Energy management within cellsEnergy management within cells
Lecture 6Lecture 6
Controlled PathwaysControlled Pathways
The various compartments of the cell The various compartments of the cell ((- what are they?)- what are they?) are populated with a very are populated with a very large number of chemical reagents, large number of chemical reagents, products, and enzymes.products, and enzymes.
How does the cell control them all?How does the cell control them all?
The various compartments of the cell The various compartments of the cell ((- what are they?)- what are they?) are populated with a very are populated with a very large number of chemical reagents, large number of chemical reagents, products, and enzymes.products, and enzymes.
How does the cell control them all?How does the cell control them all?
PathwaysPathways
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.
-Watch Multimedia--Watch Multimedia-
Biochemical Pathways FileName: Bio10.swf
Biochemical Pathways FileName: Bio10.swf
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
An average cell has both general reactions An average cell has both general reactions which it needs to perform to sustain life, as which it needs to perform to sustain life, as well as specialized ones that make that cell well as specialized ones that make that cell type unique, i.e. pancreatic 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 An average cell has both general reactions which it needs to perform to sustain life, as which it needs to perform to sustain life, as well as specialized ones that make that cell well as specialized ones that make that cell type unique, i.e. pancreatic 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…
Anabolic & CatabolicAnabolic & Catabolic
Regardless of the complexity they are of two types - ANABOLIC CATABOLIC …
Regardless of the complexity they are of two types - ANABOLIC CATABOLIC …
EnzymesEnzymes
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 1018 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 1018 fold!!!)
Enzyme pool selectively determines which reactions shall take place inside a cell & when
Enzymes…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.
Random MotionRandom 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) .…
Activation EnergyActivation Energy
An important concept that you have to learn An important concept that you have to learn
Enzymes mechanismsEnzymes 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
Enzyme kineticsEnzyme 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
Enzyme regulationEnzyme 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 -
Metabolic EnergyMetabolic 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
Glycolysis (covered in greater detail later in this course)
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?
Acetyl CoA (covered in greater detail later in this course)
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
Citric acid cycle(covered in greater detail later in this course)
Citric acid cycle(covered in greater detail later in this course)
Krebs cycle Oxidative metabolism Mitrochondria
Krebs cycle Oxidative metabolism Mitrochondria
Photosynthesis (covered in greater detail later in this course)
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
Stay Current PleaseStay Current Please
Read chapter 2 fully & visit the website. Read chapter 2 fully & visit the website.