Advanced Cell Biology. Lecture 8
Advanced Cell Biology. Lecture 8
Alexey Shipunov
Minot State University
January 30, 2012
Advanced Cell Biology. Lecture 8
Outline
Questions and answers
Lab cell images and organelles
Energy and chemistry
Free energy
Activated carriers
Advanced Cell Biology. Lecture 8
Outline
Questions and answers
Lab cell images and organelles
Energy and chemistry
Free energy
Activated carriers
Advanced Cell Biology. Lecture 8
Questions and answers
Previous final question: the answer
How living organisms are working against the second law of
thermodynamics?
Advanced Cell Biology. Lecture 8
Questions and answers
Previous final question: the answer
How living organisms are working against the second law of
thermodynamics?
I
They run catabolic reactions
Advanced Cell Biology. Lecture 8
Questions and answers
Lab cell images and organelles
Questions and answers
Lab cell images and organelles
Advanced Cell Biology. Lecture 8
Questions and answers
Lab cell images and organelles
1. Dividing bacterial cell
Advanced Cell Biology. Lecture 8
Questions and answers
Lab cell images and organelles
2. Chroomonas, unicellular alga
Advanced Cell Biology. Lecture 8
Questions and answers
Lab cell images and organelles
3. Part of cyanobacterium trichome
Advanced Cell Biology. Lecture 8
Questions and answers
Lab cell images and organelles
4. Mammal epithelial cell
Advanced Cell Biology. Lecture 8
Questions and answers
Lab cell images and organelles
5. Euglena, unicellular protist
Advanced Cell Biology. Lecture 8
Questions and answers
Lab cell images and organelles
6. Nannochloropsis, unicellular alga
Advanced Cell Biology. Lecture 8
Questions and answers
Lab cell images and organelles
7. Surface cells or Orthonectida parasitic worm
Advanced Cell Biology. Lecture 8
Questions and answers
Lab cell images and organelles
8. Pedinella, unicellular alga
Advanced Cell Biology. Lecture 8
Questions and answers
Lab cell images and organelles
9. Plant meristem cell from onion root
Advanced Cell Biology. Lecture 8
Questions and answers
Lab cell images and organelles
10. Rhodella, red alga
Advanced Cell Biology. Lecture 8
Questions and answers
Lab cell images and organelles
11. Plant root cell
Advanced Cell Biology. Lecture 8
Questions and answers
Lab cell images and organelles
12. Stomach cell of rat (Rattus)
Advanced Cell Biology. Lecture 8
Questions and answers
Lab cell images and organelles
13. Toxoplasma, parasitic protist
Advanced Cell Biology. Lecture 8
Questions and answers
Lab cell images and organelles
14. Trichomonas, parasitic amitochondrial protist
Advanced Cell Biology. Lecture 8
Questions and answers
Lab cell images and organelles
Catalysis movie
Advanced Cell Biology. Lecture 8
Energy and chemistry
Free energy
Energy and chemistry
Free energy
Advanced Cell Biology. Lecture 8
Energy and chemistry
Free energy
Free energy
I
Gibbs energy, or G, is a chemical analog of potential
energy
I
If G increases (∆G > 0), the chemical reaction is
non-favorable
I
If G decreases (∆G < 0), chemical reaction is favorable
Advanced Cell Biology. Lecture 8
Energy and chemistry
Free energy
Standard free-energy change
I
Simple chemical reaction like X → Y depends on reagent
concentrations, [X ] and [Y ]
I
Free energy (Gibbs energy) will also depend on
concentration
I
[X ]
To standardize G, we are using ∆G◦ = ∆G − RT ln [Y
],
where R (gas constant) and T (absolute temperature) are
constants
Advanced Cell Biology. Lecture 8
Energy and chemistry
Free energy
Chemical equilibrium
I
Chemical reactions are going on until they reach a state of
chemical equilibrium
I
In the equilibrium, reaction is going in both directions
without changing concentration of participating chemicals:
X Y
Advanced Cell Biology. Lecture 8
Energy and chemistry
Free energy
Equilibrium constant
I
On the stage of equilibrium,
[X ]
equilibrium constant K = [Y
],
and ∆G = 0 (why?*)
I
Consequently, standard free-energy on the stage of
equilibrium is:
[X ]
=
[Y ]
−RT ln K = −0.616 ln K =
∆G◦ = ∆G − RT ln
−1.42 log K
Advanced Cell Biology. Lecture 8
Energy and chemistry
Free energy
Equilibrium constant
I
On the stage of equilibrium,
[X ]
equilibrium constant K = [Y
],
and ∆G = 0 (why?*)
*Because equilibrium reaction does not take of give any energy
I
Consequently, standard free-energy on the stage of
equilibrium is:
[X ]
=
[Y ]
−RT ln K = −0.616 ln K =
∆G◦ = ∆G − RT ln
−1.42 log K
Advanced Cell Biology. Lecture 8
Energy and chemistry
Free energy
Equilibrium constant in complex reactions
I
In complex reactions, K depends on concentrations of all
participants
I
E.g., for A + B AB: K =
I
If reaction has several steps, all changes of free-energy
are additive
[AB]
[A][B]
Advanced Cell Biology. Lecture 8
Energy and chemistry
Activated carriers
Energy and chemistry
Activated carriers
Advanced Cell Biology. Lecture 8
Energy and chemistry
Activated carriers
Activated carrier molecules
I
Used for temporarily storage of energy
I
Have high diffusion rates
I
Processes with carriers have two steps: (a) activation and
(b) condensation
Advanced Cell Biology. Lecture 8
Energy and chemistry
Activated carriers
One component: activation and condensation
Advanced Cell Biology. Lecture 8
Energy and chemistry
Activated carriers
Two components: coupled reactions
I
Two linked reactions: either oxidizing of something +
carrier synthesis
I
Or carrier destruction + synthesis of something (e.g.,
polymer from monomers)
Advanced Cell Biology. Lecture 8
Energy and chemistry
Activated carriers
ATP often joins two molecules
I
To join A and B, ATP usually acts as intermediate:
I
A + ATP → A–0–P03 + ADP
I
B–H + A–0–P03 → A–B + Pi
Advanced Cell Biology. Lecture 8
Energy and chemistry
Activated carriers
Coupled reactions
Advanced Cell Biology. Lecture 8
Energy and chemistry
Activated carriers
Electron carriers: NADH and NADPH
I
Both are derivatives of adenine transferring electrons with
associated protons (or simply H)
I
They are active redox molecules
I
NADH typically works in catabolic reactions like cell
respiration
I
NADPH works mostly in anabolic reactions like synthesis
of DNA or synthesis of cholesterol
Advanced Cell Biology. Lecture 8
Energy and chemistry
Activated carriers
NADPH in cholesterol synthesis
Advanced Cell Biology. Lecture 8
Energy and chemistry
Activated carriers
Other possible carriers
I
FAD: transfers hydrogen like NADH/NADPH
I
CoA (or Acetyl–CoA): transfers acetyl group (CH3 –COOH)
I
Biotin: carboxyl group (–COOH)
I
S-Adenosyl methionine (SAM, SAMe): methyl group
(–CH3 )
I
Uridine diphosphate glucose (UDP-glucose): whole
glucose molecules
Advanced Cell Biology. Lecture 8
Energy and chemistry
Activated carriers
Biotin, vitamin B7
Advanced Cell Biology. Lecture 8
Energy and chemistry
Activated carriers
SAMe, S-Adenosyl methionine
Advanced Cell Biology. Lecture 8
Energy and chemistry
Activated carriers
Pyrophosphate hydrolysis of ATP
I
Normally, ATP → ADP + Pi reaction has ∆G◦ ≈-13
kcal/mole
I
Some endoenergetic reactions need more
I
The alternative way: ATP → AMP + Pi –Pi (pyrophosphate)
+ 26 kcal/mole of energy
Advanced Cell Biology. Lecture 8
Energy and chemistry
Activated carriers
Pyrophosphate
Advanced Cell Biology. Lecture 8
Energy and chemistry
Activated carriers
Final question (2 points)
Advanced Cell Biology. Lecture 8
Energy and chemistry
Activated carriers
Final question (2 points)
What are enzymes?
Advanced Cell Biology. Lecture 8
Energy and chemistry
Activated carriers
Summary
I
Some reactions are endoenergetic (∆G > 0, some are
exoenergetic (∆G < 0)
I
On the stage of equilibrium, all reactions at +37◦ C have
∆G◦ = −1.42 log K
I
Activated carriers are used in endoenergetic reactions
I
Activated carriers may transfer phosphate or different
organic groups
Advanced Cell Biology. Lecture 8
Energy and chemistry
Activated carriers
For Further Reading
A. Shipunov.
Advanced Cell Biology [Electronic resource].
2011—onwards.
Mode of access: http:
//ashipunov.info/shipunov/school/biol_250
B. Alberts et al.
Essential Cell Biology. 3rd edition.
Garland Science, 2009.
Chapter 3.