cellular and molecular physiology

8/13/2019 Cellular and Molecular Physiology

1/29


2/29

Water, other inorganic chemicals,biomoleculesuniversal components of cells

All cells have 2 major subdivisions:plasmamembrane, cytoplasm

Many biomolecules need to be flexible tofunction and to be regulated, but easilydisturbed by changes in environmentalfactorsneed for homeostasis

3 domains: Archaea, Bacteria (prokayotes),Eukaryotes


3/29
http://c/Users/owner/Documents/BIOLOGY%20LECTURES/Cell%20Parts%20&%20Functions.docx


4/29

Contains materials for genetic instructionsand inheritance

Genescodes for making RNAs and proteinsDifferent genes are expressed in different

tissues and organsProtein-coding genes make up only a small

percentage of the total DNA (1.5% inhumans); the rest had been called junk

Telomeres(stretches of repeated, noncodingDNA sequences) protect chromosome endsand their loss is associated with aging


5/29

Rough ER and its ribosomes synthesize

protein for secretion and membrane

construction

Smooth ER packages new proteins in

transport vesicles

Rough ER and smooth ER are connected

making one continuous organelleTransport vesicles carry their cargo to the

Golgi complex for further processing


6/29

Newly synthesized raw materials continueto travel via vesicles through the layers ofthe Golgi stack during which they are:

1. Processed into finished products2. Sorted and directed to their final

destinations: a. cells exterior, b. newplasma membrane, c. other organelles

Secretory vesicles are released byexocytosis


7/29

Secretory proteins contain a sorting signaland bind to the interior surface of the Golgimembrane that contains recognition markers

Coat proteins (coatomer) from cytosol bindwith specific protein on the outer surface ofthe Golgi sac and causes it to curve and budoff, exposing docking markers (v-SNAREs)

v-SNAREs bind with t-SNAREs of theplasma membrane; membranes fuse; contentis emptied to exterior of cell


8/29


9/29

Lysosomes:

1. Digest extracellular material brought into

the cell by phagocytosis

2. Remove aged or damaged organelles

3. Cause intentional self-destruction of

healthy cells as a normal part of

embryonic development (apoptosis orprogrammed cell death)


10/29

Proteasomes:1. Large, tunnel-like protein structures2. Many thousands per cell

3. Chop internal proteins (only those taggedwith a tiny protein called ubiquitin) intoreusable amino acidsa. Those that are no longer neededb. As emergency energy supplies inextreme starvationc. Misfolded proteins


11/29


12/29

Smaller than lysosomes

Contain powerful oxidative enzymes and

most of the cells catalase

Oxidative enzymes use oxygen to strip

hydrogen from certain organic molecules

detoxifies wastes produced within cell or

foreign toxic compounds that have enteredthe cell H2O2is produced

decomposed into H2O and O2by catalase


13/29

Cellular power plantsContain DNA (mtDNA) exclusively

inherited from the maternal side

Required for aerobic metabolism ineukaryotes

Densities vary among tissues and organtypes (1-10% of skeletal muscle volume;30-50% of heart)

Mitochondrial metabolism can createoxidative stress


14/29

Occurs when production of reactiveoxygen species (ROS) overwhelms thebodys antioxidant defenses

ROSsuperoxide anions, hydroxyl (-OH)radicals, peroxynitrite, hydrogen peroxide

Antioxidant systemssuperoxidedismutase, catalase, glutathione, vit C,derivatives of vit A and E, flavonoids, uricacid


15/29

Octagonal barrels 3x larger thanribosomes

Found in many but not all animal groups

Thousands in cells, but do not show upwith ordinary staining techniques

Proposed to act as cellular trucksdocking at nuclear pores to pick up cargo(may be mRNAs or ribosomal subunits)from the nucleus and deliver them to thecytoplasm


16/29


17/29

Semiliquid (gelatinous) portion of thecytoplasm that surrounds the organelles

55% of total cell volumeAssociated with:1. Enzymatic regulation of intermediary

metabolism (catabolism, anabolism,transformation of simple sugars, aminoacids, fatty acids)

2. Protein synthesis3. Storage of fat and glycogen4. Temporary storage of secretory, transport,

and endocytic vesicles


18/29

Cell bone and muscleComplex protein network; intracellular

scaffolding to

1. Support and organize cell componentsinto an appropriate arrangement

2. Control their movements Components:1. Microtubules2. Microfilaments3. Intermediate filaments


19/29

Largest element made up of tubulinVery slender, long, hollow, unbranched

tubes

Position many organellesMaintain distinct shape and size of cellsCoordinate complex cell movements:1. Transport of secretory vesicles2. Movement of cilia and flagella3. Distribution of chromosomes during cell

division


20/29

Kinesin

1

2

3

4


21/29

Dynein


22/29

Cells main microtubule organizing center

(MTOC)

Located near the nucleus

Consists of centrioles (pair, short,

cylindrical, at right angles to each other,

form the spindle apparatus)


23/29

Smallest elements

Functions:

1. Vital to cellular contractile systems

2. Act as mechanical stiffeners to specific

cellular projections (microvilli)


24/29

Tough, durable, highly stableRoles:1. Maintain structural integrity of a cell2. Resist mechanical stresses applied to a cell Only one class is found in a particular cell

type:1. Neurofilamentsin nerve cell axons (85% of

total proteins)

2. In skeletal muscle cells, holding actin-myosin units in proper alignment3. Keratinin skin cells (85% of total proteins)


25/29

1. Cell adhesion molecules (CAMs) in plasmamembranes

2. Extracellular matrix (ECM) secreted by thefibroblasts with 3 major types of fibers:

collagen(provides tensile strength), elastin(provides elasticity), fibronectin(promotescell adhesion and holds cells in place;reduced in cancerous tissue) Cells

are able to function normally and survive only whenassociated with their normal matrix components, except thecirculating blood cells.

3. Cell junctions


26/29

Desmosomesspot welds or adhering junctions;abundant is tissues that are subject toconsiderable stretching (skin, heart, uterus)

Tight junctionsimpermeable junctions; join

sheets of epithelial tissueGap junctionscommunicating junctions formed

by 2 small connecting tunnels (connexons) madeup of connexinproteins; permits small ions to pass

between cells to transmit electrical activitythroughout an entire muscle mass ,as well assmall signal molecules between cells


27/29


28/29


29/29