The Generic CellThe major parts of the cell include• Plasma membrane —the outer boundary of the cell• Nucleus—contains and protects DNA (genetic information• Cytoplasm—contains organelles, water, and dissolved substances

Plasma Membrane

Cytoplasm

Nucleus

GENERIC CELL (and its major parts)

Plasmamembrane

LysosomeGolgi apparatus

endoplasmicreticulum

Nucleus

Nucleolus

endoplasmicreticulum

Ribosomes

Mitochondrion

Cytoplasm

Peroxisome

Centriole

Cytoskeleton

Parts/Components of cell

Cell = Plasma Membrane + Cytoplasm + Nucleus

Cytosol + organelles

Cytoplasm: internal contents of cell

Cytoplasm = cytosol + organelles + inclusions

--Masses/aggregations of molecules not surrounded by membranes

-- specialized structures w/ specific functions-- Division of labor and compartmentalization

Where most cellular activity

occurs-- Liquidy/syrupy-like-- H2O + dissolved molecules & ions

Cytoplasm

The cytoplasm of the cell consists of all the material surrounded by the PM including:

• Organelles (including the nucleus): organelles are structures that perform specialized functions for the cell’s operation– some organelles are surrounded by a membrane the

processes they perform are isolated from the general cytoplasm and so organelles can perform incompatible processes

– other organelles are not surrounded by membranes

Organelles:

Non-membrane Bound• ribosomes• Centrioles/centrosomes• Cytoskeleton• proteosomes

Membrane Bound• nucleus• Endoplasmic

Reticulum• Golgi Apparatus• vessicles• lysosomes• peroxisomes• mitochondria

There are two categories of organelles:

Cytoskeleton:(microtubules & microfilaments)

Cytoskeleton

• Supports cell and gives it shape

• Creates cellular movement and shape change

• Moves or holds in place cellular contents (including chromosomes in mitosis)

Ribosomes:

• assembles/builds proteins (i.e., protein synthesis)• free in cytoplasm (free ribosomes)• bound (fixed) to endoplasmic reticulum (forming rough ER)

Ribosome(The non-purple parts are the protein being made from an RNA molecule).

Centrosome/Centrioles:

• Forms part of the cytoskeleton

• movement and organization of cytoskeleton during cell division

Organelles Surrounded by a lipid bilayer (membrane)

• Surrounded by a membrane– Phospholipid bilayer with proteins

• Membrane isolates contents and activity or organelle from cytoplasm

Includes:• Endoplasmic Reticulum• Golgi apparatus• Lysosomes• Mitochondria• Peroxisomes• Vessicles

Organelle membranes

• Membrane = phospholipid bilayer + embedded proteins

• Selectively permeable membrane

• Separates/isolates the contents or processes of the

organelle from the general cytoplasm.

• Allows interactions and regulation due to membrane

receptors, enzymes, anchors, and transporters

Endoplasmic Reticulum (ER):

• interconnected flattened sacs connected to nuclear envelope• new membrane is made by the ER• Rough ER (rER) has ribosomes on its surface

• Function: creation of proteins for release or use in membrane• Smooth ER (sER) has no ribosomes

•Function: makes lipids and carbs, detoxifies harmful chemicals

sERrER

vessicles• Sacs/bubble-like• Transport (and store) materials within cell and transport materials to and from the PM

Golgi Apparatus:

• A series of flattened sacs

• Modify, package, distribute proteins and lipids (for internal use or secretion)

•Create lysosomes

lysosomes• Created by golgi• Contain “digestive” enzymes• Destroy/breakdown molecules, foreign matter (pathogens), and

organelles• purposeful self-destruction of cells,

mitochondria• Produce ATP through breakdown of O2 and nutrients

Nutrients (e.g., glucose) + O2 CO2 + H20 + ATP + heat

• Two membranes (double membrane)• Own DNA• Semi-autonomous

nutrients

O2

ATP

CO2

Peroxisomes:

• contains enzymes that break down materials (lipids, amino acids and hydrogen peroxide [a metabolic waste]).

Mitochondrial Disorders

• Mitochondrial myopathies:– Onset between 4-15 years, progressive and leads to

death. No cure. drugs seem to be minimally effective.• cognitive impariment/dementia• Strokes/TIA’s• Deafness• Acidosis• Weaknes• Siezures

– Leber’s Hereditary Optic Neuropathy• Causes blindness

– MELAS

Lysosomal Storage Disorders

• A group of 40+ rare inhereted disorders• All based on missing or insufficient amounts of

an enzyme that should be part of a lysosome• Results in molecules accumulating/building up in

cell causing disfunction– Tay-Sachs disease– Gaucher’s Disease– Pompe disease/glycogen storage disorder– And many, many more

Lysosomal Storage Disorders• Tay-Sachs disease

– inability to break down a lipid; accumulation leads to paralysis, blindness, and deafness.

– Usually appear by age 6 mo death by age 4.• Gaucher’s Disease,

– inability to breakdown a lipid (glucocerebroside)– accumulates in white blood cells, spleen, liver, kidneys, lungs, brain

and bone marrow causing enlargment of spleen and liver, liver malfunction, bone lesions, swelling lymph noteds, anemia, joint swelling, increase succeptablity to infection. some forms can be treated by enzyme replacement.

• Pompe disease/glycogen storage disorder:– inability to breakdown glycogen in muscle cells. – causes muscle weaknes (myopathy); if present at birth and untreated

average age of death is 9 yo due to cardiorespirtory failure (also some nervous system problems)

Peroxisome Disorders

• Adrenoleukodystrophy (ALD)– Peroxisome lacks a membrane proteins that

transports a fatty acid (lipid) degrading enzyme into the peroxisome

– the lipid accumulates causes nervous system damage and adrenal gland malfunction

– early signs are lethargy, dizzyness, and weakness by age 4-10 is most common form

– leads to loss of motor function/paralysis, blindness, reflexes such as swallowing and then causes persistent vegatative space followed by death.

– no cure by diet can slow progession

The nucleus

Nucleus:

• Contains & Protects DNA

• Double membrane regulates movement of substances into and out of nucleus.

• Assembles Ribosomal parts

Endomembrane System• A series of membrane bound organelles that create and accept

vessicles.

• New membrane produced by the ER can make its way to other organelles and the PM

• Allows membrane composition to be changed, new membrane to be added, and old membrane to be replaced.

• Consists of:– ER– Golgi Apparatus– Lysosomes– Vessicles– PM

ENDOMEMBRANE SYSTEM

26

Protein Flow through the Golgi Apparatus

Membrane Flow

• The flow of membrane between components of the endomembrane system and the PM.

• How new membrane gets to PM

Endomembrane System and Membrane Flow:•Proteins and membranes move or “flow” from one organelle to another and too and/or from the PM.•This is called membrane flow. Any membrane that is involved with this process is part

of the endomembrane system.

Endomembrane System and Membrane Flow

Organelles the build/synthesize

• Free Ribosomes

• sER

• rER w/ fixed ribosomes

• mitochondria

• Golgi apparatus

Proteins for use in cytosol (cytoplasm)

• Proteins for use in a membrane or release from cell

• Creates peroxisomes

Lipids, e.g. phospholipids (and possibly carbs)

• Alters/modifies products of ER

• Makes lysosomes

ATP & CO2

Organelles the break things down

• lysosomes

• Peroxisomes

• Proteosomes

• mitochondria

• Waste, ingested macromolecules, & pathogens

• many proteins, polysaccharides, lipids, nucleic acids

• 30+ enzymes

• lipids & toxins/harmful substances

• Different enzymes than lysosomes

Proteins

Nutrients & O2

Organelles the support/connect and transport

• Vesicles

• Cytoskeleton

(microtubules, microfilaments, intermediate filaments)

•Cell shape•Cell movement•Attachement point for organelles•Transport routes

•Transport within cell. Transport to and from the PM•“Delivery packages”

Cell Differentiation• Our description of cells (above) was of a ‘generic’ cell.

• Most cells have most of the components discussed

• Specialized cells have a combination of cell features unique to their function

• The specialized (differentiated) cells of our body are different in their:1. Shape2. Organelle composition3. The DNA they use and proteins they make

Differentiated Cells:

• Note the shape differences between these cells:

• Long thin neurons

• Flat sheet of epithelial cells

• Tightly packed muscle cells