Topic 2 (CELLS) IB Biology SL

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Flip-Modus

2.1.1 Outline the Cell Theory

2.1.2 Discuss the evidence of the Cell Theory

Living things are made of cells
- observations by microscoptists of uni- and multicellular organisms, especially structure of tissue and organs
Cells are the smallest unit of life
- discovery of viruses, which can only exist with a host cell
- biochemical investigations of organelles, only functioning for a limited amount of time outside of the cell
Cells come from pre-existing cells
- Pasteurs Obseravtion
- Observations of the beahviour of cells at division

2.1.3 State the unicellular organisma carry out all functions of life

Unicellular organisms are the smallest organisms capable of human life

M ovement
R eprodcution
S ensitivity
G rowth
R espiration
E xcretion
N utrition

2.1.4 Compare the relative sizes of molecules, cell membrane thickness, viruses, bacteria, organelles and cells, using the appropiate SI unit

A molecule: 1nm
Cell membrane thickness: 7.5nm
Virus: 100nm (range: 20-200nm)
Bacteria: 1-5nm
Organelles: +10um
Eukaryotic Cells: +100um

2.1.6 Explain the importance of the surface area to volume ratio as a factor limiting cell size

The rate of metabolism of a cells is a function of its mass/volume
The rate of material exchange in and out of a cell is a functions of its surface area
As the cell grows, volume increases faster than surface area
If metabolic rate is greater than the rate of exchange of vital materials and waste, the cell will die
Cell must consequently divide in order to restore viable surface to volume ratio to survive
Cells and tissues specialized for gas or material exchange (ei.elveoli) will increase surface area to optimize the transfer of materials

2.1.7 State that multicellular organisms show emergent properties

Cells may group together to form tissues
Organs are then formed from the functional grouping of multiple tissues
Organs that interact may form organ systems capable of carrying out specific body functions
Organ systems carry out the life functions required by an organism

2.1.8 Explain that cells in multicellular organisms differentiate to carry out specialized fucntions by expressing some of their genes but not others

When a cell changes its structure in order to perform a specific function, it's called a differentiated cell
When differentiated cells perform specific functions they are termed specialized
All cells carry the same genetic information
Depending on the position of a cell in the body and the needs of the body, it becomes specialized in order to perform certain functions
This is done by switching on the relevant genes so that only certain proteins required dor the cell to function are produced
The other genes stay switched off

2.1.8 Explain that cells in multicellular organisms differentiate to carry out specialized fucntions by expressing some of their genes but not others

When a cell changes its structure in order to perform a specific function, it's called a differentiated cell
When differentiated cells perform specific functions they are termed specialized
All cells carry the same genetic information
Depending on the position of a cell in the body and the needs of the body, it becomes specialized in order to perform certain functions
This is done by switching on the relevant genes so that only certain proteins required dor the cell to function are produced
The other genes stay switched off