Metabolism: Energy and EnzymesBIO100 - chp 5

•Cell energy

•Metabolic reactions

•Energy transformation

•Metabolic pathways and Enzymes

•Oxidation-reduction of energy flow

•Cells and the flow of energy

Energy is:

  1. The ability to do work or bring about a change
  2. Living things are constantly changing and need to acquire energy
  3. Cells use acquired energy to maintain:
  • cellular organization
  • carry out reactions that allow organisms to develop grow and reproduce.

There are Two forms of energy:

  • Kineticenergy - energy of movement
  • Potentialenergy -stored energy

Cells and the flow of energy: There are 2 Laws of thermodynamics

  1. 1st law
  • Law of energy conservation
  • Energy cannot be created or destroyed, but it can be changed from one form to another
  • Total amt. of energy remains constant
  • 2nd law
  • Energy cannot be changed from one form to another without a loss of usable energy

Flow of Energy

Metabolic reactions and energy transformations

•Energy Reactions in Metabolism. There are 3 chemical reactions that occur in cells

–Reactantsare the substances that participate in chemical reactions

–Products-substances that are formed in a chemical reaction

–Free energy- amount of energy that is available to do work after a chemical reaction has occurred. Seen as the release of ATP

•ATP- the energy for cells (Adenosine triphosphate)

The Advantages of ATP as an energy carrier:

  1. Provides a common energy currency for many metabolic reactions
  2. Breakdown of ATP releases sufficient energy for biological processes - little is wasted
  3. ATP breakdown is coupled to endergonic reactions in such a way that it minimizes energy loss

How does energy flow in chemical reactions?

•Some chemical reaction release energy; while others consume energy

•Exergonic reaction= 2 substrates combine and the reactions produce a byproduct plus energy. This example show the production of 2 byproducts and ATP energy is released.

•Endergonicreaction = this type of reaction takes 2 or more products and uses up energy to change or produce a product

•Functions of ATP energy:

–Chemical work - supplies energy for synthesizing macromolecules that make up the cell and the organism.

–Transport work - supplies energy for active transport mechanisms across the plasma membrane

–Mechanical work - supplies energy for muscle contraction, cilia movement, chromosome migration, etc.

•Metabolic pathwaysand the role of enzymes

–Metabolic pathways are a series of linked reactions

–They begin with a specific reactant and produce an end product

–There are more efficient means of capturing metabolic energy than releasing it all in one step – one reaction leads to the next reaction …. to the next reaction….

–Each step is catalyzed by a specific enzyme

•Enzymes

–Protein molecule that functions as an organic catalyst to speed up rate of chemical reaction

–Reactants in an enzymatic reaction are called substrates

Enzymes + Substrates + reaction

•Enzymes are protein molecules that speed chemical reactions by lowering the energy activation.

•They do this by forming enzyme substrate complex

SubstrateEnzyme

lipidLipase

UreaUrease

MaltoseMaltase

Ribonucleic acidRibonuclease

LactoseLactase

•Enzymes are Biological Catalysts –( a protein)

•The structure of enzymes allows them to catalyze (break down) specific reactions

–The cycle of enzyme-substrate interactions

Enzymes- there are Factors affecting enzymatic speed

–The concentration of the Substrates

–The concentration of the Enzyme

–Temperature and pH (too hot denatures it, to cold, slows or even halts the process)

–Enzyme inhibition

–Enzyme cofactors

–Factors affecting enzymatic speed

Substrate concentration

•Enzyme activity increases as substrate concentration increases - because there are more collisions between substrate and enzyme

Enzyme concentration

•Cell regulates metabolism by regulating which enzymes are active

•Genes producing enzymes can be turned on or off to regulate enzyme concentration

•In some cases a signaling molecule is used to activate an enzyme

Temperature

  1. Activity increases as temperature increases
  2. Due to increased enzyme-substrate collisions
  3. High heat will denature an enzyme by breaking down the tertiary structure (p.33)
  4. Effect of temperature on rate of reaction – for example, the rate of enzymatic reaction doubles with every 10°C but it will peaks at 40°C, in which then the metabolic reactions declines with warmer temperatures – and can denatured the protein enzymes

Factors that can affect the rate of enzymes:

Enzyme inhibition (resistance of enzyme reaction) and cofactors

–It can occur when enzymes cannot bind its substrates

– Activity of cell enzymes is regulated by feedback inhibition, When product is used up, it’s removed from active site (Poisons - enzyme inhibitors)

–Cofactors assist enzymes

–Coenzymes are organic, nonprotein helper like vitamins

–A deficiency of any vitamins results in lack of certain enzymatic actions