1. The Cell

2. Chapter 3 Cells Vary in shape Measured in micrometers
Differ in size
Vary in shape
Measured in micrometers
Over 200 Types in Human Body

3. (a) Cells that connect body parts, form linings, or transport gases
Erythrocytes
Fibroblasts
Epithelial cells
(a) Cells that connect body parts,
form linings, or transport gases
Nerve cell
Skeletal
Muscle
cell
Smooth
muscle cells
(e) Cell that gathers information
and control body functions
(b) Cells that move organs and
body parts
Sperm
Macrophage
(f) Cell of reproduction
Fat cell
(c) Cell that stores nutrients
(d) Cell that
fights disease
Figure 3.1

4. Cell Theory All living things are composed of cells
They are the smallest units of life
Cells come only from pre-existing cells
Organismal functions depend on individual and collective cell functions
Biochemical activities of cells are dictated by their specific subcellular structures

5. Chromatin Nuclear envelope Nucleolus Nucleus Smooth endoplasmic
reticulum
Plasma
membrane
Mitochondrion
Cytosol
Lysosome
Centrioles
Centrosome
matrix
Rough
endoplasmic
reticulum
Ribosomes
Golgi apparatus
Secretion being
released from cell
by exocytosis
Cytoskeletal
elements
• Microtubule
• Intermediate
filaments
Peroxisome
Figure 3.2

6. Cell Membrane Phospholipid bilayer (75%) outer limit of cell
controls what moves in and out of cell
selectively permeable
Phospholipid bilayer (75%)
water-soluble “heads” form surfaces
water-insoluble “tails” form interior
permeable to lipid-soluble substances
Cholesterol stabilizes the membrane (20%) Lipid Rafts?
Proteins
receptors
pores, channels, carriers
enzymes
CAMS
self-markers

7. Cell Membrane

8. A protein (left) that spans the membrane
(a) Transport
A protein (left) that spans the membrane
may provide a hydrophilic channel across
the membrane that is selective for a
particular solute. Some transport proteins
(right) hydrolyze ATP as an energy source
to actively pump substances across the
membrane.
Figure 3.4a

9. (b) Receptors for signal transduction Signal
A membrane protein exposed to the
outside of the cell may have a binding
site with a specific shape that fits the
shape of a chemical messenger, such
as a hormone. The external signal may
cause a change in shape in the protein
that initiates a chain of chemical
reactions in the cell.
Receptor
Figure 3.4b

10. (c) Attachment to the cytoskeleton and extracellular matrix (ECM)
Elements of the cytoskeleton (cell’s
internal supports) and the extracellular
matrix (fibers and other substances
outside the cell) may be anchored to
membrane proteins, which help maintain
cell shape and fix the location of certain
membrane proteins. Others play a role in
cell movement or bind adjacent cells
together.
Figure 3.4c

11. (d) Enzymatic activity
Enzymes
A protein built into the membrane may
be an enzyme with its active site
exposed to substances in the adjacent
solution. In some cases, several
enzymes in a membrane act as a team
that catalyzes sequential steps of a
metabolic pathway as indicated (left to
right) here.
Figure 3.4d

12. (e) Intercellular joining
Membrane proteins of adjacent cells
may be hooked together in various
kinds of intercellular junctions. Some
membrane proteins (CAMs) of this
group provide temporary binding sites
that guide cell migration and other
cell-to-cell interactions.
CAMs
Figure 3.4e

13. (f) Cell-cell recognition
Some glycoproteins (proteins bonded
to short chains of sugars) serve as
identification tags that are specifically
recognized by other cells.
Glycoprotein
Figure 3.4f

14. Roles of Membrane Receptors
Contact signaling—touching and recognition of cells Ex. normal development and immunity
Chemical signaling—interaction between receptors and ligands (neurotransmitters, hormones and paracrines)
G protein–linked receptors—ligand binding activates a G protein, affecting an ion channel or enzyme or causing the release of an internal second messenger, such as cyclic AMP

15. Cascade of cellular responses (metabolic and structural changes)1
Ligand (1st
messenger) binds
to the receptor. 2
The activated receptor
binds to a G protein and
activates it. 3
Activated G protein activates
(or inactivates) effector protein
(e.g., an enzyme) by causing its
shape to change.
Extracellular fluid
Effector protein
(e.g., an enzyme)
Ligand
Receptor 4
Activated effector
enzymes catalyze reactions
that produce 2nd
messengers in the cell
Inactive 2nd
messenger
G protein
GDP
Active 2nd
messenger 5
Second messengers
activate other enzymes
or ion channels 6
Activated
kinase
enzymes
Kinase enzymes transfer
phosphate groups from ATP to
specific proteins and activate a
series of other enzymes that
trigger various cell responses.
Cascade of cellular responses
(metabolic and structural changes)
Intracellular fluid
Figure 3.16

16. Intercellular Junctions
Tight junctions
Desmosomes
Gap junctions

17. (a) Tight junctions: Impermeable junctions prevent molecules
Plasma membranes
of adjacent cells
Microvilli
Intercellular
space
Basement membrane
Interlocking
junctional proteins
Intercellular
space
(a) Tight junctions: Impermeable junctions prevent molecules
from passing through the intercellular space.
Figure 3.5a

18. (b) Desmosomes: Anchoring junctions bind adjacent cells together
Plasma membranes
of adjacent cells
Microvilli
Intercellular
space
Basement membrane
Intercellular space
Plaque
Intermediate
filament (keratin)
Linker glycoproteins
(cadherins)
(b) Desmosomes: Anchoring junctions bind adjacent cells together
and help form an internal tension-reducing network of fibers.
Figure 3.5b

19. (c) Gap junctions: Communicating junctions allow ions and small mole-
Plasma membranes
of adjacent cells
Microvilli
Intercellular
space
Basement membrane
Intercellular
space
Channel
between cells
(connexon)
(c) Gap junctions: Communicating junctions allow ions and small mole-
cules to pass from one cell to the next for intercellular communication.
Figure 3.5c

20. Cytoplasmic Organelles
Endoplasmic Reticulum
Rough ER
Smooth ER
Ribosomes
Free- Cytosol and Mito.
Membrane Bound- Integral or Export

21. (a) Diagrammatic view of smooth and rough ER
Smooth ER
Nuclear
envelope
Rough ER
Ribosomes
(a) Diagrammatic view of smooth and rough ER
Figure 3.18a

22. Cytoplasmic Organelles
Golgi apparatus
Lysosomes
Peroxisomes
Mitochondria
Endosymbiotic bacteria????

23. Golgi at Work

24. Cytoplasmic Organelles
Centrosome

25. Cytoplasmic Organelles
Cilia- produced from centrosome
short hair-like projections
propel substances on cell surface
Flagellum
long tail-like projection
provides motility to sperm

26. Cellular Extensions Microvilli
Fingerlike extensions of plasma membrane
Increase surface area for absorption

27. Microvillus
Actin
filaments
Terminal
web
Figure 3.28

28. Cytoplasmic Organelles
Vesicles
membranous sacs
store substances
Microfilaments and microtubules
protein rods and tubes
support cytoplasm
allows for movement of organelles

29. Cell Nucleus control center of cell nuclear envelope nucleolus
chromatin

30. Chromatin (condensed)
Nuclear pores
Nuclear envelope
Nucleus
Chromatin (condensed)
Nucleolus
Cisternae of rough ER
(a)
Figure 3.29a

31. Surface of nuclear envelope.
Fracture
line of outer
membrane
Nuclear
pores
Nucleus
Nuclear lamina. The netlike
lamina composed of inter-
mediate filaments formed by
lamins lines the inner surface
of the nuclear envelope.
Nuclear pore complexes.
Each pore is ringed by
protein particles.
(b)
Figure 3.29b