Before starting with the cell structure we need to understand the meaning of the word cell, it is simply defined as the basic functional and structural fundamental of living organism.
However, in every cell there are structures known as organelles each one of these organelle has a particular function, and they vary with different types of cells.
We will be studying about cells of two organisms, Plants and Animals.
Plant cell Animal cell
example: palisade cell example: Liver cell
- Cell membrane/plasma membrane: partially permeable layer that forms a boundary around the cytoplasm.
function:- 1)prevents the cell contents from escaping or leaving the cell.
2)Controls what substances enter and leave the cell. - Nucleus (plural = nuclei): Round or oval structure containing DNA in the form of chromosomes. It’s the largest organelle present in the cell and its situated in the cytoplasm.
function:- 1) controls cell division.
2) controls cell development.
3) controls cell activities. - Mitochondrion (plural = mitochondria):- organelle that produce energy to the cell by aerobic respiration also known as the power house of the cell.
- Chloroplast : An organelle that contain a green pigment called chlorophyll which trap light energy and convert them to chemical energy for photosynthesis.
- Sap Vacuole: It is a fluid filled space surrounded by a membrane called tonoplast. It is inside the cytoplasm.
function:- 1) Contains salts and sugars.
2) Helps keep the plant firm.
Difference between plant and animal cell:-
|
PLANT CELL |
ANIMAL CELL |
| Cell wall made up of cellulose is present. | Cell wall is absent |
| A large vacuole is present in the middle of the cell. | Vacuole is small or rarely present. |
| Cytoplasm is seen towards the sides of the cell. | Cytoplasm is equally distributed throughout the cell |
| Nucleus is seen towards the sides of the cell. | Nucleus is seen almost in the center of the cell. |
| centrioles absent. | centrioles present. |
| Chloroplast present. | Chloroplast absent. |
Cell specialization :-
Specialized cells are cells that are specialized (DUHHH! :P), and have specific structure, shape even type of organelle that it contain may differ, or even the cell membrane and its components. Almost all cells are specialized excluding the stem cells, these cells become specialized when required.
Name:- Palisade mesophyll
Adaptation:-
1> Has lots of chloroplasts to trap light energy for photosynthesis.
2> Cylindrical in shape to pack them self together tightly.
Location:- Below the upper epidermis of a leaf.
Function:- To make glucose by photosynthesis. It is the main cell where photosynthesis takes place.
Name:- Root hair cell.
Adaptation:-
1> Has along root hair to increase its surface area for absorption of water and minerals.
2> Has so many mitochondria to provide enough energy for active transport/ active uptake.
Location:- Close to the tip of the root.
Function:-
1> To absorb water and minerals from the soil.
2> keep the plant firm.
Name:- Guard cells
Adaptation:- Bean like structure cells that can change their shape.
Location:- On the lower surface of leaves.
Function:- To open and close the stomata o the leaf.
Name:- Red blood cell (RBC)
Adaptation:-
1>Biconcave disk-like structure/shape to increase it O2 capacity, and preventing it from rupturing due to difference in osmotic concentration of blood plasma.
2>contain a protein called Haemoglobin which bonds to oxygen.
3> Have elastic walls to squeeze them self through capillaries.
Location:- In the blood.
Function:-
1>Carry oxygen in the form of oxyhaemoglobin to respiring tissues.
2> carry CO2 away from the respiring tissues.
Name:- Ciliated cells
Adaptation:- Have tiny hairs called cilia, which move mucus.
Location:- In the trachea.
Function:- Waft mucus with bacteria and dust away from the lungs.
Name: Muscle cells
Adaptation:-
1> Cells merge together to form fibres that can contract.
2> Has a protein called myoglobin, myoglobin traps one molecule of oxygen and releases it to the respiring cells when the CO2 concentration is very high.
Function:- Cause movement.
Name :- White blood cells (WBC)
Location:- in blood.
Function:- to kill and engulf pathogens.
there are two types:-
1> LYMPHOCYTE:-
Adaptation:-
1> Spherical in shape.
2> Nucleus is large.
3> Releases antibodies to engulf pathogens.
2> PHAGOCYTE:-
Adaptation:-
1> Irregular shape.
2> Nucleus is lobbed.
3> engulf and digest pathogens by phagocytosis.
NOTE: the WBC are also present in the lymph and in some organs.
Name:- neurone
Adaptation:-
1> Has a long nerve fiber to reach other cells.
2> Nerve fibers have a covering made of myelin called myelin sheath. This prevent the leakage of the electrical impulses.
Location:- All parts of the body
Function:- carry nerve impulses around the body.
Name:- Xylem cells
Adaptation:- Long, thin cells arranged end to end to form vessels, the cells lack end walls and cell organelles such as cytoplasm and nucleus. The walls are lignified.
Location:- Roots, stem and leaves
Function:-
1>Transport water and mineral ions from roots to leaves, lignin provides strength for the stem and make it waterproof.
2>It supports the plant.
I hope the diagrams where clear enough, and I’ll be adding a diagram of Xylem cell as soon as I get time to sketch one 😛
now we jump to the last section of our topic… JUMPING =p
this is the last part of this chapter, where you have to know the difference between cell, tissue, organ and organ system.
Cell:- It is the basic functional and structural fundamental of living organism.
Tissue:- A group of cells having similar function and similar structure. Ex: palisade tissue, epidermal tissue etc.
Organ:- A group of tissues having similar functions. Ex: leaf, liver etc.
Organ system:- A group of different organs combine to form an organ system that have similar function. Ex: circulatory system, digestive system etc.
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