BIOLOGY: CELL STRUCTURE

BIOLOGY: CELL STRUCTURE

Cell Structure And Functions Of Cell Components
The cell is the basic functional and structural unit of life. Human beings are multi-cellular animals. What this means is that we humans are made of many cells of cells as opposed to unicellular organisms which are composed of only one cell. The cells in a lot of multi-cellular animals and plants are specialized.

This means that each of them carries out a specific function and when all the cells combine together with their functions, they can share out the processes of life. Each cell is dependent on the other and all of them function collaboratively to support the diverse processes in an organism.

The tables below show examples of some specialized animal and plant cells, together with their functions and special features.

Table illustrating the different types of animal and plant cells with their specific features and functions
Type of animal cell Function Special features
1. Red blood cells To transport oxygen round the body It has large surface area, for oxygen to pass through. The red blood cell contains haemoglobin, which reacts with oxygen to form oxyhaemaglobin
2. Nerve cells Nerve cells transports nervous impulses to various parts of the body It has a long connections at each end and has the capacity to carry electrical signals
3. Female reproductive cell also known as the egg cell The egg cell's function is to combine with the male cell, and subsequently to make food available for the new cell that was formed The egg cell is large and contains a lot of cytoplasm
Male reproductive cell which is also known as the sperm cell. The sperm cell function is to travel up and meet with egg cell for a fusion to form a zygote. The sperm cell has an elongated tail for swimming as well as a head which enables it to get attached with the female egg cell for a fusion.

Type of plant cell Function Special features
1. Root hair cell The root hair cell absorbs water and minerals from the soil. It has a large surface area
2. Leaf cell The leaf cell absorbs sunlight for the process of photosynthesis It has large surface area and lots of chloroplasts
Plant and animal cells have quite a few differences and similarities. For instance, animal cells do not have a cell wall or chloroplasts but plant cells have them. Animal cells are round and irregular in shape whereas plant cells have fixed rectangular shapes.

Comparison chart between plant and animal cell
Animal cells and plant cells
• Animal cells are more often than not irregular in shape, and plant cells normally have a regular shape.

• Cells are made up of various parts which can be easily explained through the use of diagrams as illustrated below:

biology
Both the animal cells and plant cells contain:

• Cell membrane

• Cytoplasm

• Nucleus

Plant cells in addition to possessing these features also found in animal cell has:

• Chloroplasts

• Vacuole

• Cell wall

The table below summarizes the Differences and Similarities of plant and animal cells in terms of the features they contain.

Features              Animal Cell                                                                              Plant Cell
Cell wall               Absent                                                                               Present. It is formed from cellulose and is known as cellulose                                                                                                                                    cell wall
Shape         It has a round or irregular shape                                              It has a rectangular or fixed shape
Vacuole      It contains one or more small vacuoles                                  It has one central vacuole that occupies about 90% of cell                                                                                                                                        volume
Centrioles It is present in all animal cells                                                    It is only present in lower plant forms.
Chloroplast Animal cells don't have chloroplasts and chlorophyll          Plant cells have chloroplasts and chlorophyll because they are                                                                                                                                     autotrophs which manufacture their own food
Cytoplasm        Present                                                                                    Present
Endoplasmic Reticulum (Smooth and Rough) Present                              Present
Ribosomes       Present                                                                                    Present
Mitochondria    Present                                                                                    Present
Plastids               Absent                                                                                    Present
Golgi Apparatus      Present                                                                              Present
Plasma Membrane   They have only cell membrane                                    They have a cell wall and a cell membrane
Microtubules/ Microfilaments   Present                                                          Present
Flagella    Flagella may be found in some animal cells                                 Flagella may also be found in some plant cells
Lysosomes    Lysosomes occur in cytoplasm.                                               Lysosomes usually not present.
Nucleus           Present                                                                                        Present
Cilia                PreseIt                                                                                           It is very rare.

A Summary Table OF Cell Organelles and their Functions

Part Function Found in
Cell membrane The cell membrane is selectively permeable. What this means is that it allows the passage of some substances through it while inhibiting the passage of others. Oxygen, food molecules, and waste products all ought to pass through the cell membrane. It controls what substances can move into and outside of the cell Plant and animal cells
Cytoplasm This is a jelly-like substance, upon which chemical reactions takes place in the cell. In plant cells the cytoplasm is a thin lining, while in animal cells the majority of the cell is cytoplasm. Plant and animal cells
Nucleus This takes charge and controls what takes place in the cell. It carries genetic information Plant and animal cells
Chloroplast The chloroplast is the place where photosynthesis occurs. It contains a green pigment known as chlorophyll. Plant cells only
Vacuole This is made up of a liquid known as cell sap, which keeps the cell rigid. Plant cells only
Cell wall The cell wall is made of a tough material known as cellulose, which supports the cell Plant cells only
Here, what we are looking at is the eukaryotic cells of plants and animals. Eukaryotic cells are differentiated from the more primitive prokaryotic cells by the presence of:

• Cytoplasmic membranous organelles

• A nuclear membrane or true nucleus

• Chromosomal proteins.

Our primary discussion here is on eukaryotic organelles, their functions inside the cell and the way they differ between plant and animal cells.

1. The Nucleus:
The nucleus is a home for the majority of genetic material of a cell. The nucleus is the "brain" of the cell and controls all activity that takes place inside the cell with the help of DNA as a outline to direct the production of proteins in the cell.

2. The Ribosomes:
The ribosomes function is to synthesize protein for the entire nucleus. They transport together all the raw ingredients like the RNA which are the replicas of the original DNA and amino acids to manufacture proteins. The proteins manufactured are very vital to cell and the optimum function of the organism.

Think of proteins as machinery for cell functions much like electricity and plumbing are essential in a real city. For example, enzymes are a type of protein without which life could not exist. The big and small subunits of ribosomal RNA translate an mRNA strand into a polypeptide chain.

3. The Endoplasmic Reticulum:
There are two types of endoplasmic reticulum (ER). The first on is the smooth endoplasmic reticulum and the second rough endoplasmic reticulum. This broad network of endoplasmic reticulum comprises about one half of all membranous tissue of the cell.

It is the site for membrane and protein synthesis. The Endoplasmic Reticulum system is very much like a road system that leads to an industry. Goods are produced in the factory and are transported to where it is needed through the same transport system

The Rough Endoplasmic Reticulum is thus named because of the presence of ribosomes along its membrane which is the source of proteins. Smooth Endoplasmic Reticulum does not have ribosomes and is in charge of lipid synthesis and processes a multiplicity of metabolic processes like the detoxification of drug.

4. Cell Membrane and Cell Wall
The cell membranes are present in animal cells while cell walls are present in plant cells. Cell walls and cell membranes have related functions. Just akin to a city outer limit, cell membranes enclose the cell and have the capability to control what enters in and out of the cell and by so doing, it regulates internal balance.

These membranes as well protect the inner cell from exterior forces. Cell walls, just like our city analogy, are much stronger than cell membranes and their function is to protect the cells from exploding in exceptionally hypotonic or diluted solutions.

5. Cytoskeleton:
The cytoskeleton is composed of an internal framework, which makes available to each one of the cell its distinctive shape and high level of organization that it contains. It is very significant for the movement of the and also for mitotic cell division or mitosis.

6. Cytoplasm:
Cytoplasm is a semi-fluid or gelatinous substance located inside the cell. The cytoplasm covers moderates and protects the inner organelles.

It is the cell background or surface area and is available anywhere in the cell where there are no organelles present. It is therefore very similar to the lawns and parks of our city which are normally cited where there are no residential or commercial houses.

7. Golgi Apparatus:
Golgi apparatus functions as a post office which is used for the transportation of the manufactured food by the endoplasmic reticulum and ribosomes to the rest of cell.

8. Chloroplasts:
Chloroplasts are organelles that are visible in the plant cells alone. They contain pigment known as chlorophyll which traps the energy of the sun to manufacture food for the plant during the process of photosynthesis.

Just similar to solar energy plant they make use of sunlight to manufacture energy for the plant. Chloroplasts are the place where photosynthesis- occurs in plants.

Photosynthesis is the process in which the plant makes use of carbon dioxide, water and sunlight to manufacture energy in the form of glucose for the plant cell as well as heterotrophs-animals that depends on plant for their food production.

9. Mitochondria:
Mitochondrion is present in both plant and animal cells and is the site where cellular respiration occurs. Through cellular respiration which would be covered in detail when explaining the process of photosynthesis and Respiration, a substance known as ATP is formed this is used for energy by the cell.

10. Lysosomes:
The lysosomes are digestive sacs that possess the tendency to be broken down into macromolecules in the cell through the process of hydrolysis. The digestion is carried out through the lysosomal enzymes located in the lysosome.

Lysosome is responsible with the disposal of excessive or bulky macromolecules in the same way the waste disposal in a city does. Lysosomes help to keep unnecessary or bulky macromolecules from mounting up in the cell.

11. The Cell Vacuoles and Vesicles:
These are similar in nature and function as membrane sacs that perform a lot of functions as control units for whatever thing that is in surplus in a city. They can contain a lot of substances starting from complex organic molecules to simple surplus water.

Plant cells possess a central vacuole that is very essential in keeping up and sustaining the turgidity of plants.