Biology Module 1 – Cells the basis of life Notes

Resource Description

Study Notes on Cells the basis of life

Inquiry question: What distinguishes one cell from another?

1. CELL

Cell Theory:

All cells are the basic theory of the structure and functional units of life formed by pre-existing cells by cell division.

1. All things are made of cells
2. The cell is the smallest unit of life
3. All new cells come from preexisting cells

Types of Cells

Eukaryotic cells – Size 10 – 100mm
➔ Are more complex and contain an array of membrane bound organelles
➔ Membrane bound nucleus
➔ Paired chromosomes
➔ Could be single celled or multi celled

Prokaryotic cells – 2.5mm
➔ Are more simple, and do not have
membrane bound organelles
➔ No nucleus
➔ Bacteria
➔ Only unicellular

Bacteria
➔ Exists only as unicellular organism
➔ Some photosynthesis or chemosynthesis; others absorb it from outside cell
➔ Contain a cell wall
➔ Bacteria and cyanobacteria e.g. E, coli, staphylococcus

Archaea
➔ Only exists as unicellular and reproduce by asexual reproduction
➔ Prokaryotic and have cell wall

Fungi
➔ Exists mostly as multicellular organisms and reproduce sexually or asexually
➔ Absorb food from their surrounding
➔ Eukaryotic and contains a cell wall

Plant
➔ Exists as multicellular organism and reproduces sexually or asexually
➔ Produce food by photosynthesis
➔ Eukaryotic and contains a cell wall
➔ E.g. flowering plants and ferns

Animal
➔ Exists as multicellular organisms and reproduce sexually
➔ Ingests food for nutrition
➔ Eukaryotic, no cell wall

The Structure of Membranes in Cells : The Fluid Mosaic Model
The cell membrane controls the exchange of material between the internal and external environments of the cells. The structure of the cell membrane allows the concentration of substances inside to remain fairly constant and different from the external environment. The fluid mosaic model describes the cell membrane as a double layer of lipids (a lipid bilayer) with the ability to flow and change shape, like a two dimensional fluid. Both proteins and phospholipids help to control the exchange of materials between external and internal environments.

The lock and key model:
For an enzyme to catalyse a reaction, the small substrate molecules must temporarily bind to the active sites. The active site is rigid and the small substrate molecule is reciprocally shaped and fits into the active site, like a lock fits a key