Animal Cell

 By Lasisi Halima Billy

 

All animal cells are multicellular. They are eukaryotic cells. Animal cells are surrounded by plasma membrane and it contains the nucleus and organelles that are membrane bound.

Animal cells are of various sizes and have irregular shapes. Most of the cells size range between 1 and 100 micrometers and are visible only with help of microscope. Trillions of cells are found in the human body. There are many different types of cells, approximately 210 distinct cell types in adult human body.

 

Animal Cell Definition 

 

Animal cells are eukarytoic. Animal cells are have outer boundary known as the plasma membrane. The nucleus and the organelles of the cell are bound by a membrane. The genetic material (DNA) in animal cells is within the nucleus that is bound by a double membrane. The cell organelles have a vast range of functions to perform like hormone and enzyme production to providing energy for the cells. 

The components of animal cells are centrioles, cilia and flagella, endoplasmic reticulum, golgi apparatus, lysosomes, microfilaments, microtubules, mitochondria, nucleus, peroxisomes, plasma membrane and ribosomes.

Parts of Animal Cell

Animal cell contains membrane bound nucleus, it also contains other membrane bound cellular organelles. These cellular organelles carry out specific functions that are necessary for the normal functioning of the cell. Animal cells lack cell wall, a large vacuole and plastids. Due to the lack of the cell wall, the shape and size of the animal cells are mostly irregular. The constituents of animal cells are structures like centrioles, cilia and flagella and lysosomes.

Parts of  the animal cell are as follows:

Cell membrane -  forms the outer covering of the cell, and is semi-permeable.

Cytoplasm - is a gel-like matrix where all the other cell organelles are suspended inside the cell.

Nucleus - contains the hereditary material DNA and directs the activities of the cell.

Centrioles -  organize the microtubules assembly during cell division.

Endoplasmic Reticulum - are a network of membranes composed of rough and smooth endoplasmic reticulum.

Golgi complex - is responsible for storing, packaging of cellular products.

Lysosomes - are enzyme sacs, that digest cellular wastes.

Microtubules - are hollow rods, function primarily as support and shape to the cell.

Mitochondria - is the site for cellular respiration and producers of energy.

Ribosomes - are made of RNA and proteins, and are sites for protein synthesis.

Nucleolus - is the structure within the nucleus and helps in synthesis of ribosomes.

Nucleopore - is the tiny hole in the nuclear membrane, allows the movement of nucleic acids and proteins in/out of the cell.

Animal Cell Structure 

Animal cells are eukaryotic cells, the nucleus and other organelles of the cell are bound by membrane. 

Cell membrane

• It is a semi-permeable barrier, allowing only a few molecules to move across it. 
• Electron microscopic studies of cell membrane shows the lipid bi-layer model of the plasma membrane, it also known as the fluid mosaic model. 
• The cell membrane is made up of phospholipids which has polar(hydrophillic) heads and non-polar (hydrophobic) tails. 

Cytoplasm

• The fluid matrix that fills the cell is the cytoplasm. 
• The cellular organelles are suspended in this matrix of the cytoplasm.
• This matrix maintains the pressure of the cell, ensures the cell doesn't shrink or burst.

Nucleus

• Nucleus is the house for most of the cells genetic material- the DNA and RNA. 
• The nucleus is surrounded by a porous membrane known as the nuclear membrane. 
• The RNA moves in/out of the nucleus through these pores. 
• Proteins needed by the nucleus enter through the nuclear pores. 
• The RNA helps in protein synthesis through transcription process. 
• The nucleus controls the activity of the cell and is known as the control center. 
• The nucleolus is the dark spot in the nucleus, and it is the location for ribosome formation. 

Ribosomes

• Ribosomes is the site for protein synthesis where the translation of the RNA takes place.
• As protein synthesis is very important to the cell, ribosomes are found in large number in all cells.
• Ribosomes are found freely suspended in the cytoplasm and also are attached to the endoplasmic reticulum. 

Endoplasmic reticulum

• ER is the transport system of the cell. It transports molecules that need certain changes and also molecules to their destination.
• ER is of two types, rough and smooth. 
• ER bound to the ribosomes appear rough and is the rough endoplasmic reticulum; while the smooth ER do not have the ribosomes. 

Lysosomes

• It is the digestive system of the cell.  
• They have digestive enzymes helps in breakdown the waste moelcules and also help in detoxification of the cell.
• If the lysosomes were not membrane bound the cell could not have used the destructive enzymes.

Centrosomes

• It is located near the nucleus of the cell and is known as the 'microtubule organizing center' of the cell.
• Microtubules are made in the centrosome. 
• During mitosis the centrosome aids in dividing of the cell and moving of the chromosome to the opposite sides of the cell.

Vacuoles 

• They are bound by single membrane and small organelles. 
• In many organisms vacuoles are storage organelles. 

Vesicles are smaller vacuoles which function for transport in/out of the cell.

Golgi bodies

• Golgi bodies are the packaging center of the cell. 
• The Golgi bodies modify the molecules from the rough ER by dividing them into smaller units with membrane known as vesicles.
• They are flattened stacks of membrane-bound sacs. 

Mitochondria

• Mitochondria is the main energy source of the cell. 
• They are called the power house of the cell because energy(ATP) is created here.
• Mitochondria consists of inner and outer membrane. 
• It is spherical or rod shaped organelle.
• It is an organelle which is independent as it has its own hereditary material. 

Peroxisomes

• Peroxisomes are single membrane bound organelle that contain oxidative enzymes that are digestive in function.
• They help in digesting long chains of fatty acids and amino acids and help in synthesis of cholesterol. 

Cytoskeleton

• It is the network of microtubules and microfilament fibres. 
• They give structural support and maintain the shape of the cell.

Cilia and Flagella

• Cilia and flagella are structurally identical structures. 
• They are different based on the function they perform and their length. 
• Cilia are short and are in large number per cell while flagella are longer and are fewer in number.
• They are organelles of movement.
• The flagellar motion is undulating and wave-like whereas the ciliary movement is power stroke and recovery stroke.

Function of Animal Cell

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All living organisms are made up of cells. Cells are differentiated into plant cells and animal cells. Structurally there are a few differences in plant and animal cells though their functionality is almost the same.

All the cells are enclosed in a protective membrane called the cell membrane however plant cells have an extra addition the cell wall. The cells have certain organelles that are membrane bound within them, these structures are called cellular organelles. These organelles are specified to perform certain activities that are important for the survival of the cell. All the cells function together in coordination with each other and help the organism to survive. The functions of animal cell is carried out by the different cell organelles. The organelles of the cell function as a unit and regulate the activities of the cell. The different cell organelles and their functions are as follows: 

Cell Nucleus - Cell nucleus is referred to as the control center of the cell. The genetic material of the organism is present in the cell. The replication of DNA, and synthesis of RNA occurs in the nucleus of the cell. It also regulates the activities of the other cellular organelles. 

Mitochondria - The mitochondria is referred to as the power house of the cell. Its main function if to produce energy for cell by the process of cellular respiration. The energy produced is ATP. 

Endoplasmic Reticulum - It is a network for transportation of certain substances in and out of the nucleus. 

Golgi Apparatus - It is involved with processing and packaging of the molecules that are synthesized by the cells. The crude proteins that are passed on by the ER to the apparatus are developed by the golgi apparatus into primary, secondary, and tertiary proteins. 

Ribosomes - The function of ribosomes is protein synthesis. 

Lysosomes - They are referred to as the suicide bags of the cell. They have digestive enzymes and are involved in clearing the in wanted waste materials from the cell. They also engulf damaged materials like the damaged cells,and invading microorganisms and digest food particles.

Vacuole - They are large storage organelles. They store excess food or water.

Functions of The Animal Cell

The animal cells perform variety of activities by the aid of the cellular organelles. These cells function as a unit and the cells together form tissues. A group go tissues with similar function form an organ and a group of organ of specific function to perform becomes and organ system. Thus, the microscopic cells form the basic unit for the activities and coordination and help survival of the organism.