Anatomy 25 cell structure - cytoplasm

Means "cell forming material", it's all the stuff inside a cell that isn't a nucleus.

Made up of three things:

• Cytosol - the goo that everything else is in
• Organelles - tiny structures with specific functions
• Inclusions - temporary structures often storing food

Tiny structures in the cytoplasm that perform specific functions. Some organelles are:

• Mitochondria
• Ribosomes
• Endoplasmic reticulum
• Golgi apparatus
• Lysosomes
• Peroxisomes
• Cytoskeleton
• Centrioles

Function: Ribosomes build proteins.

Two kinds of Ribosomes: Free and Bound

Free float around in the cytoplasm picking up amino acids, making proteins, and releasing the proteins into the cytoplasm.

Bound are attached to the Endoplasmic Reticulum, picking up amino acids and building proteins, and releasing them into the endoplasmic reticulum.

Ribosomes are made from a Large Subunit and Small Subunit and when functioning includes a mRNa.

DNA sequence inside the nucleus partialy unwinds and a mRNA attaches to read the DNA "code".

The mRNA exits the nucleus and makes its way to a ribosome which attaches Large Subunit and Small Subunit to opposite sides of the mRNA and reads the code.

Transfer RNA ( tRNA ) brings an amino acid to the functional ribosome ( ribosome + mRNA ). The tRNA and mRNA match up and stay in place until another tRNA w/ amino acid comes along. Once another tRNA attaches the first tRNA transfers its amino acid to the second tRNA's amino acid and the bond via peptide bond. The first tRNA then detaches and floats off. This process continues until enough amino acids are built into a polypeptide ( amino acid chain) / protein. The protein is then released into cytoplasm or rough endoplasmic reticulum to do its thing.

Polyribosomes are groups of ribosomes stuck together reading the same mRNA. They work together as a sort of assembly line building the same proteing, together.

Any ribosome can make any kind of protein.

The mRNA is what determines which proteins the ribosomes will make. Any ribosome can be free or bound, the mRNA will determine if the ribosome is free or bound as well as what protein it will make.

Free ribosomes make proteins for cell metabolism.

Bound ribosomes make unit membrane proteins, acid hydrolases ( enzymes ) for lysozomes, and secretory proteins.