● organisms are either: single-celled, such as most prokaryotes and protists or
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The Microscopic World of Cells. ● Organisms are either: Single-celled, such as most prokaryotes and protists or Multicelled, such as plants, animals, and most fungi. The Microscopic World of Cells. How do we study cells? - PowerPoint PPT PresentationTRANSCRIPT
● 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
Un
aid
ed
ey
e
Lig
ht
mic
rosc
op
e
Plant andanimal cells
Most bacteriaNucleus
Mitochondrion1 mm
100 nm
10 nm
1 nm
0.1 nm
Smallest bacteriaViruses
Ribosomes
Proteins
Lipids
Small molecules
Atoms
Ele
ctr
on
mic
ros
co
pe
Figure 4.3
The Microscopic World of Cells
Light Micrograph (LM)(for viewing living cells)
Light micrograph of a protist, Paramecium
LM
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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
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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)
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● 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 ofmembrane
Outside of cell Outside of cell
Hydrophilichead
Hydrophobictail
Hydrophilicregion ofprotein
Hydrophilichead
Hydrophobictail
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 ofmembrane
Outside of cell Outside of cell
Hydrophilichead
Hydrophobictail
Hydrophilicregion ofprotein
Hydrophilichead
Hydrophobictail
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
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● 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
Cytoplasm
mRNA
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
12
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
VacuolesVacuoles are membranous sacs
Traffic of Large Molecules–Exocytosis is the secretion of large molecules within vesicles.
Outside of cell
Cytoplasm
Plasmamembrane
Traffic of Large Molecules–Endocytosis takes material into a cell within vesicles that bud inward from the plasma membrane.
*Phagocytosis
Exocytosis
*Pinocytosis
*Receptor-mediated endocytosis
Endocytosis
Transport of large moleculesTypes of endocytosis found in animal cells:
Protein Sorting and Vesicle Transport
Rough ER
Transportvesicle from ER
Golgiapparatus
Secretoryvesicle from Golgi
Secretoryprotein
Vacuole Lysosome
Plasma membrane
The Endomembrane System