Lab no.1
The animal cell
The cell is the structural and functional unit of all living organisms . it was first described by the English scientist Robert Hooke around 1665.
The cell have variety of forms and function. In human body , there are two classes of cells ;
1-somatic cells : include all the type cells in human body except reproductive cells .
2-sex cells : two type of sex cells also called germ cells , they are :
A)sperms of a male .
b)oocytes of a female.
Cell is composed of several intracellular structure collectively known as organelles mean Little organs these organelles are
1-plasma membrane :
Is a selective permeable membrane composed of bilayer phospholipids with protein and steroids its function is isolation protection ,supporting and controls entrance : exit of materials.
2-mitochondria
Is double membrane with inner membrane folds (cristae) enclosing importing metabolic enzyme and produce 95% of the ATP required by the cell.
3-Endoplasmic Reticulum(RE):
It is a network of membrane channel extending throughout the cytoplasmic .there are two types of ER ,they are :
*Rough ER(RER);
Has ribosomes bound to membranes , modification packaging of newly synthezied proteins
*Smooth ER(SER) :which is lacks attached ribosomes , it s function is lipid and carbohydrates synthesis .
4- Nucleus :
Is larg part in cells ;it contained nucleotide ,enzyme and chromatin surround by double membrane (nuclear membrane ) ,it s function in control of metabolism , stprage and processing of geetic information and control of protein synthesis.
5- Golgi Apparatus :
Is stacks of flattened membrane containing chambers it s function is storage and packaging of secretory products and lysosomal enzymes.
6-lysosomes :
Is vesicle containing powerful degredative enzyme , it s function in intracellular removal of damaged organelles or of pathogens .
7-Centrosome :
Cytoplasm containing two centrioles at right angles ,each centriole is composed of microtubule triplats , it s function essential for movement of chromosome during cell division .
The Cell Cycle :
Although cells are highly adaptable , they can be danged by physical factors ,toxic chemicals , temperature change or other environmental stresses .THUS ; cell population must be maintained over time by "Cell Division
The life cycle of cell includes a relatively brief , period of mitosis alternating with an Interphase period of variable duration .
Interphase
Somatic cell spend majority of their functional lifes in a state known as interphase ,during interphase a cell perform all its normal function and if necessary it makes preparation for cell division , in all preparation to divide the interphase can be divide to G1,S and G2 phase .
G1phase
In this phase the cell manufactures enough mitochondria , endoplasmic reticulum , ribosomes , golgi membrane ,and centriole replication is is begins and continues until G2.
S phase
DNA synthesis or DNA replication occur during the S phase . the goal of this replication to copy the genetic information in the nucleus .
G2phase
During this phase protein synthesis and to the completion of centriole replication ,the cells then enters mitosis division.
Mitosis
It is a process that separates the duplicated chromosome of the original cell into two identical nuclei . there are four stages of mitosis they are :
Prophase ; Metaphase ;Anaphase ;and Telophase
Prophase
It begins when chromosomal coil become individual structures as result of DNA replication during S phase there are two copies of each chromosome , each copy called Chromatide ,it is connected at the centromere at least . the nucleoli and nuclear envelope is disappear .the centrioles move toward opposite poles of the nucleus , an array of microtubules called "Spinal fibers " extend between the centrioles pairs and the spinal fiber enter the nuclear region and the chromatids begine attaching to spinal fiber.
Metaphase
During metaphase ,chromatide move to a narrow central zone called "metaphase plate "
Anaphase:
It begine when each chromatid pairs separate . the two daughter chromosome are now pulled towards opposite ends of the cells . At end of anaphase , the daughter chromosomes arrive near the centrioles at opposite ends of the cells
Telophase :
During telophase , the nuclear membrane form , the nuclei enlarge, the chromosome gradually uncoil and nucleoli reappear .This stage mark the end of mitosis.
The shape of Animal cells :
1-Star – shaped ;such as multipolar nerve cell
2-Cubic – shaped ;such as simple cuboidal epithelial in the kidney tubules .
3-Oval – shaped ; such as red blood cell in the frog .
4 – Polygonal – shaped ; such as sequamous cell in simple sequamous epithelial in lung or inside well of blood vessels .