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                                  Cell Structure Of Animals

 

      

All living things are composed of cells.   

                             

                                                           

                                                                 

 

Cells are different in size and function.

 

The center is called the nucleus.

 

      

 The nucleus is surrounded by a fluid called the, cytoplasm.

The cell is completely covered by a membrane called the Cell Membrane.

The cytoplasm combined with the nucleus, is both referred to as the protoplasm.

                                           

The cytoplasm is the region outside of the nucleus.

It is where the nutrients are absorbed, transported and processed.

During this process waste product accumulates.

The cytoplasm is the working area of the cell and contains specialized structures called organelles.

Organelles are found in both plant and animal cells.

                                                 

                                               

The Cell Membrane is the edge of the living cell.

It is composed of a double layer of liquid fat molecules and embedded proteins; the cell membrane provides the cell with a connection to the external environment.

It holds the contents of the cell in place and regulates the movement of the molecules into and out of the cell.

The cell membrane also contains receptor sites, which serves as docks for the entry of molecules that affect cell activity. Nucleolus

                                                 

 

                                                                           

The nucleus is the control center.        

It contains the instructions for life encoded within a molecule called DNA (deoxyribonucleic acid).

DNA carries hereditary information in higher life forms; a membrane called the Nuclear Envelope encloses the nucleus.

Cells that have a true nuclear membrane are called Eukaryotic cells.

Plant and animal cells are eukaryotic cells.

Cells that lack a nuclear envelope are referred to as prokaryotic cells.

Bacteria and blue –green algae are prokaryotic cells.

Prokaryotic cells are the oldest known forms of life.

The hereditary material of these cells is not contained in a nucleus, but rather is spread throughout the cytoplasm.

The hereditary or genetic material in the nucleus is organized into the thread like structures called chromosomes.

Each chromosome contains a number of genes, which is a code for different characteristics.

Genes are units of instruction that determine the specific traits of an individual.

Some cell contains a nucleolus, a dark stained, spherical structure within the nucleus.

Although the entire function of the nucleus is not known, scientists believe that it is involved with the synthesis of proteins in the cytoplasm.

 

                                           

One of the largest organelles within the cytoplasm is the mitochondrion.

These organelles provide cells with energy.

It is often referred to the "power plant" of the cell, the mitochondria is the center of cell respiration.

Sugar molecules are combined with oxygen to form the products, carbon dioxide and water.

The formation of these products causes the release of energy.

However the energy is not made in the mitochondria.

Chemical bonds within the sugar molecules are broken down and chemical energy is converted into other forms of energy.

This energy enables muscle contraction, the synthesis of new molecules, and the transport of certain molecules within the cell.

                                          

 

Ribosomes are one of the smallest of a cells organelles, although tiny, ribsomes are the most numerous organelles within the cell.

 Ribosomes organize and build proteins for the body. Proteins are complex molecules that make up cell structure.

 Cell growth and reproduction require that proteins be made constantly.

The nucleus provides the information for the type of protein needed.

Component building blocks, called amino acids, are joined together by enzymes working with the ribosome.

                                     

 

The Endoplasmic Reticulum is a series of canals that carry materials throughout the cytoplasm.

It is composed of parallel membranes that may be rough or smooth.

They appear rough when they have many ribsomes attached to them.

Proteins made by the ribosome are often transported by the endoplasmic reticulum.

                                          

Protein molecules are packaged and stored inside the Golgi apparatus or “pancakes” filled with package proteins, which move toward the cell membrane.

The Golgi apparatus attaches itself to the cell membrane.

Small packets, called vesicles are released, this way cells release large molecules such as enzymes.

 

                                      

                                                                                                    

The Golgi apparatus forms lysosomes.

Lysosomes are sac like structures that break down large molecules.

Chemicals from the lysosomes can even digest the cell that “houses them”, which causes them to be referred to as “suicide sacs”.

They have the ability to break down cellular proteins.  This makes them an important part of the human body’s defense mechanism.

The leukocyte engulfs invading bacteria. Once inside the cytoplasm, the lysosomes destroy the bacterium and the white blood cells.

The single cell can be sacrificed to make sure that the harmful microbe does not spread and cause further damage and the injured and worn out cells are also destroyed.

 

  Special structures of plant cell

 

                         

 

All the structures discussed above are both found in plant and animal cells

Plant cells have some structures that are not found in animal cells, unlike animal cells, a large part of the cytoplasm of plant cells is composed of fluid-filled space.  These, fluid- filled space is called a vacuole.

The vacuole is filled with water, sugar, minerals, and proteins.  The outer cell membrane of a plant cell is surrounded by a cell wall.  Cell walls are non - living compared to the cell membrane.  The cell wall is made up of cellulose; they protect and support the plant cells.  The cell wall has, tiny pores that allow gases, water and some minerals to pass through.  Plant cells also contain other organelles not found in animal cells.  Plant cells can also do something animal cells can’t.  They can make their own food.  Animals must rely on plants or other animals that have eaten plants for food.  There are specialized organelles in plant cells called plastids, which are responsible for the production and storage of food.

 

 

                                                             

 

  Plastids are chemical factories and storehouses for food and color pigments. Chloroplasts are plastids that contain the green pigments Chlorophyll, which is used in photosynthesis.

Photosynthesis is the process by which plants combine carbon dioxide from the air with water from the roots and, in the presence of light, make sugar and release oxygen.

 

                                                            

                                                              Created by Salome Hart