Pengantar Biologi Sel

8/12/2019 Pengantar Biologi Sel

1/81

Cell Structure and Function


2/81

Cell Size


3/81


4/81

4

Cell Structure Eukaryotic Cells


5/81

5

Eukaryotic Cells


6/81

6

Eukaryotic Cells


7/81


8/81


9/81


10/81

Lipids

Areas of the molecule enriched for "C" and "H" are hydrophobic.Fatty acids tails are composed of carbon and hydrogen and are

hydrophobic.

Phospholipids are amphipathic, and have hydrophilic andhydrophobic character in the same molecule. Interactions with watercause the phospholipids to form a bilayer, with hydrophobic fattyacid tails inside the bilayer and hydrophilic groups exposed to water.

This basic structure makes the membrane a barrier to hydrophilicmolecules. The interior of the membrane is fluid, with a viscosityabout equal to olive oil. Cholesterol in membranes alters fluidity.


11/81

Proteins

Proteins of membranes aredivided into two generalclasses: Integral membrane proteins Peripheral membrane

proteins


12/81

Integral membrane proteins

Membrane ion channels, enzyme linked membrane receptors,

and G-protein linked receptorsare integral membrane proteins that bindtheir ligand (signal) and then cause

second messengers to be produced insidethe cell.


13/81

Movement Across the Plasma Membrane

A few molecules move freely Water, Carbon dioxide, Ammonia, Oxygen

Carrier proteins transport some molecules Proteins embedded in lipid bilayer Fluid mosaic model describes fluid nature of

a lipid bilayer with proteins


14/81


15/81

Membrane Proteins

1. Channels or transporters Move molecules in one direction

2. Receptors Recognize certain chemicals


16/81

Membrane Proteins

3. Glycoproteins Identify cell type

4. Enzymes Catalyze production of substances


17/81

Membrane receptors generally function by binding the signal, or ligand andcausing the production of a second signal (second messenger) that causes acellular response. The diagram shows how the receptor for insulin functions.


18/81

Activation of protein kinases


19/81

Cytoplasm Viscous fluid containing organelles components of cytoplasm

Interconnected filaments & fibers Fluid = cytosol Organelles (not nucleus)

storage substances


20/81


21/81

21

Endomembrane System

Endomembrane system -a series of membranes throughout thecytoplasm-divides cell into compartments wheredifferent cellular functions occur

1. endoplasmic reticulum2. Golgi apparatus3. lysosomes


22/81

Endoplasmic Reticulum

Helps move substances within cells

Network of interconnected membranes

Two types

Rough endoplasmic reticulum Smooth endoplasmic reticulum


23/81

Rough Endoplasmic Reticulum

Ribosomes attached to surface Manufacture protiens Not all ribosomes attached to rough ER

May modify proteins from ribosomes


24/81

Smooth Endoplasmic Reticulum

No attached ribosomes Has enzymes that help build molecules

Carbohydrates Lipids


25/81

25

Endomembrane System

Rough endoplasmic reticulum (RER) -membranes that create a network ofchannels throughout the cytoplasm-attachment of ribosomes to themembrane gives a rough appearance-synthesis of proteins to be secreted, sentto lysosomes or plasma membrane


26/81

26

Endomembrane System

Smooth endoplasmic reticulum (SER) -relatively few ribosomes attached

-functions:-synthesis of membrane lipids-calcium storage

-detoxification of foreign substances


27/81


28/81

28

Endomembrane System

Golgi apparatus -flattened stacks of interconnectedmembranes-packaging and distribution of materials todifferent parts of the cell-synthesis of cell wall components


29/81

Golgi Apparatus

Involved in synthesis of plant cell wall Packaging & shipping station of cell


30/81

Golgi Apparatus Function

1. Molecules come in vesicles

2. Vesicles fuse with Golgi membrane

3. Molecules may be modified by Golgi


31/81

Golgi Apparatus Function(Continued)

4. Molecules pinched-off in separate vesicle

5. Vesicle leaves Golgi apparatus

6. Vesicles may combine with plasmamembrane to secrete contents


32/81


33/81

33


34/81

34

Endomembrane System

Lysosomes -membrane bound vesicles containingdigestive enzymes to break downmacromolecules-destroy cells or foreign matter that the cellhas engulfed by phagocytosis


35/81

Lysosomes

Contain digestive enzymes Functions

Aid in cell renewal Break down old cell parts Digests invaders


36/81

36


37/81

37

Endomembrane System

Microbodies -membrane bound vesicles

-contain enzymes-not part of the endomembrane system-glyoxysomes in plants contain enzymes

for converting fats to carbohydrates-peroxisomes contain oxidative enzymesand catalase


38/81

38

Endomembrane System

Vacuoles -membrane-bound structures with variousfunctions depending on the cell type

There are different types of vacuoles:-central vacuole in plant cells-contractile vacuole of some protists-vacuoles for storage


39/81


40/81

Mitochondria

Break down fuel molecules ( cellular respiration) Glucose Fatty acids

Release energy ATP


41/81

41

Mitochondria

Mitochondria -organelles present in all types ofeukaryotic cells-contain oxidative metabolism enzymes fortransferring the energy withinmacromolecules to ATP-found in all types of eukaryotic cells


42/81

42

Mitochondria

-surrounded by 2 membranes-smooth outer membrane

-folded inner membrane with layerscalled cristae -matrix is within the inner membrane

-intermembrane space is locatedbetween the two membranes-contain their own DNA


43/81

43

Mitochondria


44/81


45/81

45

Cytoskeleton

Cytoskeleton -network of protein fibers found in alleukaryotic cells-supports the shape of the cell-keeps organelles in fixed locations

-helps move materials within the cell


46/81


47/81

47

Cytoskeleton


48/81

Examples of the cytoskeleton inepithelial cells

In the epithelial (skin)cells of the intestine, allthree types of fibers arepresent. Microfilaments

project into the villi, givingshape to the cell surface.Microtubules grow out ofthe centrosome to the cell

periphery. Intermediatefilaments connectadjacent cells throughdesmosomes.


49/81

49

Extracellular Structures

Extracellular structures include:-cell walls of plants, fungi, some protists-extracellular matrix surrounding animalcells


50/81

50


Cell walls-present surrounding the cells of plants,fungi, and some protists-the carbohydrates present in the cell wallvary depending on the cell type:

-plant and protist cell walls - cellulose-fungal cell walls - chitin


51/81

51


Extracellular matrix (ECM) -surrounds animal cells-composed of glycoproteins and fibrousproteins such as collagen-may be connected to the cytoplasm viaintegrin proteins present in the plasmamembrane


52/81

52



53/81

Centrioles

Pairs of microtubular structures Play a role in cell division


54/81

Molecule Movement & Cells

Passive Transport

Active Transport

Endocytosis

(phagocytosis & pinocytosis) Exocytosis


55/81

Passive Transport

No energy required

Move due to gradient differences in concentration, pressure, charge

Move to equalize gradient High moves toward low


56/81

Types of Passive Transport

1. Diffusion

2. Osmosis

3. Facilitated diffusion


57/81

Diffusion

Molecules move to equalize concentration


58/81

Osmosis

Special form of diffusion

Fluid flows from lower solute concentration

Often involves movement of water

Into cell Out of cell


59/81

Solution Differences & Cells solvent + solute = solution Hypotonic

Solutes in cell more than outside Outside solvent will flow into cell

Isotonic Solutes equal inside & out of cell

Hypertonic Solutes greater outside cell Fluid will flow out of cell


60/81


61/81

Facilitated Diffusion

Differentially permeable membrane

Channels (are specific) help moleculeor ions enter or leave the cell Channels usually are transport proteins

(aquaporins facilitate the movement ofwater) No energy is used


62/81

Process of Facilitated Transport

Protein binds with molecule Shape of protein changes Molecule moves across membrane


63/81

Active Transport

Molecular movement Requires energy (against gradient) Example is sodium-potassium pump


64/81


65/81

Endocytosis

Movement of large material Particles

Organisms Large molecules

Movement is into cells

Types of endocytosis bulk-phase (nonspecific) receptor-mediated (specific)


66/81

Process of Endocytosis

Plasma membrane surrounds material Edges of membrane meet Membranes fuse to form vesicle


67/81

Forms of Endocytosis

Phagocytosis cell eating Pinocytosis cell drinking


68/81

Exocytosis

Reverse of endocytosis Cell discharges material


69/81

Exocytosis

Vesicle moves to cell surface Membrane of vesicle fuses Materials expelled


70/81


71/81


72/81

Chemical Signals

What is the difference between hormones andparcrine factors?


73/81

Signal Transduction

What elements are involved in cell signaling?

Importance of signal


74/81

Importance of signaltransduction

Facilitates cell-cell signaling Coordination of growth and differentiation Inducing metabolic responses to

environmental factors Involves extracellular signaling molecules,

their interaction with target cells, and

subsequent intracellular events

Signal transduction - general


75/81

g gsteps

1) Synthesis and release of signalingmolecules

2) Transport of signal to target cell 3) Detection of signal by a specific

receptor protein 4) Intracellular events, often mediated

by second messengers, that changemetabolism or gene expression

5)Termination of the signal andresponse


76/81

Will focus on steps 3 to 5

Step 3 - involves cell-surface receptors Four main types:

Ion-channel receptors (e.g., acetylcholinereceptor)

G protein-linked receptors Receptors associated with tyrosine kinases

Receptors with intrinsic enzymatic activity


77/81


78/81

G protein-linked receptors

Overview: Signal molecule binds to recepter Receptor activates a G protein

Activated G protein activates an effectorenzyme that produces a second messenger

Second messenger molecule induces

metabolic changes

General structure of G protein-


79/81

plinked receptors

Seven transmembrane alpha helices Loop between helices 5&6 involved in

interactions with G protein

Similar in structure to rhodopsin


80/81

G Protein-Linked Receptors

What is a G protein? What does this type of receptor look like?


81/81

Pengantar Biologi Sel

Documents

Transcript of Pengantar Biologi Sel