GCSE AQA BIOLOGY UNIT 2 ( 2014 specification used)

 

 

BIOLOGY UNIT 2: REVISION NOTES.

Unit B2.1 Cells and simple cell transport:

·         All living things are made up of cells.

·         Dissolved substances have to cross a cell membrane to enter or exit from a cell.

Human & Animal Cells both have these parts:

Part:

Function:

Nucleus

Controls what happens inside the cell & carries the genetic information.

Cell membrane

Controls what substances enter and exit from the cell.

Cytoplasm

Jelly like substance where chemical reactions take place in the cell.

Mitochondria

Is where energy is released in the cell during respiration.

Ribosomes

Where protein synthesis occurs from amino acids.

 

Only plant cells:

Part:

Function:

Rigid cell wall-made of cellulose

Supports & strengthens the cell.

Permanent vacuole

Contains cell sap (weak solution of sugar & salts).

Chloroplasts

Contain green substance names Chlorophyll that absorbs light energy for photosynthesis to occur in it.

Bacterial Cell:

·         Cell membrane

·         Cell wall

·         Cytoplasm

·         No nucleus- It has genetic material floating in the cytoplasm.

Yeast Cell: (Single-celled organism-Microorganism)

·         Nucleus

·         Cell membrane

·         Cell wall

·         Cytoplasm

Specialised Cells (cells that carry a specific function):

Specialised Cell

Adapted to function

Red blood cells(ANIMAL)

·         Concave shape-big surface area to absorb oxygen.

·         Packed with haemoglobin-pigment which absorbs oxygen.

·         No nucleus-more space for haemoglobin.

Guard cells(PLANT)

·         Open & close pores (stomata) in a leaf to allow oxygen and carbon dioxide in and out of the plant cell.

Palisade cells(PLANT)

·         Packed with chloroplasts for photosynthesis.

·         Thin shaped-more can be packed together.

Sperm & Egg cell(ANIMAL)

·         Sperm- Tail to be able to swim to fertilise egg cell

·         Egg-contains food to feed the embryo

Unit B2.1.2 Dissolved substances:

·         Dissolved substances move in & out of cells by the process called DIFFUSION.

·         DIFFUSION: Is the spreading of gas particles, or a substance in solution, resulting in a net movement from an area of high to low concentration.

·         The greater the difference in concentration the faster the rate of diffusion as the concentration gradient will be steeper.

·         Only small molecules can diffuse through cell membranes such as amino acids not proteins.

·         Oxygen required for respiration is diffused through cell membranes.

·         Diffusion occurs in all mixtures; gases, liquids and solutions.

·         Anything dissolved in solution can diffuse if there is a difference in concentration from one area to another.

Unit B2.2 Tissues, organs and organ systems:

Multicellular organism- organisms that contain more than one cell which may differentiate to carry out a specific function.

Bunch of specialised cells                    Tissue             Organs               Organ system.

E.g.

 Nerve cells                   Nerve tissue            Brain            Nervous system.

 

Unit B2.2.1 Animal Organs:

Large multicellular organisms develop systems to exchange & transport materials- During the development of multicellular organism’s cells differentiate to perform different functions.

Tissue: Group of cells with

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