1. Nuclei (yellow) and actin (red)
Figure 4.6x

2. network of protein fibers
THE CYTOSKELETON
The cell’s internal skeleton helps organize its structure and activities
network of protein fibers
Figure 4.17A

3. Microfilaments of actin enable cells to change shape and move
Intermediate filaments reinforce the cell and anchor certain organelles
Microtubules
give the cell rigidity
provide anchors for organelles
act as tracks for organelle movement

4. INTERMEDIATE FILAMENT
Tubulin subunit
Actin subunit
Fibrous subunits
25 nm
7 nm
10 nm
MICROFILAMENT
INTERMEDIATE FILAMENT
MICROTUBULE
Figure 4.17B

6. How do cilia and flagella move?
A cilia or flagellum is composed of a core of microtubules wrapped in plasma membrane
Eukaryotes have “9+2” structure
Cilia and flagella move when microtubules bend

7. Electron micrograph of sections:
FLAGELLUM
Electron micrograph of sections:
Outer microtubule doublet
Plasma membrane
Flagellum
Central microtubules
Outer microtubule doublet
Plasma membrane
Basal body
Basal body (structurally identical to centriole)
Figure 4.18A

8. Slide 43

9. polar head P – cytosol nonpolar tails Phospholipid bilayer
Figure: 05-01a-b
Note: The nature of phospholipids (polar, nonpolar) gives a membrane its selective permeabiility.as far as hydrophobic and hydrophilic molecules.
Caption:
The essential building block of the cell’s plasma membrane is the phospholipid molecule, which has both a hydrophilic “head” that bonds with water, and hydrophobic “tails” that do not. Two layers of phospholipids sandwich together to form the plasma membrane. The phospholipids’ hydrophobic tails form the interior of the membrane, while their hydrophilic heads jut out toward the watery environments that exist both inside and outside of the cell. The bilayer forms a barrier to all but the smallest hydrophilic molecules, but hydrophobic molecules can pass through fairly freely.
cytosol
hydrophobic molecules
hydrophilic molecules
nonpolar
tails
Phospholipid bilayer

10. Cell surfaces protect, support, and join cells
Surfaces allow exchange of signals and molecules.
Plant cells connect by plasmodesmata

11. PLASMODESMATA Walls of two adjacent plant cells Vacuole
Layers of one plant cell wall
Cytoplasm
Plasma membrane
Figure 4.19A

12. Animal cells - extracellular matrix
sticky layer of glycoproteins
binds cells together in tissues
can also protect and support cells

13. Tight junctions can bind cells together into leakproof sheets
Anchoring junctions link animal cells
Gap junctions allow substances to flow from cell to cell
TIGHT JUNCTION
ANCHORING JUNCTION
GAP
JUNCTION
Plasma membranes of adjacent cells
Extracellular matrix
Figure 4.19B

14. Eukaryotic organelles fall into 4 functional groups
1. Manufacture and transport – dependent on network of membranes
Nucleus
Ribosomes
Rough ER
Smooth ER
Golgi apparatus

15. 2. Breakdown – all single-membrane sacs
Lysosomes (in animals, some protists)
Peroxisomes
Vacuoles (plants)

16. 3. Energy Processing – involves extensive membranes embedded with enzymes
Chloroplasts
Mitochondria

17. 4. Support, Movement, Communication
Cytoskeleton – includes cilia, flagella, filaments, microtubules
Cell walls
Extracellular matrix
Cell junctions

18. Figure: 03-00CO
Title:
Cholesterol in blood.
Caption:
Our bodies cannot function without cholesterol, yet too much cholesterol can threaten our health by contributing to hard deposits (colored gray in this photo) that restrict the flow of blood through arteries. Inside our bodies, the cell membrane shoulders much of the task of keeping blood cholesterol levels within bounds.

19. What do these have in common?
HIV infection
Transplanted organs
Communication between neurons
Drug addiction
Cystic fibrosis
hypercholesteremia

20. Membranes organize the chemical activities of cells
selectively permeable
hold teams of enzymes  
Cytoplasm
Figure 5.10

21. Plasma membrane
Contact between cell and environment
Keeps useful materials inside and harmful stuff outside
Allows transport, communication in both directions

22. Plasma membrane components
Phospholipid bilayer
Cholesterol
Proteins
Glycocalyx

23. polar head P – cytosol nonpolar tails Phospholipid bilayer
Figure: 05-01a-b
Note: The nature of phospholipids (polar, nonpolar) gives a membrane its selective permeabiility.as far as hydrophobic and hydrophilic molecules.
Caption:
The essential building block of the cell’s plasma membrane is the phospholipid molecule, which has both a hydrophilic “head” that bonds with water, and hydrophobic “tails” that do not. Two layers of phospholipids sandwich together to form the plasma membrane. The phospholipids’ hydrophobic tails form the interior of the membrane, while their hydrophilic heads jut out toward the watery environments that exist both inside and outside of the cell. The bilayer forms a barrier to all but the smallest hydrophilic molecules, but hydrophobic molecules can pass through fairly freely.
cytosol
hydrophobic molecules
hydrophilic molecules
nonpolar
tails
Phospholipid bilayer

24. Cholesterol blocks some small molecules, adds fluidity
THE PLASMA MEMBRANE
phospholipids
cholesterol
Figure: 05-02a
Title:
The plasma membrane.
Caption:
integral
protein
cytoskeleton
peripheral
protein
Cholesterol blocks some small molecules, adds fluidity

25. Membrane Proteins
span entire membrane or lie on either side
Purposes
Structural Support
Recognition
Communication
Transport

26. Glycocalyx
Composed of sugars protruding from lipids and proteins
Functions
Binding sites for proteins
Lubricate cells.
Stick cells down.

27. Many membrane proteins are enzymes
Some proteins function as receptors for chemical messages from other cells
The binding of a messenger to a receptor may trigger signal transduction
Messenger molecule
Receptor
Activated molecule
Figure 5.13
Enzyme activity
Signal transduction

28. The plasma membrane of an animal cell
Glycoprotein
Carbohydrate (of glycoprotein)
Fibers of the extracellular matrix
Glycolipid
Phospholipid
Cholesterol
Microfilaments of the cytoskeleton
Proteins
CYTOPLASM
Figure 5.12

29. Diffusion and Gradients
Diffusion = movement of molecules from region of higher to lower concentration.
Osmosis = diffusion of water across a membrane

30. In passive transport, substances diffuse through membranes without work by the cell
Molecule of dye
Membrane
EQUILIBRIUM
EQUILIBRIUM
Figure 5.14A & B

31. selectively permeable membrane
H2O
selectively
permeable
membrane
free water
molecule: can
fit through pore
sugar
pore
bound water molecules
clustered around sugar:
cannot fit through pore
Figure: 03-03
Title:
Osmosis.
Caption:
Free water molecules diffuse down their concentration gradient across a selectively permeable membrane, from a region of high water concentration to a region of lower water concentration.
(b)
selectively permeable
membrane
sugar molecule
bag
bursts
water molecule
pure water

32. Osmosis = diffusion of water across a membrane
Hypotonic solution
Hypertonic solution
water travels from an area of higher concentration to an area of lower water concentration
Selectively permeable membrane
Solute molecule
HYPOTONIC SOLUTION
HYPERTONIC SOLUTION
Water molecule
Selectively permeable membrane
Solute molecule with cluster of water molecules
NET FLOW OF WATER
Figure 5.15

33. Water balance between cells and their surroundings is crucial to organisms
osmoregulation = control of water balance
Osmosis causes cells to shrink in a hypertonic solution and swell in a hypotonic solution

34. hypertonic solution hypotonic solution 10 microns isotonic solution
Figure: 03-05
Title:
The effects of osmosis.
Caption:
Red blood cells are normally suspended in the fluid environment of the blood. (a) If red blood cells are immersed in an isotonic salt solution, which has the same concentration of dissolved substances as the blood cells do, there is no net movement of water across the plasma membrane. The red blood cells keep their characteristic dimpled disk shape. (b) A hypertonic solution, with too much salt, causes water to leave the cells, shriveling them up. (c) A hypotonic solution, with less salt than is in the cells, causes water to enter, and the cells swell.
equal movement of water
into and out of cells
net water movement
out of cells
net water movement
into cells

36. Passive transport = diffusion across membranes
Small nonpolar molecules - simple diffusion
Many molecules pass through protein pores by facilitated diffusion
Solute molecule
Transport protein
Figure 5.17

37. Active transport transport proteins needed
against a concentration gradient
requires energy (ATP)

38. Active transport in two solutes across a membrane
FLUID OUTSIDE CELL
Phosphorylated transport protein
Active transport in two solutes across a membrane
Na+/K+ pump
Protein shape change
Transport protein
First solute 1
First solute, inside cell, binds to protein 2
ATP transfers phosphate to protein 3
Protein releases solute outside cell
Second solute 4
Second solute binds to protein 5
Phosphate detaches from protein 6
Protein releases second solute into cell
Figure 5.18

39. Exocytosis and endocytosis transport large molecules
exocytosis = vesicle fuses with the membrane and expels its contents
FLUID OUTSIDE CELL
CYTOPLASM
Figure 5.19A

40. b Figure: 05-08b Title: Movement out of the cell. Caption:
b. Micrograph of material being expelled from the cell through exocytosis. b

41. or the membrane may fold inward, trapping material from the outside (endocytosis)
Figure 5.19B

42. Phagocytosis, “cell eating”
—How the human immune system ingests whole bacteria or one-celled creatures eat.
phagocytosis
food particle 1 2 3
Figure: 03-07b
Title:
Two types of endocytosis.
Caption:
(b) Pseudopodia encircle an extracellular particle. The ends of the pseudopodia fuse, forming a large vesicle that contains the engulfed particle.
particle
enclosed in vesicle

44. pinocytosis (extracellular fluid) 2 vesicle containing extracellular
Figure: 03-07a
Title:
Two types of endocytosis.
Caption:
(a) To capture drops of liquid, a dimple in the plasma membrane deepens and eventually pinches off as a fluid-filled vesicle, which contains a random sampling of the extracellular fluid.
vesicle containing
extracellular
fluid
(cytoplasm)

45. extracellular fluid plasma membrane cytosol vesicle coated pit
receptors
captured
molecules
vesicle
Figure: 05-09a-c
Title:
Three types of endocytosis.
Caption:
a. In pinocytosis, the plasma membrane invaginates to create a kind of harbor. The harbor then encloses completely, pinches off as a vesicle, and moves into the cell's cytoplasm, carrying with it whatever material was enclosed. b. In receptor-mediated endocytosis, many receptors bind to molecules. Then, while holding on to the molecules, the receptors migrate laterally through the cell, forming an invagination called a coated pit. The coated pit pinches off, delivering its receptor - held molecules into the cytoplasm. c. In phagocytosis, food particles - or perhaps whole organisms (such as bacteria)-are taken in by means of "false feet" or pseudopodia that surround the material. Pseudopodia then fuse together, forming a vesicle that moves into the cell's interior with its catch enclosed.
bacterium
pseudopodium
vesicle

46. Receptor-mediated endocytosis

47. Cholesterol can accumulate in the blood if membranes lack cholesterol receptors
Phospholipid outer layer
LDL PARTICLE
Receptor protein
Protein
Cholesterol
Plasma membrane
Vesicle
CYTOPLASM
Figure 5.20

48. Figure: 03-00CO
Title:
Cholesterol in blood.
Caption:
Our bodies cannot function without cholesterol, yet too much cholesterol can threaten our health by contributing to hard deposits (colored gray in this photo) that restrict the flow of blood through arteries. Inside our bodies, the cell membrane shoulders much of the task of keeping blood cholesterol levels within bounds.

49. What do these have in common?
HIV infection
Transplanted organs
Communication between neurons
Drug addiction
Cystic fibrosis
hypercholesteremia