Chapter 1 Basic Biology

·        Cell

Ø Cell - Smallest unit of life capable of all living functions

Ø Unicellular organism - Made up of only a single cell, eg. Amoeba, Paramecium

Ø Multicellular organism - Made up of many cells, eg. algae, plants, animals, etc.

·        Organelles visible under compound microscope

Ø Cell wall - Outermost structure present in plant, fungal, and some bacterial cells; it is absent from animal cells

Ø Plasma membrane or cell membrane - Covering of the cell, separating the contents of the cell from the external environment

·        Important functions of cell membrane:

1.      Regulates the entry and exit of substances in and out from the cell

2.      Performs certain physical activities such as diffusion and osmosis

Ø Cytoplasm - Fluid that fills the cell; contains all cell organelles. It is amorphous, translucent, colloidal fluid. Organic molecules and enzymes float in it. It helps in exchange of materials between the cell organelles.

Ø Nucleus - Controls all the cellular activities of the cell; acts like the brain of a cell

·        Important components of nucleus:

1.      Nuclear membrane

2.      Nucleoplasm, containing chromatin

3.      Nucleolus

Ø Vacuole - Found in both plant and animal cells. Provide turgidity and rigidity to plant cells and store the waste products of a cell

·        Organelles visible under electron microscope

Ø Endoplasmic reticulum – interconnected system of membrane lined channels that run throughout the cytoplasm and helps in the synthesis and packaging of proteins and lipids

·        Two types:

SER - Smooth endoplasmic reticulum

RER - Rough endoplasmic reticulum

Ø Ribosome - Site of protein synthesis. They may be found free in the cytoplasm or attached to the RER.

Ø Golgi apparatus - Also known as dictyosomes in plant cells. It helps in the storage, modification, and packaging of products in vesicles and is involved in the formation of lysosomes and peroxisomes

Ø Lysosome - Contains digestive enzymes which can destroy any foreign material; also known as the ‘suicidal bag’ of a cell

Ø Mitochondria - Also known as the ‘powerhouses of the cell’. Involved in cellular respiration and production of energy in the form of ATP (Adenosine triphosphate)

Ø Plastids - Present in plant cells

·        Two types:

1.      Chromoplasts (coloured plastids) - Include chloroplasts which are important for photosynthesis in plants

2.      Leucoplasts (white or colourless plastids) - Help in the storage of carbohydrates (starch), fats, and proteins

Differences between plant and animal cells

Animal cell		Plant cell
1.	Generally small in size	1.	Usually larger than animal cells
2.	Cell wall is absent	2.	Cell wall is present
3.	Plastids are absent	3.	Plastids are present
4.	Vacuoles are more in number and smaller in size	4.	A single large vacuole is present.
5.	Single, highly complex, and prominent Golgi apparatus is present	5.	Many simpler units of Golgi apparatus, called dictyosomes, are present