Cell Structure and Cell Organisation

Assalamualaikum.

CHAPTER 2 CELL STRUCTURE AND CELL ORGANISATION

 2.1 CELL STRUCTURE AND FUNCTIONS

Animal Cell

            

Plant cell

 

Density of Organelles in specific cells

Types of cells	Function	Organelles found abundantly in the specific cells
Sperm cells	Require energy to propel towards fallopian tube for fertilisation	Mitochondria
Muscles cells	Contract and relax to enable movement	Mitochondria
Cells in the meristems	Require energy for active cell division	Mitochondria
Mesophyll palisade cells	Absorb sunlight during photosynthesis	Chloroplast
Cells in salivary glands	Synthesise and secrete enzyme	RER Golgi apparatus
Intestinal epithelium	Secretes digestive enzymes	SER
Liver cells	Detoxification of drugs and poisons	SER
Goblet cells in the intestinal and respiratory tract	Secretes mucus	Golgi apparatus

2.2 CELL ORGANISATION

Living processes in unicellular organisms

-Unicellular organisms can feed,respire,excrete,move,respond to stimuli,reproduce and

  grow.

  Eg: Amoeba sp.-living in freshwater / soil water environment 

      

Respiration	Exchange of O₂ and CO₂ occurs through the Plasma membrane by diffusion
Responses to stimuli	-Sunlight/acidic solution cause Amoeba to retreat -Favourable stimuli -food causes it to move towards the stimuli
Growth	Increasing cytoplasm & lining of plasma membrane
Feeding	By Phagocytosis   Amoeba sp. Approaches the food Two pseudopodia extend out and enclose the food particles Food particles then packed in a food vacuole Food vacuole fuses with lysosome (contain lysozyme enzyme) Food is digested by lysozyme Nutrients then absorbed into the cytoplasm   When Amoeba moves away undigested food is left behind
Excretion	-Waste products (CO₂ and NH₃) eliminated through the plasma membrane by   diffusion. Osmoregulation -When contractile vacuole filled with water to a maximum size =>contract to expel water
Locomotion	By Cytoplasmic projection -Also known as ameboid movement -Extend its pseudopodia --Anchoring the tips on the ground --Flow of cytoplasm into the projected pseudopodia
Reproduction	Amoeba divides - nucleus divides - cytoplasm divides - 2 new cells after it grown                                                                  formed to certain size

Cell specialisation in multicellular organisms

-human life begin as a single cell known as zygote

-zygote undergo repeated division forming embryo

-embryo cells grow, change shape and differentiate to carry out specific functions.

  =>cells can perform their tasks more efficiently.

Cell organisation in multicellular organisms

                            Cell -> Tissue -> Organ -> System -> Organism

Cell organisation in animals                        

System

Integumentary

Lymphatic

Digestive

Circulatory

Respiratory

Reproductive

Endocrine

Nervous

Muscular

Excretory

Skeletal

Example:

Cell	Tissue	Organ	System	Organism
Epithelial RBC WBC Nerve	Epithelial Connective Nerve Muscle	Skin	Integumentary	Human

Cell organisation in plants

-2 types of tissue

a) Permanent tissue :

     i)  Epidermal tissue

     ii) Ground tissue : Parenchyma

                                Collenchyma

                                Sclerenchyma

     iii) Vascular tissue : Phloem

                                   Xylem

                                

Epidermal tissue	Ground tissue	Vascular tissue
-mostly coated with cuticle -functions a)prevent water loss    through evaporation b)prevent infection c)prevent mechanical    injury	Parenchyma tissue -thin walls  -large vacuole -functions a)storing starch & sugar b)provide support & shape     to plants Collenchyma tissue -uneven thick wall -functions a)support herbaceous plants,    young stems & petiols Sclerenchyma tissue -uniformly thickened wall by   Lignin / dead cell -functions a)support & give mechanical    strength to mature parts of    plants	Phloem -consists mainly of sieve tubes -sieve tubes form long   continuous tube-like   structure -functions a)Transport nutrients to all     parts of plants Xylem -cell wall thickened with   lignin -consists mainly of xylem  vessels joint together end to  end (rootsàleaves) -functions a)Transport water from roots    to other parts of plants b)Provide support &    mechanical strength

b)Meristematic tissue

    -consists of small cells with      

       -thin walls                                

       -no vacuoles                                   

       -large nuclei                         

       -dense cytoplasm

    -young & dividing actively

    -not undergone differentiation

    -located at tip of root & buds of shoots

Example:

Organ	System
Flower, Fruit, Leaf , Stem	Shoot
Root	Root

Regulating the internal environment

Internal environment of multicellular organisms

-consists of   a)Interstitial fluid – fill the spaces between cells

=>constantly bathes the cells

=> nutrients & waste products are exchanged between

      interstitial fluid & blood plasma (in the blood capillaries)

                   b)Blood plasma

The necessity for maintaining an optimal internal environment

-Physical & chemical factors within the internal environment must be maintained regardless

  of the condition outside the cell so that the cell can function optimally and effectively

-Homeostasis = maintenance of a relatively constant internal environment for the

  optimal functions of cells.

- Negative Feedaback Mechanism = Mechanism than governs homeostasis

 Blood sugar level is maintained by the negative feedback mechanism

 

Normal Body Temperature is maintained by the negative feedback mechanism      

credit to : Teacher Agnes Mojini