The document discusses the structure and function of cells. It covers several key points: 1) Cells are the fundamental unit of life, and there are two main types - prokaryotic cells which lack membrane-bound organelles, and eukaryotic cells which do have organelles like the nucleus. 2) Both cell types contain ribosomes for protein synthesis, but eukaryotic cells also contain other membrane-bound structures like the endoplasmic reticulum, Golgi apparatus, mitochondria, vacuoles, and lysosomes which carry out specialized functions. 3) The plasma membrane regulates what enters and exits the cell, and the cytoskeleton provides structure and allows movement within the cell

1. BIOLOGY 189
The cell

2. The Cell
Cell theory: first unifying theory of
biology.
Cells: fundamental units of life
All organisms are composed of cells
All cells come from preexisting
cells.

3. The Cell
Most cells are tiny, in order to maintain
a good surface area-to-volume ratio.
The volume of a cell determines its
metabolic activity relative to time
The surface area of a cell determines
the number of substances that can
enter or leave the cell

4. The Scale of Life

5. The cell
Two types of microscopes to visualize small
cells:
Light microscopes²use glass lenses and
light
Resolution = 0.2 ȝm
Electron microscopes²electromagnets
focus an electron beam
Resolution = 2.0 nm

6. Microscopy

7. The Cell
Plasma membrane:
‡ Selectively permeable barrier . Allows
cells to maintain a constant internal
environment
‡ Important in communication and
receiving signals
‡ Has proteins for binding and adhering
to adjacent cells

8. The cell
Two types of cells:
Prokaryotes are without
membrane-enclosed compartments.
Eukaryotes have membrane-
enclosed compartments called
organelles, such as the nucleus.

9. The cell

10. Prokaryotic Cells Do Not Have a Nucleus
Prokaryotic cells
‡ Enclosed by a plasma membrane
‡ DNA located in the nucleoid
The rest of the cytoplasm consists of:
Cytosol (water and dissolved
material) and suspended particles
Ribosomes²sites of protein
synthesis

11. Prokaryotic Cell

12. Prokaryotic Cells
‡ Bacteria cell walls contain peptidoglycans
‡ Other bacteria have a slimy layer of
polysaccharides, called the capsule.
‡ Some prokaryotes swim by means of
flagella
‡ Some rod-shaped bacteria have a network
of actin-like protein structures to help
maintain their shape.

13. Prokaryotic Flagella

14. Eukaryotic Cells Have a Nucleus and Other
Membrane-Bound Compartments
‡Eukaryotic cells
‡ have a plasma membrane,
‡ cytoplasm, and ribosomes,
‡ also membrane-enclosed
compartments called organelles.
‡Each organelle plays a specific
role in cell functioning.

15. Eukaryotic Cells

16. Eukaryotic Cells

17. Eukaryotic Cells
‡Ribosomes: sites of protein
synthesis
‡ Occur in both prokaryotic and
eukaryotic cells and have similar
structure²one larger and one smaller
subunit.
‡ Each subunit consists of ribosomal
RNA (rRNA) bound to smaller
protein molecules

18. Eukaryotic cell. Ribosomes
Not membrane-bound
organelles
In eukaryotes: free in the
cytoplasm, attached to the
endoplasmic reticulum, or inside
mitochondria and chloroplasts.
In prokaryotic cells, ribosomes
float freely in the cytoplasm.

19. Eukaryotic Cell. The Nucleus
‡ Usually the largest organelle.
‡ Location of DNA and of DNA
replication
‡ Site where DNA is transcribed to RNA
‡ Contains the nucleolus, where
ribosomes begin to be assembled from
RNA and proteins.

20. Eukaryotic Cells. The Nucleus
‡ Surrounded by two membranes that
form the nuclear envelope.
‡ Nuclear pores control movement of
molecules between nucleus and
cytoplasm.
‡ In the nucleus, DNA combines with
proteins to form chromatin in long, thin
threads called chromosomes.

21. Eukaryotic Cell. The endomembrane system
‡ The endomembrane system includes
‡ The nuclear envelope
‡ Endoplasmic reticulum
‡ Golgi apparatus
‡ Lysosomes.
‡ Tiny, membrane-surrounded vesicles shuttle
substances between the various components,
as well as to the plasma membrane.

22. The Endomembrane System

23. Endoplasmic Reticulum (ER)
‡ Network of interconnected membranes
in the cytoplasm, with a large surface
area
‡ The ER has two distinct regions:
Smooth ER, which lacks ribosomes
Rough ER, with ribosomes

24. Smooth ER
Rough ER Nuclear
envelope
ER lumen
Cisternae
Ribosomes Transitional ER
Transport vesicle 200 nm
Smooth ER Rough ER

25. Endoplasmic Reticulum
Smooth ER Rough ER
Synthesizes Has bound
lipids and ribosomes, secrete
steroids glycoproteins
Metabolizes Distributes
carbohydrates transport
Detoxifies vesicles, proteins
poisons surrounded by
Stores calcium membranes
Glycogen Is a membrane
degradation site factory for the cell

26. The Golgi Apparatus
‡ The Golgi apparatus consists of
flattened membranous sacs called
cisternae
‡ ³Shipping and Receiving Center´
‡ Functions of the Golgi apparatus:
Modifies products of the ER
Manufactures certain macromolecules
(polysaccharides in plants)
Sorts and packages materials into transport
vesicles

27. cis face
(³receiving´ side of Golgi 0.1 µm
apparatus) Cisternae
trans face
(³shipping´ side of Golgi TEM of Golgi apparatus
apparatus)

28. Lysosomes
‡ Primary
lysosomes
originate from the
Golgi apparatus.
‡ contain
digestive
enzymes
‡ Site where
macromolecules
are hydrolyzed
into monomers.

29. Lysosomes Isolate Digestive Enzymes from the Cytoplasm

30. Eukaryotic Cells. Mitrochondria
‡ In eukaryotes, molecules are first
broken down in the cytosol.
‡ The partially digested molecules enter
the mitochondria, here chemical
energy is converted to energy-rich
ATP.
‡ Cells that require a lot of energy often
have more mitochondria.

31. Eukaryotic Cells. Mitochondria
‡Two membranes:
‡ Outer membrane: porous
‡ Inner membrane: extensive folds
called cristae, to increase surface
area
‡The fluid-filled matrix inside the inner
membrane contains enzymes, DNA,
and ribosomes.

33. Eukaryotic Cells. Plastids
‡ Plant and algae cells contain plastids
that can differentiate into organelles²
some are used for storage.
‡ Chloroplast contains chlorophyll and
is the site of photosynthesis.
‡ Photosynthesis converts light energy
into chemical energy.

35. Eukaryotic Cells. Other organelles
‡ Specialized functions.
‡ Peroxisomes collect and break down
toxic by-products of metabolism, such
as H2O2, using specialized enzymes.
‡ Glyoxysomes, found only in plants,
are where lipids are converted to
carbohydrates for growth.

37. Eukaryotic Cell. Vacuoles
‡Mainly in plants and fungi, functions:
‡Storage of waste products and
toxic compounds
‡Structure for plant cells²water
enters the vacuole by osmosis,
creating turgor pressure

38. Eukaryotic Cell. Vacuoles
‡Reproduction: vacuoles in flowers
and fruits contain pigments whose
colors attract pollinators and aid
seed dispersal
‡Catabolism²digestive enzymes in
seeds¶ vacuoles hydrolyze stored
food for early growth

39. The Cytoskeleton Provides Strength and Movement
The cytoskeleton
‡ Supports and maintains cell shape
‡ Holds organelles in position
‡ Moves organelles
‡ Involved in cytoplasmic streaming
‡ Interacts with extracellular
structures to anchor cell in place

40. The Cytoskeleton Provides Strength and Movement
Three components
Microfilaments:
‡Help a cell or parts of a cell to
move
‡Determine cell shape
‡Made from actin

41. The Cytoskeleton

42. The Cytoskeleton Provides Strength and Movement
Intermediate filaments:
‡ At least 50 different kinds
‡ Tough, ropelike protein assemblages,
more permanent than other filaments
‡ Anchor cell structures in place
‡ Resist tension, maintain rigidity

43. The Cytoskeleton

44. The Cytoskeleton Provides Strength and Movement
Microtubules:
The largest diameter components, two
roles:
‡ Form rigid internal skeleton for some
cells or regions
‡ Act as a framework for motor proteins
to move structures in the cell

45. The Cytoskeleton

46. The Cytoskeleton Provides Strength and Movement
Microtubules line movable cell
appendages.
Cilia²short, usually many present,
move with stiff power stroke and flexible
recovery stroke
Flagella²longer, usually one or two
present, movement is snakelike

47. Cilia

48. Extracellular Structures Allow Cells to Communicate
with the External Environment
‡ Extracellular structures are secreted
to the outside of the plasma membrane.
‡ In eukaryotes, these structures have
two components:
‡ A prominent fibrous macromolecule
‡ A gel-like medium with fibers embedded

49. Extracellular Structures Allow Cells to Communicate
with the External Environment
‡Plant cell wall²semi-rigid structure
outside the plasma membrane
‡The fibrous component is the
cellulose.
‡The gel-like matrix contains cross-
linked polysaccharides and proteins.

50. The Plant Cell Wall

51. Cell wall
Three major roles:
‡ Provides support for the cell and
limits volume by remaining rigid
‡ Acts as a barrier to infection
‡ Contributes to form during growth
and development

52. An Extracellular Matrix

53. An Extracellular Matrix

54. Extracellular Structures in animal cells
extracellular matrices in animal cells
‡ Hold cells together in tissues
‡ Contribute to physical properties of
cartilage, skin, and other tissues
‡ Filter materials
‡ Orient cell movement during growth and
repair

55. Extracellular Structures
‡ Cell junctions specialized structures
that protrude from adjacent cells and
³glue´ them together
‡ Tight junctions
‡ Desmosomes
‡ Gap junctions

56. Junctions Link Animal Cells