Download SOME SUMMARY INFORMATION ON ORGANELLES Plasma (cell

2014
SOME SUMMARY INFORMATION ON ORGANELLES
Plasma (cell membrane)
Structure
Fluid-mosaic bilayer of phospholipids, proteins, cholesterol, glycolipids
Functions
Semipermeable – regulates solute traffic into/out of cell
Proteins – form channels, act as transporters, form receptors, act as
enzymes, form cell-cell recognition sites
Cytosol/cytoplasm
Structure
Water, solutes, suspended particles, inclusions
Plasmasol – more liquid phase
Plasmagel – more gel-like phase
Functions
Site of many chemical (metabolic) reactions
Cell shape, cell movement
Nucleus (“brain of cell”)
Structure
Double membrane (nuclear envelope) with nuclear pores
Contains DNA, RNA and proteins
Functions
Segregates genetic material (DNA) from rest of cell
DNA:
Genes = hereditary factors = instructions for making proteins
Uncoiled DNA = chromatin
Coiled DNA forms chromosomes for cell division (mitosis, meiosis)
Nucleolus
Structure
Found within nucleus
No separate membrane
Contains DNA, RNA and proteins
Functions
Ribosome subunits produced here
Ribosome
Structure
rRNA + proteins
Two subunits make up a functional ribosome
Produced in nucleolus
Assembled in cytoplasm
Function
Site of protein synthesis (translation)
2014
Ribosomes may be:
a. “Free ribosomes” – float free in cytoplasm
Produce proteins for use within cell cytoplasm
(e.g. enzymes of glycolysis)
b. Attached to Rough Endoplasmic Reticulum
Produce proteins for
Export from cell
Inclusion in cell membranes
Inclusion in lysosomes
Endoplasmic Reticulum (ER)
Structure
Membrane system runs throughout cell
Continuous with nuclear envelope
Functions
a. Rough ER (RER)
Has attached ribosomes (see above)
New proteins move to Smooth ER, Golgi for modification
b. Smooth ER (SER)
New proteins enclosed in transport vesicles move to Golgi
Produces lipids (e.g. steroids)
Detoxifies poisons (e.g. alcohol)
Storage area (e.g. stores calcium ions, especially in skeletal muscle
cells)
Golgi apparatus (body)
Structure
Stacked hollow membranous discs (cisternae)
Functions
Acts like the Post Office:
Sorts, packages, modifies proteins for delivery to their sites of action
Releases secretory vesicles
Vesicles
Endocytosis = entrance of substances into cell (e.g. phagocytosis, pinocytosis)
Exocytosis = release of substances from cell (e.g. neurotransmitters)
Lysosomes
Structure
Membrane-bound sacs containing digestive (hydrolytic) enzymes
Functions
a. In conjunction with phagocytosis:
Destroys engulfed particles (e.g. bacteria)
b. Autophagy (“self eating”)
Breaks down worn out cell components for recycling
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Mitochondrion (plural = mitochondria)
“The powerhouse of the cell”
Produces lots of ATP when oxygen is available
(Lots more on these later in the term)
Cytoskeleton
Structure
Various types of proteins
Overall functions
Promote cell shape, structural organization, movement
Microtubules
Structure
Tubulin (a protein)
e.g. in cilia, flagella, centrioles
Function
Physical support, maintain shape of cell
Movement of organelles, mucus or entire cell
Kinesins and dyneins are motor proteins involved with
microtubule movements
Microfilaments (or Actin filaments)
Structure
Actin (a protein)
Function
Move pseudopods during phagocytosis
With myosin, involved in muscle contraction
Mechanical support for microvilli
Intermediate filaments
Structure
Composed of several different proteins
Thicker than microfilaments, thinner than microtubules
Function
Anchor organelles
Resist mechanical stresses on cells