Bio 105 Lecture 5
What is Metabolismis?
Metabolismis...
– The collection of controlled biochemical reactions that take place in a cell
What is Anabolism?
Anabolism: synthesizes macromolecules from precursors • Requires energy to work (endergonic)
How do we store the energy from catabolism to use during anabolism? We make two kinds of energy carriers
1. Reducing equivalents: reduction (electron gain) of an electron carrier like NADH or FADH, that will pass that electron on later
2. Phosphate bonds: the potential energy stored in the covalent bonds of the phosphates of ATP
Reduced electron carriers like NADH can pass their electrons to biomolecules with?
Higher reduction potentials in catabolic reactions that release energy
Enzymes are special proteins that are the?
That are the biochemical
catalysts of the cell
– They increase the speed of reactions in the cell several-
thousand fold in many cases: rate acceleration
– They do this by bringing substrates (reactants) into close proximity with each other, at their active site, under favourable conditions for the substrates to react
Hydrolytic enzymes are often named for their substrate + ‘-
ase’: sucrase, lipase, protease, nuclease, etc.
Phosphate-phosphate bonds in ATP are?
Phosphate-phosphate bonds in ATP are hydrolyzed (cleaved/cut) to release energy; this energy can be coupled to otherwise stalled anabolic reactions to ‘power them up’
What are the steps of an Enzyme- Catalyzed Synthesis Reaction
1. Substrate enters active site of enzyme
2. Enzyme/Substrate Complex Forms
3. Substrate is Converted to Products
4. Products leave the active site of the enzyme
Enzymes don’t change the overall balance (equilibrium) of a biochemical reaction; they just make it?
More efficient by reducing the activation energy
-This happens by maintaining substrates in close proximity, proper orientation, and aiding reactions by catalysis; makes reactions take place much faster
What are the three major factors that affect Enzyme Activity at all times?
Temperature, pH, and substrate concentration
If temperature or pH exceed certain thresholds, enzymes can?
Denature (unfold) and become non-functional
Most enzymes are composed of a ___ and a ___
Protein (apoenzyme) and a non-protein ‘helper’ (cofactor) composed of minerals or vitamins: functional holoenzyme
Substrates only bind the active site of?
Holoenzymes
Enzyme activity can also be blocked by?
Enzyme inhibitors which interfere with the active site or another location crucial to enzyme function
• This is the mechanism of many antimicrobial drugs
Forms of enzyme inhibition are?
Competitibe inhibition and Non-Competitive inhibition
What is in competitive inhibition?
Enzyme, Competitive inhibitor, Substrate, Allsteric Site
What is in non-competitive substrate?
Non-competitive inhibitor, Allosteric Site
Making new reducing equivalents and ATP (from ADP + Pi)
molecules is?
Endergonic: it requires a lot of energy!
Cellular Respiration and Fermentation are?
These are the two major pathways for glucose oxidation
– The result for both is generation of recycled ATP molecules
Fermentation Produces a Net of?
2 ATPs per glucose; cellular respiration produces about 32!
After input of ATPs in the first phase of glycolysis, glucose is steadily oxidized (stripped of electrons and broken down) in a series of mostly exergonic reactions that release energy coupled to:
1.Newly recycled ATPs by substrate-level phosphorylations
2. Reduced electron carriers (mostly
NADH)
What is Oxidative phosphorylation?
Is the last step and payoff
– Uses reduced electron carriers previously generated to create a proton gradient (by the electron transport system; ETS): the proton motive force
The proton motive force results in?
Chemiosmosis: protons (H+) diffuse back down their concentration gradient the only way possible, through ATP synthase!
– As the protons pass through ATP synthase, they spin it, which causes another portion to force together ADP + Pi -> ATP production (28 ATPs/glucose)
Fermentation: when you lose your final electron acceptor (O2)
What Happens?
– Without the electron transport chain, cells must recycle electron carriers like NAD+ by an alternative method in order for glycolysis to continue
By products include lactic acid in humans must be?
Recycled to pyruvate using aerobic, endergonic reactions later
Prokaryotes may reproduce by several asexual methods
but the most common is?
Binary Fission
-Simpler than eukaryotic mitosis as we only have a single chromosome!
-Results in identical daughter cells
What are the steps of Cell Elongation?
DNA Replication, Formation of Division Septum, Cell Seperation
Microbial Growth Characteristics Include?
– Short generation time (under optimal conditions): 1-3h
– Binary fission produces
logarithmic (exponential) growth
• One E.coli cell can produce two million cells in 8 hours!
Because of exponential growth, we usually visualize?
Bacterial growth using a log scale to get a linear plot
What is Exergenic Reaction?
Reactions that are spontaneous and release energy are exergonic reactions
What are Endergonic Reactions?
Endergonic reactions require energy to proceed
What Is Anabolism?
The term anabolism refers to those endergonic metabolic pathways involved in biosynthesis, mechanism that takes smaller units like nutrients, cells, or amino acids and bonds them together to create bigger structures.
What is Catabolism?
The term catabolism refers to exergonic pathways that break down complex molecules into simpler ones.
Phases of Microbial Growth are?
1) Lag,
2) Log(arithmic),
3) Stationary
4) Death
What Happens in the Lag Phase?
No increase in number of living bacterial cells
What Happens in Log Phase?
Exponential Increase in number of living bacterial cells
What Happens in Stationary Phase?
Plateau in number of Living Bacterial Cells; rate of cell division and death roughly equal
What Happens in the Death or Decline Phase?
Exponential Decrease in Number of Living Bacterial Cells
Bacteria grow in what two Kinds of Populations?
– Colony: aggregation of cells arising from single parent cell (common in the lab)
– Biofilm: collection of microbes living on a surface in a complex community (common in nature)
Biofilms Are What?
The primary growth form of bacteria in nature: they’re found everywhere and implicated in many bacterial diseases
– Complicated structure with extracellular polymeric substances (EPS) and water channels; bacteria communicate using quorum sensing
All organisms require the same basic nutrients from their
environment, necessary for making new macromolecules. What Are They?
1. Carbon
2. Nitrogen
3. Oxygen
4. Hydrogen
– Also ‘micronutrients’ like phosphorous, sulfur, metals
These Nutrients can be Acquired from the atmosphere or organic materials in soil, water or other Organisms
Growth Requirements: Oxygen
– Essential for obligate aerobes, but toxic to obligate anaerobes
– Some oxygen used during aerobic respiration ends up as metabolic waste products called reactive oxygen species (ROS), such as:
• Singlet oxygen (1O2)
• Superoxide anion (O2-) • Peroxide anion (O22-)
• Hydroxyl radical (OH)
Aerobes Contain Enzymes That
detoxify reactive oxygen species:
– Superoxide dismutase converts superoxides into O2 and H2O2 (hydrogen peroxide)
– Catalase converts H2O2 to H2O and O2 – Peroxidase converts H2O2 to H2O
Other Microbes Have Alternative Oxygen Needs Such As?
– Facultative anaerobes are preferably aerobic, but can survive low/no oxygen environments using fermentation
– Aerotolerant anaerobes can tolerate oxygen (but don’t need it) as they have anti-ROS protective enzymes
– Microaerophilescantoleratelow-oxygenenvironments(2-10%),but not atmospheric oxygen because their anti-ROS enzymes are insufficient
Growth Requirements Temperature
– Different kinds of organisms have different optimum growth temperatures
• What’s different inside the cells of these groups?
Growth Requirements:pH
– Neutrophiles grow best at pH 7
– Acidophiles grow best at pH <7
– Alkalinophiles grow best at pH >7
Growth Requirements: Water
– Endospores form in low-water environments
– Halophiles grow in high-solute (salt) conc.
– Barophiles grow in high-pressure environments