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374401043 the cell

374401043 the cell

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Anatomy and Physiology

THE CELL

A cell is the basic , living structure and functional unit of the body . Cells are composed of characteristic

parts, the work of which is coordinated in a way the enables each type of cell to fulfill a unique

biochemical or structural role. Cells perform myriad chemical reactions to create life processes. They do

so by compartmentalization , isolation of specific kinds chemical reactions within specialized structures

inside the cell. The isolated reaction are coordinated with one another to maintain life in a cell, tissue,

organ, system,and organism.

FUNCTIONS AT THE CELLULAR LEVEL

ORGANIZATION AND GENERAL FUNCTION

In general, the cell consist of internal structure called ORGANELLE suspended in a semifluid

CYTOPLASM and surrounded by CELL MEMBRANE . Each organelle and each enzyme in the

cytoplasm perform a specific function and the cell membrane defines the boundaries of a cell ad

regulates the movement of substances into and out of the cell .

The processes whereby food molecules and oxygen are used to capture energy in adenosine

triphosphate take place in cells .All cells need adenosine triphosphate to maintain themselves and to

carry out their roles in the overall functions of the body .

Nearly all chemical reactions that take place in the body are controlled by cellular enzymes .

Many cells of the body undergo Cell division as the body grows, and new individuals are produces from

the union of specialized cells called eggs and sperm ; thus, all body functions depend on processes that

occur at the cellular level.

STRUCTURE OF THE CELLS

The cell is composed of two basic parts:

A. THE CYTOPLASM

The substance surrounding the nucleus .

It contains many discreate structures.

a. Organelles

Enclosed by a membrane and contain enzymes that participate in cellular metabolic activity .

They are permanent component of cytoplasm.

b. Incusions

Generally temporary components of certain cells and usually are accumulation of pigment ,

lipid, protein or carbohydrate that may or may not be enclosed in a membrane. They do not

participate directly in cellular metabolism .

c. Other components

Cannot be classified as either organelle or inclusion and have different strutures and

functions. They are not enclosed by a membrane and they do not participate directly in cell

metabolism .

It also contains small particles suspended in a thick .fluid called CYTOSOL. It consist of dissolved

substances , enzymes, and several kinds of granule-most of which contain glycogen or fat. The cytosol

and dissolved subtances make up INTRACELLULAR FLUID.

a. ORGANELLES

These are the functional units of a cell .these are specialized structures that have caracteristics

shapes and that perform specific functions in cellular growth, maintenance , and reproduction .

Each type of organellehas its own characteristics set of enzymes that carry out specific reaction,

and each is a functional compartment where specific physiological processes.

a.1. MITOCHONDRIA

The mitochondria are frequently called the “powerhouse” of the cell , are the sites of the most of

the oxidative reactions that transform energy into a form usable by cells.

are major sites of the most of ADENOSINE TRIPHOSPHATE PRODUCTION within cells. ATP is

the major energy source for most endergonic chemical reactions within the cells, with lower

energy equipment.

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Structurally , a mitochondrion is composed of an outer smooth membrane and an inner folded

membrane , each of which has a typical membrane structure. CRISTAE, Folds in the inner

membrane , contain enzymes and other molecules that capture and stores energy in ATP . The

MATRIX of a mitochondrion contains enzymes that break down fatty acids and pyruvic acids so

enzymes in the cristae can capture energy from these important nutrient molecules.

a.2. GOLGI APPARATUS

The golgi apparatus is a collection of membrane-enclosed sacs, and is involved in final

processing as well as packaging of proteins prior to secretion of these proteins via exocytosis.

Processing can include removal of a segment of a protein , the addition of carbohydrate or lipid

to the protein, and the wrapping of the product in a membranous envelop. The products of this

processing are extruded from the cells when a vesicles of the golgi apparatus fuses with the

plasma membrane. The golgi apparatus also packages certain enzymes into organelles called

lysosomes.

a.3. LYSOSOMES

A Membrane bound organelle that contains many different hydrolytic enzymes that function as

intracellular digestive system. The enzymes are released into vacuoles or into dead or injured

cells .

a.4. ENDOPLASMIC RETICULUM

Is an extensive network of interconnected flattened vesicles and tubules bounded by

membranes of the same basic structure a the plasma membrane. Tubules of the ER serve as a

transport system for proteins and possibly for other large molecules synthesized by a cell.

a.4.1. ROUGH ENDOPLASMIC RETICULUM(Granular)

Coated with the granules called the ribosomes attached to the cytoplasmic side of

the membrane.These ribosomes serves as sites for protein synthesis.

a.4.2. SMOOTH ENDOPLASMIC RETICULUM (Agranular)

they do not contain granules but is involved in steroid synthesis and detoxification.

Lipid and cholesterol synthesis and some lipid breakdown occur.

a.5. RIBOSOMES

These are small bodies, lacking membranes, found on the surface of the rough endoplasmic

reticulum or free in the cytosol where they serve as sites of protein synthesis.

Some ribosomes, called free ribosomes, are unattached to any structure in the cytoplasm.

Primarily , free ribosomes synthesize proteins used inside the cell . Other ribosomes, called

Membrane –bound ribosomes, are attached to the nuclear membrane and rough endoplasmic

reticulum. These ribosomes synthesized proteins destined for insertion in the plasma membrane

or for export from cell.

a.6. PEROXISOMES

Are membrane-covered organelles. It contains OXIDATIVE enzymes that destroys certain

toxins. Some reaction release hydrogen peroxide , which is broken down to oxygen and water by

peroxisomes enzymes catalase.

b. INCLUSION

Accumulation of pigments, lipids, proteins, or carbohyrates that may not be enclosed in a

membrane. They do not participate directly In cellular metabolism.

c. OTHER COMPONENTS

c.1. CYTOSKELETON

Gives the cell rigidity and allows movement of whole cells and particles within the cells . It

consist of a complex network of microtubules and microfilaments, both which consist of proteins

devoid of any membrane covering.

The network appears to hold the nucleus in place in a cell and to provide binding sites to anchor

protein molecules , organelles , and other cellular particles once thought to be randomly

distributed in the cytosol.

c.1.1. MICROTUBULES

Hallow fibers of protein TUBULIN

Provide motility and internal support for cells.

c.1.2. MICROFILAMENTS

very thin, solid structure made mainly of the protein ACTIN

Account for motility and contractility of cells

c.2. CENTROSOMES

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Anatomy and Physiology THE CELL A cell is the basic , living structure and functional unit of the body . Cells are composed of characteristic parts, the work of which is coordinated in a way the enables each type of cell to fulfill a unique biochemical or structural role. Cells perform myriad chemical reactions to create life processes. They do so by compartmentalization , isolation of specific kinds chemical reactions within specialized structures inside the cell. The isolated reaction are coordinated with one another to maintain life in a cell, tissue, organ, system,and organism. FUNCTIONS AT THE CELLULAR LEVEL ORGANIZATION AND GENERAL FUNCTION In general, the cell consist of internal structure called ORGANELLE suspended in a semifluid CYTOPLASM and surrounded by CELL MEMBRANE . Each organelle and each enzyme in the cytoplasm perform a specific function and the cell membrane defines the boundaries of a cell ad regulates the movement of substances into and out of the cell . The processes whereby food molecules and oxygen are used to capture energy in adenosine triphosphate take place in cells .All cells need adenosine triphosphate to maintain themselves and to carry out their roles in the overall functions of the body . Nearly all chemical reactions that take place in the body are controlled by cellular enzymes . Many cells of the body undergo Cell division as the body grows, and new individuals are produces from the union of specialized cells called eggs and sperm ; thus, a ...
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