Biology Chapter: Carbon Compounds in Cells

Questions and Answers

What percentage of total cell mass is accounted for by water?

60%

50%

80%

70% (correct)

All molecules found in cells are classified as organic molecules.

False

What are the four major families of small organic molecules in cells?

Carbohydrates, lipids, proteins, and nucleic acids.

The carbon compounds made by cells are called __________ molecules.

organic Signup and view all the answers

Match the following functional groups with their respective examples:

Methyl = –CH3 Hydroxyl = –OH Carboxyl = –COOH Amino = –NH2 Signup and view all the answers

What is the primary role of proteins in the body?

Providing a defense against infection Signup and view all the answers

Both the carboxyl and amino groups of amino acids are ionized at physiological pH.

True Signup and view all the answers

What is the fundamental property of proteins that enables them to act as enzymes?

Their ability to lower activation energy. Signup and view all the answers

Glycolysis is a major process for oxidizing sugars, producing _____ without the involvement of molecular oxygen.

ATP Signup and view all the answers

Match the following terms with their correct descriptions:

Proteins = Polymers of amino acids Catalysts = Substances that increase reaction rates Glycolysis = Anaerobic breakdown of glucose Fatty Acids = Hydrocarbon chains terminating in a carboxyl group Signup and view all the answers

Study Notes

Carbon Compounds and Cell Composition

Carbon forms large, diverse molecules due to its four covalent bonds and small atomic size.
Water is the most abundant molecule in cells, constituting 70% or more of cell mass.
Inorganic ions (e.g., Na+, K+, Mg2+, Ca2+, HPO42-, Cl-, HCO3-) make up 1% or less of cell mass, essential for cell metabolism.
Organic compounds are classified into four major families: carbohydrates, lipids, proteins, and nucleic acids.
Macromolecules, formed through polymerization, account for 80-90% of dry weight in cells.

Organic Molecules and Their Functions

Carbohydrates provide energy and structural support; simple sugars like glucose serve as precursors.
Proteins, composed of 20 amino acids, demonstrate diverse functions including transport, storage, and enzyme catalysis. Cells contain thousands of different proteins.
Fatty acids consist of long hydrocarbon chains ending in carboxyl groups; examples include palmitate and stearate.

Energy Production in Cells

Glycolysis, a core ATP-producing pathway, oxidizes glucose to produce pyruvate and generates a net gain of 2 ATP and 2 NADH molecules.
Fermentation occurs under anaerobic conditions, producing ATP without oxygen and relying on organic compounds.
In aerobic cells, pyruvate is transported to mitochondria for further breakdown into CO2 and H2O.

Enzymatic Activity and Catalysis

Enzymes, specialized proteins, lower activation energy and increase reaction rates by binding to substrates.
Molecular motions, driven by heat energy, allow enzymes to interact rapidly with substrates.

Citric Acid Cycle

The citric acid cycle takes place in mitochondria, utilizing compounds like pyruvate and fatty acids, producing energy-rich molecules.
This cycle contributes to biosynthetic reactions by generating carbon-containing intermediates.

Protein Structures

Fibrous proteins: long, narrow, stable structures (e.g., keratin, myosin); less sensitive to pH and temperature changes.
Globular proteins: round, functional, and more sensitive to environmental conditions (e.g., enzymes, insulin, hemoglobin); soluble in water.