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In living cells, most biochemical reactions take place in an _________
Aqueous environment
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Active participant in many biochemical reactions
Water
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It makes up 70% of the human body and other animals
Water
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All biological processes are affected by the ______ or _______ of the medium in which they occur
Acidity or alkalinity
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_________ may affect the conformation and structures of substances and the concentration of molecular and charged species
H+ concentration of an aqueous solution
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Affect the transport of substances through membranes and the efficiency of enzymes
H+ concentration of an aqueous solution
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It is important that the ______ is maintained in all biochemical reactions
H+ concentration of an aqueous solution
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The body is equipped with remarkably ________, which prevents the sudden variation of H+ concentration
Efficient control processes
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Result of either the introduction of acidic and basic substances from outside or as products of some metabolic processes
Efficient control processes of the body
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3 mechanisms of the body
- 1. the buffer systems of the body
- 2. the action of the kidneys in which acids and bases are excreted in the urine
- 3. respiratory mechanisms in which H+ concentration in the body fluids is regulated by the rate of CO2 elimination in the lungs
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One that resists drastic changes in H+ concentration when small amounts of acid or base are added
Buffer solution
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Made up of weak acids and their salts or weak bases and their salts
Buffer
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Examples of buffer solution
- -An aqueous solution of acetic acid with sodium acetate
- -An aqueous solution of ammonia with ammonium chloride
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Is conveniently expressed in terms of pH
H+ concentration
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Also known as the buffer equation
Henderson-Hasselbach equation
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Use to calculate the pH of a buffer solution made up of a weak acid and its salt
Henderson-Hasselbach equation
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Henderson-Hasselbach equation
pH=pKa+log[salt]/[acid]
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The negative logarithm of the ionization constant of the weak acid
pKa
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States that the pH of a solution containing a weak acid and its salt is determined by the value of the pKa of the acid and by the ratio of the salt/acid concentrations in the solution
Henderson-Hasselbach equation
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Buffer equation of a buffer solution made of a weak base and its salt
pOH=pKb+log[salt]/[base] or pH=(pKw-pKb)+log[salt]/[acid]
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The negative logarithm of the ionization constant of water
pKw
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The negative logarithm of the ionization constant of the base
pKb
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Examples of human body fluid
- -Blood plasma
- -Red blood cells
- -Spinal fluid
- -Urine
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pH and buffer system of blood plasma
- -7.4
- -HCO3-1/H2CO3,HPO4-2/H2PO4-
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pH and buffer system of red blood cells
- -7.2
- -HCO3-1/H2CO3,Hb-/HHb.HbO2-/HHbO2-
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pH and buffer system of spinal fluid
- -7.4
- -HPO4-2/H2PO4-, Proteinate-/H proteins, HCO3-/H2CO3
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pH and buffer system of urine
- -4.8 to 7.4
- -HPO4-2/H2PO4- Org. acid-/H Org. acid
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Importance in regulating the pH of the fluids and tissues of living organisms within limits consistent with life and normal function
Buffers
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Employed in the laboratory to control the pH of culture media for microorganisms and tissues
Buffers
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Used for many chemical reactions requiring controlled pH, including those catalyzed by enzymes
Buffers
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An important part of many industrial processes like fermentation, electroplating, manufacture of leather, photographic materials, and dyes
Use of buffers
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Steps in preparing a buffer solution from a weak acid and its salt
- 1. Choose the weak acid whose pKa is closest to the desired pH. This ensures maximum buffer capacity
- 2. Consider the individual concentration of the buffer salt and acid needed to obtain a suitable buffer capacity. Concentration ranges from 0.05M to 0.50M. Buffer capacity ranges from 0.01M to 0.10M
- 3. From the Henderson-Hasselbach equation, calculate the ratio of the salt and weak acid required to obtain the desired pH. This buffer equation is satisfactory within a pH range of 4 to 10
- 4. Mix the calculated amounts (volumes) of acid and salt
- 5. Check the pH using a pH meter
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Commonly used buffer acids
- -Acetic acid
- -Carbonic acid
- -Citric acid
- -Phosphoric acid
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Also known as saccharides
Carbohydrates
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Include a large group of polyhydroxyaldehydes or polyhydroxyketones and their derivatives
Carbohydrates
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Widely distributed in nature and make up most of the organic structures of all plants as well as being present to some extent in all animals
Carbohydrates
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Carbohydrates presents can be tested based on:
- 1. the production of furfural and its derivatives
- 2. their reducing property
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When a ______ is treated with a strong mineral acid, dehydration of _______ occurs
Monosaccharide, monosaccharide
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Dehydrated product of monosaccharide
Furfural and hydroxymethylfurfural
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A monosaccharide is a pentose
Furfural
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A monosaccharide is a hexose
Hydroxymethylfurfural
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Phenolic compounds
- -a-naphthol
- -orcinol
- -resorcinol
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Various phenolic compounds like a-naphthol, orcinol, and resorcinol will condense with the furfural and hydroxymethylfurfural to form ______
Colored dyes
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The formation of these colored condensation compounds is a _______ for the presence of carbohydrates
Positive test
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______ and ______ don't undergo this reaction since they don't possess the requisite minimum of five carbon atoms
Trioses and tetroses
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Uses a-naphthol
Molisch test
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The most general test for the presence of carbohydrates
Molisch test
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Gives a positive test with all carbohydrates larger than tetroses
Molisch test
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The furfural and hydroxymethylfurfural derivatives react with a-naphthol to form purple-colored condensation products
Molisch test
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Not a specific test for carbohydrates since it is also given by all other furfural-forming substances
Molisch test
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Useful in differentiating between hexoses and pentoses
Orcinol or Bial's test
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Orcinol condenses with furfural from pentoses to form a blue-green compound and with hydroxymethylfurfural from hexoses to form a yellow-green product
Orcinol or Bial's test
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What color will form when the orcinol condenses with furfural from pentoses
Blue-green
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What color will form when the orcinol condenses with hydroxymethylfurfural from hexoses
Yellow-brown
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Uses resorcinol
Seliwanoff's test
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Distinguishes aldohexoses and ketohexoses based on their differential rates of reaction with hot HCI
Seliwanoff's test
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_____ are dehydrated more rapidly than aldoses to give hydroxymethyl furfural compounds which then condense with resorcinol to form a cherry red complex
Ketoses
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______ gives a light pink color that takes a longer time to develop
Aldoses
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______ test is most sensitive for fructose which is a ketose
Seliwanoff's test
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_______ is one which has a free hydroxyl group at the anomeric C
Reducing sugar
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As the _____ reverts to its open-chain form, the free hydroxyl group is converted back to the aldehyde
cyclic structure
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Aldehyde group can be oxidized by _____ reagent
Benedict's reagent
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All sugars that react with Benedict's reagent are _______
Reducing sugars
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Oxidizing agent Cu2+ can be reduced to
Cu+
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______ and _______ have the ability to reduce an alkaline solution of Cu2+ ion
Monosaccharides and some disaccharides
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The ______ which is less soluble precipitates out of the alkaline solution as a brick-red precipitate of cuprous oxide
Cu2+ ion
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The formation of red cuprous oxide precipitate is the criterion of a ________ test
Positive
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Distinguishes between reducing monosaccharides and reducing disaccharides by a difference in rate of reaction
Barfoed's test
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Consists of cupric ions, like in Benedict's reagent
Barfoed's test
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In ____ test, _____ reagent reacts with reducing monosaccharides, to produce the cuprous oxide, faster than with reducing disaccharides
Barfoed's test and Barfoed's reagent
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