Chapter 2: Cells-The building block of life

Structure of a cell:

Cell is a basic unit of life. It consists of a mass of living matter called Protoplasm.
Protoplasm is the living essence of a cell. It includes the cell surface membrane, the nucleus and the cytoplasm, where numerous biochemical reactions take place.
- Mainly has water; and some proportion of mineral salts and organic compounds.
Cell Surface membrane surrounds cytoplasm externally.
- Also called plasma membrane.
- It is partially permeable and allows some substance to pass through in and out of the cell.
Nucleus is responsible for cell division and and cell reproduction.
- Also needed for the continued life of the cell, as well as for the repair of worn-out parts.
- Cell without a nucleus, for example, the red blood cells, have a short life span and are unable to reproduce.
Cytoplasm is the part of protoplasm surrounding the nucleus.
- Usually forms the larger part of the cell and is the place where most of life processes occur.
Mitochondria are small elongated organelles with folded inner membranes.
- Aerobic respiration takes place here.
Cell Wall is non-living and fully permeable.
- It protects the cell from injury and gives the cell its shape.
- It is made up of cellulose.
Cell Vacuoles are small fluid-filled spaces bound by a membrane.
- In animal cells they store water and food substances.
Chloroplast are sites where plants make their own food, combining together CO2 and water, using energy from sunlight to make sugar (Photosynthesis).
Vacuoles are large vesicles that take up a large part of the interior of plant cells.

Difference in Plant and Animal Cell:

Animal Cell:
- Cell membrane
- Cytoplasm
- Nucleus
- Mitochondria
- Vacuole
Plant Cell:
- Cell membrane
- Cell Wall
- Mitochondria
- Chloroplast
- Large/ Permanent Vacuole
- Nucleus

Cell Specification:

CELL STRUCTURE:	ADAPTATION TO FUNCTION:
	ROOT HAIR CELL - Being long and narrow, roots surface area to volume ratio increases; which helps in efficient absorption of water and mineral salts from the soil.
	The RED BLOOD CELL - Contains a red pigment called haemoglobin, enabling the cell to transport oxygen from the lungs to all parts of the body. Its circular, biconcave shape increases surface area to volume ratio. As a result, oxygen can diffuse into and out of the whole cell at a faster rate.
	XYLEM VESSELS - Transports water and mineral salts from roots to the stem and leaves. Absence of cross walls and protoplasm enables water to move easily through the lumen (space inside). It also provides mechanical support to the plant.

Levels of Organization:

Tissue:

Is the group of similar cells working together to carry out a particular process of a movement.

Organ:

Is the group of tissues working together to carry out a specific function.

Organ System:

Is the group related organs working together to carry out functions in the body.

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