Cell Structure and Function Cells and Organelles

Schwann

scientist who first postulated cell theory, stating that all organisms consist of one or more cells and the cell is the basic unit of structure.

Virchow

scientist who added the third tenet to cell theory, stating that all cells arise only from preexisting cells.

Abiotic synthesis

first phase of cell appearance involving the nonliving creation of simple organic compounds.

Abiotic polymerization

second phase of cell appearance involving the assembly of simple organic compounds into macromolecules.

Stanley Miller Experiment

A famous biochemical setup demonstrating the abiotic synthesis of organic molecules from a simulated primitive atmosphere.

Simulated atmosphere gases

specific mixture of gases used in the Miller experiment, containing CH4, NH3, H2, and H2O

Ribozymes

RNA molecules capable of performing enzymatic reactions, such as forming peptide bonds during translation.

RNA world

hypothesized early period in evolutionary history where RNA existed as the primary informational molecule before the appearance of DNA and proteins.

Protocells

Primitive cell-like structures formed when primordial lipids came together to trap RNA molecules.

Liposome

A hollow structure formed by a lipid bilayer that can encapsulate genetic material to create a primitive cell.

In 1839, Schwann postulated the foundational aspects of cell theory. Which of the following statements matches one of his original two tenets?

The cell is the basic unit of structure for all organisms.

what biochemical fact supports the idea that RNA preceded DNA in evolutionary history?

Deoxyribonucleic acids (DNA components) are derived enzymatically from corresponding ribonucleotides (RNA components).

What specialized role do ribozymes perform during modern translation that highlights their ancestral capability to drive an "RNA world"?

They catalyze the formation of peptide bonds during translation

The four-phase model for the appearance of cells states that the encapsulation of the first living molecule must occur within a simple ____________.

membrane

Primordial lipids came together in the early earth environment to enclose and trap strands of ____________, ultimately creating the first primitive cells.

RNA

Three Domains of Life

Bacteria, Archaea, Eukarya

Evolutionary Divergence

biological fact that bacteria and archaea are as divergent from one another as humans and bacteria are.

Bacterial and Archaeal Size

1-5 micrometers

Eukaryotic Size

10-100 micrometers

Eukaryotic Chromosomal DNA

Linear DNA molecules structurally associated with true histone proteins.

Archaeal Chromosomal DNA

Typically circular DNA molecules structurally associated with histone-like proteins.

which of the three domains of life contain a true nucleus and membrane-bound organelles?

Eukaryotes only

How do the structural components of microtubules and microfilaments differ between prokaryotes (Bacteria and Archaea) and Eukaryotes?

Bacteria and Archaea contain actin-like and tubulin-like proteins, whereas Eukaryotes contain true actin and tubulin proteins.

Which domain(s) are capable of performing bulk vesicular transport via exocytosis and endocytosis according to the comparison data?

Eukaryotes only

Which of the following correctly details the shape of chromosomal DNA and its associated organizing proteins across the domains?

Eukaryotes have linear DNA with histone proteins, while Archaea have circular DNA with histone-like proteins.

Unlike eukaryotes which contain true actin and tubulin proteins, Bacteria build their microfilaments and microtubules using actin-like and ____________ proteins.

tubulin-like

While bacterial chromosomal DNA is typically circular with few associated proteins, eukaryotic chromosomal DNA is linear and bound tightly to true ____________ proteins.

histone

According to the chromosomal DNA property data, Archaea possess a typically circular chromosome that uniquely complexes with ____________ proteins.

histone-like

Surface area to volume ratio

A critical ratio that severely drops as a cell's individual side length increases

which cellular processes and structures are strictly restricted to Eukaryotes, while being completely absent in both Bacteria and Archaea?

A true nucleus, membrane-bound organelles, and exocytosis/endocytosis

what are the direct internal physical consequences when a cell's size increases too much without internal compartmentalization?

Molecular concentration falls and chemical reaction rates slow down.

Unlike eukaryotes, both bacteria and archaea contain microtubules and microfilaments composed of ____________ proteins rather than true actin and tubulin.

actin-like and tubulin-like

Cells that are specialized for nutrient absorption adapt their shapes using microvilli to maximize their total structural ____________.

surface area

Cytoplasmic streaming

An active eukaryotic transport strategy (called cyclosis in plants) used to actively move cytoplasmic contents throughout large cells

Cyclosis

Movement of cytoplasm around the cell for plants

Vesicles

Membrane-bound transport packages used by eukaryotic cells to move molecules along protein fibers.

Internal organelles

Specialized cellular compartments that allow localized concentration of molecules for a particular cellular function.

Eukaryotic structural complexity

typical animal and plant cells, which are larger and more compartmentalized than prokaryotes.

Core eukaryotic components

plasma membrane, a nucleus, membrane-bounded organelles, and a cytosol interlaced by a cytoskeleton.

Plant and fungal cell boundary

rigid cell wall structure that is surrounded by an extracellular matrix.

Microtubule

A type of protein fiber shown in the transport diagram along which cellular vesicles are physically carried.

Eukaryotic cells are too large to rely purely on passive diffusion. Which of the following active strategies do plant cells specifically use to mechanically mix and distribute their cytoplasmic contents?

Cytoplasmic streaming (cyclosis)

When a cell grows in size, its average internal molecular concentration falls and reaction rates slow down. How do eukaryotic internal organelles structurally solve this specific problem?

They allow localized concentration of specific molecules needed for a particular function.

While both animal and plant cells possess a plasma membrane and a cytoskeleton, what unique boundary structures are found specifically in plant and fungal cells?

A rigid cell wall surrounded by an extracellular matrix

Eukaryotic cells move specific molecules actively through their cytoplasm packed inside membrane-bound ____________ that travel along specialized protein fibers.

vesicles

In a typical eukaryotic cell, the liquid portion of the cytoplasm known as the cytosol is extensively interlaced by a structural network called the ____________.

cytoskeleton

As cell size increases, the rate of unassisted chemical reactions inside the cell will naturally ____________ unless active transport mechanics are used

slow down

Glycoprotein

A membrane protein containing short carbohydrate side chains attached to it on the external side of the membrane.

Membrane protein domains

Functional segments of a membrane protein, where most have at least one hydrophobic membrane-spanning domain.

Nuclear envelope

double-membrane structure that surrounds the nucleus and contains regular openings called nuclear pores.

Chromatin

The complex of DNA and organizing proteins found dispersed within the nucleoplasm of the nucleus.

Nucleolus

The prominent, dense structure located inside the nucleus responsible for ribosome synthesis.

how much volume can a central vacuole occupy, and what physical phenomenon does it create?

It occupies about 90% of cell size to store nutrients, waste, and water, generating turgor pressure against the cell wall.

The plasma membrane consists of a phospholipid bilayer with embedded proteins. What is true regarding membrane protein symmetry?

Membrane proteins are not symmetrical because modification happens only at a specific part of the protein

what specific components are manufactured inside the dense sub-compartment known as the nucleolus?

Ribosome proteins and transcription cues

According to the evolutionary pathway diagrams and handwritten annotations detailing the Endosymbiont Theory, what are the distinct ancestral lineages for animal cells versus plant cells?

Ancient aerobic purple bacteria evolved into animal mitochondria; ancient photosynthetic cyanobacteria evolved into plant chloroplasts.

The endomembrane system utilizes small, membrane-bound transport vesicles to move materials between compartments. Are these transport vesicles classified as independent organelles?

No, they are not considered organelles; their role is strictly membrane packing to facilitate transport between parts of the system.

While the outer boundary of a plant cell is a rigid cell wall, the vital structure that establishes cell boundaries and houses asymmetrical proteins is the ____________ bilayer.

phospholipid

The nuclear envelope is a double-membrane structure where specialized openings called ____________ allow nucleotides to enter the nucleus and tRNAs to exit.

nuclear pores

Mitochondria

An organelle found in large numbers in most cells, in which the biochemical processes of respiration and energy production (ATP) occur.

Inside a plant chloroplast, individual thylakoid discs organize into tight horizontal stacks called a ____________, which serves as the location for photosynthesis.

granum

The specialized network of interconnected structures (Endomembrane system) includes the Endoplasmic Reticulum, the Lysosomes, and the ____________.

Golgi Apparatus

Endosymbiotic similarities

Mitochondria, chloroplasts, and bacteria all contain circular DNA without histones, allowing them to make their own RNA and proteins.

Prokaryotic ancestral clues

Mitochondria and chloroplasts share similar rRNA sequences, ribosome sizes, and translation inhibitor sensitivities with bacteria, showing they likely share a common ancestor.

Organelle double membranes

Structures where the inner membrane features bacterial-like lipids and the outer membrane features eukaryotic lipids.

Endomembrane System

synthesizes and packages proteins destined for various organelles, cellular membranes, or secretion.

vesicles

Small membrane-bound transport units that function strictly in membrane packing to act as vehicles between parts of the system

Endoplasmic Reticulum

An extensively folded organelle that sits close to the nucleus and is directly connected to the outer nuclear envelope membrane to enlarge its surface area.

Smooth ER functions

lipid synthesis and chemical detoxification

Rough ER functions

Protein synthesis via associated ribosomes, along with protein modification.

Ancient aerobic purple bacterium

specific ancestral prokaryote engulfed by a protoeukaryotic cell that evolved to propagate independently as a mitochondrion.

Ancient photosynthetic cyanobacterium

specific ancestral prokaryote engulfed by a eukaryotic descendant that evolved to propagate independently as a chloroplast.

what unique asymmetry characterizes the lipid layers of both mitochondria and chloroplasts?

The inner membrane features bacterial-like lipids, while the outer membrane contains eukaryotic lipids.

The endomembrane system utilizes small, membrane-bound vesicles to direct proteins around the cell. According to the handwritten annotations, what is the exact classification of these vesicles?

They are not considered independent organelles; they function strictly as vehicles for membrane packing between different system parts.

how is the Endoplasmic Reticulum physically organized within the cytoplasm?

located close to the nucleus, directly connected to the outer nuclear envelope membrane, and folded to enlarge its surface area.

An investigator isolates two distinct fractions of the endoplasmic reticulum. Fraction 1 is covered in ribosomes and active in protein modification. Fraction 2 lacks ribosomes and performs detoxification. How are these fractions classified?

Fraction 1 is Rough ER; Fraction 2 is Smooth ER.

The interconnected organelles that cooperate within the endomembrane system are the Endoplasmic Reticulum, the Lysosomes, and the ____________.

Golgi Apparatus

According to the Endosymbiont Theory diagram, the early ancestral cell that first engulfed an oxygen-utilizing bacterium is called a ____________.

protoeukaryote (or protoeukaryotic cell)

The detailed structural diagram of the Rough ER highlights that it contains both membrane-bound ribosomes and ____________ ribosomes.

free

the Endoplasmic Reticulum plays an important role in protein ____________.

sorting

Golgi Apparatus functions

Processing and packaging secretory proteins (such as glycosylation), along with the synthesis of complex polysaccharides.

Golgi stack composition

A series of individual, disconnected compartments typically consisting of 3-8 sacks.

Golgi polarity

A structural feature defined by having 2 sides, starting at the incoming cis side.

Lysosomes

Single-membrane enclosed compartments that serve as the specialized garbage disposal of the cell.

Lysosomal function

Storing acid hydrolases to digest different macromolecules, breaking them down into monomers to be recycled for making new macromolecules.

Transition vesicle

Vesicles that transport materials from the Rough endoplasmic reticulum to the Golgi

Secretory vesicle

A membrane package that buds off the Golgi apparatus and travels to the plasma membrane for exocytosis.

how do materials physically travel through the Golgi apparatus?

They move from one individual sack to another packed inside transport vesicles.

The slide poses the question: "Why won't lysosome enzymes digest the lysosome itself or the cell?" Based on the biochemistry of these enzymes, what mechanism protects the cell from self-digestion?

The enzymes are acid hydrolases that require a low pH to function; if they leak into the neutral cytosol, they become inactive.

what is the correct chronological sequence of structures a protein encounters when destined for secretion out of the cell?

Rough ER → Transition vesicle → Golgi apparatus → Secretory vesicle → Plasma membrane

Hand-annotated notes emphasize that the Golgi apparatus acts fundamentally as a cellular ____________ center for further chemical modification.

sorting

While mitochondria possess a double-membrane structure, lysosomes are bounded by a ____________ membrane.

single

According to the text labels on the lysosome slides, lysosomes contain specialized digestive enzymes generically classified as ____________.

hydrolases

The process depicted at the very end of the secretory pathway, where a secretory vesicle fuses with the plasma membrane to release its contents outside the cell, is called ____________.

exocytosis

Peroxisome classification

An organelle that resembles lysosomes in size and appearance but is explicitly not part of the endomembrane system.

Where are peroxisomes especially prominent in animals?

Organelles that are especially prominent in the liver and kidney cells of animals.

Catalase

The specific peroxisomal enzyme that safely converts highly toxic hydrogen peroxide (H2O2) into water and oxygen

Peroxisomal oxidation

A process that digests long-chain fatty acids by breaking them into smaller pieces and aids in detoxification by breaking down aromatic molecules.

Cis vs trans golgi

-Cis faces towards ER and is convex. Proteins enter from the cis face.

-Trans faces towards Plasma membrane and is concave. Proteins exit from trans face.

Animal and yeast vacuoles

Temporary storage units containing molecules like amino acids and sugar, or transport structures formed via phagocytosis.