Biochemistry: Structures of Glucose

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Questions and Answers

What type of glucose monomer is starch made of?

glucose-6-phosphate

β-glucose

fructose

α-glucose (correct)

Which component of starch releases glucose more rapidly for cellular respiration?

Glycogen

Amylose

Amylopectin (correct)

Cellulose

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

1-4 and 1-6 α-glycosidic bonds (correct)

1-6 and 1-7 β-glycosidic bonds

1-2 and 1-3 β-glycosidic bonds

1-5 and 1-4 α-glycosidic bonds

Glycogen differs from amylopectin in that glycogen is:

more branched Signup and view all the answers

Which of the following best describes the structural function of cellulose?

Building up the cell wall Signup and view all the answers

What type of bond is formed when a fatty acid combines with glycerol?

Ester bond Signup and view all the answers

Why are lipids insoluble in water?

They have a reduced proportion of oxygen to carbon and hydrogen Signup and view all the answers

What property of amylose contributes to its compact structure?

It has a non-branching linear chain Signup and view all the answers

What is the main role of glycogen in animal cells?

Energy storage Signup and view all the answers

Which of the following best describes triglycerides?

Consist of one glycerol and three fatty acid tails Signup and view all the answers

What is the molecular structure of glucose in its dry powder form?

Linear structure Signup and view all the answers

Which statement correctly describes the α-glucose structure?

The -OH group on carbon 1 is pointing downwards. Signup and view all the answers

What is formed as a result of the condensation reaction between monosaccharides?

Disaccharides Signup and view all the answers

What type of bond connects monosaccharides in polysaccharides?

Covalent bond Signup and view all the answers

Which effect does the presence of functional groups have on sugars indicating reducing properties?

Presence of aldehyde or ketone groups indicates reducing sugars. Signup and view all the answers

What characterizes sucrose in contrast to reducing sugars?

It has a 1-2 glycosidic bond that occupies functional groups. Signup and view all the answers

How can the presence of reducing sugars be detected using Benedict's reagent?

By seeing a color change from blue to brick red. Signup and view all the answers

What happens to glycosidic bonds during hydrolysis?

They are broken by the addition of water. Signup and view all the answers

What structural feature allows for greater stability in the ring form of glucose?

It creates multiple hydrogen bonds. Signup and view all the answers

What is a common characteristic of all reducing sugars?

They contain free functional groups. Signup and view all the answers

Study Notes

Glucose Structure and Properties

Composed of 6 carbon, 12 hydrogen, and 6 oxygen atoms (C6H12O6) with a ratio of C:H:O as 1:2:1.
Contains five hydroxyl groups (-OH), making it highly water soluble and capable of forming hydrogen bonds.
Exhibits two structural forms: a straight chain when dry and a cyclic ring form (6 membered) when dissolved in water.
Isomers: two types exist - α-glucose (OH on carbon 1 pointing down) and β-glucose (OH on carbon 1 pointing up).
Ring structure is more stable in solution, space-efficient, enhancing energy storage and stability in polymer formations like glycogen.

Disaccharides

Comprise 12 carbons, 22 hydrogens, and 11 oxygens (C12H22O11).
Formed by the condensation of two monosaccharides through a glycosidic bond.
Bond formation involves a condensation reaction, resulting in water removal, catalyzed by specific enzymes.
Glycosidic bond breakage occurs via hydrolysis, adding water and also catalyzed by enzymes.

Testing for Reducing Sugars

Utilize Benedict’s reagent and heat; a color change from blue to brick red indicates reducing sugars presence.
Test shows a semi-quantitative result: faster color change or higher intensity of red indicates greater sugar concentration.
All monosaccharides and disaccharides like maltose and lactose are reducing sugars due to free functional groups.
Sucrose is non-reducing because its 1-2 glycosidic bond occupies both functional groups.

Polysaccharides

General formula: (C6H10O5)n; polymers of monosaccharides linked by glycosidic bonds.
Key roles:
- Starch and glycogen serve as energy storage, compact, inert, and insoluble to not affect cell water potential.
- Glucose can be rapidly released through enzyme-catalyzed reactions.
- Cellulose provides structural strength for cell walls due to high tensile strength.

Starch

Composed of α-glucose monomers linked by glycosidic bonds.
Exists as two components:
- Amylose: linear, non-branching chains linked by 1-4 α-glycosidic bonds, forming a compact helical structure.
- Amylopectin: branched structure due to 1-4 and 1-6 α-glycosidic bonds, allowing rapid glucose release.
Starch accumulates in chloroplasts and storage organs like potatoes.

Glycogen

Structure consists of α-glucose with both 1-4 and 1-6 glycosidic bonds.
Highly branched, making it easier for rapid access to stored energy.
Glycogen granules form in liver and muscle cells, serving as energy reserves.

Dipoles and Hydrogen Bonds

Dipoles arise from uneven charge distribution in molecules containing -OH, -CO, or -NH groups.
Hydrogen bonds form between negatively charged atoms (O, N, F) of one molecule and positively charged hydrogen of another.

Lipids

Organic molecules mainly made of carbon, hydrogen, and lower proportions of oxygen compared to carbohydrates.
Lack of polar -OH groups renders lipids hydrophobic and insoluble in water.
Types of lipids include:
- Triglycerides: formed by three fatty acids esterified to glycerol.
- Phospholipids: contain fatty acids combined with glycerol and phosphate groups.
- Steroids and cholesterol: characterized by a distinctive four-ring structure.

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Description

Explore the fascinating structures and properties of glucose, including its molecular formula (C6H12O6) and various isomers. This quiz delves into the significance of hydroxyl groups, solubility, and the differences between α-glucose and β-glucose. Test your knowledge of these critical concepts in biochemistry.