CH3 CELL PT 2 - Organelles: Nucleus and Protein Synthesis Pathway

Key vocabulary terms related to the nucleus and protein synthesis pathway, including organelle types, structures, and the flow of protein production from DNA to secretion.

Inclusion

A clump of material in the cell that is not soluble in the cytosol and often serves as storage (e.g., fat, glycogen, or pigment).

Cytosol

The fluid portion of the cytoplasm in which organelles are suspended.

Membranous organelle

An organelle surrounded by a phospholipid bilayer (membrane).

Nonmembranous organelle

An organelle that lacks a surrounding phospholipid bilayer and is in contact with the cytosol.

Nucleus

A large membranous organelle that houses DNA and controls cellular activities.

Nuclear envelope

The double phospholipid bilayer surrounding the nucleus (outer membrane continuous with the rough ER).

Nuclear pores

Pores in the nuclear envelope that allow passage of molecules such as RNA and ribosomal subunits between the nucleus and cytoplasm.

Chromatin

DNA in the nucleus when the cell is not dividing; DNA wrapped around histones, forming a structure that can condense later.

Chromosome

Condensed form of chromatin that becomes visible during cell division.

Nucleolus

A region inside the nucleus where ribosomal subunits are assembled from rRNA and proteins.

Ribosome

A molecular machine that synthesizes proteins; can be free in the cytosol or bound to the endoplasmic reticulum.

Free ribosome

Ribosomes suspended in the cytosol that synthesize proteins for use within the cell.

Rough endoplasmic reticulum (RER)

ER with ribosomes on its surface; site of synthesis for proteins destined for export or membranes.

Endoplasmic reticulum (ER)

A network of membranous channels; includes rough ER and smooth ER; continuous with the nuclear envelope.

Messenger RNA (mRNA)

A copy of a DNA segment that exits the nucleus to guide protein synthesis at ribosomes.

DNA

Genetic material that codes for proteins and is housed in the nucleus.

Histones

Proteins around which DNA winds to form chromatin; help package DNA into the nucleus.

Primary structure

The linear sequence of amino acids in a protein.

Secondary structure

Local folded structures of a protein (e.g., alpha helices and beta sheets) formed by hydrogen bonds.

Tertiary structure

The overall three-dimensional folding of a single polypeptide chain.

Amino acids

20 different building blocks of proteins; linked together to form proteins.

Dehydration synthesis

Chemical reaction that links amino acids by forming peptide bonds, creating a protein’s primary structure.

Golgi apparatus

Organelle that modifies, sorts, and packages proteins for secretion or delivery to membranes; forms secretory vesicles.

Transport vesicle

Vesicle formed from the ER or Golgi that transports proteins to the next organelle.

Secretory vesicle

Vesicle carrying proteins to the plasma membrane for export out of the cell.

Lysosome

Organelle containing digestive enzymes; digests proteins, fats, and carbohydrates; formed from the Golgi and remains inside the cell.

Membrane flow

Dynamic movement of phospholipid bilayer membranes between ER, Golgi, and plasma membrane, aiding protein transport and membrane remodeling.

Protein synthesis

The process of building proteins from amino acids according to mRNA instructions, occurring at free ribosomes or on the rough ER and often ending with export from the cell.

Ribosomal subunits

Two subunits (large and small) of ribosomes; assembled in the nucleolus and composed of RNA and proteins.

Exocytosis

Process by which a secretory vesicle fuses with the plasma membrane to release its contents outside the cell.