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SCI I, 407M 12-3, 5:30-6:30; W 8-9, 5:30-6:30, Th 8-12, 6-7; F 8-9
● MasteringBiology Assignment due Tuesday 4/19● Exam I Tuesday 4/19● Scantron ABF-10-ID-200A
Review● Importance of Carbon● Biologically Important Molecules
Macromolecules: CarbohydratesProteinsNucleic Acids
Lipids
● Organisms are either:Single-celled, such as most prokaryotes and protists orMulticelled, such as plants, animals, and most fungi
The Microscopic World of Cells
The Microscopic World of CellsHow do we study cells?
Light microscopes can be used to explore the structures and functions of cells.
The Microscopic World of Cells● Electron Microscope 10 m
1 m
10 cm
1 cm
1 mm
100 mm
10 mm
Human height
Chicken egg
Frog eggs
Length of somenerve andmuscle cells
Una
ided
eye
Ligh
t mic
rosc
ope
Plant andanimal cells
Most bacteriaNucleus
Mitochondrion1 mm
100 nm
10 nm
1 nm
0.1 nm
Smallest bacteriaViruses
Ribosomes
ProteinsLipids
Small molecules
Atoms
Elec
tron
mic
rosc
ope
Figure 4.3
The Microscopic World of Cells
Light Micrograph (LM)(for viewing living cells)
Light micrograph of a protist, Paramecium
LM
Col
oriz
ed S
EM
Scanning Electron Micrograph (SEM)(for viewing surface features)
Scanning electron micrograph of Paramecium
TYPES OF MICROGRAPHS
Transmission Electron Micrograph (TEM)(for viewing internal structures)
Transmission electron micrograph of Paramecium
Col
oriz
ed T
EM
The Two Major Categories of Cells● The countless cells on earth fall into two categories:
Prokaryotic cells — Bacteria and ArchaeaEukaryotic cells — Eukarya
protists, plants, fungi, and animals
● All cells have several basic features.1. They are all bound by a thin plasma membrane.2. All cells have DNA. 3. All cells have ribosomes.
Cytoplasm-the entire contents of a cell
Prokaryotic Cells
Plasma membrane(encloses cytoplasm)
Cell wall (providesRigidity)Capsule (stickycoating)
Prokaryotic flagellum(for propulsion)
Ribosomes (synthesize proteins)
Nucleoid (contains DNA)
Pili (attachment structures)
Col
oriz
ed T
EM
● ProkaryotesAre smaller than eukaryotic cellsLack internal structures surrounded by membranesLack a nucleusHave a rigid cell wall
Eukaryotic Cells● Eukaryotic cells are fundamentally similar.
*Generalized animal cell
*Generalized plant cell
Membrane Structure● The plasma membrane separates the living cell from its nonliving surroundings.
(a) Phospholipid bilayer ofmembrane (b) Fluid mosaic model of
membrane
Outside of cell Outside of cellHydrophilicheadHydrophobictail
Hydrophilicregion ofprotein
HydrophilicheadHydrophobictail
Hydrophobicregions ofprotein
Phospholipidbilayer
Phospholipid
Proteins
Cytoplasm (inside of cell)
Cytoplasm (inside of cell)
Membrane Structure● Phospholipid structure
Phospholipids are amphipathic molecules
Membrane Structure● The plasma membrane separates the living cell from its nonliving surroundings.
(a) Phospholipid bilayer ofmembrane (b) Fluid mosaic model of
membrane
Outside of cell Outside of cellHydrophilicheadHydrophobictail
Hydrophilicregion ofprotein
HydrophilicheadHydrophobictail
Hydrophobicregions ofprotein
Phospholipidbilayer
Phospholipid
Proteins
Cytoplasm (inside of cell)
Cytoplasm (inside of cell)
Membrane Structure
Fibers ofextracellularmatrix
Cytoskeleton Cytoplasm
Attachment tocytoskeleton andextracellularmatrix
a
b Cell signaling
c
d
Enzymatic activity
Transport
e Intercellularjoining f Cell-cell
recognition
Cytoplasm
● Some functions of membrane proteins
● Cell surface – Extracellular Matrix
Chromatin Nucleolus PoreNuclearenvelope
Surface of nuclear envelope
Nuclear pores
TEM
TEM
● The nucleus is an organelle that houses the genetic material of the cell.
Nucleus
Chromatin
Nuclear envelope
Nucleolus
Nuclear Pore
Chromatin
DNA molecule
Chromosome
Proteins
Chromatinfiber
Figure 4.9
Ribosomes
Composed of proteins and Ribosomal RNA
Free: proteins for cytosol
Membrane-bound: proteins forcell membranes and export
● Ribosomes build all the cell’s proteins (protein synthesis)
How DNA Directs Protein Synthesis
Synthesis ofmRNA in thenucleus
1
2 Movement ofmRNA intocytoplasm vianuclear pore
3 Synthesis ofprotein in thecytoplasm
DNA
mRNA
Nucleus
CytoplasmmRNA
Ribosome
Protein
● DNA controls the cell by transferring its coded information into RNA
– The information in the RNA is used to make proteins
● Many of the membranous organelles in the cell belong to the endomembrane system
The Endomembrane System
The Endoplasmic Reticulum– Produces an
enormous variety of molecules
– Is composed of smooth and rough ER
Nuclearenvelope
Ribosomes
Rough ERSmooth ER
After the rough ER synthesizes a molecule it packages the molecule into transport vesicles
Transport vesiclebuds off
Ribosome Secretoryprotein insidetransportvesicle
ProteinRough ER
Polypeptide
1 2
3
4
The Endoplasmic Reticulum
The Golgi Apparatus
– Works in partnership with the ER– Refines, stores, and distributes the products of cells
Transportvesiclefrom ER
“Receiving” side ofGolgi apparatus
Golgi apparatus
New vesicle forming
Transport vesiclefrom the Golgi
“Shipping” side ofGolgi apparatus
Plasma membrane
• A lysosome is a membrane-enclosed sac
Lysosomes
– It contains digestive enzymes– The enzymes break down macromolecules– They break down damaged organelles
(b) Lysosome breaking down damaged organelle
Lysosome
Damagedorganelle
Digestion
Rough ER
Transportvesicle from ER
Golgiapparatus
Secretoryvesicle from Golgi
Secretoryprotein
Vacuole Lysosome
Plasma membrane
The Endomembrane System
Mitochondria are the sites of cellular respiration, which involves the production of ATP from food molecules
Figure 4.18
Outermembrane
Innermembrane
Cristae
Matrix
Space betweenmembranes
Cellular energy conversion
Cytoskeleton● Provides mechanical support to the cell and maintain its shape
The cytoskeleton can change the shape of a cell
– This allows cells like amoebae to move
Cytoskeleton
Cilia and flagella are motile appendages
Cilia and Flagella
• Flagella propel the cell in a whiplike motion
• Cilia move in a coordinated back-and-forth motion
Vacuoles are membranous sacs
Vacuoles
– Two types are the contractile vacuoles of protists and the central vacuoles of plants
Contractilevacuoles
Centralvacuole
(a) Contractile vacuoles in a protist (b) Central vacuole in a plant cell
Cytoskeleton
Mitochondrion
Nucleus
Rough endoplamsicreticulum (ER)
Ribosomes
Smoothendoplasmicreticulum (ER)
Golgi apparatus
Plasmodesmata
Plasmamembrane
Chloroplast
Cell wall
Centralvacuole
Not in animal cells
Plant Cells
Plant cells are encased by cell walls
Walls of two adjacentplant cells
Vacuole
Plasmodesmata(channels between cells)
Plant Cells
Chloroplasts are the sites of photosynthesis, the conversion of light energy to chemical energy
ChloroplastsInner and outermembranes ofenvelope
Space betweenmembranes
Stroma (fluid inchloroplast)
Granum
