Lecture Notes: Nucleic Acids, ATP, Proteins, and the Cell Membrane

Nucleotides and Nucleic Acids

• Monomer nucleotides compose nucleic acids.

• Nucleotide consists of three parts: a nitrogenous base, a pentose sugar, and a phosphate group.

• DNA (Deoxyribonucleic Acid)

  • Found in the nucleus of all body cells.

  • Carries genetic information specific to organisms.

  • Genes are specific segments of DNA that "code" for specific proteins (in synthesis).

  • DNA is formed in a "double helix" shape.

  • Condenses into specific "chromosomes" prior to replication.

• RNA (Ribonucleic Acid)

  • Single-stranded chain of nucleotides.

  • Synthesized in the nucleolus (special region in the nucleus).

  • Functions in transcription and translation of protein synthesis.

DNA

• DNA stores genetic information used to produce proteins.

• Genes encode the synthesis of specific proteins.

• Structure: double helix; major stage in replication involves chromosome formation.

RNA

• Structure: single-stranded nucleic acid.

• Synthesized in the nucleolus.

• Role: transcription (copying DNA to RNA) and translation (protein synthesis).

Adenosine Triphosphate (ATP)

• ATP is the energy molecule of living systems.

• Composition:

  • Adenine

  • Ribose (sugar)

  • 3 phosphate groups (terminal phosphates)

• ATP structure can be summarized as: adenine + ribose + 3 phosphates.

• ATP provides energy by transferring its terminal phosphate to other molecules.

How ATP gives energy

• When the terminal phosphate is cleaved (hydrolyzed) and transferred to another molecule,

  • the recipient molecule gains the phosphate group and energy is released to perform work.

• Conceptual reaction (simplified):
  ext{ATP} + ext{H}2 ext{O} ightarrow ext{ADP} + ext{P}i + ext{energy}

• This energy transfer powers various cellular processes by phosphorylation of target molecules.

Chapter 2 (Cont.): Proteins

• Proteins can be categorized as:

  • Fibrous proteins: long amino acid chains, not globular; insoluble in water.

  • Globular proteins: globular shape; soluble in water.

• Denaturation: the unfolding of a globular protein due to breaking bonds that maintain its folded form.

• Example mention: protein digestion (denaturation may occur during digestion).

• Enzymes: catalytic proteins that bind with substrates to speed up metabolic reactions.

Chapter 3: The Cell

• Three main parts to a cell: Plasma membrane, cytoplasm, nucleus.

• Plasma membrane:

  • Described as a sea of fluid lipids with embedded proteins and carbohydrates.

  • Allows soluble (water-soluble) substances to pass and act as a selective barrier.

  • It is a phospholipid bilayer.

  • Phospholipid bilayer structure:

  • Polar, hydrophilic phosphate heads face outward toward the water.

  • Nonpolar, hydrophobic lipid tails face inward away from water.

  • The membrane includes embedded proteins and carbohydrates that contribute to transport and signaling.

The Plasma Membrane: Key Concepts

• It separates the cell’s internal environment from the external environment.

• It controls movement of substances via selective permeability.

• The bilayer arrangement provides a barrier to most water-soluble substances while allowing lipid-soluble substances to diffuse.

• Hydrophilic heads are polar; hydrophobic tails are nonpolar.