Chapter 4 Notes: Cellular Metabolism and Gene Expression

A comprehensive set of practice flashcards covering cellular metabolism, enzymes, cellular respiration, DNA/RNA structure and function, transcription, translation, and the genetic code based on the lecture notes.

What organelle is the powerhouse of the cell and fuels cellular reactions?

Mitochondria.

What are the two main types of cellular processes that build up and break down molecules called?

Anabolism (building up) and Catabolism (breaking down).

What does synthesis mean in the context of metabolism?

To make or build up a molecule.

What does catabolism involve in metabolism?

Breaking down molecules via hydrolysis, which adds water to bonds.

In dehydration synthesis, what happens to water and how are monomers joined?

Water is removed; monomers are joined to form a larger molecule (e.g., disaccharide or triglyceride).

How can you identify an enzyme by its name?

Many enzymes end with ASE (e.g., sucrase, lactase, protease, lipase).

What is the role of enzymes in chemical reactions?

They speed up reactions by lowering the activation energy.

What is the active site of an enzyme?

The region where the substrate binds to the enzyme.

What is the enzyme–substrate complex?

The temporary complex formed when an enzyme binds its substrate before the reaction proceeds to form a product.

What happens to ATP when it is used to provide energy?

ATP loses a phosphate to become ADP and releases energy.

What are the components of an ATP molecule?

Ribose sugar, adenine base, and three phosphate groups.

What are the three stages of cellular respiration?

Glycolysis, Citric Acid Cycle (Krebs), and Electron Transport Chain (ETC).

Where does glycolysis occur and is it aerobic or anaerobic?

In the cytoplasm; anaerobic (no oxygen needed).

What are the products of glycolysis per glucose molecule?

Two pyruvate molecules and a net gain of 2 ATP (plus NADH produced later).

What happens to pyruvate in the presence of oxygen?

Converted to acetyl-CoA in the mitochondria, releasing CO2 and generating NADH; acetyl-CoA enters the citric acid cycle.

Where does the citric acid cycle occur and does it require oxygen?

Occurs in the mitochondrial matrix; it is part of aerobic respiration (requires oxygen indirectly via electron carriers).

What are the main outputs of the citric acid cycle per glucose molecule?

2 ATP, CO2, and high-energy electron carriers NADH and FADH2.

Where does the electron transport chain occur and does it require oxygen?

In the cristae of the mitochondria; yes, oxygen is the final electron acceptor.

How many ATP are produced by the electron transport chain per glucose?

Approximately 32–34 ATP.

What is the approximate total ATP yield from cellular respiration per glucose?

About 36–38 ATP (varies by cell type and efficiency).

What is the basic structure of DNA?

Double-stranded molecule with a sugar–phosphate backbone and four bases (A, T, C, G).

What sugar is in DNA, and which bases pair with which?

Deoxyribose sugar; A pairs with T (two hydrogen bonds), C pairs with G (three hydrogen bonds).

What bonds hold the DNA strands together?

Hydrogen bonds between complementary bases.

What is DNA replication and its key characteristic?

Semiconservative replication: each new DNA molecule contains one old strand and one new strand; occurs in the nucleus during the S phase of interphase.

Where is DNA located in the cell?

Nucleus.

What distinguishes RNA from DNA in terms of sugar and bases?

RNA contains ribose sugar and uses uracil (U) instead of thymine (T); RNA is typically single-stranded.

What base pairs with A, C, G, and U in RNA?

A pairs with U (in RNA), C pairs with G; T is replaced by U.

What are the roles of mRNA and tRNA in protein synthesis?

mRNA carries genetic information from DNA to the ribosome; tRNA brings amino acids to the ribosome and contains anticodons that pair with codons on mRNA.

What is a codon and what is an anticodon?

Codon: a three-base sequence on mRNA coding for an amino acid; anticodon: the complementary three-base sequence on tRNA.

Where do transcription and translation occur?

Transcription occurs in the nucleus (producing mRNA); translation occurs on ribosomes in the cytoplasm.

What is a polypeptide and how is it formed?

A long chain of amino acids linked by peptide bonds; formed during translation as amino acids are assembled according to mRNA codons.

How many amino acids are there and how are they coded?

There are 20 amino acids; they are coded by codons consisting of three bases on mRNA.

What is the process by which DNA is used to synthesize RNA?

Transcription; RNA polymerase reads DNA and creates a complementary mRNA strand.

What is semiconservative replication's significance for growth and development?

It ensures each new DNA molecule contains an old strand paired with a new strand, enabling accurate duplication during cell division.

What is a nuclear pore and its function in gene expression?

A channel in the nuclear envelope that allows mRNA to exit the nucleus and move to the cytoplasm for translation.

What common cofactors assist enzyme function?

Cofactors are non-protein helpers (often vitamins) that support enzyme activity.

What factors can alter enzyme activity beyond cofactors?

Radiation, chemicals, pH, and temperature extremes can affect enzyme function.