Cell Structure and
Function
Chapter 4
Hsueh-Fen Juan
阮雪芬
Sept. 25, 2012
Video: E. coli in food
Impacts, Issues:
Food For Thought
• A strain of E. coli bacteria that causes severe
illness or death occasionally contaminates foods
such as ground beef and fresh vegetables
4.1 The Cell Theory
• The cell theory, a foundation of modern biology,
states that cells are the fundamental units of life
Measuring Cells
• One micrometer (μm) is one-thousandth of a
millimeter
Animalcules and Beasties
• Van Leeuwenhoek was the first to describe
small organisms seen through a microscope,
which he called animalcules and beasties
• Hooke was the first to sketch and name cells
Development of the Microscope
Development of the Microscope
The Cell Theory Emerges
• In 1839, Schleiden and Schwann proposed the
basic concepts of the modern cell theory
• All organisms consists of one or more cells
• A cell is the smallest unit with the properties of life
• Each new cell arises from division of another,
preexisting cell
• Each cell passes its hereditary material to its
offspring
4.2 What Is a Cell?
• Cell
• The smallest unit that shows the properties of life
• All cells have a plasma membrane and
cytoplasm, and all start out life with DNA
The Basics of Cell Structure
• Eukaryotic cell
• Cell interior is divided into functional
compartments, including a nucleus
• Prokaryotic cell
• Small, simple cells without a nucleus
All Cells Have Three Things In Common
• Plasma membrane
• Controls substances passing in and out of the cell
• DNA containing region
• Nucleus in eukaryotic cells
• Nucleoid region (核質體區) in prokaryotic cells
• Cytoplasm
• A semifluid mixture containing cell components
Prokaryotic
Cells
Eukaryotic
Cells
Cell Size
• Surface-to-volume ratio restricts cell size by
limiting transport of nutrients and wastes
Animation: Surface-to-volume ratio
Preview of Cell Membranes
• Lipid bilayer
• A double layer of phospholipids organized with
their hydrophilic heads outwards and their
hydrophobic tails inwards
• Many types of proteins embedded or attached to
the bilayer carry out membrane functions
Basic Structure of Cell Membranes
Basic Structure of Cell Membranes
Basic Structure of Cell Membranes
Animation: Cell membranes
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4.1-4.2 Key Concepts:
What All Cells Have In Common
• Each cell has a plasma membrane, a boundary
between its interior and the outside environment
• The interior consist of cytoplasm and an
innermost region of DNA
4.3 How Do We See Cells?
• We use different types of microscopes to study
different aspects of organisms, from the smallest
to the largest
Modern Microscopes
• Light microscopes
• Phase-contrast microscopes
• Reflected light microscopes
• Fluorescence microscopes
• Electron microscopes
• Transmission electron microscopes
• Scanning electron microscopes
Light Microscopes
Electron Microscopes
Animation: How a light microscope
works
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Animation: How an electron microscope
works
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Different Microscopes,
Different Characteristics
a) Light
micrograph. A
phase-contrast
micro-scope yields
high-contrast
images of
transparent
specimens, such
as cells.
b) Light
micrograph. A
reflected light
micro-scope
captures light
reflected from
opaque
specimens.
c) Fluorescence
micro-graph. The
chlorophyll
molecules in these
cells emitted red
light (they
fluoresced)
naturally.
d) A transmission
electron
micrograph
reveals
fantastically
detailed images
of internal
structures.
e) A scanning
electron micrograph shows
surface details of
cells and
structures. Often,
SEMs are
artificially colored
to highlight certain
details.
Stepped Art
Fig. 4-8, p. 59
Resolving Power
human eye, no microscope
light microscopes
humans
electron microscopes
hummingbirds
most animal
lipids
virus
mitochondria, cells and plant cells
chloroplasts
most
small
bacteria
proteins
molecules
frog egg
0.1 nm 1 nm 10 nm 100 nm 1 µm 10 µm
100 µm1 mm 1 cm 0.1 m 1 m
10 m
100 m
Fig. 4-9, p. 59
4.3 Key Concepts:
Microscopes
• Microscopic analysis supports three
generalizations of the cell theory:
• Each organism consists of one or more cells and
their products
• A cell has a capacity for independent life
• Each new cell is descended from a living cell
4.4 Introducing Prokaryotic Cells
• Bacteria and archaea are the prokaryotes
(“before the nucleus”), the smallest and most
metabolically diverse forms of life
• Bacteria and archaea are similar in appearance
and size, but differ in structure and metabolism
General Prokaryote Body Plan
• Cell wall surrounds the plasma membrane
• Made of peptidoglycan (in bacteria) or proteins
(in archaea) and coated with a sticky capsule
• Flagellum for motion
• Pili help cells move across surfaces
• Sex pilus aids in sexual reproduction
General Prokaryote
Body Plan
flagellum
capsule
cell wall
plasma membrane
cytoplasm, with
ribosomes
DNA in nucleoid
pilus
Archaeans
Bacteria
4.5 Microbial Mobs
• Although prokaryotes are all single-celled, few
live alone
• Biofilm
• Single-celled organisms sharing a secreted layer
of polysaccharides and glycoproteins
• May include bacteria, algae, fungi, protists, and
archaeans (多種物種)
A Biofilm
4.4-4.5 Key Concepts:
Prokaryotic Cells
• Archaeans and bacteria are prokaryotic cells,
which have few, if any, internal membraneenclosed compartments
• In general, they are the smallest and structurally
the simplest cells
4.6 Introducing Eukaryotic Cells
• Eukaryotic (“true nucleus”) cells carry out much
of their metabolism inside membrane-enclosed
organelles
• Organelle
• A structure that carries out a specialized function
within a cell
Organelles of Eukaryotic Cells
Eukaryotes: Animal and Plant Cells
4.7 Visual Summary of Eukaryotic Cells
Plant cells
4.7 Visual Summary of Eukaryotic Cells
Animal cells
4.8 The Nucleus
• The nucleus keeps eukaryotic DNA away from
potentially damaging reactions in the cytoplasm
• The nuclear envelope controls when DNA is
accessed
The Nuclear Envelope
• Nuclear envelope
• Two lipid bilayers pressed together as a single
membrane surrounding the nucleus
• Outer bilayer is continuous with the ER
• Nuclear pores allow certain substances to pass
through the membrane
Animation: Nuclear envelope
The Nucleoplasm and Nucleolus
• Nucleoplasm
• Viscous fluid inside the nuclear envelope, similar
to cytoplasm
• Nucleolus
• A dense region in the nucleus where subunits of
ribosomes are assembled from proteins and RNA
(此為rRNA)
The Chromosomes
• Chromatin
• All DNA and its associated proteins in the
nucleus
• Chromosome
• A single DNA molecule with its attached proteins
• During cell division, chromosomes condense and
become visible in micrographs
• Human body cells have 46 chromosomes
Chromosome Condensation
4.9 The Endomembrane System
• Endomembrane system
• A series of interacting organelles between the
nucleus and the plasma membrane
• Makes lipids, enzymes, and proteins for secretion
or insertion into cell membranes
• Other specialized cell functions
The Endoplasmic Reticulum
• Endoplasmic reticulum (ER)
• An extension of the nuclear envelope that forms a
continuous, folded compartment
• Two kinds of endoplasmic reticulum
• Rough ER (with ribosomes) folds polypeptides
into their tertiary form
• Smooth ER (no ribosomes) makes lipids, breaks
down carbohydrates and lipids, detoxifies poisons
Vesicles
• Vesicles
• Small, membrane-enclosed saclike organelles
that store or transport substances
• Peroxisomes
• Vesicles containing enzymes that break down
hydrogen peroxide, alcohol, and other toxins.
Also digest fatty acids and amino acid.
• Vacuoles
• Vesicles for waste disposal
Golgi Bodies and Lysosomes
• Golgi body
• A folded membrane containing enzymes that
finish polypeptides and lipids delivered by the
ER (記得也會運送脂肪)
• Packages finished products in vesicles that carry
them to the plasma membrane or to lysosomes
• Lysosomes
• Vesicles containing enzymes that fuse with
vacuoles and digest waste materials
The Endomembrane System
The Endomembrane System
The Endomembrane System
Animation: The endomembrane system
4.10 Lysosome Malfunction
• When lysosomes do not work properly, some
cellular materials are not properly recycled,
which can have devastating results
• Different kinds of molecules are broken down by
different lysosomal enzymes
• One lysosomal enzyme breaks down
gangliosides, a kind of lipid
Tay Sachs Disease (河西高盛病)
• In Tay Sachs disease, a genetic mutation alters
the lysosomal enzyme that breaks down
gangliosides, which accumulate in nerve cells
• Affected children usually die by age five
4.11 Other Organelles
• Eukaryotic cells make most of their ATP in
mitochondria
• Plastids (色素體) function in storage and
photosynthesis in plants and some types of
algae (色素體包含葉綠體chloroplast、雜色體
chromoplast、澱粉體amyloplast)
Mitochondria
• Mitochondrion
• Eukaryotic organelle that makes the energy
molecule ATP through aerobic respiration
• Contains two membranes, forming inner and
outer compartments; buildup of hydrogen ions in
the outer compartment drives ATP synthesis
• Has its own DNA and ribosomes
• Resembles bacteria; may have evolved through
endosymbiosis (內共生)
Mitochondrion
Animation: Structure of a
mitochondrion I
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Plastids
• Plastids (色素體)
• Organelles that function in photosynthesis or
storage in plants and algae; includes
chromoplasts (雜色體), amyloplasts(澱粉體), and
chloroplasts(葉綠體)，注意澱粉體不含色素
• Chloroplasts (葉綠體)
• Plastids specialized for photosynthesis
• Resemble photosynthetic bacteria; may have
evolved by endosymbiosis
The Chloroplast
The Central Vacuole
• Central vacuole
• A plant organelle that occupies 50 to 90 percent
of a cell’s interior
• Stores amino acids, sugars, ions, wastes, toxins
• Fluid pressure keeps plant cells firm
4.12 Cell Surface Specializations
• A wall or other protective covering often
intervenes between a cell’s plasma membrane
and the surroundings
Eukaryotic Cell Walls
• Animal cells do not have walls, but plant cells
and many protist and fungal cells do
• Primary cell wall
• A thin, pliable wall formed by secretion of
cellulose into the coating around young plant cells
• Secondary cell wall
• A strong wall composed of lignin (木質素，單體是
醇類而非醣類), formed in some plant stems and
roots after maturity
Plant Cell Walls
Plant Cell Walls
Plant Cell
Walls
Animation: Plant cell walls
Plant Cuticle
• Cuticle (表皮)
• A waxy covering that protects exposed surfaces
and limits water loss
Matrixes Between Animal Cells
• Extracellular matrix (ECM)
• A nonliving, complex mixture of fibrous proteins
and polysaccharides secreted by and
surrounding cells; structure and function varies
with the type of tissue
• Example: Bone is mostly ECM, composed of
collagen (fibrous protein) and hardened by
mineral deposits
ECM
• A bone cell surrounded by extracellular matrix
Cell Junctions
• Cell junctions allow cells to interact with each
other and the environment
• In plants, plasmodesmata extend through cell
walls to connect the cytoplasm of two cells
• Animals have three types of cell junctions: tight
junctions, adhering junctions, gap junctions
Cell Junctions in Animal Tissues
Animation: Animal cell junctions
4.6-4.12 Key Concepts:
Eukaryotic Cells
• Cells of protists, plants, fungi, and animals are
eukaryotic; they have a nucleus and other
membrane-enclosed compartments
• They differ in internal parts and surface
specializations
4.13 The Dynamic Cytoskeleton
• Eukaryotic cells have an extensive and dynamic
internal framework called a cytoskeleton
• Cytoskeleton
• An interconnected system of many protein
filaments – some permanent, some temporary
• Parts of the cytoskeleton reinforce, organize, and
move cell structures, or even a whole cell
Components of the Cytoskeleton
• Microtubules
• Long, hollow cylinders made of tubulin
• Form dynamic scaffolding for cell processes
• Microfilaments
• Consist mainly of the globular protein actin
• Make up the cell cortex
• Intermediate filaments
• Maintain cell and tissue structures
Components of the Cytoskeleton
Yellow: microtubules
Blue: microfilaments
Motor Proteins
• Motor proteins
• Accessory proteins that move molecules through
cells on tracks of microtubules and
microfilaments (兩者都會動，所以都有)
• Energized by ATP
• Example: kinesins
Motor Proteins: Kinesin
Animation: Motor proteins
Cilia, Flagella, and False Feet
• Eukaryotic flagella and cilia
• Whiplike structures formed from microtubules
organized into 9 + 2 arrays
• Grow from a centriole which remains in the
cytoplasm as a basal body
• Psueudopods
• “False feet” used by amoebas and other
eukaryotic cells to move or engulf prey
Moving Cells
• Flagellum of the human sperm, and pseudopods
of a predatory amoeba
Eukaryotic Flagella and Cilia
Eukaryotic Flagella
and Cilia
Eukaryotic Flagella
and Cilia
Animation: Flagella structure
4.13 Key Concepts:
A Look at the Cytoskeleton
• Diverse protein filaments reinforce a cell’s shape
and keep its parts organized
• As some filaments lengthen and shorten, they
move cell structures or the whole cell
Summary: Components of
Prokaryotic and Eukaryotic Cells