Download - UNIT III – CELL STRUCTURE & FUNCTION Hillis – Ch 4,5 Baby Campbell – Ch 4,5 Big Campbell – Ch 6,7,11
UNIT III – CELL STRUCTURE & FUNCTION
• Hillis – Ch 4,5• Baby Campbell – Ch 4,5• Big Campbell – Ch 6,7,11
I. DISCOVERY OF CELLS
• History of Microscopes Anton van Leeuwenhoek
Robert Hooke
• Cell Theory All living things are made of cells. Cells are the smallest working unit. All cells come from pre-existing cells through cell division.
I. DISCOVERY OF CELLS, cont.
• Types of Microscopes Compound Light Microscope
MagnificationResolutionAdvances in light microscopy
include o Confocalo Fluorescento Phase Contrasto Super-resolution
Electron MicroscopeScanning Electron
Microscope (SEM)Transmission Electron
Microscope (TEM)
I. DISCOVERY OF CELLS, cont.
• Cell Size o Metabolic needs impose
both upper & lower limits on cell size
o How small?Must have enough space for
DNA, enzymesMycoplasma sp. - < 1 μm
o How large?Surface Area to Volume RatioAdaptations
II. CELL TYPES• Prokaryotic Cells
Typically smaller than euks
BacteriaKingdom Kingdom
No true nucleus – DNA found as a single chromosome in region called nucleoid
II. CELL TYPES, cont• Prokaryotic Cells
II. CELL TYPES, cont
• Eukaryotic Cells Larger, more complex Contain true nucleus, membrane-
bound organelles suspended in cytosol
Composed of Nucleus Ribosomes Endomembrane System
o ERo Golgi Apparatuso Lysosomeso Vacuoles
Mitochondria/Chloroplasts Peroxisomes Cytoskeleton
III. EUKARYOTIC CELL STRUCTURES
_____________ Cell
_______________ Cell
III. EUKARYOTIC CELL STRUCTURES, cont
• Control center of eukaryotic cell
Double membrane that protects nucleus; continuous with ER
Contains pores
Site of ribosome production
DNA wrapped in protein
III. EUKARYOTIC CELL STRUCTURES, cont
• Suspended in cytosol or found on rough ER Site of protein production in a cell
III. EUKARYOTIC CELL STRUCTURES, cont
• Endomembrane System Endoplasmic Reticulum
Interconnected network continuous with nuclear envelope
Rough ER
Smooth ER
III. EUKARYOTIC CELL STRUCTURES, contEndomembrane System, cont
“Cell postmaster” Receives transport vesicles from ER; modifies, stores, and ships
products Receiving side is known as the cis face; shipping side is known as the trans face
III. EUKARYOTIC CELL STRUCTURES, contEndomembrane System, cont
Sacs containing hydrolytic enzymes Used for recycling cellular materials, destroying pathogens
III. EUKARYOTIC CELL STRUCTURES, contEndomembrane System, cont
Storage sac Plants typically have large,
central vacuole surrounded by membrane called tonoplast. Absorbs water and helps plant cell to grow larger
Some protists have contractile vacuole to pump out excess water
III. EUKARYOTIC CELL STRUCTURES, cont
• Site of oxidative respiration Contain own DNA, ribosomes Found in virtually all euk cells Enclosed by 2 membranes; inner membrane has folds called cristae
to increase surface area
III. EUKARYOTIC CELL STRUCTURES, cont
• Type of plastid that carries out photosynthesis by converting solar energy
to chemical energy (glucose) Contain membranous system of flattened sacs called thylakoids – stack is
called a granum Fluid surrounding thylakoids is called stroma Contains DNA, ribosomes
III. EUKARYOTIC CELL STRUCTURES, contEndosymbiont Theory
III. EUKARYOTIC CELL STRUCTURES, cont
• Membrane-bound compartments that use O2 to carry out metabolism H2O2 is produced; broken down by _________________
III. EUKARYOTIC CELL STRUCTURES, cont
• Provides structural support to cell Allows for movement Attachment site for organelles, enzymes More extensive in animal cells Composed of three types of proteins
Actin
More fixedKeratin
III. EUKARYOTIC CELL STRUCTURES, contCytoskeleton, cont
IV. CELL BOUNDARIES• Cell Wall
Found in
Rigid structure; protects, maintains shape of cells
Prevents excess water uptake Plant cell wall
CellulosePectin - Sticky polysaccharide
found between cell walls of adjacent cells
Plasmodesmata - Perforations between adjacent cell walls that allow for movement of materials from one cell to another
IV. CELL BOUNDARIES, cont• Extracellular Matrix of Animal Cells
Holds cells together, protects & supports cells Allows for communication between cells Composed primarily of glycoproteins – proteins with covalently-bonded
carbohydrate chains attached Must abundant glycoprotein in most animals is collagen
IV. CELL BOUNDARIES, cont• Intracellular Junctions
in Animal Cells Tight Junctions – Press
membranes together very tightly; prevents leakage of fluid
Desmosomes (Anchoring Junctions) – Fasten cells together in sheets
Gap Junctions – Allow for movement of cytoplasm from one cell to another; important in communication between cells
IV. CELL BOUNDARIES, cont• Cell (Plasma) Membrane
Selectively-permeable barrier found in all cells Composed primarily of phospholipid bilayer Fluid Mosaic Model
“Fluid” – Not a rigid structure. Organization due to high concentration of water inside & outside cell
IV. CELL BOUNDARIES, cont• Organization of Plasma Membrane
IV. CELL BOUNDARIES, cont
• Fluidity of Plasma Membrane
IV. CELL BOUNDARIES, cont• Cell Membrane, cont
Proteins - “Mosaic” – Assortment of different proteins embedded in bilayer; determine most of membrane’s specific functions. Act as channels, pumps, enzymes in metabolism, binding sites, etc
o Integral Proteins – Embedded in phospholipid layero Peripheral Proteins – Bound to surface of membrane
IV. CELL BOUNDARIES, contMembrane Proteins
IV. CELL BOUNDARIES, cont
• Cell Membrane, cont Carbohydrates
“ID tags” that identify cell.
Enable cells to recognize each other and foreign cells.
May be bonded to lipids (glycolipids) or proteins (glycoproteins)
IV. CELL BOUNDARIES, cont
V. CELL TRANSPORT
V. CELL TRANSPORT, cont• Passive Transport – Movement of materials from high to low
concentration. No energy output required. Diffusion
Random movement of a substance across membrane down concentration gradient
No net movement once equilibrium is reached
V. CELL TRANSPORT, cont• Passive Transport, cont
Facilitated Diffusion Passive transport of molecules across cell membrane with the help of
transport proteins Utilized by large molecules, charged particles, polar molecules Water
V. CELL TRANSPORT, cont• Passive Transport, cont
Osmosis – Diffusion of water across a membrane. Tonicity refers to tendency of cell to gain or lose water. If the solution is Isotonic relative to the cell – Solute concentration is same on both sides of
membrane. No net movement of water. Hypertonic relative to the cell – Concentration of solute is greater outside
cell → water moves out of cell until equilibrium is reached. Cell may shrivel. Hypotonic relative to the cell – Concentration of solute is lower outside cell
→ water moves into cell until equilibrium is reached. Cell may swell to bursting point.
V. CELL TRANSPORT, cont• Passive Transport / Osmosis, cont
Water Potential Used to predict the passive movement of water Designated as Ψ Water always moves from an area of higher water potential →
lower water potential
ΨS =
ΨP =
V. CELL TRANSPORT, cont• Passive Transport/Osmosis, cont
Osmoregulation Cells must have mechanism to prevent excess loss, uptake of waterCell wall, contractile vacuolePlasmolysis – Seen in plants; excessive water loss causes cell
membrane to pull away from cell wall
V. CELL TRANSPORT, cont
V. CELL TRANSPORT, cont• Active Transport
• Movement of materials against concentration gradient. Requires energy output by cell Carrier Proteins – Na+ / K+ Pump
V. CELL TRANSPORT, cont• Active Transport, cont
Proton Pump
V. CELL TRANSPORT, cont
• Active Transport, cont Exocytosis
Secretion of biomolecules by fusion of vesicles with cell membrane. Biomolecules “spit out”.
Hormones, neurotransmitters, etc
V. CELL TRANSPORT, cont• Active Transport, cont
Endocytosis – “Sucking In”. Cell membrane surrounds, engulfs particle or biomolecule, pinches in to form vesicle.Phagocytosis – “Sucking in” food particlesPinocytosis – “Sucking in” fluid dropletsReceptor-mediated Endocytosis – Very specific
VI. CELL SIGNALING
• Autocrine Signaling
VI. CELL SIGNALING, cont• Coordinates cell activities, development• Typically involves 3 steps:
Reception – Target cell’s detection of signal molecule due to binding of signal molecule to receptor protein in cell membrane
Transduction – Binding of signaling molecule changes receptor protein; triggers a sequence of events within cell
Response – Results in specific cellular response; for example, activation of genes, enzyme catalysis, etc.
VI. CELL SIGNALING, cont
• Reception Typically involves G Proteins
VI. CELL SIGNALING, cont• Transduction
Typically multi-step pathway Relay molecules are usually protein kinases
VI. CELL SIGNALING, cont
• Transduction Non-protein
molecule known as cAMP is often second messenger
VI. CELL SIGNALING, cont• Response
Nuclear May “turn on” or “turn off” genes
CytoplasmicMay regulate enzyme activity
ApoptosisControlled cell suicide
VI. CELL SIGNALING, cont
• Regulation