Autotrophs and Energy Processes

Autotrophs, Heterotrophs, Producers, Consumers, Decomposers

• Autotrophs: Organisms that create their own food (e.g., plants, algae) typically through photosynthesis.
• Heterotrophs: Organisms that cannot make their food, and consume other organisms for energy (e.g., animals, fungi).
• Producers: Autotrophs that make food for others (often glucose).
• Consumers: Organisms that eat producers or other consumers to obtain energy (e.g., herbivores, carnivores).
• Decomposers: Organisms that break down dead matter and return nutrients to the ecosystem (e.g., bacteria, fungi).

ATP (Adenosine Triphosphate)

• ATP is the main energy currency in cells.
• Composed of adenine, ribose, and three phosphate groups.
• Stores energy in high-energy phosphate bonds.
• Energy is released when these bonds break, powering cellular processes.

Photosynthesis

• Equation: 6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂
• Converts carbon dioxide and water into glucose and oxygen using light energy.
• Stages:
  • Light-dependent reactions (thylakoid membranes): Use light to make ATP and NADPH.
  • Calvin Cycle (stroma): Uses ATP and NADPH to convert CO₂ into glucose.

Cellular Respiration

• Equation: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP
• Breaks down glucose and oxygen to produce carbon dioxide, water, and ATP.
• Stages:
  • Glycolysis (cytoplasm): Breaks down glucose into pyruvate, creating 2 ATP and 2 NADH.
  • Krebs Cycle (mitochondria): Further breaks down pyruvate, releasing CO₂ and producing NADH, FADH₂, and ATP.
  • Electron Transport Chain (inner mitochondrial membrane): NADH and FADH₂ donate electrons, creating a large amount of ATP through oxidative phosphorylation.
• Aerobic respiration produces up to 38 ATP per glucose.

Aerobic vs. Anaerobic Respiration

• Aerobic respiration: Requires oxygen; involves glycolysis, Krebs cycle, and the electron transport chain.
• Anaerobic respiration: Occurs without oxygen; includes glycolysis followed by fermentation. ATP production is limited (2 ATP per glucose).

Energy Sources in Cellular Respiration

• Glucose is the primary energy source. Other macromolecules (lipids, proteins) can be used if glucose is unavailable.

Protein Structure and Function

• Proteins are chains of amino acids.
• Perform diverse functions: structural support, catalyzing reactions (enzymes), antibodies, hormones, etc.
• Levels of structure:
  • Primary: Amino acid sequence.
  • Secondary: Local structures (alpha-helices, beta-pleated sheets).
  • Tertiary: 3D shape of the protein.
  • Quaternary: Arrangement of multiple polypeptide chains.
• Denaturation: Loss of 3D structure and function due to environmental factors (heat, pH, chemicals).

Transcription & Translation

• Transcription (nucleus): DNA is copied into mRNA. RNA polymerase builds mRNA using DNA as a template.
• Translation (cytoplasm): mRNA is translated into a protein sequence, at ribosomes, using tRNA and rRNA.

Monomers vs. Polymers

• Monomers: Small units that form larger molecules. (e.g., amino acids, nucleotides)
• Polymers: Larger molecules made up of repeating monomers. (e.g., proteins, DNA)

DNA & RNA Structure

• DNA: Double-stranded helix; nucleotides with deoxyribose sugar, phosphate, and bases (A, T, C, G).
• RNA: Single-stranded; nucleotides with ribose sugar, phosphate, and bases (A, U, C, G).

Gene vs. Chromosome

• Gene: A section of DNA coding for a specific protein.
• Chromosome: A long DNA structure containing many genes.

Prokaryotic Cell Division

• Binary fission: Prokaryotic cells divide, replicating DNA, and splitting into two identical daughter cells.

DNA Replication

• Copies DNA before cell division.
• Key enzymes: Helicase (unwinds DNA), Polymerase (synthesizes new strand), Ligase (joins fragments).

Base Pairing Rules

• DNA: A with T, C with G
• RNA: A with U, C with G

Elements of Life

• Essential elements: Carbon (C), Hydrogen (H), Oxygen (O), Nitrogen (N), Phosphorus (P), Sulfur (S).

Atom and Atomic Structure

• Atoms are composed of protons (positive), neutrons (neutral), and electrons (negative).
• Atomic number: Number of protons. Mass number: Sum of protons and neutrons.

Bonds

• Hydrogen bond: Weak bond between H and an electronegative atom (O, N).
• Ionic bond: Electron transfer forms charged ions.
• Polar covalent bond: Unequal electron sharing.
• Nonpolar covalent bond: Equal electron sharing.