Cell Structure

All cells have a similar structure.

The small structures found in cells are called organelles.

ORGANELLES
NUCLEUS
– It is the control center of the cell, it tells the cell what to do.
– It is found in both plant and animal cells.
– It contains the genetic information of the cell.
– Reproduction of DNA and RNA takes place in the nucleus.
– It controls the chemical activities that take place in the cell.

CELL MEMBRANE (also called the Plasma Membrane)
– It is made up of proteins and lipids
– It is a structure that surrounds the cell and controls the flow of material into and out of the cell.
– It helps regulate the flow of materials in and out of the cell. Smaller particles can pass through the membrane and larger particles can’t.
– It defines the size and shape of the cell and provides protection and strength to the cell.

CELL WALL (found in plants, bacteria and fungi)
– It is a supportive, protective structure that surrounds the cell membrane.
– Materials can easily pass through this wall.

CYTOPLASM
– It is a gel-like substance that fills the entire cell’s volume.
– All of the other organelles live in the cytoplasm.
– It is made up of 90% water, sugar, amino acids and salts.
– It provides a liquid environment for chemical reactions to take place.
– All of the cells chemical reactions take place in the cytoplasm.

ENDOPLASMIC RETICULUM
– It is the collection of membranes that form channels throughout the cytoplasm.
– It is a tiny network in the cytoplasm that carries materials around the cell, like a miniature highway system.
– The channels separate sections of the cell where specific chemical reactions take place.
– The surface of the channels provide space for enzymes to perform chemical reactions.
– The channels also help move chemicals to their destinations inside the cell.
– There are 2 types of endoplasmic reticulum:
– 1. ROUGH ENDOPLASMIC RETICULUM (It is lined with protein ribosomes on it’s surface. The ribosomes are where protein is synthesized).
– 2. SMOOTH ENDOPLASMIC RETICULUM (It has no ribosomes. It is where lipids are synthesized).

RIBOSOMES
– They are the smallest organelle in the cell.
– They are tiny granules that can exist as free floating organelles in the cytoplasm or on the surface of the rough endoplasmic reticulum.
– They are the site of protein synthesis.
– They are involved in building proteins from amino acids.
– They usually exist in two parts; they come together when it is time to work.
– They contain 3 main types of RNA.
– The RNA found in the ribosomes function in protein synthesis and is called rRNA (ribosomal RNA).

GOLGI BODIES or APPARATUS
– They are made up of stacks of flattened membranes that package chemicals for removal from the cell.
– They function in areas of the cell where the products of the endoplasmic reticulum, like proteins or lipids are stored and packages for transport to their final destination outside the cell.
– The proteins and lipids are enclosed in small membranes for travel.
– It is the site of protein modification into more complex molecules.

VACUOLES
– They are a bag-like structure in the cytoplasm.
– They store food in both plant and animal cells.
– They are usually large in plants and small in animals.
– They store water and other nutrients used by plant and animal cells.
– Different kinds of vacuoles have different functions, ex: some store sap (maple, pine trees) others store toxins.

Lysosomes
– They are single layered membrane-enclosed storage vesicles that contain digestive enzymes.
– It dissolves large food molecules and breaks up old and damaged cell structures into the organic molecules that they are made of. These molecules are then reused by the cell.

MITOCHONDRIA
– It is the power house of the cell, where aerobic respiration and energy production take place.
– It is often one of the largest organelles in the cytoplasm.
– It is found in both plant and animal cells.
– It contains DNA and ribosomes, it is semi-autonomous and it can replace itself.
– It is enclosed in a double membrane.
– The smooth outer membrane is highly permeable to small items but it blocks the passage of larger items.
– The inner membrane has many folds that have enzymes that help with cellular respiration.
– It is oval shaped and contains the enzymes to aid the cell in getting energy from food.
– It converts food to usable energy,
– The energy released from food is stored in a high energy molecule called ATP (adenosine triphosphate).
– ATP supplies the cell with chemical energy.

CYTOSKELETON
– It is the skeleton of the cell, it gives the cell its rigidity and support.
– It consist of hallow microtubules and solid microfilaments.
– MICROTUBULES
– They are the support structures of the cell; they support the shape of the cell, like a skeleton.
– They are small, thin support tubes that cross the inside of the cell membrane to membrane.
– They have many functions, including movement (cell mobility) and the separation of chromosomes during cell division.
– MICROFILAMENTS
– They are tiny threads of long protein fibers.
– They provide cellular support, when they combine with other proteins.
– They participate in muscle contractions.
– During cell division they form a ring that pinches the cell in 2.

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