The Living Cell
Chapter 21
Great Idea:
Life is based on chemistry, and chemistry
takes place in cells
1
Chapter Outline
• The Nature and Variety of Cells
• How Does a Cell Work?
• Metabolism: Energy and Life
• Cell Division
2
The Nature and
Variety of Cells
3
The Cell Theory
• All living things are composed of cells
• The cell is the fundamental unit of
life
• All cells arise from previous cells
4
Observing Cells:
The Microscope
5
Cell theory
• (1839)Theodor Schwann & Matthias
Schleiden
“ all living things are made of cells”
• (50 yrs. later) Rudolf Virchow
“all cells come from cells”
6
Principles of Cell Theory
• All living things are made of cells
• Smallest living unit of structure
and function of all organisms is
the cell
• All cells arise from preexisting
cells
(this principle discarded the idea of
spontaneous generation)
7
Cell Size
8
iClicker Question
• What is a cell?
– A) The largest living units within our
bodies.
– B) Enzymes that "eat" bacteria
– C) Microscopic fundamental units of all
living things.
– D) All of the above.
9
iClicker Question
• All cells are too small to be seen
with the unaided eye and must be
studied with a microscope.
– A
– B
True
False
10
Cells Have Large Surface
Area-to-Volume Ratio
11
Characteristics of All Cells
• A surrounding membrane
• Protoplasm – cell contents in thick fluid
• Organelles – structures for cell function
• Control center with DNA
12
iClicker Question
• What does an electron microscope
use to illuminate objects?
–
–
–
–
A
B
C
D
light
protons
proteins
electrons
13
Molecule Movement & Cells
• Passive Transport
• Active Transport
• Endocytosis
(phagocytosis & pinocytosis)
• Exocytosis
14
Water: Medium for Metabolism
• Liquid medium for metabolism and its
importance
• Role of water (H2O)
– Physical properties (e.g., polarity, phases)
– Chemical properties (e.g., pH, solution)
• Exquisite and unique properties of H2O
15
Passive Transport
• No energy required
• Move due to gradient
– differences in concentration, pressure,
charge
• Move to equalize gradient
– High moves toward low
16
Types of Passive Transport
1. Diffusion
2. Osmosis
3. Facilitated
diffusion
17
iClicker Question
• An essential and distinctive feature
of all cells is a membrane that
isolates and protects the interior
from the outer environment.
– A
– B
True
False
18
Diffusion
• Molecules move to equalize concentration
19
Osmosis
• Special form of diffusion
• Fluid flows from lower solute
concentration
• Often involves movement of water
– Into cell
– Out of cell
20
Solution Differences & Cells
• solvent + solute = solution
• Hypotonic
– Solutes in cell more than outside
– Outside solvent will flow into cell
• Isotonic
– Solutes equal inside & out of cell
• Hypertonic
– Solutes greater outside cell
– Fluid will flow out of cell
21
22
Facilitated Diffusion
• Differentially permeable membrane
• Channels (are specific) help
molecule or ions enter or leave the
cell
• Channels usually are transport
proteins
(aquaporins facilitate the
movement of water)
• No energy is used
23
Process of Facilitated Transport
• Protein binds with molecule
• Shape of protein changes
• Molecule moves across membrane
24
Active Transport
• Molecular movement
• Requires energy (against gradient)
• Example is sodium-potassium pump
25
Endocytosis
• Movement of large material
– Particles
– Organisms
– Large molecules
• Movement is into cells
• Types of endocytosis
– bulk-phase (nonspecific)
– receptor-mediated (specific)
26
Process of Endocytosis
• Plasma membrane surrounds
material
• Edges of membrane meet
• Membranes fuse to form vesicle
27
Forms of Endocytosis
• Phagocytosis – cell eating
• Pinocytosis – cell drinking
28
Exocytosis
• Reverse of endocytosis
• Cell discharges material
29
Exocytosis
• Vesicle moves to cell surface
• Membrane of vesicle fuses
• Materials expelled
30
iClicker Question
In which decade were you born?
• A 1990s
• B 1980s
• C 1970s
• D 1960s
• E 1950s
31
iClicker Question
In which year was Geller’s first peerreviewed paper published?
• A 1964
• B 1974
• C 1984
• D 1994
• E 2004
32
iClicker Question
• In which journal was Geller’s first
pee-reviewed paper published?
• A Astrophysical Journal
• B Astronomical Journal
• C Journal of Chromatography
• D Journal of Physics
• E The Physics Teacher
33
How Does a Cell Work?
34
Cell Membranes
• Cell Membranes
– Isolate cell
– Separates cell parts
• Transport
– Individual molecules
– Specific materials
• channels
• Receptors
– Bind molecules
• Cell Wall
– Plants
35
Plant Cell
36
The Nucleus
• Nucleus
– Contains genetic material
• Prokaryotes
– No nucleus
• Eukaryotes
– Nucleus
• Double Membrane
37
The Energy Organelles:
Chloroplasts and Mitochondria
• Organelle
– Specialized structure in cell
• Chloroplasts
– Energy transformation
• chlorophyll
– Plant cells only
– Double membrane
• Mitochondria
– Produces cells energy
– Double membrane
– Own DNA
38
39
40
Cytoskeleton
• Cytoskeleton
– Gives cell shape
– Anchors
– Allows movement
– Transport system
• Within cell
• Structure
– Strong filaments
– Complex web
41
iClicker Question
• Cells that do not contain a nucleus
are called:
– A
– B
– C
eukaryotes
prokaryotes
likaryotes
42
iClicker Question
• Any specialized structure in the cell
is called:
– A
– B
– C
an endoplasmic reticulum
a chromatin
an organelle
43
iClicker Question
• What is the basic molecular
structure of cell membranes?
– A
– B
– C
lipid bilayer
carbohydrate bilayer
protein bilayer
44
iClicker Question
• The fluid that takes up the spaces
between all the complexity of the
specialized structures in cells is
called:
–
–
–
–
A
B
C
D
deionized water
protoplasm
cytoplasm
molasses
45
iClicker Question
• The cell structure which divides the
inside of the cell from the outside is
the:
– A
– B
– C
cell membrane
cell coat
nuclear membrane
46
iClicker Question
• What structure connects plant cells
to each other and often account for
about a third of a living plant’s
mass?
– A
– B
– C
middle lamella
cell wall
cell membrane
47
iClicker Question
• In most cells the most prominent
and important interior structure is
the:
– A
– B
– C
nucleus
chromosome
endoplasmic reticulum
48
iClicker Question
• Which organelle is the place where
molecules react with oxygen to
produce the cell’s energy?
– A
– B
– C
endoplasmic reticulum
mitochondria
chloroplasts
49
iClicker Question
• More advanced single-celled
organism that do contain a nuclei
are called:
– A
– B
– C
eukaryotes
prokaryotes
likaryotes
50
Metabolism: Energy and Life
51
The Cell’s Energy Currency
• Adenosine triphosphate (ATP)
– Provides energy
• Structure
– 3 phosphate groups
– Sugar molecule:
ribose
– adenine
• Function
– Removal of phosphate group provides
energy
52
Photosynthesis
• Photosynthesis
– Convert sunlight to energy
• Process
– Energy + CO2 + H2O Æcarbohydrate + O2
• Colors
53
Glycolysis: The First Step in
Energy Generation in the Cell
• Respiration
– Oxidation of carbohydrate
– Retrieves energy in glucose
– Aerobic
• Process
– Glycolysis
• Split glucose
• Result
– Pyruvic acid
– 2 ATP
– 2 energy carriers
• Convert energy carriers to 2-3 ATP
– 1 molecule glucose = 6-8 ATP
54
Fermentation: A Way to
Keep Glycolysis Going
• Fermentation
– Anaerobic
– Inefficient
• Yeast
– alcohol
• Animal cells
– Lactic acid
55
The Final Stages
of Respiration
• Krebs cycle
– Glucose broken down
– CO2 produced
– ATP
– Energy-carrying molecules
• Result
– 36-38 ATP
56
iClicker Question
• The cell’s process of deriving
energy form its surroundings is
called:
– A
– B
– C
photosynthesis
metabolism
respiration
57
iClicker Question
• What mechanism do plants use to
convert the energy of sunlight into
energy stored in carbohydrates?
– A
– B
– C
photosynthesis
metabolism
glycolysis
58
Cell Division
59
Mitosis
• Mitosis
– Cell division
– Not for sexual reproduction
• Chromosomes
• Process
– Copy chromosomes
– Spindle fibers
– Migration of chromosomes
– Nuclear membrane reforms
60
61
Meiosis
• Meiosis
– Sexual reproduction
– 1 cell forms 4 gametes
• Gametes are genetically
unique
• Process
–
–
–
–
Copy chromosomes
Crossing over
Segregation
Segregation again
• Result
– 4 daughter cells
– ½ normal chromosomes
62
Meiosis
63
iClicker Question
• By what process do most cells
divide?
– A
– B
– C
mitosis
meiosis
glycolysis
64