Cell Structure

Cell or plasma membrane:
- It functions as a selective barrier which separates the cell’s contents from its surroundings.
- It controls the exchange of materials such as nutrients and waste products.
- The plasma membrane is a partially permeable membrane, allowing some substances to cross freely, but not others.

Cytoplasm:
- The cytoplasm is the fluid inside a cell.
- The cytoplasm allows for the movement of molecules and organelles within the cell.
- It provides a medium for chemical reactions to occur, enabling metabolism and energy production.
- The cytoplasm also supports cell structure and helps maintain the cell's shape.

Mitochondrion:
- Mitochondrion is crucial for cellular energy production through cellular respiration.
- Generates cellular energy in the form of ATP through cellular respiration, supporting energy-intensive processes.

Ribosomes:
- Ribosomes are made of RNA (ribonucleic acid) and proteins and are the site of protein synthesis.
- They read messenger RNA (mRNA), which carries genetic instructions from the DNA.
- When a ribosome reads the mRNA, it translates the sequence into a chain of amino acids, linking them together in the correct order to form a protein.

Rough endoplasmic reticulum (ER):
- As proteins are produced, they enter the lumen of the rough ER, where they undergo folding and post-translational modifications, such as glycosylation.
- Ensures that proteins are correctly formed and functional before being transported to their final destinations.

Smooth endoplasmic reticulum:
- Uses its membrane-bound structure to create and transport lipids, which are fats and oils, throughout the cell.
- It has enzymes that help synthesize these lipids from smaller molecules.
- When the cell needs to detoxify harmful substances, the SER modifies these toxins into less harmful forms, making it easier for the cell to handle them.

Chromatin:
- It helps package the DNA so that it fits inside the nucleus and keeps it organized.
- When a cell is not dividing, chromatin is loosely packed, which allows the DNA to be used for making proteins and other important functions.
- When a cell prepares to divide, chromatin condenses into tightly packed structures called chromosomes.

Golgi body:
- In its vesicles, lipids and proteins synthesized in the ER are chemically changed and prepared for secretion.
- Ensures that newly synthesized molecules are properly processed and directed to their appropriate locations.

Lysosomes:
- Contain digestive enzymes, which break down large molecules, old organelles, and waste materials, and recycles them.
- They fuse with other vesicles that contain these substrates, creating an acidic environment where the enzymes can effectively digest the contents.

Cytoskeleton:
- It helps maintain the cell's shape and organization, while also enabling movement and transport within the cell.
- During cell division (mitosis), it separates chromosomes, ensuring that each daughter cell receives the correct number.

Centrioles:
- Help organize the spindle fibers that separate chromosomes, ensuring that each daughter cell receives the correct genetic material.
- Centrioles contribute to proper mitosis.

Nucleus:
- It houses the cell's genetic material, DNA, which contains the instructions for controlling all cellular processes.
- Its membrane, known as the nuclear envelope, protects the DNA and allows the exchange of materials between the nucleus and the rest of the cell.

Nucleolus:
- Produces and assembles ribosomes, which are essential for protein synthesis.
- The nucleolus organizes ribosomal RNA (rRNA) and proteins to form ribosomal subunits, which are then transported to the cytoplasm where they combine to create functional ribosomes.