Cytoplasm & Organelles - Cellular Level of Organization

Comprehensive practice flashcards covering Cytoplasm, Cytosol, Organelles, Cellular Respiration, Energy Homeostasis, Cytoskeleton, Motility, and Synthesis/Digestive Organelles from HTHS 2110 Unit 5.

What are the two primary components that make up the cytoplasm of a cell?

The cytoplasm consists of the cytosol (a solvent of water containing dissolved salts, glycerides, and proteins) and organelles ("little organs").

What structural adaptation of the mitochondrial inner membrane helps maximize its functional capacity?

The inner membrane is extensively folded into cristae to significantly increase the surface area available for cellular respiration and energy production.

How is mitochondrial DNA (mtDNA) inherited in humans?

Mitochondrial DNA is inherited strictly maternally, passed directly from mother to daughter and mother to son.

What are the core characteristics of anabolic chemical reactions?

Anabolic reactions are endergonic/endothermic processes that combine simple molecules to build complex molecules; they require energy supplied by $ATP$ and absorb that energy into chemical bonds.

How do catabolic chemical reactions differ from anabolic reactions in terms of energy flow?

Catabolic reactions are exergonic/exothermic processes that break down complex molecules into simple ones, releasing chemical energy that is captured and stored in the high-energy bonds of $ATP$.

What is the primary advantage of cellular metabolism over direct combustion (burning)?

Metabolism releases chemical energy in small, controlled steps so that most energy is captured as $ATP$ and uncaptured energy is released gradually as heat, preventing cellular damage.

How do the digestive, respiratory, circulatory, and excretory systems collaborate to maintain cellular energy homeostasis?

The digestive system absorbs nutrients from food; the respiratory system takes in $O_2$ and expels $CO_2$; the circulatory system transports nutrients and $O_2$ to cells while carrying waste and $CO_2$ away; and the excretory system eliminates waste from the body.

What is the overall balanced equation for cellular respiration?

$$\text{C}_6\text{H}_{12}\text{O}_6 + 6\,\text{O}_2 \rightarrow 6\,\text{CO}_2 + 6\,\text{H}_2\text{O} + 26\text{--}38\,\text{ATP}$$

What is the chemical difference between the "acid" and "-ate" forms of cellular molecules such as pyruvic acid and pyruvate?

The "acid" form (e.g., pyruvic acid, lactic acid) represents the non-ionized state, whereas the "-ate" form (e.g., pyruvate, lactate) represents the ionized state.

What is the specific function of Coenzyme A (CoA) during cellular respiration?

Coenzyme A acts as a two-carbon carrier "shovel" that holds a single two-carbon acetyl group (acetate) and delivers it into the citric acid cycle without being consumed in the process.

Which cofactors function as proton ($H^+$) and electron ($e^-$) carriers during cellular respiration?

Flavin adenine dinucleotide ($FAD$) and nicotinamide adenine dinucleotide ($NAD^+$).

Where does glycolysis take place within the cell, and what is its net output per glucose molecule?

Glycolysis takes place in the cytosol and produces a net output of $2\,\text{ATP}$, $2\,\text{NADH}$ (carrying $4\,\text{H}^+$ and $4\,\text{e}^-$), and $2\text{ pyruvate}$ molecules per glucose.

How many $ATP$ molecules are invested and generated during the two phases of glycolysis?

The energy investment phase requires $2\,\text{ATP}$, and the energy payoff phase generates $4\,\text{ATP}$, yielding a net gain of $2\,\text{ATP}$.

What metabolic pathway occurs if oxygen ($O_2$) is absent following glycolysis?

Anaerobic respiration occurs, converting the $2\text{ pyruvates}$ into $2\text{ lactates}$ for a final net yield of only $2\,\text{ATP}$ in a metabolic dead end.

What products are generated during the formation of acetyl-CoA per glucose molecule?

The reaction produces $2\text{ acetyl-CoA}$, $2\,\text{CO}_2$, and $2\,\text{NADH} + 2\,\text{H}^+$ in the mitochondrial matrix ($1$ of each per pyruvate).

What products are produced per glucose molecule by two turns of the citric acid cycle?

$4\,\text{CO}_2$, $6\,\text{NADH} + 6\,\text{H}^+$, $2\,\text{FADH}_2$, and $2\,\text{ATP}$.

How does the electron transport chain produce $ATP$ in the inner mitochondrial membrane?

Transmembrane enzymes use high-energy electrons brought by $NADH$ and $FADH_2$ to pump protons ($H^+$) into the intermembrane space; as protons flow down their concentration gradient back into the matrix, $ATP$ synthase synthesizes $ATP$.

What is the realistic net yield of $ATP$ per glucose molecule in aerobic cellular respiration?

While theoretical yields range from $26\text{--}38\,\text{ATP}$, real cellular efficiency typically produces about $30\text{--}32\,\text{ATP}$ per glucose molecule.

Where is glycogen stored in the human body, and in what amounts?

Glycogen is stored in the liver ($70\text{--}100\,\text{g}$ or $280\text{--}400\,\text{Cal}$), skeletal muscle ($200\text{--}400\,\text{g}$ or $800\text{--}1600\,\text{Cal}$), and cardiac muscle ($\approx 2\,\text{g}$).

What is gluconeogenesis and how does it relate to glycolysis?

Gluconeogenesis is the creation of new glucose from non-carbohydrate sources (fats or proteins); it is essentially glycolysis running in reverse to build a 6-carbon glucose from 2- and 3-carbon molecules.

What are the three structural filaments of the cytoskeleton, ordered from smallest to largest diameter?

Microfilaments (actin, $7\text{--}8\,\text{nm}$), intermediate filaments (keratin, GFAP, neurofilaments, etc., $8\text{--}12\,\text{nm}$), and microtubules (tubulin, $25\,\text{nm}$).

What protein subunits form microtubules, and how are they assembled?

Microtubules are composed of $\alpha$-tubulin and $\beta$-tubulin joined into dimers, which assemble into hollow tubes $25\,\text{nm}$ in diameter and are stabilized by microtubule-associated proteins (MAPs).

What components make up a centrosome, and what is its role in cell division?

A centrosome consists of two centrioles (each composed of $9 \times 3$ microtubule triplets) surrounded by pericentriolar material; it acts as a microtubule-organizing center (MTOC) that forms the mitotic spindle.

What cytoskeletal structure forms the core of microvilli in absorptive epithelial cells?

Microvilli are supported by an internal core of actin microfilaments (filamentous actin, F-actin).

What microtubule arrangement is found in the basal body versus the main shaft of cilia and flagella?

The basal body at the base contains $9$ microtubule triplets, whereas the main shaft contains $9$ microtubule doublets surrounding $2$ central single microtubules ($9+2$ structure).

How do cilia and flagella differ in their movement mechanics and primary functions?

Cilia use a rowing motion (power stroke and return stroke) to move fluids across the surface of a stationary cell, whereas flagella use a wave-like whipping motion to move an entire cell (such as a sperm cell) through fluid.

What is the function of the spliceosome in RNA processing?

The spliceosome is an editing machine that removes non-coding loops of RNA (introns) from pre-mRNA and splices together the coding segments (exons) to form mature messenger RNA (mRNA).

What subunits compose eukaryotic ribosomes, and where are functional ribosomes found in the cell?

Eukaryotic ribosomes consist of a large subunit ($60\text{S}$) and a small subunit ($40\text{S}$); they exist either free in the cytoplasm or attached to the surface of the rough endoplasmic reticulum.

Which destination pathways utilize proteins synthesized on the Rough Endoplasmic Reticulum (RER)?

Proteins synthesized on the RER are destined for export out of the cell via exocytosis, insertion into the cell membrane, or packaging inside lysosomes.

What are the three specialized functional types of Smooth Endoplasmic Reticulum (SER)?

1. SER for lipid synthesis; 2. SER for processing toxins and cellular components; 3. SER for calcium storage (such as the sarcoplasmic reticulum in muscle cells).

How do proteins traverse the Golgi complex during modification and packaging?

Proteins enter through the cis (entry) face, move through the cisternae for processing and finishing, and exit through the trans (exit) face packaged inside secretory vesicles.

What sequential pathway defines the endomembrane system for exported cell products?

DNA is transcribed into pre-mRNA in the nucleus -> spliceosomes edit pre-mRNA to mRNA -> mRNA is translated into protein on the Rough ER -> protein is transferred to and packaged in the Golgi apparatus -> protein exits via secretory vesicles, lysosomes, or membrane insertion.

How do lysosomes maintain an acidic internal pH, and what enzymes do they contain?

Lysosomes use proton ($H^+$) pumps to concentrate $H^+$ ions $100\times$, maintaining an acidic internal pH of $5.0$ (versus cytosolic pH $7.4$), and contain acid-optimal hydrolytic enzymes such as lysozyme.

What key chemical reactions occur within peroxisomes?

Peroxisomes contain oxidases that perform $\beta$-oxidation on fatty acids, producing hydrogen peroxide ($\text{H}_2\text{O}_2$); the enzyme catalase then breaks down $\text{H}_2\text{O}_2$ into water and oxygen ($2\,\text{H}_2\text{O}_2 \rightarrow 2\,\text{H}_2\text{O} + \text{O}_2$).

How do proteasomes target and degrade cellular proteins?

Unneeded, misfolded, or damaged proteins are tagged by ubiquitin, which directs the protein into the barrel-shaped proteasome to be broken down into individual amino acids.