Chapter 6: Cell Structure and Function

Prokaryotic vs. Eukaryotic Cells

Cells are the basic units of life, and they can be classified as prokaryotic or eukaryotic based on their structural characteristics.

• Prokaryotic cells lack a nucleus and membrane-bound organelles. Example: Bacteria.

• Eukaryotic cells have a nucleus and various membrane-bound organelles. Examples: Animal and Plant cells.

• Key differences include the presence of a nucleus, organelles, and complexity of internal structures.

Cellular Organelles and Their Functions

Organelles are specialized structures within cells that perform distinct functions.

• Mitochondria: Site of cellular respiration; generates ATP.

• Chloroplasts: Site of photosynthesis in plant cells.

• Plasma membrane: Controls movement of substances in and out of the cell.

• Cytoskeleton: Provides structural support and facilitates cell movement.

• Microtubules: Part of the cytoskeleton; involved in cell division and transport.

Energy Reactions in Organelles

Mitochondria and chloroplasts are responsible for key energy transformations in cells.

• Mitochondria: Perform aerobic respiration to produce ATP.

• Chloroplasts: Carry out photosynthesis, converting light energy to chemical energy.

Cellular Transport and Protein Sorting

Eukaryotic cells use organelles and membranes to sort and transport proteins to their correct destinations.

• Example: Proteins synthesized in the rough endoplasmic reticulum are sorted via the Golgi apparatus and transported to the plasma membrane.

Additional info:

• Energy reactions include glycolysis, Krebs cycle, and electron transport chain in mitochondria.

• Microtubules also play a role in chromosome movement during cell division.

Chapter 8: Metabolism

Basic Principles of Metabolism

Metabolism refers to all chemical reactions that occur within living organisms to maintain life.

• Anabolic reactions: Build complex molecules from simpler ones (require energy).

• Catabolic reactions: Break down complex molecules into simpler ones (release energy).

• Examples: Protein synthesis (anabolic), cellular respiration (catabolic).

Thermodynamics in Biology

Thermodynamics governs the energy changes in biological systems.

• First Law of Thermodynamics: Energy cannot be created or destroyed, only transformed.

• Second Law of Thermodynamics: Entropy (disorder) increases in spontaneous processes.

• Biological systems use energy transformations to maintain order and function.

Enzymes and Their Functions

Enzymes are biological catalysts that speed up chemical reactions without being consumed.

• Enzymes lower the activation energy required for reactions.

• They are specific to substrates and reactions.

• Enzyme activity can be affected by temperature, pH, and substrate concentration.

ATP: The Energy Currency

ATP (Adenosine Triphosphate) is the primary energy carrier in cells.

• ATP stores energy in its high-energy phosphate bonds.

• Hydrolysis of ATP releases energy for cellular processes.

Spontaneous vs. Non-Spontaneous Reactions

Spontaneous reactions occur without input of energy; non-spontaneous reactions require energy.

• Spontaneity is determined by changes in free energy ().

• If , the reaction is spontaneous.

Additional info:

• Enzyme specificity is determined by the shape of the active site.

• ATP powers cellular work by transferring phosphate groups to other molecules (phosphorylation).

Chapter 9: Cellular Respiration

Overview of Cellular Respiration

Cellular respiration is a series of metabolic processes that convert biochemical energy from nutrients into ATP.

• Overall reaction:

• Occurs in three main stages: Glycolysis, Krebs Cycle (Citric Acid Cycle), Electron Transport Chain.

Stages and Locations

• Glycolysis: Occurs in the cytoplasm; breaks down glucose into pyruvate.

• Krebs Cycle: Occurs in the mitochondrial matrix; processes pyruvate to produce electron carriers.

• Electron Transport Chain: Occurs in the inner mitochondrial membrane; produces most ATP.

ATP Synthesis and Oxidative Phosphorylation

• ATP synthase enzyme generates ATP using a proton gradient.

• Oxidative phosphorylation produces the majority of ATP in cellular respiration.

Fermentation

Fermentation is an anaerobic process that allows cells to generate ATP without oxygen.

• Occurs in the cytoplasm.

• Produces less ATP than aerobic respiration.

• Types: Lactic acid fermentation (humans), alcoholic fermentation (yeast).

Redox Reactions

Cellular respiration involves oxidation-reduction (redox) reactions.

• Glucose is oxidized; oxygen is reduced.

• Electron carriers (NADH, FADH2) transport electrons to the electron transport chain.

Table: Stages of Cellular Respiration

Additional info:

• Oxidized molecules lose electrons; reduced molecules gain electrons.

• ATP yield varies between organisms and conditions.

Chapter 10: Photosynthesis

Overview and Organismal Location

Photosynthesis is the process by which plants, algae, and some bacteria convert light energy into chemical energy.

• Occurs in the chloroplasts of plant cells.

• Autotrophs perform photosynthesis; heterotrophs obtain energy by consuming other organisms.

Summary Reaction

• Overall reaction:

Stages of Photosynthesis

• Light Reactions: Occur in the thylakoid membranes; convert light energy to chemical energy (ATP and NADPH).

• Calvin Cycle (Dark Reactions): Occur in the stroma; use ATP and NADPH to fix carbon dioxide into glucose.

Key Molecules and Enzymes

• NADPH: Electron carrier produced in the light reactions.

• ATP: Energy carrier produced in the light reactions.

• Rubisco: Enzyme that catalyzes carbon fixation in the Calvin cycle.

Calvin Cycle Steps

• Carbon fixation

• Reduction

• Regeneration of RuBP

Table: Comparison of Autotrophs and Heterotrophs

Additional info:

• Light reactions produce oxygen as a byproduct.

• Calvin cycle does not require light directly but depends on products of light reactions.