1. The Mechanisms of Body Function and The Metabolic Pathways
Chapter 3
Vander’s
Human Physiology
The Mechanisms of Body Function and The Metabolic Pathways

2. Chapter 3 Cell structure and protein function
Structure determines function.
That which alters structure alters function.
Cells:
membranes─internal and external partitions
nucleus─genomic DNA
ribosomes─protein synthesis
endoplasmic reticulum─synthesis and calcium dynamics
Golgi apparatus─secreted proteins
mitochondria─ATP synthesis
miscellaneous organelles

3. Chapter 3 Cell structure and protein function (cont.)
Central dogma: genes to proteins
transcription (DNA to RNA) 
splicing (RNA to mRNA) 
translation (mRNA code determines
amino acid sequence in protein synthesis)
ATP/chemical energy: substrate/oxidative phosphorylation
Enzymes and metabolic pathways

4. Figure 3-2
Sizes, on a log scale.

5. Figure 3-3
Electron Micrograph of organelles in a hepatocyte (liver cell).

6. Organelles have their own membranes.
Figure 3-4
Organelles have their own membranes.

7. Electron micrograph and sketch of plasma membrane
Figure 3-6
Electron micrograph and sketch of plasma membrane
surrounding a human red blood cell.

8. Figure 3-7
Phospholipid bilayer

9. the linear sequence of the protein Circles represent amino acids in
Figure 3-8
The amino acids along
the membrane section
non-polar side chains
are likely to have
the linear sequence of the protein
Circles represent amino acids in
Schematic cartoon of a transmembrane protein.

10. Figure 3-9
Drawing of the fluid-mosaic model of membranes, showing the phospholipid bilayer and imbedded proteins.

11. Figure 3-10a
Desmosomes provide strong attachments.

12. Tight junctions prevent leaks.
Figure 3-10b

13. Figure 3-10d
Gap junctions communicate and coordinate.

14. {site of ribosome assembly}
Figure 3-11
{site of ribosome assembly}
{genomic DNA}

15. Figure 3-12

16. Figure 3-13

17. Figure 3-14

18. Figure 3-15
Protein filaments function in movement and support.

19. Figure 3-16
NUCLEUS
The DNA code is “transcribed” into mRNA.
RIBOSOMES
The mRNA is “translated” to give instructions for proteins synthesis.

20. (note: mRNA intermediate not shown)
Figure 3-17
(note: mRNA intermediate not shown)
GENES “CODE FOR” PROTEINS
The “triplet code” of DNA determines
which amino acid will be placed in
each position of the protein.

21. Figure 3-18
Transcription of a gene from the DNA template
to RNA transcript. [RNA triplets are called
“codons.”]

22. Introns stay “in” the nucleus; exons “exit” the nucleus.
Figure 3-19

23. Codon sequence on mRNA pairs with anticodon of tRNA to determine
Figure 3-20
Codon sequence
on mRNA pairs
with anticodon of
tRNA to determine
which amino acid
gets put into
the new protein.

24. Arrow indicates movement of the ribosome along the mRNA.
Figure 3-21

25. An mRNA molecule may have several ribosomes on it.
Figure 3-22
An mRNA molecule may have
several ribosomes on it.

26. Large proteins can be cut
Figure 3-23
Large proteins can be cut
into smaller proteins.

27. Figure 3-24
Transcription is precisely regulated.

28. … from mRNA to secreted protein …
Figure 3-25

29. Shape and charge work together in matching up ligands with their
Figure 3-26
Shape and
charge
work together
in matching
up ligands
with their
receptors.

30. The amino-acid sequence of a protein determines both shape and the
Figure 3-27
ligand
The shape and
charge distribution
of a binding protein
determine which
ligands it will bind.
binding protein
The amino-acid sequence
of a protein determines
both shape and the
distribution of charge.

31. Protein X binds a wider diversity of ligands than does Protein Y.
Figure 3-28
Protein X
binds a
wider
diversity
of ligands
than does
Protein Y.
Protein Y
has
greater
ligand-
specificity
than
Protein X.

32. Figure 3-29
Protein 1 has the best ligand fit in terms of both shape and charge, so, of these three proteins, it has the greatest affinity for this ligand.

33. Saturation occurs when ligands become so abundant that every binding site is occupied.
Figure 3-30

34. When two proteins can bind the same ligand,
saturation occurs more readily for the protein that
has a higher affinity (Protein Y, here) for the ligand.
Figure 3-31

35. A covalent modulator forms a covalent bond with the protein.
An allosteric
modulator
forms a non-
covalent bond
with the
protein.
A covalent modulator forms a
covalent bond with the protein.
Figure 3-32

36. A + B C + D For the reversible reaction:
the law of mass action applies,
meaning that an increase in the
amount of reactants will increase
the rate of product formation, i.e.,
Alternatively, an increase in the
the amount of products will decrease
the rate of product formation. i.e.,

37. Enzymes accelerate the reactions they catalyze by
using binding sites to bring substrates together.
Figure 3-33

38. Figure 3-34
Saturation of enzymes occurs when
substrates become so abundant that
all enzymes are participating fully.

39. Figure 3-35
Increasing the availability of enzymes
results in an increased rate of reaction.

40. Figure 3-36
An allosteric or covalent modulator that
increases an enzyme’s affinity for its substrates
will increase the rate of product formation.

41. Figure 3-37
Any given enzyme can have a diversity of
allosteric and/or covalent modulation sites.

42. Figure 3-38
The amount of enzyme and its allosteric and/or covalent inhibitors/activators determine the rate of product formation.

43. Figure 3-39
E, the “end-product,” acts as an inhibitory modulator
of enzyme e2, the rate-limiting enzyme in this sequence.

44. Figure 3-40
Breaking down
fuels
provides
chemical energy
to rebuild
ATP supplies.

46. Figure 3-41
Glycolysis: A net gain of 2
molecules of ATP and 4 atoms
of hydrogen.

47. Anaerobic conditions can occur
in periods of high energy demand;
lactate  lactic acid is formed,
increasing acidity in the tissue.
Figure 3-42

48. Figure 3-43
Each transition of pyruvate
to acetyl coenzyme A yields
one NADH and one CO2.
The acetyl coenzyme A
then enters the Krebs cycle.

49. Figure 3-44
In aerobic conditions,
two spins of the Krebs cycle
occur for each glucose
that enters glycolysis.

50. Figure 3-45
For each NADH, 3 ATPs are formed.
For each FADH2, 2 ATPs are formed.

51. Glucose catabolism “powers”
ATP synthesis via a combination of
substrate and oxidative phosphorylation.
Figure 3-46

52. Figure 3-47
Glycogen is a storage polymer of glucose.
When fed, “glycogenesis” occurs (up arrows).
When fasted, “glycogenolysis” occurs (down arrows).

53. Figure 3-48
Glucose catabolism
occurs in most cells
(black arrows).
During fasting, the
liver synthesizes
glucose
(= gluconeogenesis; red arrows).
This new glucose is
needed in the central
nervous system.

55. The catabolism of the many covalent bonds in fatty acids that occurs in
mitochondria.
Figure 3-49

56. Figure 3-50
Amino acids are used as fuels after removal of the amino group.
One amino acid can be converted to another amino acid
by altering the position of some of the atoms.

57. Figure 3-51
Transamination
and deamination
routes by which
the amino acids
alanine and
glutamic acid
contribute to
energy metabolism.

58. Figure 3-52
Consideration of the inputs and outputs
of the body’s overall pool of amino acids

59. Figure 3-53
Inter-conversions of the molecules that
serve as building blocks and as fuels.

61. The End.