cytoplasm and cytosol

Figure 1. basic structure of cell and the difference between cytoplasm and cytosol

cytoplasm is a gel-like matrix of water, enzymes, nutrients, wastes, and gases and contains cell structures (organelles).

Cytosol is fluid around the organelles.

Most of the cell’s metabolic reactions occur in the cytoplasm.

Endoplasmic reticulum

network of interconnected parallel membranes (maze), that is continuous with the nuclear membrane;

Two types:

Rough Endoplasmic Reticulum (RER)

ER studded with ribosomes;

Function: protein synthesis and intracellular transportation of molecules

Smooth Endoplasmic Reticulum (SER)

lacks ribosomes;

Function: lipid & cholesterol synthesis and Stores calcium.

ribosomes

Every cell contains thousand of ribosome’s and many of them attached to the RER.

Each ribosome is non membranous structure, made of two pieces large unit and small unit and each subunit composed of rRNA.

Function: protein synthesis

Protein released from the ER are not mature, need further processing in Golgi complex before they are able to perform their function within or outside the cell.

Golgi apparatus

flattened membranous sacs  (cisternae).

arranged in stacks (“stack of pancakes”) associated with many vesicles (membrane bound sacs containing proteins);

Function: modification, packaging, and transport of proteins;

Encloses digestive enzymes into membranes to form lysosomes.

Lysosomes

spherical membranous sacs containing digestive enzymes;

“suicide sacs” which destroy anything the cell no longer wants or needs.

Autolysis is the process by which worn cell parts are digested by autophagy.

Peroxisomes

membranous sacs containing oxidase enzymes;

Function: detoxification of harmful or toxic substances (i.e. alcohol, formaldehyde, oxygen free radicals);

H2O2 (peroxide) —-> water

Mitochondria

kidney-shaped organelle whose inner membrane is folded into shelf-like partitions called cristae;

“Powerhouse” of the cell = site of cellular respiration where energy is released from glucose.

Nucleus

the central core, control center or “brain” of the cell.

the largest organelle of the cell;

filled with nucleoplasm;

Nuclear Membrane (or nuclear envelope) is a double membrane that separates the contents of the nucleus from the cytoplasm;

At various point, these two membranes fuse = nuclear pore.

The nuclear membrane is “selectively permeable”; pores serve as sites where mRNA can pass out of the nucleus during protein synthesis, and how ribosomes exit the nucleus.

Nucleoli

Nucleolus (s) = a spherical body within the nucleus;

composed of RNA and proteins;

Function: synthesis of ribosomes.

 Figure 2. Structures found in most human cells.

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