General Biology Study Guide: Enzymes, Metabolism, Photosynthesis, Climate Change, and Cell Division

Ch. 4: Enzymes, Metabolism, and Cellular Respiration

Types of Energy and Energy Storage

Cells require energy to perform essential functions, and energy can be stored in various molecular forms.

• Chemical energy is stored in the bonds of molecules such as glucose and ATP.

• Potential energy is stored due to an object's position or structure, such as in concentration gradients.

• Kinetic energy is the energy of motion, such as the movement of molecules.

• ATP (Adenosine Triphosphate) acts as the primary energy currency in cells, storing energy in its phosphate bonds.

Example: Glucose stores chemical energy that can be released during cellular respiration.

Structure and Function of ATP

ATP is a nucleotide composed of adenine, ribose, and three phosphate groups. It releases energy when its terminal phosphate bond is broken.

• ATP structure: Adenine base, ribose sugar, three phosphate groups.

• Acts like a rechargeable battery by cycling between ATP and ADP.

Equation:

$\text{ATP} \rightarrow \text{ADP} + \text{P}_i + \text{energy}$

Cellular Respiration: Location and Electron Flow

Cellular respiration occurs in the mitochondria of eukaryotic cells and involves the transfer of electrons through a series of reactions.

• Electron flow: Electrons are transferred from glucose to oxygen via electron carriers (NADH, FADH2).

• Stages: Glycolysis, Krebs cycle, Electron Transport Chain (ETC).

Steps and Inputs/Outputs of Cellular Respiration

Cellular respiration consists of multiple steps, each with specific inputs and outputs.

• Glycolysis: Glucose is broken down into pyruvate, producing ATP and NADH.

• Krebs Cycle: Pyruvate is further oxidized, generating CO2, ATP, NADH, and FADH2.

• Electron Transport Chain: NADH and FADH2 donate electrons, leading to ATP synthesis and water formation.

Example: The ETC uses oxygen as the final electron acceptor.

Comparison of Starting and Ending Materials

Cellular respiration starts with glucose and oxygen and ends with carbon dioxide, water, and ATP.

• Starting materials: Glucose, O2

• Ending materials: CO2, H2O, ATP

Ch. 5: Photosynthesis & Climate Change

Greenhouse Effect and Greenhouse Gases

The greenhouse effect is the warming of Earth's surface due to the trapping of heat by greenhouse gases.

• Greenhouse gases: CO2, CH4, H2O vapor, N2O

• These gases absorb and re-emit infrared radiation, warming the atmosphere.

Example: Increased CO2 from fossil fuel burning enhances the greenhouse effect.

Water Cycle and Carbon Cycle

The water cycle describes the movement of water through evaporation, condensation, and precipitation. The carbon cycle involves the exchange of carbon among the atmosphere, biosphere, and geosphere.

• Water cycle: Evaporation, transpiration, condensation, precipitation, runoff.

• Carbon cycle: Photosynthesis, respiration, decomposition, fossilization.

Photosynthesis: Process and Equation

Photosynthesis is the process by which plants convert light energy into chemical energy, producing glucose and oxygen.

• Location: Chloroplasts in plant cells.

• Equation:

$6\text{CO}_2 + 6\text{H}_2\text{O} + \text{light energy} \rightarrow \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$

• Stages: Light-dependent reactions (produce ATP and NADPH), Light-independent reactions (Calvin cycle, produce glucose).

Climate Change: Causes and Effects

Climate change refers to long-term shifts in temperature and weather patterns, primarily due to human activities.

• Main causes: Burning fossil fuels, deforestation, industrial processes.

• Effects: Rising global temperatures, melting ice caps, sea level rise, extreme weather events.

Example: Increased atmospheric CO2 leads to more heat retention and global warming.

C3, C4, and CAM Plants

Plants have different photosynthetic pathways to adapt to their environments.

• C3 plants: Use the Calvin cycle directly; most common in temperate climates.

• C4 plants: Minimize photorespiration by separating initial CO2 fixation and the Calvin cycle in different cell types.

• CAM plants: Fix CO2 at night to reduce water loss; common in arid environments.

Ch. 6: DNA Synthesis & Mitosis (Cell Reproduction & Mitosis)

Prokaryotic vs. Eukaryotic Genomes

Prokaryotic and eukaryotic cells differ in genome structure and organization.

• Prokaryotic genomes: Usually a single circular DNA molecule, no nucleus.

• Eukaryotic genomes: Multiple linear chromosomes within a nucleus.

Chromosome Structure and Terminology

Chromosomes are DNA molecules containing genetic information. Key terms include diploid, haploid, locus, and homologous chromosomes.

• Diploid (2n): Two sets of chromosomes.

• Haploid (n): One set of chromosomes.

• Locus: Specific location of a gene on a chromosome.

• Homologous chromosomes: Chromosome pairs with the same genes but possibly different alleles.

Distinguishing Chromosomes, Genes, and Loci

Chromosomes are structures that carry genes, which are units of heredity located at specific loci.

• Gene: Sequence of DNA coding for a protein.

• Locus: Position of a gene on a chromosome.

Sister Chromatids vs. Homologous Chromosomes

Sister chromatids are identical copies formed during DNA replication, while homologous chromosomes are similar but not identical.

• Sister chromatids: Joined at the centromere, separated during mitosis.

• Homologous chromosomes: One from each parent, pair during meiosis.

Chromosome Condensation and Mitosis

Chromosome condensation is essential for proper segregation during cell division.

• Condensation: Chromosomes become tightly packed and visible under a microscope.

Interphase and DNA Replication

Interphase is the cell cycle phase where the cell grows and DNA is replicated.

• Stages: G1 (growth), S (DNA synthesis), G2 (preparation for mitosis).

• DNA replication: Involves helicase (unwinds DNA), DNA polymerase (synthesizes new DNA), and ligase (joins fragments).

Phases of Mitosis

Mitosis is divided into distinct phases, each with specific events.

Phase	Main Events
Prophase	Chromosomes condense, spindle forms
Prometaphase	Nuclear envelope breaks down, spindle attaches to chromosomes
Metaphase	Chromosomes align at the cell equator
Anaphase	Sister chromatids separate and move to opposite poles
Telophase	Nuclear envelopes reform, chromosomes decondense

Cytokinesis

Cytokinesis is the division of the cytoplasm, resulting in two daughter cells.

• Occurs after mitosis, involves formation of a cleavage furrow in animal cells or cell plate in plant cells.

Cell Cycle Checkpoints

Checkpoints ensure proper cell cycle progression and prevent errors.

• G1/S checkpoint: Checks for DNA damage before replication.

• G2/M checkpoint: Ensures DNA is fully replicated and undamaged before mitosis.

• Metaphase checkpoint: Verifies chromosome alignment and attachment to spindle fibers.

Cancer and Tumor Suppression

Cancer results from uncontrolled cell growth due to failed regulation of the cell cycle.

• Apoptosis: Programmed cell death that removes damaged cells.

• Tumor: Abnormal mass of cells; can be benign (non-cancerous) or malignant (cancerous).

• Tumor suppressor genes: Prevent uncontrolled cell division; mutations can lead to cancer.

• Synergistic substances: Compounds that enhance the effect of other substances.

Example: Mutations in the p53 tumor suppressor gene are common in many cancers.