"a set of propositions and concepts that provides a reliable, systematic, and rigorous account of an aspect of nature"
Explain the significance of Robert Hooke
He was the first to describe microbes. He saw fungal hyphae and illustrated the fruiting structure of molds.
Explain the significance of Anton van Leevwenhoek
He was the first to describe bacteria and he revived the theory of spontaneous generation.
What is the theory of Spontaneous Generation?
Living organisms arise from non-living matter.
What were Anton van Leevwenhoek's thoughts on spontanous generation?
1) Proposal: If you leave out a piece of meat, it goes bad; things that make meat go bad spontaneously appear. 2) Counter proposal: if you put a piece of paper on the meat, no maggots appear; direct contact with air is required for spontaneous generation.
Explain the significance of Louis Pasteur
He discovered that alcoholic fermentation was biologically mediated, he disproved the theory of spontaneous generation, showed how to keep a liquid sterile, and he developed a vaccine for anthrax, fowl cholera, and rabies.
How was spontanous generation disproved?*
Louis Pasteur designed an experiment (figure 1.13)
Explain Robert Koch's significance
He demonstrated the link between microbes and infections diseases, idenfied the causative agents of anthrax and tuberculosis, and developed techniques for obtaining a pure culture of microbes.
What are Koch's Postulates?
1) Microbe must be present in all cases of disease and absent from healthy organisms. 2) Putative pathogen must be isolated and grown in pure culture. 3) Isolated organism must cause same disease in healthy host. 4) Same organism must be isolated again from newly diseased host.
Explain the significance of Martinus Beijerinck
He developed the Enrichment Culture Technique
What is the Enrichment Culture Technique?
Microbes are isolated from natural samples in a highly selective fashion by manipulating nutrient and incubation conditions. Ex: Nitrogen-fixing bacteria
Explain the significance of Sergei Winogradsky
He demonstrated that specific bacteria are linked to specific biogeochemical transformations (ex: sulfur and nitrogen cycles) and he proposed the concept of chemolithotrophy oxidation of inorganic compounds linked to energy conservation.
What is the function of microscopes?
To produce an enlarged image of an object.
What are the two broad classes of microscopes and what are examples?
1) Simple: single lens (ex: magnifying glass) 2) Compound: more than one lens (ex: light microscope).
What are two kinds of microscopes used in microbiology?
1) Light microscope 2) Electron microscope
What are the important parts of a light microscope and what do they do?
1) Light source - provides illumination. 2) Condeser - focuses light on the slide. 3) Stage - platform for holding slides, has clips to hold slides in place and knobs to move platform. 4) Objective lenses - produces an immediate image 5) Eyepiece lens or Ocular - Magnifies the primary image to produce a visualized image.
Which part of a light microscope is absolutely essential to obtain an good image?
How does an Electron microscope work?
It uses electrons to produce an image. It involves electromagnets instead of glass lenses and electrons instead of light.
How do you calculate total magnification?
Multiply the objective lens magnification by the eyepiece lens magnification
What is the maximum magnification?
What is resolution?
The ability to distinguish two very close objects as distinct entities (the objective lens plays an important role). It is measured as the minumum distance between the two objects that reveal them as sepearate entities.
What is the maximum resolution of a light microscope?
about 0.2 ?m; a small bacterium
How do you get better resolution?
d = 0.5 ? / NA (? is wavelength of light used to view the object, NA is the numerical aperture of the lens). You need a small d to get good resolution. To get this, increase the amount of light or NA, and decrease the wavelenth.
What are the common types of Light Microscopes?
Bright-field, Dark-field, and Phase-contrast
What is a Bright-field Microscope?
Its the most common microscope. It produces a dark image on a bright background and it is mainly used to observe fixed and stained (dead) cells.
What is a Dark-field Microscope?
It is used to observe living and unstained cells. The light reaches the specimen from the sides and is scattered by the specimen. The image appears light on a dark background.
What is a Phase-contrast Microscope?
It is used to observe living and unstained cells. It enhances contrast between intracellular structures having slight differences in refractive index.
What is Differential Interference Contrast Microscopy?
DIC Microscopy is used to visualize specimens that fluoresce. It emits light of one color when illuminated with another color of light. It can be used with live cells. Some cells fluoresce naturally (autofluoresce). You can identify a subcellular localization of the components of the cell by overlaying (expressing a fluorescent protein)
Why is staining used in Bright-Field Microscopy?
Specimens are visualized on a bright-field microscope because of differences in contrast between them and surroundings. Improving contrast results in a better final image and staining is an easy way to improve contrast.
What are dyes?
Organic compouds that have different affinities for specific cellular materials. Used for staining.
List the steps of fixation and staining of specimen
1) Spread culture on slide. 2) Air dry. 3) Fix with heat (attachs cells to slide) over Bunsen Burner; can also used fromaldehyde to kill and preserve. 4) Apply stain, rinse, and dry. 5) Microscopy: can use oil immersion.
What are the two types of staining?
1) Simple staining: used of a single dye. 2) Differencial staining: used of more than one dye. Ex: Gram staining
What is the Gram Stain?
The Gram Stain is widely used in microbiology. Bacteria can be divided into two groups: Gram positive and Gram negative. The Gram stain reders different kinds of cells different colors - Gram positive bacteria appear purple and Gram negative bacteria appear red after staining.
How does the electron microscope compare to the light microscope?
The electron microscope provides a much higher resolution than a light microscope because electrons have a shorter wavelength. (light is about 200 nm, electrons are about 0.5 nm).
What are two main types of electon microscopes?
1) Transmission EM - reveals great detail of internal structure of cells; 2D image. 2) Scanning EM (SEM) - reveals great detail of external structure of cells; 3D image.
What are biological macromolecules?
Large molecules unique to living organisms including carbohydrates, lipids, nucleic acids, and proteins.
What are bacterial cells made of?
Mostly water, the rest is made up of macromolecules
How many elements are found in living organisms?
about 20 elements: 6 found in high amounts (C, H, O, P, S, N)
What kind of bonds are macromolecules joined by?
Chemical bonds: Covalent bonds (strong), Hydrogen bonds, Ionic bonds (weak), and Hydrophobic interactions (weak). Weak bonds form and break spontaneously.
What are hydrogen bonds and what do they do for macromolecules?
It is a bond between hydrogen and a more electronegative element. Many hydrogen bonds within and between macromolecules enhances stability of the entire structure.
What is a covalent bond?
Sharing of electrons. They are formed and broken by enzymes.
What is an ionic bond?
What are hydrophobic interactions?
when nonpolar molecules and parts of molecules come together
What are macromolecules made up of?
They are made up of monomers or monomeric subunits. Subunits may be connected to eachother by covalent bonds, H-bonds, ionic bonds, or hydrophobic bonds. Polymers are made up of similar or identical monomers.
What are Carbohydrates used for?
They act as an energy source, are a constituent of the cell wall, and are a component of nucleic acids.
What are the subunits of carbohydrates and how do they bind?
They are bound by covalent glycosidic bonds: Disaccharide (2), Trisaccharide (3), Oligosaccharide (more than 4), Poly saccharide (more than 50)
Explain the characteristics of lipids and what they are used for
They are relatively insoluble in water and soluble in non-polar organic solvents. They are an important energy source and constituent in cell membranes. Most lipids contain fatty acids. Bacteria and eukarya have fatty acids in their lipis but arhaea do not.
What is the difference between simple lipid and a complex lipid?
A simple lipid is a glycerol with a fatty acid. A complex lipid is a simple lipid and an additional compound.
What are the monomers and polymers of nucleic acids?
Monmers are nucleotides and polymers are DNA and RNA
Explain the characteristics of proteins and what they are used for
Proteins are made up of amino acid monomers connected by a covalent peptide bond. Most (not all) known enzymes are protiens. Proteins also form important structural components of cells (e.g. the Eukaryotic cytoskeleton) They can form machines such as flagella.
Briefly explain the structure of Proteins
Proteins are highly folded molecules i.e. they have a specific shape/structure. This structure defines function of individual proteins.
What are the four different levels of organization in protein structure?
1) Primary structure - linear order of amino acids. 2) Secondary structure - shape along a single axis in space. 3) Tertiary structure - 3D organization of the individual secondary structures. 4) Quaternary structure - occurs when a protein has more than one subunit. Shows how subunits associate with eachother.
All proteins have _______, _________, and _________ structures. Only those with two or more subunits possess _________ structure.
All proteins have primary, secondary, and tertiary structures. Only those with two or more subunits possess quaternary structure.
Which levels of protein structure are stabalized by non-covalent bonds? Which are stabalized by convalent bonds?
Secondary, tertiary, and quaternary structures are primarily stabalized by non-covalent bonds. Only primary structure is stabalized by covalent bonds.
What are some examples of prokaryotes and what separates them from eukaryotes?
Prokaryotes are bacteria and archaea. They do not have membrane-enclosed organelles and they do not have a nucleus. They are generally smaller than eukaryotic cells and they are metabolically diverse.
What are some examples of eukaryotes and what separates them from prokaryotes?
Eukaryotes are algae, fungi, and protozoa. They have DNA-enclosed in a membrane-bound nucleus and the contain organelles. They are also generally larger and more complex than prokaryotes.
What are viruses?
They are not considered cells. They have no metabolic abilities of theyre own and they rely completely on biosynthetic machinery of the infected cell. They infect all types of cells. They are generally smaller than prokaryotes and eukaryotes.
What are the three major shapes of cells?
cocci (spheres), bacilli (rods), and spirilla (rods that twist)
What is the morphology of a cell determined by?
What is the size range for prokaryotes?
0.2 0.2 ?m to more than 700 ?m in diameter; most cultured rod-shaped bacteria are between 0.5 and 4.0 ?m wide and less than 15 ?m long. There are few very large prokaryotes.
What is the size range for eukaryotic cells?
10 to more than 200 ?m in diameter
What is the cytoplasm of a prokaryotic cell and what does it contain?
The cytoplasm of a prokaryotic cell is the interior of the cell (everything inside). It consists of mostly water and it harbors the following substances: Nucleoid, ribosomes, and other macromolecules (such as enzymes) and small organic molecules (mostly precursors for macromolecules)
What is the Nucleoid of a prokaryotic cell and what does it contain?
The nucleoid is the genomic DNA that forms a large double stranded molecule called the chromosome. It is highly compacted in the cell and it is almost always a single, circular chromosome.
What is the cytoplasmic membrane in prokaryotic cells?
The cytoplasmic membrane encloses the cytoplasm, is selectively permeable, and is comprised of proteins and lipids (phospholipids which have polar heads and hydrophobic tails). It also lacks cholesterol; instead it contains cholesterol-like Hopanoids.
What are two main classes of membrane proteins?
1) integral - embedded in membrane and also amphipathic. Not static but can diffuse in plane of membrane. 2) peripheral - associated with one side or the other of the membrane.
What are the major functions of the cytoplasmic membrane in the prokaryotic cell?
1) permeability barrier - prevents leakage and functions as a gateway for transport of nutrients into and out of the cell. 2) Protein anchor - site of many proteins involved in transport, bioenergetics, and chrmotaxis. 3) Energy conservation - site of generation and used of the proton motive force.
Explain the permability barrier function of the cytoplasmic membrane in the prokaryotic cell.
Polar and charged molecules must be transported and the concentration of most solutes is higher inside the cell than outside the cell, so most transport proteins accumulate solutes against the concentration gradient. One type of protien membrane transport is Carrier-mediated transport systems.
What are carrier-mediated transport systems?
It is one type of protein membrane transport. It is faster than diffusion and it is highly specific. The biosynthesis of transporters are often regulated. It also shows a saturation effect (at low concentrations, you will get a high rate of solute entry. rate of solute entry will eventually level off when the transporter is saturated with substrate).
What are three major classes of transport systems in prokaryotes? (just name them)
1) Simple transport 2) Group translocation 3) ABC system
What is simple transport?
It is one of three major classes of transport systems in prokaryotes. It is driven by energy in the proton motive force. Integral membrane protein makes a channel in the membrane and the transporter binds to specific molecules and then changes conformation to bring the molecule into the cell.
What are the three types of simple transporters and when are the used?
1) Uniporter - only desired molecule is transported and it is transported in the direction of the concentration gradient. Energy is not required. 2) Antiporter - The molecule is transported in and another is transported out. 3) Symporter - Molecule is transported in along with antoher (usually H+)
What is true for both anti and symporters?
1) the desired molecule has a higher concentration inside the cell than outside the cell. 2) energy is required. 3) Co-transported molecule moves in direction of concentration gradient and provides energy to bring in desired molecule.
What is Group Translocation?
It is one of three major classes of transport systems in prokaryotes. The substance transported is chemically modified during transport across the membrane. This is found only in prokaryotes. An example of group translocation is The Phosphotransferase System in E. coli.
What is The Phosphotransferase System in E. coli?
It is an example of group translocation of prokaryotes. The Phosphate group is added to the transported sugar. It moves sugars such as glucose, fructose, and mannose. Five proteins are required and energy is derived from phosphoenolpyruvate.
What are ABC Systems?
ATP-Binding Cassette Systems are one of three major classes of transport systems in prokaryotes. There are about 200 different systems identified in prokaryotes adn they are often involved in the uptake of organic compounds, inorganic nutrients, and trace minerals. They typically display high stubstrate specificity and they involve binding proteins that bring compounds to transporter. The energy is from the hydrolysis of ATP.
What does a bacteria's cell wall consist of?
The cell wall consists of all structures external to plasma membrane/cytoplasmic membrane. It contains Peptidoglycan which gives the cell its shape and rigidity.
What is peptidoglycan?
It is only found in bacterial cell walls. It is a polymer of identical subunits which consist of two linked glucose derivatives [N-acetyl-glucosamine (NAG) and N-acetyl-nuramic acid (NAM)] and a short chain of amino acids.
What does the peptidoglycan backbone consist of?
1) alternating NAG and NAM residues covalently attached to eachother. 2) Peptide of four alternating D and L amino acids connected to Nam: in most Gram +, amino acid 3 is L-Lysine and in most Gram -, amino acid 3 is Diaminopimelic acid (DAP). 3) D-amino acids and DAP are not seen in proteins. 4) Linkage of PG subunits between amino acid 3 and 4 of adjacent subunits: most common - direct cross-linking beween amino acid 3 and 4; some gram + have peptide interbridge.
What is the role of peptidoglycan?
It imparts shape to cell and protection from osmotic lysis. The cell can only swell until it hits the PG layer and it wont burst. This can be removed by penicilin (inhibits cell wall synthesis) or Lysozyme (hydrolyzes NAM-NAG bond). A bacterial cell lacking a PG layer can result in a protoplast and is osmotically sensitive.
What unique characteristics does a Gram positive cell have?
A Gram positive cell wall has a thick peptidoglycan layer for protection. It is also common to have teichoic acids (acidic substances) embedded in their cell wall such as lipoteichoic acid.
What is Lipoteichoic acid?
teichoic acids covalently bound to membrane lipids
What unique characteristices does a Gram negative cell have?
A Gram negative cell wall has a thin PG layer and an outer membrane. It is more complex than a Gram positive cell. The outer membrane (OM) contains LPS (lipopolysaccharide) which replaces most of the phospholipids in the outer half of the OM. The toxic component of LPS is the endotoxin. OM is more permeable than cytoplasmic membranes due to Porins. The cell wall also contains periplasm.
What are Porins?
Protein channels for movement of hydrophillic low molecular-weight substances. Located in the OM of Gram negative cell walls. Causes OM to be more permeable than cytoplasmic membranes.
What is the Periplasm?
It is the space located between cytoplasmic and outer membranes. It houses many protiens and the PG.
What are two prokarytoes that lack cell walls?
Mycoplasmas (group of pathogenic bacteria) and Thermoplasma (species of Archaea)
What is unique to Archaeal membranes?
1) they lack fatty acids and have isoprenes instead. 2) their phospholipids have different chemical linkage that in Bacteria and Eukarya. 3) for some archaea, major lipids are glycerol diethers: can exist as lipid monolayers, but not bilayers.
What is unique to the cell walls of Archaea?
1) No peptidoglycan. 2) no outer membrane 3) has Pseudomurein
What is Pseudomurein and where is it found?
Pseudomurein is a polysaccharide similar to peptidoglycan. It is composed of N-acetylglucosamine (NAG) and N-acetylalosaminuronic acid. This substance is found in the cell walls of certain methanogenic Archaea (produce methane).
What are S-Layers and where are they found?
S-layers are the most common cell wall type found among Archaea. They consist of protein or glycoprotien. They are also found in some bacteria, external to the cell wall.
What are capsules and slime layers and where are they found?
They are not seen in all bacteria (when they are they are external to the cell wall). They are polysaccharide layers that assist in attachment to surfaces. They aid in evasion of the immune system and help the cell resist desiccation.
What are three different appendages discussed in class?
Fimbriae, Pili, and Flagella
What are fimbriae?
Appendages: They are filamentous protein structures that are short and hair-like on the cell surface. They play a role in the attachment to surfaces and the formation of pellicles.
What are pili?
Appendages: They are filamentous protein structures that are typically longer than fimbriae. They assist in surface attachment and facilitate genetic exchange between cells. Type IV pili are involved in twitching motility.
What are flagella?
Appendages: They are structures that assist in swimming. It is a filament conposed of a protien called flagellin and it moves by rotation.
What are ribosomes?
They are the main component of translation machinery in translation in prokaryotes and eukaryotes. They contain 2 subunits made of proteins and ribosomal RNA and prokaryotic ribosomes are smaller than eukaryotic ribosomes.
Which are smaller? Prokaryotic ribosomones or Eukaryotic ribosomes?
Prokaryotic ribosomes are smaller
What are inclusion bodies?
1) They act as storage granules for nutrients and contains organic and inorganic material. 2) Carbon storage 3) Polyphosphates: accumulates of inorganic phosphate. 4) Sulfur globules: composed of elemental sulfur. 5) Magnetosomes: magnetic storage inclusions.
What are Bacterial Endospores?
They are highly differentiated cells that are resistant to heat, harsh chemicals, and radiation. It is the dormant stage of the bacterial life cycle. They are ideal for dispersal via wind, water, or animal gut and they are only present in some Gram-positive bacteria.
What are eukaryotic cells characterized by?
The presence of membrane-enclosed organelles. They provide environment for distinct metabolic reactions.
What is an organelle?
a structure within a cell that performs specialized functions. ex: nucleus, chloroplasts, mitochondria, lysosomes, ribosomes
What is the Nucleus?
It contains the chromosomes. DNA is wound around histones. It also contains the nucleolus: the side of rRNA syntehsis and assembly of ribosomal sub-units.
What is the Endoplasmic Reticulum?
It is a network of tubules and flat sacs involved in protein and lipid transport. Two types of ER are Smooth and Rough.
What is the difference between the Smooth and Rough Endoplasmic Reticulum?
The rough ER has ribosomes on its outer surface which are involved in intracellular transport and modification of secreted protiens. The smooth ER lacks ribosomes and is involved in the synthesis of lipids and detoxification of chemicals.
What is the Golgi Apparatus?
It is a series of flattened sacs in close association with the ER. It recieves material from the ER and acts as a "Packaging and Sorting" organelle for transport of lipids and protein to their final destination e.g. secretory vesicles, plasma membrane, lysosomes.
What are lysosomes?
They are membrane-enclosed compartments made by proteins and lipids form the Golgi Complex. They contain various digestive enzymes to digest macromolecules (old or non-functional protiens, nucleic acids, carbohydrates, etc.) and destruction of ingested microbes. The digestive enzymes function at low pH (pH of lysosomes is lower than cytoplasm). This allows for lytic activity to occur within the cell without damaging other cellular components.
What is unique about mitochondria and chloroplasts?
They have two membranes: one outer membrane and one inner membrane
What are mitochondria?
It is an organelle where respiration occurs. Respiration occurs on the cristae (the folds of the inner membrane). The area inside the inner membrane is called the matrix and it contains TCA cycle enzymes.
For eukaryotes, respiration occurs in the _________ and the TCA cycle enzymes are found in the ________. For Gram-negative bacteria, respiration occurs in the __________ and the TCA cycle enzymes are found in the _________.
They are organelles found in photosynthetic organisms. Photosynthesis occurs on the discs of the inner membrane called thylakoid membranes. The area inside the inner membrane is called the stroma and it contains the Calvin cycle enzymes.
What are cristae?
They are the folds of the inner membrane of the mitochondira.
What is the matrix?
the area inside the inner membrane of the mitochondria
What is the thylakoid membrane?
Its the discs of the inner membrane of chloroplasts.
What is the Endosymbiosis Theory?
Chloroplasts and mitochondria are descendants of ancient prokaryotic cells living inside another cell.
What is the evidence for the Endosymbiosis Theory?
1) Mitochondira and chloroplasts contain bacterial-like circular DNA chromosome. 2) Eukaryotic nuclei contain genes derived from bacteria. 3) Mitochondira and chloroplasts contain their own bacterial-like ribosomes. 4) rRNA genes in mitochondrial and chloroplast genomes show similarities to bacterial rRNA genes.
What is a cytoskeleton?
It is important for cell shape and motion. It is made of proteins that form filamentous structures (actin, microtubules, intermediate filaments). Prokaryotes have a version of a cytoskeleton.
compound required for biosynthesis and energy
What are three biological classification of the elements?
1) Macroelements 2) Microelements or trace elements 3) Growth Factors
What are macroelements?
They are the biological classification of the elements that are required in large amounts (g/L or mg/L). 1) C, H, O, N, P, S: Found in the major biological macromolecules thus form structural and enzymatic components of cells. 2) K, Ca, Mg, Na: Required as the enzyme co-factors or for activity of certain enzymes. Required to stabalize cell structures. 3) Fe: Key component of enzymes involved in electron transport.
What are microelements or trace elements?
Mn, Zn, Co, Ni, Mo, Cu, and others. They are also required as enzymes co-factors or for activity of certain enzymes, but in micrograms/L amounts.
What are growth factors?
1) organic compounds are required in small amounts by certain organisms. Ex: vitamins, amino acids, purines, pyrimadines. 2) Vitamins: most commonly required growth factors and most function as coenzymes.
What is a culture medium?
They are preparations devised to support growth of microorganisms. They can be solid or liquid and they are important for the isolation and identification of microorganisms.
What are the two broad classes of media?
1) Defined media: precise chemical composition is known. 2) Complex/Rich media: composed of digests of chemically defined substances (e.g. yeast and meat extracts)
What are two classifications of media based on how growth occurs?
Selective and Differential
What is selective media?
It can be defined or complex media. It contains compounds that selectively inhibit growth of some microbes but not others. Examples are McConkeys(contains bile salts- Gram-positive bacteria dont grow, Gram-negative bacteria can grow) and antibiotic agar (only antibiotic resistant microbes grow).
What is differential media?
It can be defined or complex media. It contains an indicator, usually a dye, that detects particular chemical reactions occuring during growth. It distinguishes between different subsets of microbes - all microbes grown but colony appearance is different. E.g. McConkeys contains dye to distinguish between lactose fermenting and non-fermenting microbes (E.coli grows on it pink bc ferments lactose, S. typhimurium grows on white).
What is a pure culture?
A culture containing only a single kind of organism
What are contaminants?
any unwanted organisms in a culture
What is one way to obtain a pure culture?
Use selective and differential media.
What are three different classifications of how cells obtain energy?
1) phototrophs: contain pigments that allow them to use light as an energy source such as algae and photosynthetic bacteria 2) chemotrophs: oxidation of organic and inorganic compounds
What are two different classifications of how cells obtain their carbon?
1) Autotrophs: use carbon dioxide as their carbon source, generally photosynthetic organisms, sometimes referred to as primary producers. 2) heterotrophs: require one or more organic molecules for their carbon source, feed directly on autotrophs or live off products produced by autotrophs.
What are two different classifications of where cells obtain electrons from?
What does a photolithotrophic autotroph need to survive?
light, inorganic molecules, and carbon dioxide
What does a chemoorganotrophic heterotroph need to survive?
What is metabolism?
the sum of all chemical reactions that occur in the cell
What are catabolic reactions?
they are energy-releasing metabolic reactions that generally involve the breakdown of nutrients
What are the anabolic reactions?
they are energy-requiring metabolic reactions
What is energy?
The capacity to do work or to cause particular changes
What are the different types of work carried out by organisms?
1) Chemical work: synthesis of complex molecules. 2) Transport work: take up of nutrients, elimination of wastes , and maintenance of ion balances. 3) Mechanical work: movement of organisms or cells and movement of internal structures.
What are two broad classes of metabolic reactions?
1) Endergonic: energetically unfavorable, energy input is required. 2) Exergonic: energetically favorable, energy is released.
Most biosynthetic reactions are _________ and thus requires energy input. Such energy is derived from the ________ reactions.
They are enzymes that have great specificity for the reaction catalyzed and the molecules acted on. Ex: recognition of L or D amino acids
a substance that increases the rate of reaction without being permanently altered. It lowers the activation energy of a reaction and does not affect energetics or equilibrium of a reaction.
substances formed by the reaction
resembles both the substrates and the products
energy is needed in order for the reaction to happen, enzymes lower this to increase the rate of reaction.
where substrates interact with enzymes
Catalysis depends on...
substrate binding and the position of substrate relative to catalytically active amino acids in the active site
loss of electrons
gain of electrons
tendency of a compound to donate electrons (expressed in volts V)
the more negative the reduction potential, the better electron (acceptor/donor)
the more positive the reduction potential, the better electron (acceptor/donor)
What is a redox tower?
The redox tower represents the range of possible reduction potentials for redox couples in nature. the reduced substance in the redox couple at the top of the tower has the greatest tendency to donate electrons. The oxidized substance in the redox couple at the bottom of the tower has the greatest tendency to accept electrons. The farther the electrons "drop" from the donor to the acceptor, the greater the amount of energy released.
Redox reactions usually involve reactions between intermediates (carriers). Electron carriers are often used to transfer electrons from an electron donor to an electron acceptor.
What are the two classes that electron carriers are divided into?
1) Prosthetic groups (attached to enzymes): e.g. heme group of a cytochrome. 2) Coenzymes (can diffuse from one enzyme to another): e.g. NAD+, NADP. NAD+ and NADH facilitate redox reactions without being consumed; they are recycled.
What happens to the chemical energy released in redox reactions?
It is primarily conserved in certain phosphorylated compounds. It is used to transfer energy from cell's energy-conserving systems to the systems that carry out cellular work. ATP is the prime energy currency as well as Coenzyme A.
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