Announcements
● Tutoring
Center
SCI I, 407
M 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:
Carbohydrates
Proteins
Nucleic Acids
Lipids
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?
Light microscopes can be used to explore the
structures and functions of cells.
The Microscopic World of Cells
10 m
Human height
1m
Length of some
nerve and
muscle cells
10 cm
Chicken egg
1 cm
Frog eggs
1 mm
Plant and
animal cells
10 mm
1 mm
100 nm
Nucleus
Most bacteria
Mitochondrion
Smallest bacteria
Viruses
Ribosomes
10 nm
Electron microscope
100 mm
Light microscope
Microscope
Unaided eye
● Electron
Proteins
Lipids
1 nm
0.1 nm
Small molecules
Atoms
Figure 4.3
The Microscopic World of Cells
TYPES OF MICROGRAPHS
Light micrograph of a protist, Paramecium
Scanning electron micrograph of Paramecium
Colorized TEM
Transmission Electron Micrograph (TEM)
(for viewing internal structures)
Colorized SEM
Scanning Electron Micrograph (SEM)
(for viewing surface features)
LM
Light Micrograph (LM)
(for viewing living cells)
Transmission electron micrograph of Paramecium
The Two Major Categories of Cells
● The
● All
countless cells on earth fall into two categories:
Prokaryotic cells — Bacteria and Archaea
Eukaryotic cells — Eukarya
protists, plants, fungi, and animals
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
● Prokaryotes
Are smaller than eukaryotic cells
Lack internal structures surrounded by membranes
Lack a nucleus
Have a rigid cell wall
Plasma membrane
(encloses cytoplasm)
Cell wall (provides
Rigidity)
Capsule (sticky
coating)
Prokaryotic flagellum
(for propulsion)
Ribosomes
(synthesize proteins)
Colorized TEM
Nucleoid (contains DNA)
Pili (attachment structures)
Eukaryotic Cells
● Eukaryotic
cells are fundamentally similar.
*Generalized plant cell
*Generalized animal cell
Membrane Structure
● The
plasma membrane separates the living cell from its
nonliving surroundings.
Outside of cell
Hydrophilic
head
Hydrophobic
tail
Hydrophilic
region of
protein
Outside of cell
Hydrophilic
head
Phospholipid
bilayer
Hydrophobic
tail
Phospholipid
Cytoplasm (inside of cell)
(a) Phospholipid bilayer of
membrane
Hydrophobic
regions of
protein
Proteins
Cytoplasm (inside of cell)
(b) Fluid mosaic model of
membrane
Membrane Structure
● Phospholipid
structure
Phospholipids are amphipathic molecules
Membrane Structure
● The
plasma membrane separates the living cell from its
nonliving surroundings.
Outside of cell
Hydrophilic
head
Hydrophobic
tail
Hydrophilic
region of
protein
Outside of cell
Hydrophilic
head
Phospholipid
bilayer
Hydrophobic
tail
Phospholipid
Cytoplasm (inside of cell)
(a) Phospholipid bilayer of
membrane
Hydrophobic
regions of
protein
Proteins
Cytoplasm (inside of cell)
(b) Fluid mosaic model of
membrane
Membrane Structure
● Some
functions of membrane proteins
Cytoplasm
Fibers of
extracellular
matrix
c Enzymatic activity
b Cell signaling
a Attachment to
cytoskeleton and
extracellular
matrix
e Intercellular
joining
d Transport
Cytoskeleton
● Cell
Cytoplasm
surface – Extracellular Matrix
f Cell-cell
recognition
Nucleus
nucleus is an organelle that houses the genetic
Nuclear
material of the cell.
Chromatin envelope Nucleolus Pore
Chromatin
Nucleolus
TEM
Nuclear
envelope
TEM
● The
Nuclear Pore
Surface of nuclear
envelope
Nuclear pores
Chromatin
DNA molecule
Proteins
Chromatin
Chromosome
fiber
Figure 4.9
Ribosomes
● Ribosomes
build all the cell’s proteins (protein synthesis)
Composed of proteins and
Ribosomal RNA
Free: proteins for cytosol
Membrane-bound:
proteins for
cell membranes and export
How DNA Directs Protein Synthesis
● DNA
controls the cell
by transferring its coded
information into RNA
– The information in
the RNA is used to
make proteins
DNA
1 Synthesis of
mRNA in the
nucleus
mRNA
Nucleus
Cytoplasm
2 Movement of
mRNA into
cytoplasm via
nuclear pore
3 Synthesis of
protein in the
cytoplasm
mRNA
Ribosome
Protein
The Endomembrane System
● Many
of the
membranous organelles
in the cell belong to the
endomembrane system
The Endoplasmic Reticulum
– Produces an
enormous variety
of molecules
– Is composed of
smooth and rough
ER
Nuclear
envelope
Ribosomes
Rough ER
Smooth ER
The Endoplasmic Reticulum
After the rough ER synthesizes a molecule it packages
the molecule into transport vesicles
4
Transport vesicle
buds off
Ribosome
3
Secretory
protein inside
transport
vesicle
Protein
1
Polypeptide
2
Rough ER
The Golgi Apparatus
– Works in partnership with the ER
– Refines, stores, and distributes the products of cells
Transport
vesicle
from ER
“Receiving” side of
Golgi apparatus
Golgi apparatus
New vesicle forming
Transport vesicle
from the Golgi
“Shipping” side of
Golgi apparatus
Plasma membrane
Lysosomes
• A lysosome is a membrane-enclosed sac
– It contains digestive enzymes
– The enzymes break down macromolecules
– They break down damaged organelles
Lysosome
Digestion
Damaged
organelle
(b) Lysosome breaking down damaged organelle
The Endomembrane System
Rough ER
Transport
vesicle from ER
Golgi
apparatus
Secretory
vesicle from Golgi
Secretory
protein
Vacuole
Plasma membrane
Lysosome
Cellular energy conversion
Mitochondria are the sites of cellular respiration,
which involves the production of ATP from food
molecules
Outer
membrane
Inner
membrane
Cristae
Matrix
Space between
membranes
Figure 4.18
Cytoskeleton
● Provides
mechanical support to
the cell and maintain
its shape
Cytoskeleton
The cytoskeleton can change
the shape of a cell
– This allows cells like
amoebae to move
Cilia and Flagella
Cilia and flagella are motile appendages
• Flagella propel the cell in
a whiplike motion
• Cilia move in a coordinated
back-and-forth motion
Vacuoles
Vacuoles are membranous sacs
– Two types are the contractile vacuoles of protists and
the central vacuoles of plants
Central
vacuole
Contractile
vacuoles
(a) Contractile vacuoles in a protist
(b) Central vacuole in a plant cell
Plant Cells
Not in animal cells
Cytoskeleton
Mitochondrion
Central
vacuole
Nucleus
Cell wall
Rough endoplamsic
reticulum (ER)
Chloroplast
Ribosomes
Plasma
membrane
Smooth
endoplasmic
reticulum (ER)
Plasmodesmata
Golgi apparatus
Plant Cells
Plant cells are encased by cell walls
Walls of two adjacent
plant cells
Vacuole
Plasmodesmata
(channels between cells)
Chloroplasts
Chloroplasts are the
sites of photosynthesis,
the conversion of light
energy to chemical
energy
Inner and outer
membranes of
envelope
Granum
Space between
membranes
Stroma (fluid in
chloroplast)