Biochemistry of Glucose Metabolism
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Questions and Answers

What is the primary reason glucose is phosphorylated within cells?

  • To facilitate the breakdown of glucose into smaller molecules.
  • To prevent glucose from leaving the cell. (correct)
  • To create a positive charge on the glucose molecule.
  • To increase the stability of glucose.

Which of the following statements accurately describes the role of phosphorylation in blood glucose regulation?

  • Phosphorylation decreases as blood glucose levels decrease.
  • Phosphorylation levels have no impact on blood glucose levels.
  • Phosphorylation increases as blood glucose levels decrease. (correct)
  • Phosphorylation levels remain constant regardless of blood glucose levels.

Why is phosphate commonly used for energy transfer within cells?

  • Phosphate is highly reactive and easily forms bonds with other molecules.
  • Phosphate is readily available within cells.
  • Phosphate is the most efficient form for storing energy.
  • Phosphate has a high transfer potential, making it suitable for exchanging energy between molecules. (correct)

What happens when a molecule has two phosphate groups located close together?

<p>The molecule is likely to be broken down by an enzyme. (D)</p> Signup and view all the answers

What is the primary function of amination in the context of glucose?

<p>To modify glucose into a derivative with a different function. (B)</p> Signup and view all the answers

What is the preferred position for adding an amine group to glucose?

<p>Carbon 2 (B)</p> Signup and view all the answers

What is the significance of adding an acetic acid group to the amino group at position 2 of glucose?

<p>It is the first step in a metabolic pathway for producing a specific compound. (C)</p> Signup and view all the answers

Why is phosphorylation considered important for preparing fructose for breakdown?

<p>It destabilizes the molecule, making it easier to break down. (D)</p> Signup and view all the answers

What is the primary function of the extracellular matrix (ECM)?

<p>To provide structural support and organization to tissues (C)</p> Signup and view all the answers

What are the three main classes of biomolecules found in the extracellular matrix?

<p>Structural proteins, specialized proteins, and heteropolysaccharides (C)</p> Signup and view all the answers

Which of the following is NOT a function of the extracellular matrix?

<p>Regulation of cellular metabolism (B)</p> Signup and view all the answers

What is the defining structural feature of glycosaminoglycans (GAGs)?

<p>They are composed of repeating disaccharide units. (B)</p> Signup and view all the answers

Which of the following is NOT a characteristic of glycosaminoglycans due to their negative charge?

<p>High resistance to enzymatic degradation (D)</p> Signup and view all the answers

What is the name of the acidic sugar found in glycosaminoglycans?

<p>Glucuronic acid (A)</p> Signup and view all the answers

Which of these is NOT a type of glycosaminoglycan?

<p>Keratin (C)</p> Signup and view all the answers

What is the main reason for the negatively charged nature of glycosaminoglycans?

<p>The presence of acidic sugars like glucuronic acid (C)</p> Signup and view all the answers

What is the primary function of aggrecan in the context of trauma?

<p>Aggrecan acts as a buffer, absorbing and releasing water to manage stress. (B)</p> Signup and view all the answers

Which of the following is NOT a function of glycoproteins?

<p>DNA replication (C)</p> Signup and view all the answers

What is the main structural difference between blood groups A, B, AB, and O?

<p>The specific sugar present at the non-reducing end of the oligosaccharide chain. (D)</p> Signup and view all the answers

In the context of blood transfusions, what is the primary concern regarding blood group incompatibility?

<p>The risk of the recipient's immune system attacking and destroying the donated red blood cells. (C)</p> Signup and view all the answers

Which of the following is a key characteristic of mucopolysaccharidoses (MPS)?

<p>Accumulation of complex glycosaminoglycans (GAGs) within lysosomes, leading to various symptoms. (B)</p> Signup and view all the answers

What is the specific enzyme deficiency that causes Hurler's syndrome (MPS Type I)?

<p>α-L-iduronidase (A)</p> Signup and view all the answers

What is the role of L-fucose in the context of blood group antigens?

<p>L-fucose forms the basis of the oligosaccharide chain and is modified to create different blood group antigens. (D)</p> Signup and view all the answers

Which of the following is NOT a common characteristic of mucopolysaccharidoses (MPS)?

<p>Increased risk of developing autoimmune disorders. (B)</p> Signup and view all the answers

What distinguishes a chiral carbon atom in amino acids?

<p>It is bonded to four different atoms or groups. (A)</p> Signup and view all the answers

Why are amino acids designated as alpha (α) amino acids?

<p>Their amine and carboxyl groups are attached to the second carbon. (C)</p> Signup and view all the answers

Which group of amino acids includes aspartate and glutamate?

<p>Acidic charged side chains (D)</p> Signup and view all the answers

What characteristic do nonpolar neutral side chains in amino acids share?

<p>They consist of hydrocarbon components. (C)</p> Signup and view all the answers

Which of the following amino acids is essential and must be obtained from the diet?

<p>Methionine (B)</p> Signup and view all the answers

What role do R groups (side chains) play in the function of proteins?

<p>They influence the charge and polarity of proteins. (A)</p> Signup and view all the answers

Which of the following is NOT a basic charged side chain amino acid?

<p>Threonine (C)</p> Signup and view all the answers

Which of the following characteristics best describes acidic amino acids?

<p>Tend to give H+ to the solution. (A)</p> Signup and view all the answers

What happens to the pH of the stomach during digestion?

<p>It becomes more acidic. (D)</p> Signup and view all the answers

What does pKa represent in the context of amino acids?

<p>The negative logarithm of the acid dissociation constant. (C)</p> Signup and view all the answers

What is the typical pKa range for the carboxyl group (COOH) and amine group (NH3+) of amino acids?

<p>2.34 and 9.69 (C)</p> Signup and view all the answers

Why are amino acids generally considered neutral at a physiological pH of 7.4?

<p>The charges of the carboxyl and amine groups balance each other. (D)</p> Signup and view all the answers

What determines the overall charge of an amino acid with a charged R-side chain?

<p>The pH of the surrounding environment. (A)</p> Signup and view all the answers

Why are amino acids that have no charged R-side chain considered 'neutral' in terms of charge?

<p>They have a net charge of zero at physiological pH. (A)</p> Signup and view all the answers

How does the pKa of a group relate to its tendency to release and acquire protons?

<p>The lower the pKa, the more readily a group releases a proton. (C)</p> Signup and view all the answers

Which statement correctly explains the significance of pKa values in determining the overall charge of an amino acid?

<p>PKa values are used to predict the charge of the R-side chain and its contribution to the overall charge of the amino acid. (A)</p> Signup and view all the answers

What causes the peptide bond to have an intermediate length between a single and a double bond?

<p>The bond exhibits resonance, with electron movement between the nitrogen, carbon, and oxygen atoms. (C)</p> Signup and view all the answers

Why is the peptide bond considered to be not truly covalent?

<p>The bond has a strong ionic component due to the unequal sharing of electrons between the nitrogen and oxygen atoms. (C)</p> Signup and view all the answers

Why is the oxygen atom in a peptide bond considered to be more electronegative than nitrogen and carbon?

<p>Oxygen has a smaller atomic radius, leading to a stronger attraction for electrons. (A)</p> Signup and view all the answers

Which of the following correctly describes the direction of electron flow in a peptide bond due to resonance?

<p>From nitrogen to carbon to oxygen. (D)</p> Signup and view all the answers

What is the key consequence of the electron movement in the peptide bond due to resonance?

<p>The formation of a permanent dipole moment within the peptide bond. (D)</p> Signup and view all the answers

Which of the following accurately describes the two different forms of the peptide bond?

<p>The charged form has a positive charge on the nitrogen atom and a negative charge on the oxygen atom, while the neutral form has no charges. (A)</p> Signup and view all the answers

Why is the end of a peptide chain referred to as the C-terminus?

<p>The end of the chain is characterized by a carboxyl group. (A)</p> Signup and view all the answers

Which of the following statements best explains the concept of resonance in the context of the peptide bond?

<p>The electrons are continuously fluctuating between the nitrogen, carbon, and oxygen atoms, leading to partial charges. (A)</p> Signup and view all the answers

Flashcards

Phosphorylation

The process of adding a phosphate group to a molecule, often glucose, to trap it inside the cell.

Phosphate Transfer Potential

The ability of a molecule to transfer a phosphate group to another molecule, often used to exchange energy

Amination

The process of adding an amino group (-NH2) to a molecule, such as glucose.

β-D-glucosamine

A modified form of glucose with an amino group attached to carbon 2, important for various biological processes.

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N-acetylglucosamine

A modified form of glucose with an amino group attached at carbon 2 and an acetic acid attached to the amino group.

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Acetylation

The process of introducing an acetic acid group to an amino group.

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Glucose-6-phosphate

Glucose modified by having a phosphate group added to the sixth position.

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Glycolysis

The process of breaking down glucose into simpler molecules, usually involving the addition of phosphate groups and the cleavage of bonds.

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Extracellular Matrix (ECM)

A complex, gel-like substance surrounding most mammalian cells in tissues. Provides support, structure, and regulates cell behavior.

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Glycosaminoglycans (GAGs)

A major component of the ECM, these are long, unbranched chains of repeating disaccharide units. They are negatively charged due to the presence of uronic acid.

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Amino Sugar

One of the two monomers found in GAGs, it is a modified sugar with an amino group attached to the nitrogen.

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N-acetylglucosamine (GlcNAc)

A type of amino sugar found in GAGs. It is a derivative of glucose, with an acetyl group and an amino group attached.

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N-acetylgalactosamine (GalNAc)

The other type of amino sugar found in GAGs. It is a derivative of galactose, with an acetyl group and an amino group attached.

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Uronic Acid

A type of sugar found in GAGs, formed by oxidation of the sixth carbon (C6) of a hexose sugar. It carries a negative charge.

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Glucuronic Acid

The specific uronic acid found in GAGs, formed by oxidation of glucose.

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Properties of GAGs

Characteristics of GAGs: high viscosity, low compressibility, and structural integrity. These properties are due to the presence of negatively charged glucuronic acid.

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Aggrecan

A large molecule found in cartilage that can absorb and release water to manage the force applied to the tissue. It does this by releasing water when pressure is applied and reabsorbing water when pressure is relieved.

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Glycoproteins

Proteins with attached sugar chains (glycans). They play important roles in various cellular functions.

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Glycolipids

Lipids with attached sugar chains (glycans). They are found in cell membranes and serve as recognition sites for cell-cell interactions.

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Blood Group Antigens

The different types of blood groups (A, B, AB, and O) are determined by the specific sugar chains attached to glycolipids on the surface of red blood cells.

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Mucopolysaccharidoses (MPS)

A group of genetic disorders that result from the accumulation of GAGs (Glycosaminoglycans) in lysosomes.

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Hurler's Syndrome (MPS Type I)

A specific type of MPS caused by a deficiency of the enzyme α-L-iduronidase, leading to the accumulation of heparan sulfate and dermatan sulfate. This can cause growth and mental retardation with characteristic facial changes.

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Lysosome

A lysosome is a cellular organelle that acts as a recycling center, breaking down old or damaged cell parts and molecules.

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Alpha Carbon

The carbon atom in an amino acid directly attached to both the amino (-NH2) group and the carboxyl (-COOH) group.

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Alpha Amino Acids

Amino acids that have their amino group attached to the alpha carbon, meaning the carbon adjacent to the carboxyl group. They are a crucial building block of proteins.

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R group (Side Chain)

The side chain (R group) of amino acids directly influences their polarity and charge. It determines how they interact with water and other amino acids.

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Nonpolar Neutral Amino Acids

Amino acids with side chains that are hydrophobic and do not have a charge. These amino acids prefer to avoid water and cluster together in protein structures.

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Polar Neutral Amino Acids

Amino acids with side chains that are hydrophilic and do not have a charge. They interact readily with water and participate in hydrogen bonding in proteins.

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Acidic Charged Amino Acids

Amino acids with side chains that have a negative charge. They are acidic because they can release a proton (H+) into solution.

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Basic Charged Amino Acids

Amino acids with side chains that have a positive charge. They are basic because they can accept a proton (H+) from solution.

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Essential Amino Acids

These amino acids cannot be synthesized by humans. They must be obtained from the diet, as they are essential for building and maintaining tissues.

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Peptide Bond

The special type of bond that connects amino acids in a peptide chain. It is neither a true single nor a double bond.

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Resonance

The movement of electrons within a molecule, leading to a different distribution of charge throughout the molecule.

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Electronegativity

The tendency of an atom to attract electrons towards itself in a covalent bond.

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N-Terminus

The end of a peptide chain that contains a free amino group (-NH2).

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C-Terminus

The end of a peptide chain that contains a free carboxyl group (-COOH).

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Peptide Bond Length

The peptide bond is a hybrid between single and double bonds due to resonance. This makes it shorter than a single bond but longer than a double bond.

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Peptide Bond Forms

The peptide bond can be represented in two extreme forms: one with a neutral charge and one with a charged structure. These two forms constantly switch back and forth.

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Planar Conformation

The peptide bond has a partial double bond character that restricts rotation around the bond, creating a planar conformation.

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pH, what is it?

The concentration of hydrogen ions (H+) in a solution, expressed as a negative logarithm (base 10) of the molar concentration.

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Physiological pH

The pH of a solution where the concentration of hydrogen ions (H+) is equal to the concentration of hydroxide ions (OH-), typically around 7.4.

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pKa

The negative logarithm (base 10) of the acid dissociation constant (Ka). It measures the strength of an acid by indicating its tendency to donate a proton (H+).

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pKa, and its meaning

The point at which an acid is half dissociated (half in its protonated form, half in its deprotonated form).

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Amino acid pKa

Amino acids have two main ionizable groups: the carboxyl group (COOH) and the amino group (NH3+). They have specific pKa values which determine their charge at different pHs.

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pKa and charge

At a pH greater than the pKa, the acidic group will be deprotonated (lose its H+) and carry a negative charge. Conversely, at a pH lower than the pKa, the acidic group will be protonated (gain H+) and carry a positive charge. This is how their charge changes as pH changes.

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Amino acids at pH 7.4

When the pH is roughly 7.4 (physiological pH), the charge on the amino acid is neutral. This happens because the carboxyl group is deprotonated (negative) and the amino group is protonated (positive), resulting in a balanced charge.

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Charged side chains

Some amino acids have side chains (R groups) that can also be charged depending on the pH. This can influence the overall charge of the amino acid and contribute to its behavior in various environments.

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Study Notes

Biochemistry Study Notes

  • Biochemistry is the study of chemical processes within and relating to living organisms.
  • Macromolecules are large molecules consisting of similar building blocks.
  • Lipids, carbohydrates, proteins, and nucleic acids are the four major classes of biological macromolecules.
  • Carbohydrates are composed of monomers like sugars and are a major fuel source for metabolism.
  • Carbohydrates include monosaccharides (simple sugars), disaccharides (double sugars), and polysaccharides (complex sugars)
  • Polysaccharides function as both sources of energy (starch) and storage forms (glycogen).

Carbohydrate Structure

  • Carbohydrates are literally "hydrates of carbon" and can be classified as polyhydroxy aldehydes or ketones.
  • Sugars are carbohydrates that are soluble in water and sweet in taste.
  • Carbohydrates have many functions including a source of energy, storage of energy, and as structural components
  • Monosaccharides, a simple sugar, includes glucose, fructose, galactose.
  • Disaccharides are two monosaccharides linked together by a glycosidic bond and include sucrose, maltose and lactose.
  • Polysaccharides are multiple monosaccharides linked together and include starch, glycogen, and cellulose.

Carbohydrate Classification

  • The classification of carbohydrates is based on the number of carbon atoms (triose, tetrose, pentose, hexose) as well as on the functional group (aldehyde or keto).
  • Aldoses have an aldehyde group.
  • Ketoses have a ketone group.
  • Important monosaccharides in metabolism include glucose, fructose, and galactose.

Carbohydrates in Metabolism

  • Monosaccharides are the primary fuel for metabolism.
  • Plants store energy in the form of starch, whereas animals store it as glycogen.
  • Carbohydrates are converted into simpler units like glucose for metabolism, supplying energy to all living cells in plants and animals.

Isomers

  • Isomers have the same chemical formula but a different arrangement of atoms.
  • Stereoisomers are isomers that differ in spatial arrangement.
  • Enantiomers are non-superimposable mirror images.
  • Epimers are stereoisomers that differ in the configuration around one chiral carbon only.
  • Glucose and fructose are examples of isomers and epimers.

Structural Components

  • Carbohydrates form structural components in organisms such as plant fibers (cellulose), insect/crustacean exoskeletons (chitin), and bacterial cell walls.

Other Functions

  • Some carbohydrates are part of RNA and DNA components.
  • Some carbohydrates are conjugated with proteins and lipids.
  • Carbohydrates are involved in some cell-cell interactions and recognition events.

Other Categories

  • Oligosaccharides: The link between the two or more monosaccharides is the glycosidic bond. Oligosaccharides are small chains of monosaccharides (2-10)
  • Polysaccharides are long chains of many monosaccharides

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This quiz explores key concepts related to the metabolism of glucose, focusing on phosphorylation, amination, and the role of the extracellular matrix in cellular functions. Delve into the biochemical processes that regulate energy transfer and the structure of biomolecules involved. Test your understanding of these essential metabolic pathways.

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