Biology Notes: Photosynthesis and Energy in Biology
Photosynthesis Guide:
Definition: Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy into chemical energy stored in glucose.
Location: It occurs primarily in chloroplasts of plant cells, specifically in mesophyll cells of leaves.
Main Stages:
Light Reactions:
Location: Thylakoid membranes.
Process:
Chlorophyll absorbs light energy.
Light energy splits water molecules, releasing oxygen.
Electrons from chlorophyll move through the electron transport chain, generating ATP and NADPH.
Calvin Cycle:
Location: Stroma of the chloroplast.
Process:
Carbon dioxide is fixed by attaching to RUBP (ribulose bisphosphate).
ATP and NADPH from the light reactions provide energy and reducing power.
G3P (glyceraldehyde-3-phosphate) is produced, which can be converted into glucose.
RUBP is regenerated to continue the cycle.
Importance of Photosynthesis: Provides energy for life, synthesizes glucose for immediate use, and releases oxygen essential for cellular respiration.
Calvin Cycle Guide:
Definition: The Calvin Cycle is a series of biochemical reactions that occur in the stroma of chloroplasts during photosynthesis; it converts carbon dioxide into organic compounds.
Phases of the Calvin Cycle:
Carbon Fixation:
CO₂ attaches to RUBP, forming an unstable 6-carbon intermediate that immediately splits into two 3-carbon molecules (3-PGA).
Reduction:
ATP and NADPH from light reactions convert 3-PGA into G3P.
Some G3P leaves the cycle to form glucose and other carbohydrates.
Regeneration:
Remaining G3P is used to regenerate RUBP to keep the cycle going.
Overall Process:
Fixation of CO₂ to organic molecules.
Use of ATP and NADPH to convert these molecules into G3P.
Regeneration of RUBP, allowing the cycle to continue.
Importance of the Calvin Cycle: It synthesizes glucose, which is crucial for energy supply in plants and serves as the basis for food chains.
RUBP (ribulose bisphosphate) is a five-carbon sugar that plays a crucial role in the Calvin Cycle of photosynthesis. It serves as the molecule that captures carbon dioxide, forming an unstable six-carbon intermediate that immediately splits into two three-carbon molecules (3-PGA). RUBP is regenerated during the Calvin Cycle, allowing the cycle to continue its process of synthesizing glucose and other organic compounds.
G3P (glyceraldehyde-3-phosphate) is a three-carbon sugar molecule produced during the Calvin Cycle of photosynthesis. It is created from the reduction of 3-PGA (3-phosphoglycerate) using ATP and NADPH generated during the light reactions. Some G3P molecules exit the cycle to be utilized in the synthesis of glucose and other carbohydrates, while the remaining G3P is used to regenerate RUBP (ribulose bisphosphate) to keep the Calvin Cycle functioning.
Chapter 10: Photosynthesis
Autotrophs vs. Heterotrophs
Autotrophs: Organisms that produce their own food using light or chemical energy. Example: Plants, algae, some bacteria.
Heterotrophs: Organisms that consume other organisms to obtain energy. Example: Animals, fungi, most bacteria.
Location of Photosynthesis
Organismal: Plants, algae, some protists and bacteria.
Tissue: Leaf mesophyll tissue.
Cellular: Occurs in chloroplasts of plant cells.
Structures of a Chloroplast
Thylakoids: Flattened sacs where light reactions occur.
Grana: Stacks of thylakoids.
Stroma: Fluid-filled space around thylakoids; site of Calvin cycle.
Double Membrane: Outer and inner membranes enclose the organelle.
Summary Reaction for Photosynthesis
Chemical Reaction: 6CO2 + 6H2O + light energy → C6H12O6 + 6O2
In Words: Carbon dioxide and water, using sunlight, produce glucose and oxygen.
Main Steps of Photosynthesis
Light Reactions (in thylakoid membrane)
Inputs: Light, H2O, NADP+, ADP
Outputs: O2, ATP, NADPH
Calvin Cycle (in stroma)
Inputs: CO2, ATP, NADPH
Outputs: G3P (sugar), ADP, NADP+
Relation to Overall Equation
Light reactions use H2O and produce O2.
Calvin cycle uses CO2 and the products of light reactions to make sugar.
Photosystems I & II
Photosystem II (PSII): Captures light first, splits water, releases O2, and passes electrons.
Photosystem I (PSI): Captures electrons from PSII, boosts them to make NADPH.
Both are part of the electron transport chain.
ATP Generation in Light Reactions
ATP is produced by chemiosmosis via ATP synthase powered by a proton gradient created by electron transport.
Carbon Fixation
The conversion of inorganic CO2 into organic molecules like glucose.
Importance: Provides the carbon backbone for all organic molecules.
Role of Rubisco
Rubisco is an enzyme that fixes CO2 during the Calvin cycle.
Active when CO2 is available; begins sugar synthesis.
Three Major Steps of the Calvin Cycle
Carbon Fixation
Reduction (of 3-PGA to G3P)
Regeneration of RuBP
Predicting Disruptions
Lack of sunlight: Light reactions fail.
Damaged chloroplasts: No photosynthesis.
Rubisco malfunction: Calvin cycle halts.
Chapter 12: Cell Cycle and Mitosis
Purpose of Cell Division
Single-celled: Reproduction.
Multi-cellular: Growth, repair, and maintenance.
Functions in Reproduction, Growth, Repair
Enables organisms to grow, replace damaged cells, and reproduce.
Terms
Genome: Entire set of DNA.
Chromosome: Condensed DNA.
Chromatin: Loosely packed DNA.
Sister Chromatids: Identical copies of a chromosome.
Phases of the Cell Cycle
G1: Growth
S: DNA synthesis
G2: Prep for division
M: Mitosis + Cytokinesis
Stages of Mitosis
Prophase: Chromosomes condense; spindle forms.
Metaphase: Chromosomes align at the equator.
Anaphase: Sister chromatids separate.
Telophase: Nuclear envelopes reform.
Key Structures
Centrosome: Organelle that organizes spindle.
Kinetochore: Protein on centromere where spindle attaches.
Spindle Microtubules: Move chromosomes.
Aster Microtubules: Anchor spindle to cell.
Centromere: Region joining sister chromatids.
Spindle Function per Phase
Moves and segregates chromosomes.
Cytokinesis
Animals: Cleavage furrow.
Plants: Cell plate.
Genetic Result of Mitosis
Two identical diploid daughter cells.
G1 Checkpoint
Decides if cell will divide. Influenced by size, nutrients, DNA integrity.
Chapter 13: Meiosis
Sexual vs Asexual Reproduction
Asexual: One parent, identical offspring.
Sexual: Two parents, genetic variation.
Gene, Locus, Homologous Chromosomes
Gene: Unit of heredity.
Locus: Gene’s location on a chromosome.
Homologous Chromosomes: Same genes, possibly different alleles.
Homologs vs. Sister Chromatids
Homologs: One from each parent, similar genes.
Sister Chromatids: Identical copies post-replication.
Autosome vs Sex Chromosome
Autosome: Non-sex chromosomes.
Sex Chromosome: X and Y.
Haploid vs Diploid
Haploid (n): One set.
Diploid (2n): Two sets.
n Number Practice
If n = 23: Diploid = 46; Haploid = 23.
Human Life Cycle
Meiosis: Produces haploid gametes.
Fertilization: Creates diploid zygote.
Mitosis: Zygote grows into adult.
Chromosome Drawing in Meiosis
Meiosis I: Homologs separate.
Meiosis II: Sister chromatids separate.
Identifying Chromosome Types
Meiosis I: Homologous chromosomes.
Meiosis II: Sister chromatids.
Mitosis vs Meiosis
Mitosis: 2 diploid cells.
Meiosis: 4 haploid cells.
Purpose Comparison
Mitosis: Growth, repair.
Meiosis: Gamete production, genetic diversity.
Sources of Genetic Variation
Independent Assortment: Random homolog alignment.
Crossing Over: Homologs exchange segments.
Fertilization: Random egg + sperm combination.
Chapter 14: Mendelian Inheritance
Genes and Chromosomes
Genes are segments of DNA on chromosomes.
Gene Definitions
Gene (DNA): Instructions for protein.
Gene (Protein): Determines trait.
Gene vs Allele
Gene: Region coding for a trait.
Allele: Variation of a gene.
Genotype vs Phenotype
Genotype: Genetic makeup.
Phenotype: Observable traits.
Trait Determination
Alleles code for proteins that influence traits.
Homozygous vs Heterozygous
Homozygous: Two same alleles (AA or aa).
Heterozygous: Two different alleles (Aa).
Autosomal Dominance
Dominant allele masks recessive in heterozygote.
Monohybrid Cross (One Trait)
Example: Aa x Aa
Genotypic ratio: 1 AA : 2 Aa : 1 aa
Phenotypic ratio: 3 dominant : 1 recessive
Dihybrid Cross (Two Traits)
Example: AaBb x AaBb
Possible gametes: AB, Ab, aB, ab
Use Punnett square to find combinations
Definition: Photosynthesis is the process by which green plants, algae, and some bacteria convert light energy, primarily from the sun, into chemical energy stored in glucose. This process is essential for converting solar energy into a form that can be used by living organisms.
Location: It occurs primarily in chloroplasts of plant cells, specifically in mesophyll cells of leaves, which contain chlorophyll that captures light energy.
Main Stages:
Light Reactions:Location: Thylakoid membranes.
Process:
Chlorophyll absorbs light energy.
Light energy splits water molecules, releasing oxygen as a byproduct.
Electrons from chlorophyll move through the electron transport chain, generating ATP and NADPH, which are essential energy carriers for the Calvin cycle.
Calvin Cycle:
Location: Stroma of the chloroplast.
Process:
Carbon dioxide is fixed by attaching to RUBP (ribulose bisphosphate) with help from the enzyme Rubisco, forming an unstable 6-carbon intermediate.
ATP and NADPH from the light reactions provide energy and reducing power, converting the intermediate into G3P (glyceraldehyde-3-phosphate).
Some G3P leaves the cycle to form glucose and other carbohydrates, while the remaining G3P is used to regenerate RUBP to allow the cycle to continue.
Importance of Photosynthesis: Provides energy for life, synthesizes glucose for immediate energy use, supports the food chain, and releases oxygen essential for cellular respiration.
Calvin Cycle Guide:
Definition: The Calvin Cycle is a series of biochemical reactions that occur in the stroma of chloroplasts during photosynthesis; it converts carbon dioxide into organic compounds.
Phases of the Calvin Cycle:
Carbon Fixation:
CO₂ attaches to RUBP, forming an unstable 6-carbon intermediate that immediately splits into two 3-carbon molecules (3-PGA).
Reduction:
ATP and NADPH from light reactions convert 3-PGA into G3P.
Some G3P leaves the cycle to form glucose and other carbohydrates.
Regeneration:
Remaining G3P is used to regenerate RUBP to keep the cycle going.
Overall Process:
Fixation of CO₂ to organic molecules.
Use of ATP and NADPH to convert these molecules into G3P.
Regeneration of RUBP, allowing the cycle to continue.
Importance of the Calvin Cycle: It synthesizes glucose, which is crucial for energy supply in plants and serves as the basis for food chains.
RUBP (ribulose bisphosphate) is a five-carbon sugar that plays a crucial role in the Calvin Cycle of photosynthesis. It serves as the molecule that captures carbon dioxide, forming an unstable six-carbon intermediate that immediately splits into two three-carbon molecules (3-PGA). RUBP is regenerated during the Calvin Cycle, allowing the cycle to continue its process of synthesizing glucose and other organic compounds.
G3P (glyceraldehyde-3-phosphate) is a three-carbon sugar molecule produced during the Calvin Cycle of photosynthesis. It is created from the reduction of 3-PGA (3-phosphoglycerate) using ATP and NADPH generated during the light reactions. Some G3P molecules exit the cycle to be utilized in the synthesis of glucose and other carbohydrates, while the remaining G3P is used to regenerate RUBP (ribulose bisphosphate) to keep the Calvin Cycle functioning.
Chapter 10: Photosynthesis
Autotrophs vs. Heterotrophs
Autotrophs: Organisms that produce their own food using light or chemical energy, essential for energy flow in ecosystems.
Example: Plants, algae, some bacteria.
Heterotrophs: Organisms that consume other organisms to obtain energy, relying on autotrophs for sustenance.
Example: Animals, fungi, most bacteria.
Location of Photosynthesis:
Organismal: Plants, algae, some protists, and bacteria.
Tissue: Leaf mesophyll tissue.
Cellular: Occurs in chloroplasts of plant cells.
Structures of a Chloroplast:
Thylakoids: Flattened sacs where light reactions occur.
Grana: Stacks of thylakoids, increasing surface area for light absorption.
Stroma: Fluid-filled space around thylakoids; site of Calvin cycle.
Double Membrane: Outer and inner membranes enclose the organelle, creating a distinct internal environment.
Summary Reaction for Photosynthesis:
Chemical Reaction: 6CO₂ + 6H₂O + light energy → C₆H₁₂O₆ + 6O₂
In Words: Carbon dioxide and water, using sunlight, produce glucose and oxygen, underpinning the foundation of life.
Main Steps of Photosynthesis:
Light Reactions (in thylakoid membrane)
Inputs: Light, H₂O, NADP⁺, ADP
Outputs: O₂, ATP, NADPH
Calvin Cycle (in stroma)
Inputs: CO₂, ATP, NADPH
Outputs: G3P (sugar), ADP, NADP⁺
Relation to Overall Equation:
Light reactions use H₂O and produce O₂, storing energy in the form of ATP and NADPH.
Calvin cycle uses CO₂ and the products of light reactions to make sugar.
Photosystems I & II:
Photosystem II (PSII): Captures light first, splits water, releases O₂, and passes electrons along the electron transport chain.
Photosystem I (PSI): Captures electrons from PSII, boosts them to a higher energy state to make NADPH.
Both are essential components of the electron transport chain for photosynthesis.
ATP Generation in Light Reactions:
ATP is produced by chemiosmosis via ATP synthase powered by a proton gradient created by electron transport through thylakoid membranes.
Carbon Fixation:
The conversion of inorganic CO₂ into organic molecules like glucose, essential for sustaining life.
Importance: Provides the carbon backbone for all organic molecules.
Role of Rubisco:
Rubisco is an enzyme that fixes CO₂ during the Calvin cycle, ensuring the incorporation of carbon into organic molecules.
Active when CO₂ is available; it initiates sugar synthesis critical for plant growth.
Three Major Steps of the Calvin Cycle:
Carbon Fixation
Reduction (of 3-PGA to G3P)
Regeneration of RuBP
Predicting Disruptions:
Lack of sunlight: Light reactions fail, halting ATP and NADPH production.
Damaged chloroplasts: No photosynthesis, leading to energy deficits in the plant.
Rubisco malfunction: Calvin cycle halts, preventing the synthesis of