13.12.2014

    Animal Cell Parts and Functions

    All animals, including you and I, are made of the same basic building block called the animal cell. Animal cells are generally smaller than plant cells and lack a cell wall and chloroplasts; these are organelles pertinent to plant cells.

    In the title “Animal Cell Parts and Functions”, the word “Part” pertains to “Organelles”; these are specialized parts inside a living cell.

     

    Organelles in an animal cell are suspended in a fluid called the cytoplasm. A cell membrane encloses the cytoplasm and all contents of the animal cell.

    Diagram of an animal cell
    Diagram of an animal cell

    Animal Cell Parts and Functions | Summary Table

    Organelle Summary of Function
    Cell membrane
    • Protects the cell
    • Controls the entry and exit of molecules
    • Gives the cell a shape
    • Adheres to neighboring cells to form tissue
    • Helps the cell to communicate with the exterior

     Cytoplasm &

    Cytoskeleton

    		 
    • The cytoplasm holds water and nutrients
    • The cytoskeleton gives structural rigidity to cell
    • The cytoskeleton helps movement of organelles and chromosomes

    Nucleus 
    • Command center of the cell
    • Duplicate and store genetic information
    • Makes ribosomes
    • Sends commands to ribosomes for protein synthesis
    Ribosomes
    • Protein synthesis

    Endoplasmic

    Reticulum (ER)

    Summary of the function of the Smooth ER:

    • Lipid synthesis
    • Detoxification of alcohol and drugs

    Summary of the function of the Rough ER:

    • Protein synthesis
    Golgi apparatus
    • Processes and packages proteins and transports them to other parts of the cell or outside the cell.
    Mitochondria 
    • Converts food we eat into energy we use
    • Assist in cell growth, cell cycle and cellular death
    Lysosomes & Peroxisomes
    • Break down cellular waste into building blocks
    • Destroy foreign invaders
    • Peroxisomes break down hydrogen peroxide – harmful compound
    • Peroxisomes are involved in the synthesis of lipids and bile acids
    Vacuoles 
    • Store food, water and waste
    Cilia &Flagellum 
    • Lung cells use cilia to move mucus out of the lungs
    • A sperm cell uses its flagellum to swim through the female reproductive tract

    Animal Cell Parts and Functions | Details

    The Cell Membrane

    Think of the cell membrane like the border control of the cell, controlling what comes in and what goes out.

     

    The cell membrane also called the plasma membrane encloses the animal cell and its contents. It separates the inside of the cell from the outside. It is a selectively permeable membrane that monitors what enters and exits the cell.

     

    The cell membrane is mostly made up of special proteins (membrane proteins) and lipids (phospholipid).

     

    The phospholipids are arranged is a double layer – the Phospholipid Bilayer. The top and bottom of this double layer arrangement are hydrophilic (water-loving) while the inside of the double layer arrangement is hydrophobic (water-hating).

    Structure of the cell membrane
    Structure of the cell membrane

    Most cell membranes have special membrane proteins embedded in the phospholipid bilayer. These proteins help in the transportation of molecules across the cell membrane. The proteins have other functions such as giving a shape to the cell as well as adhesion to neighboring cells to form tissues.

    The Cytoplasm and the Cytoskeleton

    The animal cell is filled with a solution of water and nutrients to form a fluid called the Cytoplasm. Organelles of the animal cell are suspended in the cytoplasm. The cytoplasm contains the cytoskeleton; a network of protein filaments that reinforce the cell and hold all structures together.

     

    There are three main types of filaments namely; Microfilaments, Intermediate filaments and Microtubules.

     

    Microfilaments and intermediate filaments are thinner than microtubules. They stretch over the whole cytoplasm helping to maintain cellular shape. Microtubules are straight hollow filaments that act like support beams. They help guide the movement of organelles as well as chromosomes.

     

    The main microtubule organizing center is called the Centrosome. It is located close to the nucleus. Not only does it participate in the network of microtubules, it is involved in the cell cycle.

    The Nucleus

    The nucleus is the command center of a cell. This is where most of the cell’s DNA is stored. It is enclosed in a double membrane. The double membrane has pores which allow the movement of molecules between the nucleus (Nucleoplasm) and the cytoplasm.

     

    The Nucleolus is located inside the nucleus. The main function of the nucleolus is to make ribosomal RNA (rRNA). rRNA then combines with special proteins to form the basic units of ribosomes. Once these units are formed the nucleolus releases them out of the nuclear envelope where they will be fully assembled into ribosomes. The nucleus sends messages to the ribosomes through messenger RNA, (mRNA). mRNA carry out orders from the nucleus to the rest of the cell.


    Long strands of DNA in the nucleus combine with special protein to form long fibers called Chromatin. Chromatin is then used to make Chromosomes.

     

    The number of chromosomes present in a cell depends on the species of animal. The human sperm and egg cell both have 23 chromosomes. The number of chromosomes found in all of the other body cells is 46.


    Here is a quick guided tour of the animal cell.

    Ribosomes

    Ribosomes are tiny structures found floating around in the cytoplasm or attached to the ER. Ribosomes maybe small but are essential for the proper functioning of a cell. They are responsible for protein synthesis.

    The Endoplasmic Reticulum (ER)

    The ER is like a factory for the production of proteins and lipids. It also forms a network of tubes that carry substances around the cell. There are two types of ER; the rough ER and the smooth ER. They have slightly different structure and function.

     

    The rough ER is called “rough” because it is studded ribosomes while the smooth ER is called “smooth” because it lacks ribosomes.

     

    The Smooth ER contains enzymes that are involved in the creation of lipids. Other enzymes in the smooth ER help in the detoxification of drugs and alcohol.

     

    Ribosomes attached to the Rough ER are responsible for protein synthesis. These ribosomes assemble amino acids into polypeptides. When synthesis is complete the ER packages the polypeptides in special vesicles and sends them to the Golgi apparatus where they will be packaged and “shipped”.

    Smooth and Rough Endoplasmic Reticulum
    Illustration of Smooth and Rough ER

    The Golgi Apparatus

    The Golgi apparatus is the cell’s shipping department. It processes and packages proteins and sends them out to where they are needed.

     

    The Golgi apparatus is made up of stacks of membranous layers that are referred to as Golgi bodies. Golgi bodies create hormones from proteins. They can also combine proteins with carbohydrate to make other molecules such as snot (nasal mucus).

     

    The golgi apparatus packages its products into sacs called vessicles. These sacs have membranes made of phospholipid just like the cell membrane. These vessicles are then shipped to other parts of the cell or out of the cell.

    Golgi apparatus
    Golgi apparatus illustrating incoming and outgoing vesicles

    Mitochondria

    The mitochondrion (singular) is the power house of the cell. It is responsible for converting the food that you eat into energy that your body can use. The energy that our body uses is called Adenosine Triphosphate (ATP). ATP is a super energized molecule that gives you the energy you need to function properly.

     

    Mitochondria generate ATP from carbohydrates and fat and other fuels. They also assist in cell growth, cell cycle and cellular death.

     

    A mitochondrion is a smooth oblong organelles with an outer smooth membrane and an inner membrane. The inner membrane has numerous infoldings called Cristae.

     

    Some cells such as muscle cells need to power and hence have a lot more mitochondria than other cells.

    Diagram of a mitochondrion
    Diagram of a mitochondrion

    Lysosome & Peroxisome

    Lysosomes are digestive sacs that contain enzymes to break down cellular waste or debris from outside the cell into new building material.

     

    Lysosomes break down big macro molecules into smaller molecules which can be used to nourish the cell. They also break down damaged organelles and destroy foreign invaders such as bacteria.

     

    Peroxisomes are similar to Lysosomes in structure. They break down molecules by oxidative reaction and produces hydrogen peroxide – harmful compound. Peroxisomes break down the hydrogen peroxide to produce water. Or they may use the hydrogen peroxide to break down other molecules. Peroxisomes are also involved in the synthesis of lipid and bile acid (liver cells).

    Vacuole

    Vacuoles are storage sacs filled with fluid. They store food, water and waste products. The vacuoles in animal cells are generally smaller than that in plant cells. Animal cells can have multiple small vacuoles while plant cells usually have a single large vacuole.

    Cilia and Flagellum

    Some animal cells have cilia or a flagellum. Cilia (singular is cilium) are hairlike processes that extend from the cell’s surface. Flagellum is a wipe-like tail that protrudes from the cell. Both cilia and flagella are made of small protein fibers known as microtubules. Some cells have neither cilia nor a flagellum. A sperm cell has a flagellum. It uses its flagellum to propel itself through the female reproductive tract. Lung cells have cilia. They use cilia to push mucus up and out of the lungs.

     

    Here is a quick guided tour of the animal and plant cell.

    Do you have anything to share about ‘Animal Cell Parts and Functions’? Tell us in the comment section below.

    Tags: eukaryotic-cells

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