lecture 4 Flashcards
(28 cards)
3 types of bio systems
Energy can be defined as the capacity to do work or put matter into motion.
3 specific types of work in biological systems:
Chemical work – making and breaking of chemical bonds
Transport work – moving ions, molecules, and larger particles through membranes.
Mechanical work – moving organelles, changing cell shape, beating flagella and cilia. At the macroscopic level, movement by contracting muscles.
effiency of energy in human body
Many physiological processes in the human body are not very efficient.
70% of the energy used in physical exercise is lost as heat rather than transformed into the work of muscle contraction
bioenergetics
Bioenergetics is the study of energy flow through biological systems.
In a biological systems, chemical reactions are a critical means of transferring energy from one part of the system to another.
In a chemical reaction, a substance becomes a different substance, usually by breaking and/or making of covalent bonds.
how is rate of chemical reactions affected
Affected by ↑ Temperature → ↑ Rate ↑ Concentration of reactant → ↑ Rate ↓ Particle size → ↑ Rate Catalysts: ↑ Rate without being chemically changed or part of product Enzymes are biological catalysts
?
The purpose of chemical reactions in cells is to gain access to the potential energy stored in reactant molecules.
Potential energy stored in the chemical bonds of a molecule is known as the free energy of the molecule.
Stored potential energy in the chemical bonds of reactants (substrates) can be:
transferred to the chemical bonds of the products
released as heat (usually waste)
used to do work
The energy released from or stored in the chemical bonds of biomolecules during metabolism is commonly measured in kilocalories (kcal). A kilocalorie = amount of energy needed to raise the temperature of 1 liter of water by 1ºC.
Question 2: What happens to the free energy of the products and reactants during a reaction?
Answer: The difference in free energy between reactants and products is the net free energy change of the reaction.
The products of a reaction have either a lower free energy than the reactants (Exergonic reaction) or a higher free energy than the reactants (Endergonic reaction).
enzymes
Enzymes are proteins
Enzymes speed up the rate of chemical reactions by lowering the activation energy
Enzymes serve as biological catalysts, meaning the enzyme molecules are not changed in any way during the reaction
Enzymes do not change the nature of the reaction nor the results
Enzymes are specific
Without enzymes, most chemical reactions in a cell would go so slowly that the cell would be unable to live.
enzyme reactions
In enzymatically catalyzed reaction, the reactants are called substrates.
The common shorthand for enzymatic reactions shows the name of the enzyme above the reaction arrow, like this.
Enzymes are instantly recognizable by the suffix –ase
(Ex. Phosphatase – subtracts a phosphate group from a molecule; Dehydratase – removes water to make one large molecule from several smaller ones; Kinase – exchanges a phosphate group)
enzymes lower activation energy of reactants By binding their substrates and bringing them into the best position for reacting with one another
enzyme activity depends on what
Enzyme activity depends on:
Proteolytic Activation (for some) – Enzymes ending in the suffix –ogen (proenzymes or zymogens) are synthesized as inactivated molecules
Cofactors & Coenzymes (for some) – Enzymes requiring inorganic cofactors, such as Ca2+ or Mg+2, before they become active. Or requiring coenzymes which act as receptors or carriers for atoms or functional groups that are removed from the substrates during the reaction.
Temperature & pH – Most enzymes in human body have optimal activity near normal levels
Other molecules that act as inhibitors or inducers
metabolism
Enzyme activity depends on:
Proteolytic Activation (for some) – Enzymes ending in the suffix –ogen (proenzymes or zymogens) are synthesized as inactivated molecules
Cofactors & Coenzymes (for some) – Enzymes requiring inorganic cofactors, such as Ca2+ or Mg+2, before they become active. Or requiring coenzymes which act as receptors or carriers for atoms or functional groups that are removed from the substrates during the reaction.
Temperature & pH – Most enzymes in human body have optimal activity near normal levels
Other molecules that act as inhibitors or inducers
what is metabolism
Metabolism is a network of highly coordinated chemical reactions.
Each step in a metabolic pathway is a different enzymatic reaction, and the reactions of a pathway proceed in sequence.
Molecules within the pathway are called intermediates because the products of one reaction become the substrates for the next.
ratio of atp to adp
ATP powers all processes involved in metabolism
When ATP levels are low, the cells sends substrates through pathways that result in more ATP synthesis. When ATP levels are high, production of ATP decreases.
Because ATP needs to be constantly replenished, reactions are constantly continuing in the reverse order (regeneration).
atp
ATP is a 3-part molecule consisting of a:
Nitrogen base (adenine)
Ribose sugar
Three phosphate groups
High energy of ATP comes from the negatively charged phosphate groups.
Removal of the terminal phosphate releases energy
atp regeneration
ATP is a 3-part molecule consisting of a:
Nitrogen base (adenine)
Ribose sugar
Three phosphate groups
High energy of ATP comes from the negatively charged phosphate groups.
Removal of the terminal phosphate releases energy
catabolic pathways produce atp
Aerobic Respiration is the catabolic pathway that extracts energy from glucose and transfers it to produce ATP.
Aerobic production of ATP from glucose follows 3 pathways:
Glycolysis
Citric Acid (Kreb’s) Cycle
Electron Transport System
glycolysis, kreb, electron transport chain summary
Glycolysis, in the cytosol,
breaks down each glucose
molecule into two molecules of
pyruvic acid.
The pyruvic acid then enters
the mitochondrial matrix, where
the Krebs cycle decomposes it to
CO2. During glycolysis and the
Krebs cycle, substrate-level
phosphorylation forms small
amounts of ATP.
Energy-rich electrons picked up
by coenzymes are transferred to the
electron transport chain, built into
the cristae membrane. The electron
transport chain carries out oxidative
phosphorylation, which accounts
for most of the ATP generated by
cellular respiration.glycolysis
Occurs in the cytoplasm
No oxygen is required
Starts with one molecule of Glucose (6 carbons) that is converted by a series of enzymatically catalyzed reactions into two Pyruvate (3 carbons) molecules
Two phases in glycolysis:
Energy Investment Phase – 2 ATPs are required to start
Energy Payoff Phase – 4 ATPs are produced at the end of glycolysis (Net gain of 2 ATPs)
kreb’s cycle
Also known as the Tricarboxylic Acid (TCA) Cycle or Citric Acid Cycle
Each 3 carbon Pyruvate molecule reacts with Coenzyme A to form one Acetyl CoA, 1 NADH and 1 CO2
Each Acetyl CoA then enters the TCA Cycle
Occurs in the matrix of the mitochondria
The cycle makes a never-ending circle of reactions that produces ATPs, high-energy electrons, and CO2
citric acid cycle
Yield Per Pyruvate: 1 ATP 4 NADH 1 FADH2 3 CO2
Yield Per Glucose: 2 ATP 8 NADH 2 FADH2 6 CO2
oxidation vs reduction
Oxidation/Reduction & Energy
Oxidation is the loss of electrons
Reduction is the gain of electrons
chemiosmosis
ATP formation based on the production of a proton (H+) gradient across a membrane during electron transport. Movement of the protons across an ATP Synthase causes the formation of ATP.
chemiosmosis
ATP formation based on the production of a proton (H+) gradient across a membrane during electron transport. Movement of the protons across an ATP Synthase causes the formation of ATP.
- 5 ATP made per NADH
- 5 ATP made per FADH2
glucose catabolism summary
One glucose molecule metabolized aerobically through the citric acid cycle yields 30-32 ATP
Byproducts of aerobic respiration are H2O and CO2
anerobic fermentation
When oxygen supply can’t keep pace with a cell’s ATP demand, glucose shifts from aerobic to anaerobic metabolism
After Glycolysis, pyruvate is converted to lactate instead of being transported into the mitochondria
The only ATP yield is 2 from glycolysis
Muscle cells can tolerate fermentation for a limited period of time but eventually must shift back to aerobic metabolism
