Lecture 11: Photosynthesis

Photosynthesis

The process by which green plants and some other organisms use sunlight to synthesize foods with the help of chlorophyll.

Autotrophs

Organisms that produce their own food, primarily through photosynthesis.

Heterotrophs

Organisms that obtain their food by consuming other organisms.

Metabolism

The set of life-sustaining chemical reactions in organisms.

Redox reactions

Chemical reactions that involve the transfer of electrons between two substances.

Photosynthetic pigments

Substances in plants that absorb specific wavelengths of light to drive photosynthesis.

Chlorophyll A

The primary pigment involved in photosynthesis, absorbing light mainly in the blue and red wavelengths.

Chlorophyll B

A pigment that assists chlorophyll A by capturing light energy and transferring it.

Carotenoids

Pigments found in plants responsible for yellow, orange, and red colors, and aid in photosynthesis.

Thylakoid membranes

Membrane-bound structures within chloroplasts where photosynthesis occurs.

Calvin Cycle

The series of reactions in photosynthesis where carbon dioxide is fixed into glucose.

Ribulose bisphosphate (RuBP)

A five-carbon sugar that is a substrate in the Calvin Cycle, used to fix carbon dioxide.

Rubisco

An enzyme that catalyzes the first step of the Calvin cycle, fixing carbon dioxide.

G3P (Glyceraldehyde-3-phosphate)

A three-carbon sugar produced in the Calvin cycle that can be converted into glucose.

NADPH

An electron carrier involved in photosynthesis and respiration; used to reduce carbon compounds.

ATP synthase

An enzyme that produces ATP from ADP and inorganic phosphate during photosynthesis.

Photophosphorylation

The process of generating ATP from ADP and phosphate by utilizing light energy.

Electron transport chain

A series of proteins in the thylakoid membrane that facilitate the transfer of electrons and the production of ATP.

Photorespiration

A process where Rubisco fixes oxygen instead of carbon dioxide, leading to a waste of energy.

Cyanobacteria

Photosynthetic bacteria believed to be the ancestors of chloroplasts in plants.

Stomata

Pores on the leaf surface that allow gas exchange, specifically for carbon dioxide and oxygen.

Guard cells

Cells surrounding the stomata that control their opening and closing.

Chemiosmosis

The process where the movement of protons across a membrane generates ATP.

Photon

A quantum of light or electromagnetic radiation.

Light-dependent reactions

The first stage of photosynthesis that converts solar energy into chemical energy (ATP and NADPH).

Light-independent reactions

Reactions of photosynthesis that do not require light to occur; includes the Calvin Cycle.

Photosystem I

A protein complex in thylakoids that absorbs light to excite electrons and ultimately produce NADPH.

Photosystem II

A protein complex in thylakoids that absorbs light to split water, releasing oxygen and generating ATP.

Electromagnetic spectrum

The range of all types of electromagnetic radiation, including visible light.

Action spectrum

A graph showing the effectiveness of different wavelengths of light in driving photosynthesis.

Absorption spectrum

A graph showing the wavelengths of light absorbed by a particular pigment.

ATP (Adenosine triphosphate)

The primary energy carrier in all living organisms.

Glucose

A simple sugar that is an important energy source in living organisms.

Oxygen (O2)

A byproduct of photosynthesis, essential for cellular respiration in animals.

Carbon dioxide (CO2)

A gas taken in by plants during photosynthesis and released as a byproduct of cellular respiration.

Grana

Stacks of thylakoids within the chloroplast, where photosynthesis occurs.

Stroma

The fluid-filled space surrounding the thylakoids in chloroplasts, involved in the Calvin Cycle.

Oxidation

A chemical process in which a molecule loses electrons.

Reduction

A chemical process in which a molecule gains electrons.

Protons (H+)

Positively charged particles that are crucial in creating a proton gradient for ATP synthesis.

Rubisco's promiscuity

The tendency of Rubisco to catalyze reactions with both CO2 and O2.

Phosphoglycolate

A byproduct of photorespiration that is generally not useful for the plant.

Carbon fixation

The process of converting inorganic CO2 into organic compounds during photosynthesis.

NADP+

The oxidized form of NADPH, which can accept electrons during the light-dependent reactions.

Fluorescence

The emission of light by a substance that has absorbed light.

Chloroplasts

Organelles in plant cells where photosynthesis takes place.

Endosymbiotic event

An evolutionary event where one organism lives inside another, leading to the development of chloroplasts.

Sulfur bacteria

Bacteria that can perform photosynthesis using different pigments and mechanisms than plants.

Algae

Photosynthetic organisms that can live in aquatic environments, contributing to global photosynthesis.

Palisade mesophyll

The layer of cells in a leaf where most photosynthesis occurs.

Spongy mesophyll

Cells located below the palisade layer that facilitate gas exchange.

Water vapor

Water in the gas phase, released as a byproduct of photosynthesis through stomata.

Gravitropic response

The growth response of plants to gravity, important for water transport.

Photoautotrophs

Organisms that use light to produce their own organic compounds.

Z-scheme

The model describing the flow of electrons during photosynthesis, highlighting the roles of Photosystems I and II.

Enzyme-catalyzed reactions

Biochemical reactions that are accelerated by enzymes.

Transpiration

The loss of water vapor from plant surfaces, aiding in nutrient uptake.

Cyclic photophosphorylation

A process in which electrons are recycled within Photosystem I to generate additional ATP.

Non-cyclic photophosphorylation

A process that uses both Photosystems I and II to produce ATP and NADPH.

Anaerobic respiration

Respiration occurring without oxygen, primarily in certain bacteria.

Aerobic respiration

Respiration that requires oxygen to produce ATP from glucose.

Energy currency

Molecules like ATP that store and provide energy for cellular processes.

Mitochondria

Organelles responsible for cellular respiration, generating ATP from sugars.

Ecosystem productivity

The rate at which energy is converted by photosynthetic and chemosynthetic autotrophs.

Biochemical pathways

Series of chemical reactions occurring within a biological system.

Decarboxylation

The removal of a carboxyl group from a molecule, releasing CO2.

Translocation

The movement of nutrients and sugars through a plant.

Macromolecules

Large complex molecules, such as proteins, lipids, carbohydrates, and nucleic acids.

Signal transduction

The process by which a cell responds to signals from the environment.

Hydrophilic

Substances that can interact well with water.

Hydrophobic

Substances that repel water and do not dissolve in water.

Trophic levels

The levels of the food chain, representing energy flow through the ecosystem.

Biological nitrogen fixation

The process by which atmospheric nitrogen is converted into ammonia or related nitrogenous compounds.

Decomposition

The breakdown of organic matter, releasing energy and nutrients back into the ecosystem.

Cellular structure

The arrangement and organization of cells within tissues and organs.

Bioenergetics

The study of energy flow through living systems.

Carbon cycle

The series of processes by which carbon compounds are interconverted in the environment.

Sugar transport

Movement of sugars from photosynthetic tissues to where they're needed in a plant.

Plant hormones

Chemical messengers that regulate plant growth and development.

Environmental signaling

The response of plants to various environmental cues.

Plant defense mechanisms

Strategies plants use to protect themselves from herbivores and pathogens.

Plant adaptation

Changes in a plant's structure or function to better survive in its environment.

Photosynthetic efficiency

The effectiveness of plants in converting light energy into chemical energy.

Ecological relationships

The interactions between various organisms in an ecosystem, including symbiosis and competition.

Biomes

Large geographical biotic communities with distinct climates, flora, and fauna.

Sustainability

The ability to maintain ecological balance and resource availability.

Soil quality

The capability of soil to provide the nutrients, water, and support needed for plant growth.

Climate change

Long-term alterations in temperature and typical weather patterns in a place.

Plant breeding

The science of changing the traits of plants in order to produce desired characteristics.

Ethylene

A plant hormone involved in the regulation of plant growth and ripening of fruits.

Root structure

The formation and arrangement of roots in plants, crucial for nutrient and water uptake.

Stomatal conductance

The rate of gas exchange through the stomata, influencing transpiration and photosynthesis.

Xylem

The vascular tissue responsible for the transport of water and nutrients from roots to the leaves.

Phloem

The vascular tissue responsible for transporting sugars and other metabolic products downward from the leaves.

Leaf morphology

The study of the shape, size, and structure of leaves.

Plant physiology

The study of how plants function, including processes such as photosynthesis and respiration.

Climatic effects on agriculture

The impact of climate on farming operations and crop yield.

Glycolysis

The metabolic process that converts glucose into pyruvate, releasing energy.

Fermentation

The metabolic process that converts sugars to acids, gases, or alcohol in the absence of oxygen.

Cellular respiration

The metabolic process that converts glucose and oxygen into energy, carbon dioxide, and water.