General Biology: Cellular Respiration, Photosynthesis, and Plant Structure & Diversity

Comprehensive vocabulary flashcards covering metabolic pathways (cellular respiration and fermentation, photosynthesis) and plant biology (tissues, growth, anatomy, and phylogenetic diversity).

Substrate-Level Phosphorylation

The enzymatic transfer of a phosphate group directly from an organic substrate molecule to $ADP$, forming $ATP$, without using an electron transport chain.

Oxidative Phosphorylation

The production of $ATP$ using energy derived from the redox reactions of the electron transport chain and driven by chemiosmosis in the inner mitochondrial membrane.

Reducing Agent

The electron donor in a redox reaction that loses electrons, thereby becoming oxidized.

Oxidizing Agent

The electron acceptor in a redox reaction that gains electrons, thereby becoming reduced.

Glycolysis

A ten-reaction metabolic pathway in the cytosol that oxidizes glucose into two molecules of pyruvate, generating a net yield of $2\text{ ATP}$ and $2\text{ NADH}$.

Pyruvate Oxidation

The multi-step process in which pyruvate enters the mitochondrion via active transport and is converted into acetyl $CoA$, releasing $\text{CO}_2$ and producing $\text{NADH}$.

Citric Acid Cycle

An eight-step cyclical pathway in the mitochondrial matrix that decomposes acetyl $CoA$ into $\text{CO}_2$, yielding $1\text{ ATP}$, $3\text{ NADH}$, and $1\text{ FADH}_2$ per cycle turn.

Chemiosmosis

An energy-coupling mechanism that utilizes the potential energy stored in a hydrogen ion ($H^+$) gradient across a membrane to drive the synthesis of $ATP$.

ATP Synthase

A complex molecular rotary motor that harnesses the exergonic flow of $H^+$ ions passing down their gradient to synthesize $ATP$ from $ADP$ and inorganic phosphate.

Alcohol Fermentation

An anaerobic catabolic pathway in which pyruvate is converted to acetaldehyde with the release of $\text{CO}_2$, and acetaldehyde is subsequently reduced by $\text{NADH}$ to form ethanol.

Lactic Acid Fermentation

An anaerobic catabolic pathway in which pyruvate is reduced directly by $\text{NADH}$ to form lactate without the release of $\text{CO}_2$.

Phosphofructokinase

An allosteric pacemaker enzyme of glycolysis that is inhibited by $ATP$ and citrate, but stimulated by $AMP$.

Autotrophs

Organisms that sustain themselves without consuming anything derived from other organisms, serving as the producers of the biosphere by making organic molecules from $\text{CO}_2$.

Heterotrophs

Organisms that obtain organic nutrients and energy by consuming other organisms or their organic by-products, serving as the consumers of the biosphere.

Stomata

Microscopic pores on the leaf surface that regulate gas exchange, allowing $\text{CO}_2$ to enter and $\text{O}_2$ and water vapor to exit.

Stroma

The dense fluid envelope within the chloroplast surrounding the thylakoid membranes, serving as the site of the Calvin cycle.

Thylakoid

A flattened, interconnected membranous sac inside a chloroplast that houses the photosynthetic pigments, photosystems, and electron transport machinery for light reactions.

Carotenoids

Accessory plant pigments that appear yellow and orange, functioning to broaden the absorption spectrum and provide photoprotection by dissipating excess light.

Photosystem

A light-capturing unit located in the thylakoid membrane consisting of a reaction-center complex surrounded by several light-harvesting complexes.

Photosystem II (PS II)

The photosystem that functions first in linear electron flow, containing reaction-center chlorophyll $a$ molecules designated as P680 that absorb light best at a wavelength of $680\,\text{nm}$.

Photosystem I (PS I)

The photosystem that functions second in linear electron flow, containing reaction-center chlorophyll $a$ molecules designated as P700 that absorb light best at a wavelength of $700\,\text{nm}$.

Cyclic Electron Flow

An alternative photosynthetic light reaction pathway utilizing only Photosystem I to generate $ATP$ without producing $\text{NADPH}$ or oxygen.

Rubisco

The enzyme that catalyzes the initial carbon fixation step of the Calvin cycle by attaching $\text{CO}_2$ to ribulose bisphosphate (RuBP).

Glyceraldehyde 3-phosphate (G3P)

The 3-carbon sugar intermediate produced directly as the net carbohydrate output of the Calvin cycle.

Monocot

A flowering plant clade characterized by seeds containing a single embryonic seed leaf (cotyledon), leaves with parallel veins, and scattered vascular bundles in the stem.

Eudicot

A clade containing the vast majority of flowering plants, characterized by two embryonic seed leaves (cotyledons), net-like leaf venation, and vascular bundles arranged in a ring.

Root Hairs

Thin, finger-like extensions of root epidermal cells that emerge near root tips to dramatically increase the absorptive surface area for water and minerals.

Taproot System

A root system consisting of one main vertical root penetrating deeply into the soil with lateral branch roots, typical of eudicots and gymnosperms.

Petiole

The structural stalk of a leaf that joins the flattened leaf blade to a node on the stem.

Periderm

A protective tissue layer that replaces the epidermis in older regions of stems and roots in woody plants during secondary growth.

Xylem

Vascular plant tissue that conducts water and dissolved minerals upward from roots to the shoot system.

Phloem

Vascular plant tissue that transports sugars and other organic nutrients throughout the plant from sources to sinks.

Pith

Ground tissue that is located internal to the vascular tissue within a plant stem or root.

Cortex

Ground tissue located external to the vascular cylinder, between the dermal tissue and the vascular tissue.

Parenchyma Cells

Relatively unspecialized plant cells with thin, flexible primary cell walls that carry out photosynthesis, cellular storage, and metabolic synthesis.

Collenchyma Cells

Elongated plant cells with unevenly thickened primary walls grouped in strands that provide flexible structural support to young, developing plant shoots.

Sclerenchyma Cells

Rigid supporting plant cells possessing thick secondary cell walls hardened with lignin, present in plant regions that have ceased elongation.

Tracheids

Long, thin, water-conducting xylem cells with tapered ends and lignified walls that are dead at functional maturity.

Vessel Elements

Short, wide, tubular water-conducting cells in the xylem that align end-to-end to form continuous micropipes.

Apical Meristems

Localized regions of undifferentiated, dividing cells at the tips of roots and shoots responsible for primary growth (lengthening).

Lateral Meristems

Cylindrical zones of dividing cells (vascular cambium and cork cambium) that produce secondary growth, expanding plant stem and root diameter.

Pericycle

The outermost cell layer of the vascular cylinder in a root, located adjacent to the endodermis, from which lateral roots originate.

Charophytes

Green algae that represent the closest living relatives of land plants.

Zygnematophyceae

The specific clade of charophyte green algae identified by genetic evidence as the closest living relatives of land plants.

Sporopollenin

A durable polymer layer found in charophytes and plant spore walls that prevents exposed zygotes and spores from desiccation.

Alternation of Generations

A plant life cycle in which a multicellular haploid gametophyte ($n$) and a multicellular diploid sporophyte ($2n$) alternate generations.

Gametophyte

The multicellular haploid ($n$) phase of the plant life cycle that produces haploid gametes through mitosis.

Sporophyte

The multicellular diploid ($2n$) phase of the plant life cycle that produces haploid spores through meiosis.

Sporangia

Multicellular reproductive organs situated on the sporophyte where walled haploid spores are formed.

Bryophytes

The informal group of nonvascular land plants comprising liverworts, mosses, and hornworts.

Lycophytes

A clade of seedless vascular plants belonging to Phylum Lycophyta that includes club mosses, spikemosses, and quillworts.

Monilophytes

A clade of seedless vascular plants belonging to Phylum Monilophyta that includes ferns, horsetails, and whisk ferns.

Seed

A reproductive structure consisting of a plant embryo packaged alongside a nutrient food supply inside a protective seed coat.

Gymnosperms

Vascular seed plants that produce 'naked seeds' that are exposed on modified leaves (sporophylls) or in cones rather than enclosed within protective chambers.

Angiosperms

Vascular seed plants whose seeds develop enclosed inside protective ovaries that originate within flowers.

Ovule

A seed plant structure consisting of a megaspore contained within a megasporangium and surrounded by protective integuments.

Pollination

The mechanical transfer of pollen grains to the portion of a seed plant containing the ovules.

Atropine

A plant-derived compound extracted from the Belladonna plant used clinically as an eye pupil dilator.

Taxol

A medicinal compound extracted from the Pacific yew used as an ovarian cancer chemotherapy drug.