Biology 190 : Unit 3 : Cells : Organelles & their Interaction

Example of organelles surrounded by one membrane

ER (RER and SER), Golgi, Lysosome

What are the specific advantages of this compartmentalization in eukaryotes?

Increased surface area Increased concentration of reactants used in chemical reactions Separation of incompatible reactions / reaction environments Separation of products based on whether they are for internal and export use

Example of organelles surrounded by two membranes (two adjacent phospholipid bilayers)

Nucleus, Mitochondria

Mitochondrion

- Double membrane - cellular respiration : ATP synthesis - Smooth outer membrane - Inner membrane - Huge surface area thrown into long folds called cristae in order to fit inside of smaller outer membrane - site of mitochondrial e- transport chain (ETC)

Nucleus

- Double membrane (nuclear envelope) - continuous with ER - Stores DNA - Control of cell structure & function - Heredity

Free

- Floating ribosomes in cytoplasm, make proteins in cytoplasm to be used in cytoplasm - Translation of proteins used in cytoplasm, e.g. Hexokinase (1st enzyme in glycolysis - all cell types) Hemoglobin (carries O2 in RBC's)

Cytoskeleton

- Function : structural support (scaffolding) & cell movement - Chromosome separation - Mitosis - Intracellular transport of proteins

Intermediate Filament

- Intermediate fibers; generally not disassembled and reassembled - Protein = keratin - Function = cell shape; reinforcement of cell junctions, organelle placement; esp. Nucleus

What separates one organelle from another and from the surrounding cytosol (cytoplasm)?

- Membranes (in most cases) - Phospholipid bilayers with embedded proteins and cholesterol (no CHO)

Bound

- Ribosomes attached to RER, involved with translation of membrane-associated proteins - Proteins to be inserted into P-L bilayers of membranes, e.g. glucose transport protein insulin receptor proteins - Proteins for export from cell by exocytosis, e.g. trypsin for protein digestion in digestive system (cells in pancreas) collagen for ECM (fibroblasts) insulin to regulate blood glucose levels (β cell in pancreas) - Proteins for membrane-enclosed cellular organelles, e.g. hydrolytic enzymes in lysosomes

Lysosome

- Single membrane - Contains mixture of hydrolytic enzymes - ACID HYDROLASES - Intracellular digestion - "Cell Recycling Center" - unneeded molecules - damaged organelles internal pH is ~100x more acidic than cytoplasm

Golgi apparatus

- Single membrane - Finishes, sorts, packages/ships cell products - Composed of stack of membrane-bound sacs - Sacs coalesce from E.R. transport vesicles break up into internal organelles (lysosomes), vesicles for export (secretion vesicles)

Rough Endoplasmic Reticulum (RER)

- Single membrane - Ribosomes that attach to this part of ER membrane synthesize membrane-associated proteins - proteins for delivery to other membrane-bound organelles - proteins for release to outside of cells RER and SER are continuous with each other and with the nuclear membrane.

Nucleolus

- Site of rRNA-coding genes

Chromatin

- Stretched out form of chromosome / DNA active gene expression - Nuclear Pore - Protein & RNA traffic

What are organelles?

- Structures within a cell, each with characteristic morphology and specialized function ("division of labor" within the cell)

Microtubules

- Thickest fibers; hollow tubes; can be disassembled and reassembled - Protein = tubulin (globular protein) - Function = arrangement of organelles, intracellular transport (along with accessory protein, e.g. kinesin); cell motility (e.g. flagellum of sperm)

Microfilament

- Thinnest fibers; solid fibers; can be disassembled and reassembled - Protein = actin (globular protein) - Function = cell shape; whole cell movement (e.g. amoeboid movement)

How many membranes surround organelles?

1 , 2 , or none

How ribosome works with RER

1. A free-floating ribosome attaches to a free-floating mRNA and begins translation. 2. IF protein is to be enclosed in a membrane, this ribosome-mRNA complex attaches to RER so that protein (open interior space) of the ER as it is synthesized. 3. The protein may be modified by the addition of sugar chains, but then is released from the RER in a transport vesicle that pinches off of RER.

2 forms present in Ribosomes

Free and Bound

Types of protein fibers

Microfilament Intermediate Filament Microtubules

Example of organelles surrounded by no membranes

Ribosomes and Fibers of cytoskeleton

2 forms of Endoplasmic Reticulum (ER)

Rough & Smooth