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.