Anatomy unit 1

 Part 4

                          CELL

Cell is the smallest functional unit of the body.

Cell are two types_______

Eukaryotic :- It contains nucleus.

Prokaryotic :- It do not contain nucleus.

Group of cell makes tissues; group of tissues make organs; group of organ make organ systems.

Structure and function of cell

Human body develop in a single unit called zygote, which forms by the fusion of female ovum and male sperm.

Ovum + sperm = zygote

Cell multiply and forms the fetus.

Cell is too small to be not seen with naked eyes.

Cell contain of plasma membrane, inside which their are numbers of organelles, floating in watery fluids are called cytosol or cytoplasm.

Organelles are small structure with highly specialised functions.

Cell contains

1. Plasma membrane

The cell membrane is protective sheath envelope the cell body. It separates the fluid outside the cell called extra cellular and the fluid inside the cell called intracellular fluids.

It consists of two layers of protein and phospholipids, some protein molecules embadded in them.

Function

It provides protection.

It is selective permeable

It absorbs nutrients.

It excreted wast materials.

Exchange of gases

2. Cytoplasm

It is the fluid present inside the cell. It contains a clear liquid called cytosol, which contains various substance such as protein, carbohydrates, lipids and electrolytes.

3. Nucleus

* The cells with nucleus are called eukaryotes and those cells without nucleus are called prokaryotes.

* Except mature Erythrocytes (RBC) , every cell in the body has a nucleus but Skeleton muscles have several nucleus.

* It consists of two membranes outer and inner.

Nucleus consists of four components___

# Nuclear membrane or nuclear envelope

# Nucleoplasm

# Nucleolus

# Chromatin

4. Mitochondria

It is spherical shaped organelles situated in the cytoplasm. They are called the" power house" of the cell because energy ( ATP adenosine triphosphate) is created here. It is main energy source of the cell consist of inner and outer membrane.

5. Ribosomes

Ribosomes is found in all cell of prokaryotic and eukaryotic. They are not membrane bounded.  It is tiny granules composed of r-RNA and r- Protein.

Function

The main function of ribosome is protein synthesis with the help of ribosomal RNA (r-RNA) , messenger RNA (m- RNA) and transfer RNA (t-RNA)

6. Endoplasmic reticulum

It is  present in almost all eukaryotic cells. It made up of protein and lipids. It is absent in RBC or spermatozoa.

It is of two types_____

Smooth endoplasmic reticulum

* It is an arrangement of tubules and vesicles.

* The size and structure of the SER varies between the cells.

* There are no ribosomes attached to the membrane surface, giving it a smooth appearance.

Function

* It is responsible for synthesis of essential lipids such as phospholipids and cholesterol.

* It is also responsible for production and secretion of steroids of hormones,sex hormones.

* It stores and release calcium ions. These are quite important for the nervous system and muscular system.

Rough endoplasmic reticulum

Ribosomes are present in outer surface of the endoplasmic reticulum, giving it a rough appearance.

It is also called granular endoplasmic reticulum.

Function

It provides site for protein synthesis due to presence of ribosomes.

7. Golgi apparatus

* It is also known as Golgi body, Golgi complex,Golgi .

* It is made up of protein, lipids and several stack of parallel, flattened sac called cisternae. Found in cytoplasm of most eukaryotic cells and absent in prokaryotic, RBCs and sperm cells.

* It has the two poles are cis and trans face responsible for receiving and shipping departments.

* An outer ends of golgi complex, newly modified protein arrives at the trans face of golgi network where it is send off to different parts of the cell via transport vesicles.

Function

It is responsible for______

# Transportation

# Modification

# Packaging

8. Lysosomes

* Lysosome is membrane bound organelle.

* It is spherical sac like structure.

* It is filled with digestive enzymes ( hydrolytic enzymes).

* Enzyme is made up of rough endoplasmic reticulum and Golgi apparatus.

* It helps to clean up digestive foreign material ( bacteria or virus, food,etc).

* It is also known as sucidal bag of the body or recycling machine.

9. Microfilament

* It is thinest form of cytoskeleton.

* It has thread like structure made up of actin protein.

* It helps in muscles contraction.

* It provides structural support, maintain the characteristic shape of the cell.

10. Microtubules

* It is thickest form of cytoskeleton.

* It has tube like hollow structure made up of tubulin protein.

* It helps in movement of material within the cell.

* Microtubules form spindle fibres.

* They form centriole, cillia and flagella.

* It gives shape and support to cell.

 Intermediate filaments

* They have great tensile strength.

* It is made up of kerotin protein.

* It is smaller than microtubules but larger than microfilament.

* It provides mechanical support for the plasma membrane where it comes in contact with other cells or with the extra cellular matrix.

Note:- microtubules, microfilament and intermediate filaments commonly called  cytoskeleton.