Biochemistry: Carbohydrates Overview

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Questions and Answers

What is one of the primary functions of carbohydrates in humans?

Serving as the only source of cellular energy

Providing structural components of cell membranes

Providing energy through oxidation (correct)

Synthesis of nucleic acids

Which of the following best describes monosaccharides?

Complex carbohydrates consisting of multiple sugar units

Always contain 8 or more carbon atoms

Cannot be hydrolyzed into simpler sugars (correct)

Are commonly found as polysaccharides

What is the general formula for carbohydrates?

CnH2nOn (correct)

C(n+1)H2nO2

C2nH2O2

C2nH2O

Which of the following examples are disaccharides?

Lactose and sucrose Signup and view all the answers

In terms of structure, what is a polysaccharide?

Multiple monosaccharides linked together Signup and view all the answers

What does chirality refer to in the context of molecules?

The property of having mirror images Signup and view all the answers

Which carbohydrate provides a short-term energy reserve in the human body?

Glycogen Signup and view all the answers

Which type of carbohydrate is defined as containing two monosaccharide units?

Disaccharide Signup and view all the answers

What is a characteristic of oligosaccharides?

They are usually found associated with proteins and lipids. Signup and view all the answers

What is true about chiral centers?

They require a carbon atom with four different groups. Signup and view all the answers

Which of the following defines an achiral molecule?

A molecule whose mirror image is superimposable. Signup and view all the answers

How are enantiomers of glyceraldehyde distinguished?

Using the D, L system. Signup and view all the answers

What are stereoisomers?

Isomers that have the same molecular formula but differ in spatial arrangement. Signup and view all the answers

Polysaccharides are characterized by what feature?

They are polymeric carbohydrates composed of many monosaccharides. Signup and view all the answers

Which of the following is not a property of a chiral molecule?

It has superimposable mirror images. Signup and view all the answers

What happens during hydrolysis of oligosaccharides?

They yield multiple monosaccharides. Signup and view all the answers

What is produced when an enzyme oxidizes the primary alcohol end of an aldose?

Alduronic acid Signup and view all the answers

Which process involves the replacement of a hydroxyl group with an amino group in a monosaccharide?

Amino sugar formation Signup and view all the answers

Which type of reaction results in the formation of alditols from monosaccharides?

Reduction reaction Signup and view all the answers

What characterizes lipids compared to other biomolecules?

Mostly hydrophobic with C-H bonds Signup and view all the answers

Which of the following best describes glycoside formation?

It involves the reaction of hemiacetals with acids. Signup and view all the answers

Which statement is true regarding phosphates and monosaccharides?

They react with hydroxyl groups to form inorganic esters. Signup and view all the answers

What is a common use of lipids in organisms?

Making up cell membranes Signup and view all the answers

Which of the following is NOT a characteristic of lipids?

Composed mainly of carbohydrates Signup and view all the answers

What characterizes a polyunsaturated fatty acid (PUFA)?

It contains two or more carbon-carbon double bonds. Signup and view all the answers

What does the IUPAC name '9,12-octadecadienoic acid' indicate?

Double bonds are located at carbon 9 and 12. Signup and view all the answers

How does the solubility of fatty acids change with increasing carbon chain length?

Solubility decreases with chain length. Signup and view all the answers

What is the significance of the position of the double bonds in unsaturated fatty acids?

It affects the overall polarity of the molecule. Signup and view all the answers

Which of the following correctly describes the structure of triacylglycerols?

They are formed from a glycerol backbone and three fatty acids. Signup and view all the answers

What type of fatty acids are characterized by having hydrogen atoms on opposite sides of the double bond?

Trans unsaturated fatty acids. Signup and view all the answers

What does the notation '18:3 (Δ9,12,15)' signify?

It describes a PUFA with 3 double bonds at specific locations. Signup and view all the answers

Which characteristic best describes long-chain fatty acids?

They are generally insoluble in water. Signup and view all the answers

What factor most significantly influences the melting point of triacylglycerols?

The degree of saturation Signup and view all the answers

Which type of fatty acids tend to be solids at room temperature?

Long-chain saturated fatty acids Signup and view all the answers

What happens to the number of 'bends' in a fatty acid chain when the number of double bonds increases?

The number of bends increases Signup and view all the answers

What type of triacylglycerol is formed from the esterification of glycerol with three identical fatty acid molecules?

Simple Triacylglycerol Signup and view all the answers

Which type of fatty acid is considered 'good fat' that can help reduce heart disease?

Monounsaturated Fatty Acids (MUFA) Signup and view all the answers

What is the current recommended percentage of total fat intake in calories for Monounsaturated Fatty Acids (MUFA)?

15% Signup and view all the answers

What type of triacylglycerol is formed from the esterification of glycerol with more than one kind of fatty acid molecule?

Mixed Triacylglycerol Signup and view all the answers

Which of the following statements is true about the energy storage properties of triacylglycerols?

They provide materials for energy when demand is high in human cells Signup and view all the answers

Study Notes

Biochemistry

Study of chemical substances in living organisms and their interactions
Includes bioinorganic and bioorganic substances

Bioinorganic Substances

Water (70% of mass)
Inorganic salts (5% of mass)

Bioorganic Substances

Proteins (15% of mass)
Lipids (8% of mass)
Carbohydrates (2% of mass)
Nucleic acids (2% of mass)

Carbohydrates

About 75% of the dry mass of plant material
Important for energy production, storage, structure, and cell recognition

Carbohydrate Functions

Oxidation provides energy
Storage as glycogen provides a short energy reserve
Supplies carbon atoms for other biomolecules
Structural component of DNA and RNA
Structural component of cell membranes
Linked to protein function in cell-cell and cell-molecule recognition process

Carbohydrate Classification

General formula: CnH2nOn or Cn(H2O)n
Polyhydroxy aldehydes or ketones

Monosaccharide

Single polyhydroxy aldehyde or ketone unit
Cannot be broken down by hydrolysis
Common examples: Glucose, fructose

Disaccharide

Contains two monosaccharide units covalently bonded
Common examples: Sucrose, lactose

Oligosaccharide

Contains 3 to 10 monosaccharides
Usually found associated with proteins and lipids
Can be broken down into multiple monosaccharides via hydrolysis

Polysaccharide

Polymeric carbohydrates with many monosaccharides
Undergo hydrolysis under appropriate conditions
Common examples: Cellulose and starch

Chirality

Related to handedness of molecules
Left-handedness and right-handedness are forms of isomerism

Mirror Images

Reflection of an object in a mirror
Superimposable mirror images coincide at all points when laid on top of each other
Nonsuperimposable mirror images do not coincide at all points when laid on top of each other

Chirality in Molecules

Presence of a carbon atom with four different groups bonded in a tetrahedral orientation
Chiral center: carbon atom that generates handedness
Chiral molecule: mirror images are not superimposable
Achiral molecule: mirror images are superimposable

Stereoisomers

Isomers with the same molecular and structural formula but differ in the orientation of atoms in space
Two types: Enantiomers and diastereomers

Fischer Projection Formula

Two-dimensional notation showing the spatial arrangement of groups around chiral centers in molecules

D, L System for Handedness

Glyceraldehyde enantiomers are used as a reference to designate handedness
Applied to monosaccharides with more than one chiral center in the lower manner

Haworth Projection Formula

Two-dimensional notation specifying the three-dimensional structure of cyclic forms of monosaccharides

Enzymatic Oxidation Reaction

Enzymes oxidize the primary alcohol end of an aldose, such as glucose
Produces alduronic acid

Phosphate Ester Formation

Hydroxyl groups of monosaccharides react with inorganic oxyacids to form inorganic esters

Reduction Reaction to Produce Sugar Alcohols

Reduction of a monosaccharide results in a polyhydroxy alcohol
Polyhydroxy alcohols are called sugar alcohols or alditols

Amino Sugar Formation

Replacement of a hydroxyl group of a monosaccharide with an amino group

Glycoside Formation

Hemiacetal reacts with alcohols in acid solution to produce acetals
Glycoside: acetal form of a cyclic monosaccharide with the hemiacetal carbon –OH group replaced with an -OR group

Lipids

Organic compounds found in living organisms that are insoluble (or sparingly soluble) in water, but soluble in nonpolar solvents
Can be esters, amides, and alcohols (acyclic, cyclic, and polycyclic)
Do not have a common structural feature that defines all lipids

Lipid Characteristics

Mostly hydrophobic
Made up of mostly C-H bonds
Useful for long-term energy storage
Make up the membranes of cells

Fatty Acids

Carboxylic acids with a hydrocarbon chain
Saturated: no double bonds in carbon chain (single bond)
Unsaturated: one or more double bonds in carbon chain (double bonds)

Polyunsaturated Fatty Acids

Fatty acids with two or more carbon-carbon double bonds in the carbon chain

Omega (ω)-6 Fatty Acids

Unsaturated fatty acids with their endmost double bond six carbon atoms away from the methyl end

IUPAC Names for Fatty Acids

Example: cis,cis-9,12-octadecadienoic acid indicates a double bond at carbons 9 and 12

Trans Unsaturated Fatty Acids

The H atoms on the double bond are on opposite sides

Physical Properties of Fatty Acids

Water solubility: directly related to carbon chain length; solubility decreases as chain length increases
Short-chain fatty acids: slightly soluble
Long-chain fatty acids: insoluble in water; nonpolar nature dominates solubility
Melting point: strongly influenced by carbon chain length and degree of unsaturation
Longer carbon chains have higher melting points
Saturated fatty acids tend to be solid at room temperature
Unsaturated fatty acids tend to be liquid at room temperature

Energy Storage Lipids: Triacylglycerols

Human cells store small amounts of these materials
Used as an energy source when energy demands are high

Triacylglycerols: Basic Structure

Dehydration synthesis reaction
Triacylglycerols are triesters (3 ester functional groups)
Alcohol: glycerol
Esterification reaction: one molecule of glycerol reacts with three fatty acids
Acyl group: portion of a carboxylic acid remaining after the -OH group is removed from the carboxyl carbon atom

Triacylglycerols: Types

Simple triacylglycerol: all three fatty acids are identical
Mixed triacylglycerol: more than one kind of fatty acid is present

Types of Fatty Acids:

Saturated Fatty Acids: Mostly solid at room temperature; commonly found in animal fats (butter, lard)
Monounsaturated Fatty Acids (MUFA): "Good fats"; decrease heart disease and breast cancer risk; help reduce blood platelet stickiness and prevent blood clots; found in olive, avocado, and canola oils
Polyunsaturated Fatty Acids (PUFA): "Good fats" and "bad fats"; found in many sources: vegetable oils, nuts, seeds
Essential Fatty Acids: Required by the body but not produced by the body; include omega-3 and omega-6 fatty acids.

Recommended Fatty Acid Intake

15% of total fat intake should be MUFA
10% of total fat intake should be PUFA

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Description

Explore the essential biochemistry of carbohydrates, including their classification, functions, and significance in living organisms. This quiz covers the structures and roles of monosaccharides and their contributions to energy production, storage, and structural integrity in cells.