Cells

What are cells?
Cells are the building block of life. Most animals and plants are made up of thousands of cells.
A cell is the smallest unit of life
There are two types of cells
-Plant Cell
-Animal Cell
Cells are alive. They do everything living things do to stay alive.
Cells have different parts to do all these functions.


Function of different parts of a cell

Protoplasm
A cell consist of a mass of living matter is called protoplasm
It includes the cell surface membrane, the nucleus and the cytoplasm.

Nucleus
The nucleus consist of a small spherical mass of denser protoplasm, the nucleoplasm, surrounded by a membrane called nucleus envelope.
It is embedded withing the cytoplasm and controls all cell activities.
Within the cells, there are a network of long thread-like structures called the chromatin, spgerical structures called the nicleoli and a nuclear envelope

The chromatin contain herditary materials.
The nucleolus is responsible for building up the proteins
The nuclear enveloe separates the nuclear content from the surrounding cytoplasm
The nucleus is responsible for cell production and is needed for the continued lief of the celll and the repair of worn-out parts in the cell.

Cytoplasm
The part of the protoplasm surrounding the nucleus is called the cytoplasm.
It forms the larger part of the cell and is the place where most life processes occur.

There are some important organelles embedded within the cytoplasm
-mitochondira
-chloroplast
-vacuole
-centriole
-ribosome

Mitochondria is small and sperical or rod-shaped.
It release energy from food subdtance during cell respiration

Chloroplast is the site where plants make food. It combine together carbon dioxide and watter and uses the light energy from the sun to make sugar(glucose)

Vacuole is a fluid-filled space enclosed by a membrane.
Animal cells have many small vacuoles but the are not permanent. Vacuoles contian water and food substances.
Plant cell has alarge central vacuole which contain cell sap which contains dissolved substances such a sugar and mineral salt.

Cell membrane surrounds the cytoplasm
It is a partically permeable membrane which controls substances entering or leaving the cell.

Cell wall is in the plant cell which encloses the whole cell.
It is made of cellulose and protects the cell from injury

Ribosome is the smallest organelles in the protoplasm.
It produces protein from a set of genetic instructions
It floats freely in the cytoplasm

Tissue.
Many cells make up a tissue.
Mant tissues working together will make an organ.
Many organ working together will form an organ system.
Many organ syste mwill form an organism


Tissue is a group of cells which has a commob origin and a simlar structure which enables them to perform a particular function.

Tissues of plant cell

Epidermal tissue protects the underlying cells of a leaf by preventing water los and acts as a barrier to fungi and other invaders.

Xylem Tissue transport water and dissolved mineral salts to the leaf.

Phloem tissue transpors the manufactured food away from the leaf to other part of the plant.

Photosynthetic Tissue carries out photosynthesis.

Tissues of animal cell

Epithelial tissue is a sheet of cells which covers the internal and external surface of an organ.
Functions include secretion, absorbtion, protection, trancellular transport, sense of touch.

Muscle tissue is divided into 3 main groups.
Smooth muscle tissue controls slow, involuntary movement
Skeletal muscle tissue bring about the coordinated movement of the limbs, trunk, jaws, eyeballs, etc.
Cardiac muscle tissue contract the atria and ventricles of the heart.

Connective tissue is divided into 4 main group

Dense connective tissue forms ligaments and tendons. It is densely packed amd have great tensile strength
Loose connective tissue holds organs in place.
Reticular connective tissue form a soft skeleton to support the lymphoid organs
Adipose tissue is used for cushioning, thermal insulation and energy storage.

Nerve tissue make up the nervous system that carry information within the body.

Gandular tissue forms gland that produces substance to secrete hormones or sweat.