1. Cell Structure & Function
Chapter 3

2. The Diversity of Cells in the Human Body
There are over 200 different kinds of cells in the body
Figure 3-1

3. Anatomy of a representative cell
Figure 3-2

4. Parts of a “representative” cell
Plasma (Cell) Membrane
Lipid barrier between outside and inside
Cytoplasm
Cytosol (intracellular fluid)
Organelles

5. Structure of the cell membrane
Plasma membrane comprised primarily of phospholipids, proteins & carbohydrates
Phospholipid bilayer
acts as a selective physical barrier

6. Structure of the cell membrane
Proteins
Integral (transmembrane)
Peripheral

7. Structure of the cell membrane
Functions of Membrane Proteins include:
Receptors
Channels
Carriers
Enzymes
Anchors
Identifiers

8. Structure of the cell membrane
Carbohydrates
act as receptors & identity markers

9. Functions of The Cell Membrane
Functions of the plasma membrane include:
Physical isolation
Regulation of exchange with the environment (“selective permeability”)
Sensitivity to surrounding environment
Shape and structural support
Cell identification & communication (signaling)
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10. The Cytoplasm Cytoplasm All the “stuff” inside a cell The “stuff”:
The cytosol (a.k.a. intracellular fluid)
The organelles
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11. The Cytosol The Cytosol
Intracellular fluid that usually has a “gel-like” consistency
Contains dissolved nutrients (including amino acids & lipids), ions, proteins (enzymes), and wastes
Functions include: distribution of materials by diffusion, site of some enzymatic reactions
ICF not the only place we have fluids in body
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

12. Fluid compartments of the body
Intracellular fluid (ICF) – a.k.a. cytosol
Extracellular fluid (ECF)
interstitial fluid
plasma
lymph
ISF
Blood vessel (plasma)
One of the things the cell membrane is important for is separating fluids of the body. Fluids separated into compartments” (ICF/ECF). These fluids are mainly H2O with different concentrations of solutes dissolved within each. We will look at how these fluids & solutes can move between these fluid compartments in the lab next week.
Cell
(ICF)
Cell
ISF
Lymphatic vessel (lymph)
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13. The Organelles Membranous organelles Nonmembranous organelles
- Isolated compartments
Nucleus
Mitochondria
Endoplasmic reticulum (smooth & rough ER)
Golgi apparatus
Lysosomes
Peroxisomes
Membranous organelles have membrane that is similar structure to plasma membrane (phospholipids & proteins)
Nonmembranous organelles
- In direct contact with cytosol
Cytoskeleton (including microvilli, centrioles, cilia, flagella)
Ribosomes
Proteasomes

14. The Nucleus The Nucleus Figure 3-16
Largest organelle in the cell; most cells have single nucleus, some (skel. musc.) are multinucleate, some (RBCs) are anucleate. Often described as “control center” of a cell but what is it controlling & how?
Surrounded by a nuclear membrane (nuclear envelope) that contains nuclear pores. The envelope separates the nucleoplasm from the cytosol, & the pores allow for some chemical communication between. Nucleoplasm contains DNA, RNA, & one or more Nucleoli (a/w/a proteins, ions, enzymes, etc)
Figure 3-16

15. DNA/Chromosomes/Chromatin/Genes
Structure of DNA molecule is a double helix shaped pair of DNA strands comprised of nucleotide units (made of a sugar (deoxyribose), a phosphate group & a nitrogenous base (A, G, C, T)). A gene is a segment of the DNA strand that codes for a particular protein.
DNA molecules coil up around histone proteins to form loosely arranged chromatin or tightly coiled chromosomes (depending on whether cell dividing or not). Human body cells have 23 pair (46) of chromosomes/cell. Gametes have 23 single (unpaired) chromosomes.
Adenine
Guanine
Cytosine
Uracil (RNA only)
Thymine
Figure 3-17

16. The Nucleus “The Big Picture”
The nucleus contains DNA, the genetic code, within chromosomes. Genes, segments of chromosomes, contain the “blueprint” for the production of specific proteins. The proteins synthesized not only determine cell structure and function, but the organism’s structure (anatomy) & function (physiology).
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

17. Nucleoli Nucleoli are non membranous organelles within the nucleus
Synthesize ribosomal RNA (rRNA) – building block that creates ribosomes

18. Ribosomes Made of ribsosomal RNA & protein subunits
Found free in cytoplasm (free ribosomes) or attached to rough endoplasmic reticulum (ER) (fixed ribosomes)
Site of protein synthesis

19. Protein Synthesis Two step process:
Transcription – occurs in the nucleus
Translation – occurs on ribosomes in the cytoplasm

20. Protein Synthesis
Transcription—the production of RNA from a single strand of DNA
Occurs in nucleus with production of messenger RNA (mRNA)
mRNA exits through nuclear pore to go to ribosome
DNA
Gene
Codon 1
RNA
nucleotide
KEY
Adenine
Guanine
Cytosine
Uracil (RNA)
Thymine
mRNA
strand 2 3
Codon 4
(stop signal)
Promoter
Triplet 1
Triplet 2
Triplet 3
Triplet 4
Complementary
triplets
polymerase

21. Protein Synthesis Translation—the assembling of a protein on ribosomes
Adenine
Guanine
Cytosine
Uracil (RNA)
Thymine
KEY
NUCLEUS
mRNA
Amino acid
tRNA
Anticodon
tRNA binding sites
Small
ribosomal
subunit
mRNA strand
Start codon
The mRNA strand binds to the small ribosomal subunit and is joined at the start codon by the first tRNA, which carries the amino acid methionine. Binding occurs between comple-mentary base pairs of the codon and anticodon.
The small and large ribosomal subunits interlock around the mRNA strand.
Large
A second tRNA arrives at the adjacent binding site of the ribosome. The anticodon of the second tRNA binds to the next mRNA codon.
Stop
codon
Peptide bond
The first amino acid is detached from its tRNA and is joined to the second amino acid by a peptide bond. The ribosome moves one codon farther along the mRNA strand; the first tRNA detaches as another tRNA arrives.
The chain elongates until the stop codon is reached; the components then separate.
Small ribosomal
Completed
polypeptide
Translation—the assembling of a protein on ribosomes
Transfer RNAs (tRNA) bring specific amino acids based on transcribed “message” of mRNA
Occurs in cytoplasm

22. Protein Synthesis

23. The Endoplasmic Reticulum
Network of intracellular membranes primarily for molecular synthesis, storage & intracellular tranport
Rough ER (RER)
Contains ribosomes
Stores, modifies & transports newly made proteins
Smooth ER (SER)
Lacks ribosomes
Synthesizes, stores & transports lipids & carbohydrates
Figure 3-13

24. Golgi apparatus Receives new proteins from RER & lipids from SER
Modifies proteins by adding carbohydrates and lipids
Packages proteins & lipids in vesicles
Secretory vesicles (for exocytosis)
Membrane renewal vesicle
Synthesizes Lysosomes

25. Golgi apparatus EXTRACELLULAR FLUID CYTOSOL (b) Exocytosis
Endoplasmic reticulum
CYTOSOL
Cell
membrane
Lysosomes
Secretory
vesicles
Transport
vesicle
(b)
Exocytosis
Golgi apparatus
Membrane renewal
vesicles
Vesicle
Incorporation in
cell membrane
(a)
Figure 3-14
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26. Lysosomes, Peroxisomes, Proteasomes
Produced by golgi apparatus
Vesicles containing digestive enzymes
Clean-up cellular debris & recycle worn out organelles
Defend against bacteria
Peroxisomes:
contain digestive enzymes to break down fatty acids & other organic compounds
Proteasomes:
contain digestive enzymes (proteases) to break down proteins

27. Mitochondria Site of ATP production
Double layered membrane with inner folds (cristae) enclosing metabolic enzymes for cellular (aerobic) respiration
Figure 3-15

28. Mitochondria “The Big Picture”
Mitochondria provide most of the energy needed to keep your cells (and you) alive. They consume oxygen and organic substrates, and they generate carbon dioxide and ATP.
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

29. The Cytoskeleton
Internal protein framework to provide strength & structural support, movement of cellular structures & materials
Comprised mainly of:
Microfilaments (actin)
Intermediate filaments (varies)
Microtubules (tubulin)
Figure 3-12

30. The Cytoskeleton Microfilaments
a. myofilaments of muscle cells – muscle contraction
b. microvilli – increase cell surface area

31. The Cytoskeleton 2. Microtubules
a. centrioles - move chromosomes during mitosis
b. cilia - move substances across cell surface
c. flagella - moves cell through fluid (sperm)
3. Intermediate filaments – provide structural support

32. Cell division
Somatic Cell division - The reproduction of body cells; necessary for growth & repair. Results in the formation of 2 genetically identical “daughter” cells
Mitosis - The nuclear (chromosomal) division of somatic cells (after chromosomal replication has occurred).
Cytokinesis - The division of cytoplasmic contents
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33. Nucleus Spindle fibers Mitosis begins Chromosome with two
Interphase
Early prophase
Late prophase
Nucleus
Spindle
fibers
Mitosis
begins
Chromosome
with two
sister chromatids
Centrioles
(two pairs)
Centromeres
Metaphase
Anaphase
Telophase
Separation
Daughter
chromosomes
Cytokinesis
Metaphase
plate
Cleavage
furrow
Daughter
cells
Figure 3-22
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34. Cell Diversity and Differentiation
Somatic (Body) Cells
All have same genes
Some genes inactivate during development
Cells thus become functionally specialized. This specialization is known as “differentiation” of cells
Specialized (differentiated) cells form distinct tissues in the body
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

35. Processes of Transport
Lab

36. Two types of processes of transport (movement):
Passive – no energy needed
Active – energy needed

37. Passive processes of transport
No energy required for movement
Movement occurs with (“down”) the concentration gradient
- Includes:
Diffusion
Facilitated diffusion (facilitated transport)
Osmosis
Filtration
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38. Diffusion
Diffusion
Random movement down a concentration gradient (from higher to lower concentration)
Movement continues until “equilibrium” is reached

39. Diffusion Across Cell Membranes
Figure 3-5

40. Passive Membrane Transport
Facilitated diffusion
no ATP required but requires a carrier protein

41. Osmosis
Osmosis
Movement of water across a membrane, down a water concentration gradient (from higher H2O concentration to lower) & due to osmotic pressure (from lower to higher osmotic pressure)
Osmotic pressure – relates to the concentration of solutes. The higher the concentration of solutes, the higher the osmotic pressure.
Water will always move from lower to higher osmotic pressure

42. Osmosis
Figure 3-6

43. Osmotic Effects of Solutions on cells
Isotonic solution- same concentration solutes (equal osmotic pressure)
Cells maintain normal size and shape
Hypertonic solution- more solutes in solution (higher osmotic pressure) therefore less H2O
Cells lose water osmotically and shrink and shrivel
Hypotonic solution- less solutes in solution (lower osmotic pressure) therefore more H2O
Cells gain water osmotically and swell and may burst.
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44. Osmotic Flow across a Cell Membrane
Fig. 3-7
Figure 3-7

45. RBCs in hypertonic solution (crenation)
9% NaCl
RBCs in isotonic solution
0.9% NaCl
RBCs in hypotonic solution (hemolysis)
Distilled H20

46. Passive Membrane Transport
Filtration
Hydrostatic pressure (blood pressure in the body) pushes on water
Water crosses membrane (across capillary endothelium in the body)
If membrane is permeable to solutes, solutes follow water movement
Dialysis – using a semi-permeable membrane to “filter” blood of wastes if kidneys are unable
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

47. Active processes of transport
- Cell must generate energy (ATP) for movement
Movement can occur against (“up”) the concentration gradient
Larger substances can move in/out of the cell
Includes:
Active transport
Vesicular transport
endocytosis
- receptor mediated endocytosis
- phagocytosis
- pinocytosis
exocytosis

48. Active transport Carrier-Mediated
Transport Membrane proteins act as carriers
ATP consumed
Independent of concentration gradients
Ion pumps (e.g., Na-K exchange)
Copyright © 2007 Pearson Education, Inc., publishing as Benjamin Cummings

49. Vesicular Transport Membranous vesicles requiring energy for movement
Transport in both directions
Endocytosis - movement into cell
Receptor-mediated endocytosis
Pinocytosis
Phagocytosis
Exocytosis - movement out of cell
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50. Receptor-Mediated Endocytosis
EXTRACELLULAR
FLUID
Ligands
Receptor-Mediated Endocytosis
Ligands binding
to receptors
Target molecules (ligands) bind to receptors in cell membrane.
Endocytosis
Ligand
receptors
Areas coated with ligands form deep pockets in membrane surface.
Exocytosis
Coated
vesicle
CYTOPLASM
Pockets pinch off, forming vesicles.
Vesicles fuse with lysosomes.
Ligands are removed and absorbed into the cytoplasm.
Fusion
Detachment
The membrane containing the receptor molecules separates from the lysosome.
Lysosome
Ligands
removed
Fused vesicle
and lysosome
The vesicle returns to the surface.
Figure 3-10

51. Pinocytosis - “Cell drinking”
- Cell membrane folds inward “engulfing” ECF
- No receptor proteins involved

52. Phagocytosis Phagocytosis Lysosomes Vesicle Foreign object CYTOPLASM
Cell membrane
of phagocytic
cell
Lysosomes
A phagocytic cell comes in contact with the foreign object and sends pseudopodia (cytoplasmic extensions) around it.
The pseudopodia approach one another and fuse to trap the material within the vesicle.
Vesicle
The vesicle moves into the cytoplasm.
Lysosomes fuse with the vesicle.
Foreign
object
CYTOPLASM
Pseudopodium
(cytoplasmic
extension)
This fusion activates digestive enzymes.
Undissolved
residue
EXTRACELLULAR FLUID
The enzymes break down the structure of the phagocytized material.
Residue is then ejected from the cell by exocytosis.
Figure 3-11
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53. Phagocytosis animation & video

54. Exocytosis
Exocytosis