Biology Study Guide: Organic Molecules, Macromolecules, and Biomolecules

Q1. What is lactose? What is lactase? How are they related?

Background

Topic: Enzymes and Substrates

This question tests your understanding of the relationship between a substrate (lactose) and the enzyme (lactase) that acts on it, which is a foundational concept in biochemistry and metabolism.

Key Terms:

• Lactose: A type of sugar (disaccharide) found in milk.

• Lactase: An enzyme that breaks down lactose into simpler sugars.

• Enzyme-Substrate Relationship: Enzymes are proteins that catalyze (speed up) chemical reactions involving specific substrates.

Step-by-Step Guidance

1. Define what lactose is, including its chemical nature and where it is commonly found.

2. Define what lactase is, specifying its role as an enzyme and what reaction it catalyzes.

3. Explain how lactase interacts with lactose, focusing on the enzyme-substrate relationship.

4. Discuss the biological significance of this relationship (e.g., lactose intolerance).

Try solving on your own before revealing the answer!

Final Answer:

Lactose is a disaccharide sugar found in milk, composed of glucose and galactose. Lactase is an enzyme that catalyzes the hydrolysis of lactose into these two monosaccharides. They are related because lactase specifically acts on lactose, allowing organisms to digest milk sugar.

Q2. What do organic compounds usually contain?

Background

Topic: Organic Chemistry

This question tests your understanding of the basic elements that define organic compounds, which is essential for studying biomolecules.

Key Terms:

• Organic Compounds: Molecules primarily composed of carbon atoms bonded with other elements.

Step-by-Step Guidance

1. Recall the definition of organic compounds in chemistry and biology.

2. Identify the main element that is always present in organic compounds.

3. List other common elements found in organic molecules (think CHNOPS: Carbon, Hydrogen, Nitrogen, Oxygen, Phosphorus, Sulfur).

Try solving on your own before revealing the answer!

Final Answer:

Organic compounds usually contain carbon atoms, often bonded to hydrogen, oxygen, nitrogen, and sometimes other elements. The presence of carbon is what primarily defines a compound as organic.

Q3. How many covalent bonds does carbon form? Why is that important?

Background

Topic: Chemical Bonding and Molecular Structure

This question tests your understanding of carbon's bonding properties, which are fundamental to the diversity of organic molecules.

Key Terms and Concepts:

• Covalent Bond: A chemical bond formed by the sharing of electron pairs between atoms.

• Valence Electrons: Electrons in the outer shell of an atom that are involved in bonding.

Step-by-Step Guidance

1. Recall the atomic number of carbon and its electron configuration.

2. Determine how many valence electrons carbon has.

3. Use the octet rule to figure out how many covalent bonds carbon can form.

4. Explain why the ability to form this number of bonds is important for the structure and diversity of organic molecules.

Try solving on your own before revealing the answer!

Final Answer:

Carbon forms four covalent bonds because it has four valence electrons and needs four more to complete its outer shell. This allows carbon to form a wide variety of complex and stable molecules, making it essential for life.

Q4. What are isomers?

Background

Topic: Organic Molecule Structure

This question tests your understanding of how molecules with the same molecular formula can have different structures and properties.

Key Terms:

• Isomer: Compounds with the same molecular formula but different structural arrangements.

Step-by-Step Guidance

1. Define what is meant by a molecular formula.

2. Explain how isomers can have the same formula but different structures.

3. Give examples of types of isomers (structural, geometric, enantiomers).

Try solving on your own before revealing the answer!

Final Answer:

Isomers are molecules that have the same molecular formula but different structural arrangements, leading to different properties. Examples include structural isomers and stereoisomers.

Q5. Some drugs occur as two isomers in which one form is effective and the other form is not. How can you explain these differing effects?

Background

Topic: Stereochemistry and Biological Activity

This question explores how the three-dimensional arrangement of atoms in isomers can affect their biological function, especially in pharmaceuticals.

Key Terms:

• Enantiomers: Isomers that are mirror images of each other.

• Chirality: A property where a molecule cannot be superimposed on its mirror image.

• Biological Specificity: The concept that enzymes and receptors are specific to certain molecular shapes.

Step-by-Step Guidance

1. Recall that many biological molecules are chiral and can exist as enantiomers.

2. Explain how the shape of a molecule affects its interaction with enzymes or receptors.

3. Discuss why only one isomer might fit properly into a biological target, making it effective, while the other does not.

Try solving on your own before revealing the answer!

Final Answer:

The differing effects are due to the fact that only one isomer (enantiomer) fits correctly into the active site of a biological molecule, such as an enzyme or receptor. The other isomer may not fit or may even cause adverse effects, so only one form is biologically active.

Q6. Testosterone and estradiol (an estrogen) are both lipid hormones. Why do these otherwise similar structures function so differently?

Background

Topic: Structure-Function Relationship in Biomolecules

This question examines how small differences in molecular structure can lead to significant differences in biological function.

Key Terms:

• Lipid Hormones: Hormones derived from lipids, such as steroids.

• Functional Groups: Specific groups of atoms within molecules that determine their chemical behavior.

Step-by-Step Guidance

1. Identify the basic structure shared by testosterone and estradiol (the steroid backbone).

2. Note the small differences in functional groups attached to this backbone.

3. Explain how these small structural differences affect the way each hormone interacts with its specific receptor, leading to different biological effects.

Try solving on your own before revealing the answer!

Final Answer:

Although testosterone and estradiol have very similar structures, small differences in their functional groups cause them to bind to different receptors, resulting in distinct biological effects.