1. A Tour of the Cell
Chapter 3

2. Answer the Following:
What functions must a cell perform in order to maintain life?
What cellular structures perform each of these properties.

3. A Typical Cell 3 main structural components
Plasma or Cell Membrane – surrounds the cell
Cytoplasm – gel like substance, holds organelles
Nucleus – surrounded by a membrane

4. Cell Membrane Fluid Mosaic Model –
Membrane molecules can float around the membrane
Double layer of phospholipid molecules
Hydrophilic phosphate heads
Hydrophobic fatty acid tails
In aqueous solutions these phospholipids form a sheet with fatty acid tails away from water and phosphate heads toward the water

6. Cell Membrane Different molecules are embedded in the membrane
Cholesterol –
keeps the membrane from becoming brittle
Forms rafts for proteins to move on

7. Membrane proteins: Protein Channels = Transport Proteins
Enzymes = Enzymatic activity
Receptor Proteins = Signal transduction
Glycoproteins = Cell-cell recognition
Proteins for Intercellular joining

8. Transport Enzymatic activity Signal transduction Signal Enzymes
LE 7-9a
Signal
Enzymes
Receptor
ATP
Transport
Enzymatic activity
Signal transduction

9. Cell-cell recognition Intercellular joining Attachment to the
LE 7-9b
Glyco-
protein
Cell-cell recognition
Intercellular joining
Attachment to the
cytoskeleton and extra-
cellular matrix (ECM)

10. The endomembrane system regulates protein traffic and performs metabolic functions in the cell
Parts of the endomembrane system:
Nuclear envelope
Endoplasmic reticulum
Golgi apparatus
Lysosomes
Vacuoles
Plasma membrane
These are either continuous or connected by vesicles moving from part to part
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11. Endomembrane Animation

12. Endoplasmic Reticulum
2 Types
Rough ER – with ribosomes
Smooth ER – without ribosomes
Structure –
Broad, flattened sacs
Extend outward from the nucleus

13. Smooth ER Nuclear envelope Rough ER ER lumen Cisternae Transitional ER
Fig. 6-12
Smooth ER
Nuclear envelope
Rough ER
ER lumen
Cisternae
Transitional ER
Ribosomes
Transport vesicle
200 nm
Smooth ER
Rough ER
Figure 6.12 Endoplasmic reticulum (ER)

14. Functions of ER The smooth ER (no Ribosomes)
Makes lipids for making membranes throughout the cell
Removes Calcium ions from the cytoplasm and stores them
Detoxifies poison
The rough ER (Has Ribosomes)
Has bound ribosomes
Ribosomes produce polypeptide strands that enter the ER and are folded or joined with other proteins
Proteins may be embedded in the ER membrane or move to the Golgi Apparatus in transport vesicles

15. Ribosomes Made of RNA 2 sub units, not membrane bound
May be free or attached to the endoplasmic reticulum
Site of protein synthesis
Translation of mRNA into polypeptide chain

16. The Golgi Apparatus Functions of the Golgi apparatus include
Receives many of the transport vesicles produced in the rough ER
Consists of flattened membranous sacs
Functions of the Golgi apparatus include
To sort and modify of the products of the rough ER
Packages these into vesicles to be transported
Produces lysosomes

17. Golgi Animation

18. (a) Phagocytosis: lysosome digesting food
Lysosomes carry out intracellular digestion by
Phagocytosis
Break down proteins
that are not needed
The monomers can
be reused
Peroxisomes contain peroxidase to break down hydrogen peroxide
(a) Phagocytosis: lysosome digesting food
1 µm
Lysosome contains
active hydrolytic
enzymes
Food vacuole fuses with lysosome
Hydrolytic
enzymes digest
food particles
Digestion
Food vacuole
Plasma membrane
Lysosome
Digestive
Nucleus

19. Lysosome Animation

20. Mitochondria Found in nearly all eukaryotic cells
Mitochondria are enclosed by two membranes
A smooth outer membrane
An inner folded membrane
This increases the
surface area for
reactions to occur
Mitochondrion
Intermembrane space
Outer
membrane
Free
ribosomes
in the
mitochondrial
matrix
Mitochondrial
DNA
Inner
Cristae
Matrix
100 µm
Figure 6.17

21. Mitochondria change energy from one form to another
Are the sites of cellular respiration
Breaks down large molecules to produce ATP
Much of this process takes place in the inner membrane

22. Eukaryotes: The Nucleus
DNA is located in the nucleus and does not leave
Transcription of DNA into mRNA occurs
Pre-mRNA is edited before leaving the nucleus
Nuclear envelope
has nuclear pores
Is double sided
Nucleolus – ribosomes are produced

23. The cytoskeleton
Is a network of fibers extending throughout the cytoplasm
Microtubule
0.25 µm
Microfilaments
Figure 6.20
Figure 6.20

24. There are three main types of fibers that make up the cytoskeleton

25. Microtubules Microtubules Shape the cell Guide movement of organelles
Help separate the chromosome copies in dividing cells

26. Microfilaments (Actin Filaments)
Are built from molecules of the protein actin

27. Microfilaments that function in cellular motility
Contain the protein myosin in addition to actin
Actin filament
Myosin filament
Myosin motors in muscle cell contraction.
(a)
Muscle cell
Myosin arm
Figure 6.27 A

28. Centrosomes and Centrioles
The centrosome
Is considered to be a “microtubule-organizing center”
Plants and yeast cells lack centrosomes

29. Molecular Motors

30. Cell Extensions Microvilli
Found on cells where absorption is important
Functions
Increase surface area
Allow for quick absorption

31. Cell Extensions Cilia and flagella
Contain specialized arrangements of microtubules
Are locomotor appendages of some cells

32. Cilia versus Flagellum

33. Cell Connections
In animals, there are three types of intercellular junctions
Desmosomes –
like spot welds, hold cells together like velcro
Example – Skin Cells

34. Cell Connections Gap junctions – Tight Junctions –
When membranes of adjacent cells stick together
Form tunnels that join cytoplasm
Fuse the two membranes into one
Tight Junctions –
Membrane proteins from different cells fuse
Like soft drink cans held by plastic

35. Cell Animation

36. Variety of Cell Types

37. Plasma Membrane Structure: – Lipid bi-layer:
2 layers of phospholipids clustered back to back
with polar heads and non-polar tails
Proteins:
are embedded in the lipid
bi-layer or on the surface

38. Cell Membrane Function:
Regulates what enters and leaves the cell.
Cell membranes are selectively permeable.
Also provides protection and support
2 ways in which molecules can be transported into a cell:
Passive transport
Active transport

39. Passive Transport = Diffusion
Osmosis – diffusion of water through a selectively permeable membrane
Facilitated diffusion - the use of membrane proteins to aid diffusion of a substance through a membrane

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43. Types of Solutions
Hypertonic – contains higher concentration of solute
Hypotonic – contains lower concentration of solute
Isotonic –
Contains an
equal
concentration
of solute.

45. Active Transport
Energy must be used to transport molecules into the cell.
Molecular Transport - Using membrane proteins:
ATP (energy) is required

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47. Review of Diffusion

48. Active Transport Other types of active transport:
Endocytosis –Taking particles into the cell
Phagocytosis – endocytosis of solids
Pinocytosis – endocytosis of liquids
Exocytosis – Secreting particles from the cell