. Glandular tissue - makes digestive juices to digest food
   3. Epithelial tissue - covers outside and inside of stomach

Anotações:

• Working together to perform a particular function

1. e.g. Digestive system is made of these organs...
   1. Glands

      Anotações:

      • Produce digestive juices
   2. Stomach & small intestine

      Anotações:

      • Digest food
   3. Liver

      Anotações:

      • Produces bile
   4. Small intestine

      Anotações:

      • Absorbs soluble food molecules
   5. Large intestine

      Anotações:

      • Absorbs water from undigested food - leaving faeces

1. Has cytoplasm, cell membrane & wall
   1. No nucleus - strands of genetic material instead
2. Have flagella

   Anotações:

   • Long protein strands - to move about

1. Have a nucleus, cytoplasm, cell membrane & wall