1. Energy management within cells Lecture 6

2. Controlled Pathways  The various compartments of the cell (- what are they?) are populated with a very large number of chemical reagents, products, and enzymes.  How does the cell control them all?  The various compartments of the cell (- what are they?) are populated with a very large number of chemical reagents, products, and enzymes.  How does the cell control them all?

3. Pathways Each step in this pathway is regulated by specific enzymes - this is one mechanism which allows multiple reactions to occur in a common environment. A complex pathway can further be regulated by a number of different feedback mechanisms - both up regulation and down regulation, feedback inhibition and feedback initiation, and other more complex interactions.

4. -Watch Multimedia-  Biochemical Pathways  FileName: Bio10.swf  Biochemical Pathways  FileName: Bio10.swf

5.  The biosynthetic pathway for the two amino acids E and H is shown schematically below. You are able to show that E inhibits enzyme V, and H inhibits enzyme X. Enzyme T is most likely to be subject to feedback inhibition by __________________ alone.  (a)A  (b)B  (c)C  (d)E  (e)H  The biosynthetic pathway for the two amino acids E and H is shown schematically below. You are able to show that E inhibits enzyme V, and H inhibits enzyme X. Enzyme T is most likely to be subject to feedback inhibition by __________________ alone.  (a)A  (b)B  (c)C  (d)E  (e)H

6.  An average cell has both general reactions which it needs to perform to sustain life, as well as specialized ones that make that cell type unique, i.e. pancreatic cell.  The general reactions are called housekeeping reactions  These can be many in number and their interactions are pretty complex…  An average cell has both general reactions which it needs to perform to sustain life, as well as specialized ones that make that cell type unique, i.e. pancreatic cell.  The general reactions are called housekeeping reactions  These can be many in number and their interactions are pretty complex…

8. Anabolic & Catabolic  Regardless of the complexity they are of two types -  ANABOLIC  CATABOLIC  …  Regardless of the complexity they are of two types -  ANABOLIC  CATABOLIC  …

10. Enzymes  Vast majority are P’s (however, some RNA)  Increase the rate of virtually ALL chemical reactions - fact: A reaction that takes just milliseconds in the presence of an enzyme would take millions of years without (some increase the rate by as much as 1 x 10 18 fold!!!)  Enzyme pool selectively determines which reactions shall take place inside a cell & when  Vast majority are P’s (however, some RNA)  Increase the rate of virtually ALL chemical reactions - fact: A reaction that takes just milliseconds in the presence of an enzyme would take millions of years without (some increase the rate by as much as 1 x 10 18 fold!!!)  Enzyme pool selectively determines which reactions shall take place inside a cell & when

11. Enzymes…  Catalysts - Biological Catalysts  2 Main Properties  1. Increase rate without change to enzyme  2. Do not alter chemical equilibrium  Just speed things along by bringing molecules together and reducing the activation energy of the reactions too.  Catalysts - Biological Catalysts  2 Main Properties  1. Increase rate without change to enzyme  2. Do not alter chemical equilibrium  Just speed things along by bringing molecules together and reducing the activation energy of the reactions too.

12. Random Motion  The meeting of substrates and substrates and enzymes is random.  The meeting is driven by the thermal energy of the molecules at these temperatures  Quicktime movie (rmotion.mov).…  The meeting of substrates and substrates and enzymes is random.  The meeting is driven by the thermal energy of the molecules at these temperatures  Quicktime movie (rmotion.mov).…

13. Activation Energy  An important concept that you have to learn

15. Enzymes mechanisms  Enzymes are specific  AA’s from different parts of the P’ come together to form the active site (binding pocket)  ‘Lock-and-key’ model - exact fit  Induced fit model - alteration of the substrate by the binding process  Enzymes are specific  AA’s from different parts of the P’ come together to form the active site (binding pocket)  ‘Lock-and-key’ model - exact fit  Induced fit model - alteration of the substrate by the binding process

17. Enzyme kinetics  Initial binding is ionic  Subsequent interactions may involve covalent exchanges  Atomic distances involved  Prosthetic groups - small molecules that participate in catalysis - metal ions  Coenzymes - small molecules that enhance rates - organic molecules - Biotin  Initial binding is ionic  Subsequent interactions may involve covalent exchanges  Atomic distances involved  Prosthetic groups - small molecules that participate in catalysis - metal ions  Coenzymes - small molecules that enhance rates - organic molecules - Biotin

18. Enzyme regulation  Activity can be modulated - controlled to suit the needs of the cell  Feedback inhibition - product inhibits more product formation  Allosteric regulation - ‘other - site’ - molecules which bind to the enzymes to alter its physical properties  Phosphorylation - adding of phosphate groups to P’ to regulate activity - serine, threonine, or tyrosine AA’s - : + or -  Activity can be modulated - controlled to suit the needs of the cell  Feedback inhibition - product inhibits more product formation  Allosteric regulation - ‘other - site’ - molecules which bind to the enzymes to alter its physical properties  Phosphorylation - adding of phosphate groups to P’ to regulate activity - serine, threonine, or tyrosine AA’s - : + or -

19. Metabolic Energy  Cells need energy to function, grow and multiply  A large portion of the cells resources are spent on obtaining energy  Most reactions utilize energy  Gibbs FREE ENERGY = ∆G - release of energy is -∆G  ATP = ∆G of @ -12kcal/mol - releases energy on hydrolysis  Cells need energy to function, grow and multiply  A large portion of the cells resources are spent on obtaining energy  Most reactions utilize energy  Gibbs FREE ENERGY = ∆G - release of energy is -∆G  ATP = ∆G of @ -12kcal/mol - releases energy on hydrolysis

20. Glycolysis (covered in greater detail later in this course)  Breakdown of glucose for energy to Pyruvate  ∆G = -686 kcal/mol  Nearly every cell performs glycolysis  No oxygen required - anaerobic reaction  Location - cytoplasm  Does this same reaction occur in bacteria?  Where does this same reaction occur in bacteria?  Breakdown of glucose for energy to Pyruvate  ∆G = -686 kcal/mol  Nearly every cell performs glycolysis  No oxygen required - anaerobic reaction  Location - cytoplasm  Does this same reaction occur in bacteria?  Where does this same reaction occur in bacteria?

21. Acetyl CoA (covered in greater detail later in this course)  Acetyl coenzyme A  Intermediary in metabolism  Forms when Coenzyme A reacts with pyruvate  Eukaryotes - mitrochondria  Acetyl coenzyme A  Intermediary in metabolism  Forms when Coenzyme A reacts with pyruvate  Eukaryotes - mitrochondria

22. Citric acid cycle (covered in greater detail later in this course)  Krebs cycle  Oxidative metabolism  Mitrochondria  Krebs cycle  Oxidative metabolism  Mitrochondria

23. Photosynthesis (covered in greater detail later in this course)  Sunlight is the ultimate source of energy  Plants and bacteria produce carbohydrates through photosynthesis  Chlorophylls - photosynthetic pigments  Sunlight is the ultimate source of energy  Plants and bacteria produce carbohydrates through photosynthesis  Chlorophylls - photosynthetic pigments

24. Stay Current Please  Read chapter 2 fully & visit the website.