Carbohydrates Overview Quiz
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Questions and Answers

Which statement best describes lactose?

  • It is a non-reducing sugar.
  • It is obtained from the hydrolysis of starch.
  • It is formed from 6-D-galactose and 1-D-fructose.
  • It contains a 1,4-glycosidic bond. (correct)

What type of glycosidic bond is present in sucrose?

  • 1,6-glycosidic bond
  • 1,3-glycosidic bond
  • 1,2-glycosidic bond (correct)
  • 1,4-glycosidic bond

Which disaccharide is known as malt sugar?

  • Maltose (correct)
  • Fructose
  • Sucrose
  • Lactose

Which of the following is true about sucrose?

<p>It consists of a-D-glucose and b-D-fructose. (B)</p> Signup and view all the answers

How is maltose formed?

<p>By the hydrolysis of starch. (A)</p> Signup and view all the answers

Which of the following describes a ketose?

<p>Contains a ketone group with multiple hydroxyl groups (A)</p> Signup and view all the answers

What is the classification of D-glucose?

<p>Monosaccharide (D)</p> Signup and view all the answers

Which of the following carbohydrates is classified as a polysaccharide?

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

What is the normal blood glucose level range?

<p>70-90 mg/dl (D)</p> Signup and view all the answers

What is the unique feature of cysteine among standard amino acids?

<p>It has a side chain that contains a sulfhydryl group. (B)</p> Signup and view all the answers

What structural representation of monosaccharides shows the straight chain formula?

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

Which sugar is found freely in nature?

<p>D-glucose (A)</p> Signup and view all the answers

What naming convention is used for the N-terminal amino acid in a peptide?

<p>It retains its full amino acid name. (D)</p> Signup and view all the answers

What is the formula for D-fructose?

<p>C6H12O6 (C)</p> Signup and view all the answers

How many amino acids are present in a tripeptide?

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

Which of the following correctly describes a disulfide bond in relation to cysteine?

<p>It forms through the oxidation of two cysteine molecules. (B)</p> Signup and view all the answers

What condition reflects abnormally high blood sugar levels?

<p>Hyperglycemia (D)</p> Signup and view all the answers

Which term describes peptides containing the same amino acids arranged in different sequences?

<p>Isomeric peptides (D)</p> Signup and view all the answers

What is the full name of the peptide formed from valine, threonine, and cysteine?

<p>Valinylthreonylcysteine (D)</p> Signup and view all the answers

What defines an oligopeptide?

<p>A chain containing 10 to 20 amino acids. (B)</p> Signup and view all the answers

Where does the C-terminal amino acid residue appear in a peptide sequence?

<p>At the right side of the peptide chain. (C)</p> Signup and view all the answers

What type of glycosidic bonds link the glucose units in amylose?

<p>a-1,4 glycosidic bonds (A)</p> Signup and view all the answers

Which statement about glycogen is accurate?

<p>It is more highly branched than amylopectin. (D)</p> Signup and view all the answers

What type of polysaccharide is cellulose categorized as?

<p>Homopolysaccharide (A), Unbranched polysaccharide (C)</p> Signup and view all the answers

What is the primary function of glycogen in the body?

<p>Provides short-term energy reserves (D)</p> Signup and view all the answers

Which of the following statements about amylopectin is true?

<p>It has a branched-chain structure. (A)</p> Signup and view all the answers

Which component of carbohydrates cannot be digested by humans?

<p>Cellulose (D)</p> Signup and view all the answers

Which term refers to compounds with the same molecular formula but different structural arrangements?

<p>Structural isomers (A)</p> Signup and view all the answers

How are chiral centers defined in terms of their molecular structure?

<p>Atom bonded to four different groups (D)</p> Signup and view all the answers

What primary function do hormones like insulin serve?

<p>Regulate processes such as metabolism and growth (A)</p> Signup and view all the answers

What is the correct name for the peptide formed from Glycine and Alanine?

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

Which type of isomerism involves compounds with the same molecular formula and structure, but differ in spatial configuration?

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

Which of the following peptide hormones is known to be produced by the pituitary gland?

<p>Oxytocin (D)</p> Signup and view all the answers

What is the main reason humans cannot digest cellulose?

<p>Lack of b-1,4-glycosidic bond enzymes (A)</p> Signup and view all the answers

Which amino acid does not follow the usual naming convention when forming peptide names?

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

Amylose is described as which of the following?

<p>Unbranched with a-1,4 bonds (A)</p> Signup and view all the answers

What is a characteristic of non-superimposable mirror images?

<p>They cannot be overlaid perfectly (D)</p> Signup and view all the answers

Which of the following compounds represents structural isomerism?

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

What type of protein consists of only one peptide chain?

<p>Monomeric Protein (A)</p> Signup and view all the answers

What does the handedness ('left handed' and 'right handed') in biochemical context refer to?

<p>The configuration at the chiral centers (D)</p> Signup and view all the answers

What term describes a complex protein that includes amino acids bonded with other substances?

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

Which of the following statements about carbohydrates is false?

<p>All carbohydrates are structural isomers (B)</p> Signup and view all the answers

What is the primary protein structure defined as?

<p>The sequence of amino acids in a chain (A)</p> Signup and view all the answers

Which of the following is a pentapeptide neurotransmitter that reduces pain?

<p>Met-enkephalin (C)</p> Signup and view all the answers

Which statement accurately describes a small peptide hormone?

<p>Is generally made up of 9 amino acid residues (A)</p> Signup and view all the answers

Flashcards

Carbohydrates

Carbohydrates are organic compounds composed of carbon, hydrogen, and oxygen. They are the primary source of energy for living organisms, providing fuel for cellular processes.

Glucose

Glucose is a simple sugar, a monosaccharide, that is the primary source of energy for most cells. It serves as a building block for more complex carbohydrates.

Glycogen

Glycogen is a branched polysaccharide that serves as the storage form of glucose in animals. It is primarily stored in the liver and muscles.

Structural Isomerism

Structural isomers have the same molecular formula but differ in the arrangement of their atoms, leading to different chemical properties.

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Stereoisomers

Stereoisomers have the same molecular formula and the same sequence of atoms but differ in their three-dimensional spatial arrangement.

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Chiral Center

A chiral center is an atom in a molecule that is bonded to four different groups. This creates two non-superimposable mirror image forms, known as enantiomers.

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Dextrorotatory & Levorotatory

Dextrorotatory molecules rotate polarized light clockwise, denoted by (d) or (+). Levorotatory molecules rotate it counterclockwise, denoted by (l) or (-).

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Isomers

Isomers are compounds with the same molecular formula but different structures or spatial arrangements. They exhibit different properties due to their structural differences.

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Disaccharide

A sugar composed of two monosaccharide units linked by a glycosidic bond.

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Sucrose

A disaccharide composed of glucose and fructose linked by an α,β-1,2-glycosidic bond. Found in sugar cane and sugar beets.

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Lactose

A disaccharide composed of glucose and galactose linked by a β-1,4-glycosidic bond. Found in milk products.

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Maltose

A disaccharide composed of two glucose units linked by an α-1,4-glycosidic bond. Found in malt.

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Glycosidic bond

The bond formed between two monosaccharides in a disaccharide, involving the hydroxyl group on one sugar and the anomeric carbon on the other.

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Ketose

A type of carbohydrate that contains a ketone group and multiple hydroxyl groups (OH groups). They are classified by the number of carbon atoms they have (e.g., triose, tetrose, pentose, hexose).

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Monosaccharide

The simplest form of carbohydrates, consisting of a single sugar molecule. They are classified by the number of carbon atoms they have (e.g., triose, tetrose, pentose, hexose).

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Fructose

A type of monosaccharide with six carbon atoms (C6H12O6). It is a ketohexose, meaning it contains a ketone group and six carbon atoms. It is found in fruits, honey, and vegetables.

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Glucose Tolerance Test

A test that measures blood glucose levels over several hours after the ingestion of glucose. It helps to assess how the body processes sugar.

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Hyperglycemia

A condition where blood glucose levels are higher than normal. It can be a symptom of diabetes.

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Hypoglycemia

A condition where blood glucose levels are lower than normal. It can occur due to various factors like low blood sugar or insulin overdose.

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Pentapeptide

A peptide chain consisting of 5 different amino acids.

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Nonapeptide

A peptide chain composed of 9 amino acids.

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Primary Protein Structure

The linear sequence of amino acids in a protein determining its primary structure.

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Secondary Protein Structure

The folding pattern of a protein chain due to hydrogen bonding, creating alpha-helices and beta-sheets.

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Monomeric Protein

A protein composed of a single polypeptide chain.

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Multimeric Protein

A protein composed of multiple polypeptide chains.

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Simple Protein

A protein containing only amino acid residues.

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Conjugated Protein

A protein formed by the combination of a simple protein and a non-protein component.

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Cysteine or Cys

An amino acid that has a side chain containing a sulfhydryl group (SH group). It is the only standard amino acid with this feature.

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Dimerization of Cysteine

The process where two cysteine molecules react to form a cystine molecule. The reaction is catalyzed by mild oxidizing agents.

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Cystine

A molecule formed when two cysteine molecules are linked via a disulfide bond. It is an important structural element in proteins.

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Peptides

A chain of amino acids linked covalently. They are the building blocks of proteins.

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C-terminal amino acid

The amino acid at the end of a peptide chain where the carboxyl group is free.

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N-terminal amino acid

The amino acid at the beginning of a peptide chain where the amino group is free.

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Isomeric Peptides

Peptides with the same amino acids but in different sequences. Since the order is different, properties and functions of these peptides will also vary.

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Tripeptide

A peptide composed of three amino acid residues. It is named by combining the names of the amino acids in order, starting with the N-terminal amino acid.

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Homopolysaccharide

A type of carbohydrate that consists of only one type of monosaccharide monomer.

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Heteropolysaccharide

A type of carbohydrate that has more than one type of monosaccharide monomer.

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Branched Polysaccharide

A carbohydrate that is branched, forming branches from two different types of polymers.

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Unbranched Polysaccharide

A carbohydrate that is linear, forming a straight chain without branches.

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Amylose

A type of polysaccharide that is a polymer of alpha-D-glucose molecules, linked by alpha 1,4 glycosidic bonds, forming a continuous unbranched chain.

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Amylopectin

A branched chain polysaccharide that is a polymer of alpha-D-glucose molecules, with alpha 1,4 glycosidic bonds between glucose units and alpha 1,6 bonds at branching points.

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Cellulose

A polysaccharide of glucose units in unbranched chains, linked by beta 1,4 glycosidic bonds, that cannot be digested by humans.

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Study Notes

Carbohydrates

  • Major sources of energy from plants
  • Synthesized by plants from CO2 and H2O
  • Glucose is a key example
  • Saccharides are a Greek word for sugars

Functions

  • Provide energy
  • Glycogen: short-term energy storage
  • Supply carbon for other biochemicals
  • Component of DNA and RNA
  • Linked to lipids & proteins
  • Spare protein use
  • Breakdown fatty acids and prevent ketosis
  • Provide flavor and sweetness
  • Source of dietary fiber

Structural Properties

  • Handedness is determined by the configuration at the highest numbered chiral center
  • Presence of chiral centers leads to stereoisomerism
  • Superimposable mirror image coincides at all points.
  • Non-superimposable mirror images do not coincide.
  • Chiral center has four different groups bonded tetrahedrally.

Isomerism

  • Compounds with identical molecular formulas but different structures.
  • Glucose and Fructose are structural isomers.
  • Stereoisomers have identical molecular formulas and structures. but differ in arrangement.
  • Presence of chiral centers allows stereoisomers formation.

Types of Stereoisomerism

  • D and L isomers
  • Epimers
  • Anomers

Optical Isomerism

  • Optical activity is the capacity to rotate plane-polarized light.
  • D-sugars rotate light clockwise.
  • L-sugars rotate light counter-clockwise.

Epimerism

  • If two monosaccharides differ at a carbon other than the anomeric carbon, they are epimers.

Anomerism

  • Difference in position of the hydroxyl group at the anomeric carbon.
  • D-Glucose's cyclic form can exist in a and β anomeric forms.

Classification (carbohydrates)

  • Monosaccharides
  • Disaccharides
  • Oligosaccharides
  • Polysaccharides

Classification (based on reaction to oxidizing agents)

  • Reducing sugars (positive Benedict's/Tollen's test)
  • Glucose, galactose, fructose
  • Non-reducing sugars (negative Benedict's/Tollen's test)
  • Sucrose, maltose

Monosaccharides

  • Consist of 3–6 carbon atoms
  • Glucose, fructose, galactose & others

Polysaccharides

  • Condensation of many monosaccharides
  • Amylose & amylopectin are types
  • Glycogen (animal starch)
  • Cellulose (plant starch)

Blood Glucose Level

  • Normal blood glucose level: 70/90 mg/dl.
  • Glucose tolerance test measures blood sugar after glucose intake.

Blood Glucose Conditions

  • Hyperglycemia: high blood sugar
  • Hypoglycemia: low blood sugar

D-Fructose and D-Glucose

  • Ketohexose
  • Sweetest of carbohydrates
  • Component of fruits, vegetables & honey

D-Galactose

  • Aldohexose
  • Component of lactose, a disaccharide

Disaccharides

  • Formed by the condensation of two monosaccharides
  • Maltose (glucose + glucose)
  • Sucrose (glucose + fructose)
  • Lactose (glucose + galactose)

Lipids

  • Organic substances
  • Insoluble in water; soluble in organic solvents
  • Types:
    • Fatty acids
    • Triglycerides
    • Phospholipids

Fatty Acids

  • Long hydrocarbon chain
  • Carboxyl group
  • Saturated (no double bonds)
  • Unsaturated (one or more double bonds)

Triacylglycerols

  • Fats and oils
  • Formed from glycerol and three fatty acids (ester linkage)

Phospholipids

  • Similar to triglycerides, but with a phosphate group
  • Important components of cell membranes

Steroids

  • Four-ring structures
  • Cholesterol, important component of cell membranes

Glycolipids

  • Lipids with carbohydrate groups
  • Cell surface markers

Micelles

  • Spherical structures of surfactants
  • Hydrophobic tails inward; hydrophilic heads outward

Other Lipids

  • Waxes
  • Leukotrienes

Proteins

  • Polymers of amino acids linked by peptide bonds
  • Essential for structure, function, and regulation in organisms
  • Types of Proteins:
    • Simple proteins: only amino acids
    • Conjugated proteins: contain non-amino acid components

Amino Acids

  • Building blocks of proteins
  • 20 common amino acids
  • Central carbon with amino group, carboxyl group, and R group
  • Polar, nonpolar, acidic, or basic based on R group
  • Protein structure depends on sequence and properties of amino acids

Peptides

  • Chains of 2 or more amino acids linked by peptide bonds
  • Dipeptides, tripeptides, oligopeptides, and polypeptides

Protein Structure

  • Primary: amino acid sequence
  • Secondary: alpha helix and beta sheets (hydrogen bonding)
  • Tertiary: 3D structure (interactions between R groups),
  • Quaternary: multiple polypeptide chains

Protein Denaturation

  • Loss of protein's 3D structure due to heat, chemicals, etc.
  • Loss of function
  • Example: cooking an egg

Protein Hydrolysis

  • Breaking down proteins into amino acids by adding water
  • Enzymes catalyze this process in the body during digestion

Nucleic Acids

  • Polymers of nucleotides
  • DNA and RNA
  • Store and transmit genetic information

Nucleotides

  • Monomers of nucleic acids
  • Sugar, phosphate group, and nitrogenous base
  • Adenine, guanine, cytosine, thymine, and uracil

DNA

  • Deoxyribonucleic acid
  • Double helix structure
  • Stores genetic information
  • Base pairs: A-T, G-C

RNA

  • Ribonucleic acid
  • Single-stranded
  • Three types: mRNA, tRNA, rRNA
  • Involved in protein synthesis

Genetic Code

  • Set of rules that determines how mRNA codons translate into specific amino acids during protein synthesis

Replication

  • Process of producing identical copies of DNA molecules

Transcription

  • Process of copying DNA's genetic information into mRNA.

Translation

  • Process of using mRNA's genetic information to synthesize proteins from amino acids.

Regulation

  • Protein synthesis is regulated at different levels (transcription, translation).

Viruses

  • Infectious agents
  • DNA or RNA enclosed in protein coat
  • Need host cell for reproduction

Mutation

  • Change in a DNA sequence
  • Can be substitution or frameshift
  • Can affect protein structure and function

HIV and AIDS

  • Retrovirus that causes AIDS
  • Infects T4 lymphocytes
  • Treatment involves preventing reverse transcriptase and modifying protease.

Classification of Proteins

  • Fibrous (structural)
  • Globular (functional)

Biological Waxes

  • Water insoluble
  • Protective coatings and lubrication

Phospholipids

  • Important membrane components
  • Hydrophilic head; hydrophobic tail
  • Form lipid bilayers

Micelles

  • Surfactant molecules
  • Hydrophobic tails cluster inward

Sphingolipids

  • Lipids containing sphingosine and other components
  • Cell membrane components
  • Cerebrosides, sphingomyelins, gangliosides

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Test your knowledge on carbohydrates, their functions, and structural properties. This quiz covers key concepts such as energy sources, glycemic responses, and isomerism. Delve into the crucial role carbohydrates play in biochemistry and nutrition.

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