BIOL 1000 B - Lecture 6: Eukaryotic Cell Structure and Function

A comprehensive vocabulary flashcard set consisting of 100 flashcards based on BIOL 1000 Lecture 6, covering differences between Bacteria and Archaea, surface area to volume ratio, nuclear structure and transport, the endomembrane system, protein signal targeting, vesicle transport, lysosomes, and plant vacuoles.

Bacteria RNA Polymerase

A single type of RNA polymerase found in bacteria consisting of 5 subunits.

Archaea RNA Polymerase

A single type of RNA polymerase found in archaea consisting of 13 subunits, which is similar to RNA polymerase II in eukaryotes.

Peptidoglycan in Bacteria

A structural polymer present in the cell walls of bacteria.

Peptidoglycan in Archaea

A cell wall constituent that is absent in archaea.

Bacterial Translation Initiator

Formylmethionine, the first amino acid incorporated into polypeptides during translation in bacteria.

Archaeal Translation Initiator

Methionine, the first amino acid incorporated into polypeptides during translation in archaea.

Bacterial DNA Histones

Proteins associated with DNA packaging that are absent (No) in bacteria.

Archaeal DNA Histones

Proteins associated with DNA packaging that are present (Yes) in archaea.

Bacterial Plasma Membrane Phospholipids

Phospholipid tails made of a pair of fatty acids in bacterial cell membranes.

Archaeal Plasma Membrane Phospholipids

Phospholipid tails made of a pair of isoprene chains in archaeal cell membranes.

Surface Area to Volume Ratio

The relationship between cell surface area and volume; a high ratio facilitates efficient transport of ions, nutrients, and waste across the plasma membrane.

Cell Size Constraint

The limitation on cell growth where volume increases faster than surface area, requiring surface area to adequately sustain the volume.

Prokaryotic vs Eukaryotic Cell Diameter

Prokaryotes are on average about $10\times$ smaller in diameter than eukaryotic cells.

Prokaryotic vs Eukaryotic Cell Volume

Prokaryotes are on average about $1000\times$ smaller in volume than eukaryotic cells.

Neuronal Morphological Adaptation

A structural adaptation where neurons form many thin projections (dendrites and an axon) to maximize their surface area to volume ratio.

Microvilli

Cellular membrane folds that increase surface area while minimizing total cell volume.

Multicellularity Surface Adaptation

An adaptation where organisms increase their total cell number rather than individual cell size to overcome low surface area to volume ratios.

Eukaryotic Cell

A cell containing a distinct nucleus surrounded by a nuclear envelope and membrane-bound organelles.

Nucleus

The organelle that holds the nuclear genome and physically separates it from the rest of the cell.

Nuclear Envelope

A double membrane structure consisting of two lipid bilayers that surrounds the nucleus.

Nucleolus

A non-membrane-bound structure inside the nucleus composed of proteins and nucleic acids, serving as the site of rRNA synthesis and ribosomal subunit assembly.

rRNA Synthesis

The production of ribosomal RNA taking place inside the nucleolus.

Nuclear Lamina

A structural lattice found inside the nucleus under the double membrane that provides structural support.

Intermediate Filaments of Nuclear Lamina

The specific protein filaments that compose the nuclear lamina.

Nuclear Pores

Openings in the nuclear envelope through which molecular movement between the nucleus and cytoplasm is controlled.

Nuclear Pore Complex

A multiprotein complex embedded in the nuclear envelope that actively controls traffic between the cytoplasm and nucleus.

Nuclear Localization Signal

An amino acid sequence tag on cytosolic proteins that directs them through the nuclear pore complex into the nucleus.

Pyruvate Kinase NLS Experiment

An experiment showing that modifying the cytosolic protein pyruvate kinase to include a nuclear localization signal causes it to be imported into the nucleus.

Endomembrane System

A collection of interrelated membranous sacs and tubules that divide the eukaryotic cell into functional and structural compartments.

Endomembrane System Components

The interrelated membrane structures consisting of the nuclear membrane, ER, Golgi apparatus, lysosomes, vesicles, vacuoles, and plasma membrane.

Origin of the Nuclear Envelope Hypothesis

The hypothesis proposing that infoldings of the plasma membrane surrounded chromosomes in an ancestor of eukaryotes to form the nuclear envelope and ER.

Endomembrane Protein Secretion Function

The major endomembrane system function involving synthesis, modification, transport, and secretion of proteins.

Endomembrane Lipid Synthesis Function

The major endomembrane system function involving synthesis of lipids and detoxification of toxins.

Endomembrane Digestive Function

The major endomembrane system function involving transportation and breakdown (digesting) of large biomolecule-containing particles.

Membrane Fusion Principle

The property of endomembrane organelles allowing them to either be directly connected or fuse portions of their membranes with each other.

Secretory Pathway

The protein pathway proceeding from Rough ER (synthesis, folding, modification) to transport vesicles, Golgi apparatus (modification), transport vesicles, and plasma membrane (secretion).

Free Ribosomes

Ribosomes floating unattached in the cytosol where all protein synthesis starts.

Bound Ribosomes

Ribosomes attached to the rough endoplasmic reticulum portion of the endomembrane system.

Initial Site of Translation

The cytosol, where all protein synthesis begins on free ribosomes.

Polysome

A complex formed when multiple ribosomes simultaneously translate a single mRNA strand.

Peptide Bond

The chemical bond formed between the carboxyl group of one amino acid and the amino group of a second amino acid.

Peptide Bond Double-Bond Character

The structural property given to a peptide bond due to electron sharing between the carboxyl carbon and amino nitrogen.

N-terminus

The amino-terminal end of a polypeptide that is synthesized and exits the ribosome first (start).

C-terminus

The carboxyl-terminal end of a polypeptide chain where the next incoming amino acid is added.

Polypeptide Synthesis Direction

The elongation direction of protein chains growing from the N-terminus to the C-terminus.

ER Signal Sequence

A sequence of approximately $∼ 20$ amino acids on a newly translated protein that targets it to the ER.

Signal-Recognition Particle

A cytosolic complex (SRP) that binds to the ER signal sequence, halts translation, and directs the ribosome to an SRP receptor on the ER membrane.

SRP Receptor

A receptor located in the ER membrane that binds the signal-recognition particle bound to a ribosome.

Translocon

A protein translocator complex in the ER membrane associated with the SRP receptor through which the polypeptide enters the ER lumen.

Co-translational Translocation

The process where a peptide moves into the ER lumen or inserts into the ER membrane simultaneously while being synthesized by a ribosome.

Signal Hypothesis

The model describing how an ER signal sequence is synthesized by a ribosome, bound by SRP, docked at an SRP receptor, and translocated into the RER.

Vesicle Budding

The pinching off of a donor compartment membrane to form a transport vesicle containing selected lumenal and membrane cargo.

Donor Compartment

The membrane compartment from which a budding transport vesicle originates.

Transport Vesicle

A small membrane-enclosed sphere in the cytoplasm that shuttles selected proteins and lipids between organelles.

Target Compartment

The destination membrane compartment with which a transport vesicle fuses.

Vesicle Fusion

The process where a transport vesicle merges its lipid bilayer with the membrane of a target compartment.

Golgi Apparatus

A system of flattened membrane sacs called cisternae where products from the ER are sorted, modified, and shipped.

Cisternae

The individual flattened membrane sacs that make up the Golgi apparatus.

Cis Face of Golgi Apparatus

The receiving side of the Golgi apparatus that faces the nucleus and endoplasmic reticulum.

Trans Face of Golgi Apparatus

The shipping side of the Golgi apparatus that faces the plasma membrane.

Golgi Glycosylation Modifications

Chemical modifications performed in the Golgi apparatus, such as adding or removing sugars and adding phosphate groups to proteins.

Molecular Postal Codes

Distinct molecular tags carried by proteins in the endomembrane system that bind specific Golgi receptors to target them to correct destinations.

Exocytosis

The cellular process where secretory vesicles fuse with the plasma membrane and release their lumenal contents to the exterior of the cell.

Secretory Vesicles

Vesicles that transport proteins bound for secretion from the trans face of the Golgi to the plasma membrane.

Smooth Endoplasmic Reticulum

A tubular membrane network lacking ribosomes that synthesizes lipids, detoxifies poisons, synthesizes steroid hormones, and stores calcium.

SER Lipid Synthesis

The function of the smooth ER responsible for producing lipids that become part of cell membranes.

Hepatic SER Detoxification

The liver smooth ER process of converting drugs, poisons, and toxic by-products into safer, tolerable substances.

SER Steroid Hormone Synthesis

The production of steroid sex hormones taking place in the smooth ER of reproductive organ cells.

SER Calcium Storage

The function of the smooth ER lumen in sequestering calcium ions required for cellular signaling.

Rough Endoplasmic Reticulum

A membrane network studded with ribosomes involved in protein synthesis, folding, and initial carbohydrate modification.

RER Lumen

The internal fluid-filled space of the rough ER where translocated proteins undergo folding and carbohydrate addition.

Lysosome

An acidic organelle containing hydrolytic enzymes that serves as the cell's recycling center by breaking down macromolecules.

Lysosomal Acidic pH

The low internal pH environment required for optimal hydrolytic activity of lysosomal enzymes.

Lysosomal Enzyme Source

Digestive enzymes synthesized in the RER and processed/tagged within the Golgi apparatus before delivery to lysosomes.

Lysosomal Membrane Origin

Organelle membrane components originating from both the Golgi apparatus and the plasma membrane.

Endocytosis

The inward pinching of the plasma membrane to form vesicles that bring external molecules into the cell.

Phagocytosis

A form of endocytosis where a cell engulfs large food particles or smaller cells to form an internal phagosome.

Phagosome

A membrane-bound vesicle containing ingested particles or organisms formed during phagocytosis.

Macrophage Phagocytosis

An immune process where macrophage cells engulf pathogenic bacteria and digest them inside lysosomes.

Receptor-Mediated Endocytosis

An endocytic process using specific cell-surface receptors to bind and import targeted macromolecules into an endocytic vesicle.

Receptor Recycling

The return of cell-surface receptors back to the plasma membrane after sorting inside early endosomes.

Early Endosome

An initial endocytic vesicle that acidifies and matures into a late endosome while recycling cell receptors.

Late Endosome

An intermediate sorting compartment receiving lysosomal enzymes from the Golgi before becoming a functional lysosome.

Autophagy

The degradative pathway where a cell encloses a damaged organelle within a membrane to deliver it to a lysosome for digestion.

Autophagosome

A double-membrane vesicle formed around a damaged organelle during autophagy prior to lysosomal fusion.

Lysosomal Monomer Release

The export of small molecules derived from digested materials out of the lysosome and into the cytosol.

Central Vacuole

A large membrane-bound organelle found in plant cells formed by the fusion of smaller vacuoles.

Central Vacuole Formation

The development of the plant central vacuole through the fusion of smaller precursor vacuoles.

Cell Sap

The solution contained within the central vacuole composed of water, ions, enzymes, and metabolic waste.

Central Vacuole Waste Degradation

The breakdown of plant metabolic waste using hydrolytic enzymes localized inside the central vacuole.

Central Vacuole Pigment Storage

The accumulation of pigments within the plant central vacuole to provide coloration.

Central Vacuole Chemical Defense

The storage of toxic molecules or poisons in the central vacuole to protect plants from herbivores.

Turgor Pressure

The internal hydrostatic pressure created by water storage in the central vacuole that maintains plant cellular turgidity and drives growth.

Structure of the Mitochondrion

An organelle with outer and inner membranes defining an intermembrane space and matrix, where pyruvate processing occurs.

Mitochondrial Outer Membrane

The smooth outer phospholipid bilayer enclosing the entire mitochondrion.

Mitochondrial Inner Membrane

The inner phospholipid bilayer containing cristae folds that encloses the mitochondrial matrix.

Mitochondrial Intermembrane Space

The fluid-filled region located between the outer and inner mitochondrial membranes.

Mitochondrial Matrix

The innermost compartment enclosed by the inner mitochondrial membrane where pyruvate processing occurs.

Cristae

Sac-like expansions of short tubes formed from the inner mitochondrial membrane.

Chloroplast

An organelle present in plant cells (and absent in animal cells) responsible for photosynthesis.