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.