Biology Chapter: Chemical Basis of Life

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Questions and Answers

What characteristic of saturated fats contributes to their solid state at room temperature?

All carbons linked by single bonds (correct)

Presence of double bonds between carbon atoms

Lower melting points compared to unsaturated fats

High levels of trans fats

Which type of fat is typically derived from animals?

Phospholipids

Unsaturated fats

Saturated fats (correct)

Trans fats

What distinguishes phospholipids from typical fats?

Phospholipids have three fatty acids

Phospholipids are fully hydrophobic

Phospholipids are saturated only

Phospholipids contain a phosphate group (correct)

How do trans fats usually form?

By artificially altering the structure of cis fats (B) Signup and view all the answers

What is a key property of steroids that affects their solubility in water?

Insolubility due to a ring structure (A) Signup and view all the answers

What type of isomerism involves molecules with identical bonding relationships but different spatial positioning?

Stereoisomers (B) Signup and view all the answers

What is the process called when a polymer is broken down by adding a water molecule?

Hydrolysis (D) Signup and view all the answers

Which of the following is a characteristic of lipids?

Nonpolar and insoluble in water (A) Signup and view all the answers

What type of bond is formed when two monosaccharides join in a disaccharide?

Glycosidic bond (C) Signup and view all the answers

Which carbohydrates are considered the simplest sugars?

Monosaccharides (D) Signup and view all the answers

Which of the following is not a characteristic of structural isomers?

Mirror image structures (D) Signup and view all the answers

What defines a polymer's formation during dehydration reactions?

A molecule of water is removed per bond (D) Signup and view all the answers

Which of the following is an example of a polysaccharide used for energy storage?

Glycogen (C) Signup and view all the answers

How many fatty acids are bonded to glycerol in a triglyceride?

Three (C) Signup and view all the answers

Which monosaccharide is known to have five carbon atoms?

Ribose (C) Signup and view all the answers

Which of the following statements accurately describes the characteristics of carbon atoms in the context of organic molecules?

The ability of carbon to form both single and double bonds contributes to the diversity of organic molecules. (B) Signup and view all the answers

Why are molecules with polar bonds generally water-soluble, while those with nonpolar bonds are not?

Water molecules are polar and can interact favorably with other polar molecules through hydrogen bonds. (D) Signup and view all the answers

Which of the following statements is TRUE regarding the bonds formed between carbon and other atoms in organic molecules?

The electronegativity difference between carbon and oxygen contributes to the polar nature of C—O and C=O bonds. (B) Signup and view all the answers

Which of the following is a characteristic of macromolecules?

Macromolecules are typically formed through the process of dehydration synthesis, where water is removed. (A) Signup and view all the answers

What is the primary reason for the abundance of organic molecules in living organisms?

Organic molecules can readily form complex structures necessary for life. (D) Signup and view all the answers

Study Notes

Chemical Basis of Life: Macromolecules

Macromolecules are large, complex organic molecules abundant in living organisms.
Organic molecules contain carbon.
Carbon has four electrons in its outer shell, allowing it to form up to four covalent bonds (octet rule).
Carbon forms nonpolar or polar bonds.
Molecules with polar bonds are water-soluble; those with nonpolar bonds (like hydrocarbons) are not.

Functional Groups

Functional groups are groups of atoms with special chemical features.
Each type of functional group shows the same properties in all molecules where it occurs.

Isomers

Isomers are molecules with the same molecular formula but different structures.
Structural isomers contain the same atoms but in different bonding relationships.
Stereoisomers have identical bonding relationships but different spatial positioning of atoms.
- Cis-trans isomers have different positioning around a double bond.
- Enantiomers are mirror image molecules.

Polymer Formation

Polymers are formed when monomers are linked together via dehydration reactions.
A molecule of water is removed each time a new monomer is added.
The process repeats to form long polymers.
Polymer formation is catalyzed by enzymes.
Polymers are broken down via hydrolysis reactions, where a water molecule is added to break a bond.

Carbohydrates

Carbohydrates are composed of carbon, hydrogen, and oxygen atoms.
The general formula is C_n(H₂O)_n.
Most carbon atoms are linked to a hydrogen atom and a hydroxyl group.
Monosaccharides are the simplest sugars.
- Pentoses have 5 carbon atoms (e.g., ribose, deoxyribose).
- Hexoses have 6 carbon atoms (e.g., glucose).
Glucose isomers exist (structural and stereoisomers, D and L).
Disaccharides are formed from two monosaccharides linked by a glycosidic bond.
- Examples include sucrose, maltose, and lactose.
Polysaccharides are long polymers of monosaccharides.
- Examples include starch (energy storage) and cellulose (structural).

Lipids

Lipids are composed predominantly of hydrogen and carbon atoms.
A defining feature of lipids is their insolubility in water due to nonpolar properties.
Lipids include fats, phospholipids, steroids, and waxes.
Lipids comprise about 40% of the organic matter in the average human body.
Fats (triglycerides or triacylglycerols) are formed by bonding glycerol to three fatty acids via dehydration reactions.
Fatty acids can be saturated (all single bonds) or unsaturated (one or more double bonds).
- Saturated fats tend to be solids at room temperature; unsaturated fats tend to be liquids (oils).
- Cis forms are natural; trans forms are artificial and linked to disease.
Phospholipids are amphipathic molecules consisting of a hydrophilic phosphate head and hydrophobic fatty acid tails.
Steroids are characterized by four interconnected rings of carbon atoms.
- Cholesterol is a common example.
- Tiny structural differences can alter biological properties dramatically (e.g., estrogen vs. testosterone).

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Description

Explore the fundamentals of macromolecules, functional groups, and isomers in this quiz. Understand the significance of carbon's bonding capabilities and the characteristics of various molecular structures. Test your knowledge on how these concepts contribute to the chemical basis of life.