Cell Biology - Cellular Structure & Function Flashcards

Question 1

What is the primary function of the cell nucleus?

Accepted Answer

The nucleus houses the cell's genetic material (DNA) organized into chromosomes, controls gene expression, and regulates cell growth, metabolism, and reproduction. It is also the site of ribosome synthesis (nucleolus).

Question 2

Describe the main role of mitochondria in a eukaryotic cell.

Accepted Answer

Mitochondria are known as the "powerhouses" of the cell. Their primary function is to generate most of the cell's supply of adenosine triphosphate (ATP) through cellular respiration, using oxygen to convert nutrients into energy.

Question 3

Differentiate between the functions of the Rough Endoplasmic Reticulum (RER) and the Smooth Endoplasmic Reticulum (SER).

Accepted Answer

The RER is studded with ribosomes and is involved in the synthesis, folding, modification, and transport of proteins destined for secretion or insertion into membranes. The SER lacks ribosomes and is involved in lipid synthesis, detoxification of drugs and poisons, and storage of calcium ions.

Question 4

Explain the function of the Golgi apparatus (or Golgi complex).

Accepted Answer

The Golgi apparatus modifies, sorts, and packages proteins and lipids synthesized in the ER into vesicles for secretion or delivery to other organelles. It has a cis face (receiving) and a trans face (shipping).

Question 5

What is the primary role of lysosomes?

Accepted Answer

Lysosomes are membrane-bound organelles containing hydrolytic enzymes that break down waste materials, cellular debris, and foreign invaders (like bacteria and viruses). They are crucial for cellular digestion and recycling.

Question 6

Describe the function of peroxisomes.

Accepted Answer

Peroxisomes are small, membrane-bound organelles involved in various metabolic reactions, including the breakdown of very long-chain fatty acids and amino acids. They produce hydrogen peroxide ($H_2O_2$) as a byproduct, which is then converted to water and oxygen by the enzyme catalase.

Question 7

Outline the main stages of aerobic cellular respiration and its overall goal.

Accepted Answer

Aerobic cellular respiration involves Glycolysis, Pyruvate Oxidation, the Citric Acid Cycle (Krebs Cycle), and Oxidative Phosphorylation (Electron Transport Chain and Chemiosmosis). Its overall goal is to convert glucose and oxygen into ATP, carbon dioxide, and water, generating approximately 30-32 ATP molecules per glucose.

Question 8

Where does glycolysis occur, and what are its main products?

Accepted Answer

Glycolysis occurs in the cytoplasm. It breaks down one molecule of glucose into two molecules of pyruvate, producing a net gain of 2 ATP and 2 NADH molecules.

Question 9

What are the key inputs and outputs of the Citric Acid Cycle?

Accepted Answer

The Citric Acid Cycle occurs in the mitochondrial matrix. For each acetyl-CoA molecule, it produces 2 $CO_2$, 3 NADH, 1 $FADH_2$, and 1 ATP (or GTP).

Question 10

Briefly explain the process of oxidative phosphorylation.

Accepted Answer

Oxidative phosphorylation occurs in the inner mitochondrial membrane. It involves the electron transport chain, where electrons from NADH and $FADH_2$ are passed along protein complexes, creating a proton gradient. This gradient drives ATP synthase to produce a large amount of ATP (chemiosmosis).

Question 11

What is the overall equation for photosynthesis, and where does it primarily occur?

Accepted Answer

The overall equation for photosynthesis is $6CO_2 + 6H_2O + 	ext{light energy} ightarrow C_6H_{12}O_6 + 6O_2$. It primarily occurs in the chloroplasts of plant cells and some prokaryotes.

Question 12

Describe the main events of the light-dependent reactions of photosynthesis.

Accepted Answer

Light-dependent reactions occur in the thylakoid membranes of chloroplasts. Light energy is absorbed by chlorophyll, splitting water molecules ($H_2O$) to release electrons, protons ($H^+$), and oxygen ($O_2$). This energy is used to produce ATP and NADPH.

Question 13

What is the purpose of the Calvin Cycle (light-independent reactions)?

Accepted Answer

The Calvin Cycle occurs in the stroma of chloroplasts. It uses the ATP and NADPH generated during the light-dependent reactions to fix carbon dioxide ($CO_2$) from the atmosphere and convert it into glucose (or other sugars).

Question 14

What is the primary purpose of mitosis, and what are its main phases?

Accepted Answer

Mitosis is a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus. Its purpose is growth, repair, and asexual reproduction. Main phases: Prophase, Metaphase, Anaphase, Telophase (PMAT), followed by Cytokinesis.

Question 15

Explain the purpose and outcome of meiosis.

Accepted Answer

Meiosis is a type of cell division that reduces the number of chromosomes by half, creating four haploid cells (gametes) from one diploid parent cell. Its purpose is sexual reproduction, ensuring genetic diversity. It involves two rounds of division: Meiosis I and Meiosis II.

Question 16

What are the three main stages of cell signaling?

Accepted Answer

The three main stages of cell signaling are: 1. Reception (a signaling molecule binds to a receptor protein), 2. Transduction (a series of steps converting the signal into a cellular response), and 3. Response (the specific cellular activity triggered by the signal).

Question 17

Name and briefly describe four common types of cell signaling based on distance.

Accepted Answer

1. **Autocrine**: Cell signals itself. 2. **Paracrine**: Signals local cells. 3. **Endocrine**: Hormones travel via bloodstream to distant target cells. 4. **Synaptic**: Neurotransmitters across a synapse (specialized paracrine).

Question 18

Differentiate between simple diffusion, facilitated diffusion, and osmosis.

Accepted Answer

All are passive transport (no ATP). **Simple diffusion**: Small, nonpolar molecules move directly across the membrane down their concentration gradient. **Facilitated diffusion**: Ions and polar molecules move across the membrane down their concentration gradient with the help of transport proteins (channels or carriers). **Osmosis**: The diffusion of water across a selectively permeable membrane.

Question 19

Explain the difference between primary and secondary active transport.

Accepted Answer

Both require energy to move substances against their concentration gradient. **Primary active transport** directly uses ATP (e.g., $Na^+/K^+$ pump). **Secondary active transport** (co-transport) uses the electrochemical gradient established by primary active transport to move another substance (e.g., $Na^+$-glucose co-transporter).

Question 20

Describe the function of the Sodium-Potassium ($Na^+/K^+$) pump.

Accepted Answer

The $Na^+/K^+$ pump is a primary active transport protein that uses ATP to pump three $Na^+$ ions out of the cell and two $K^+$ ions into the cell, against their concentration gradients. This maintains membrane potential and helps regulate cell volume.

Question 21

Briefly explain endocytosis and exocytosis.

Accepted Answer

Both are bulk transport mechanisms. **Endocytosis**: The cell takes in substances by engulfing them in a vesicle (e.g., phagocytosis, pinocytosis, receptor-mediated endocytosis). **Exocytosis**: The cell releases substances by fusing vesicles with the plasma membrane.

Question 22

Name and describe the main types of cell junctions in animal cells.

Accepted Answer

1. **Tight junctions**: Form a watertight seal between cells, preventing leakage. 2. **Desmosomes**: Provide strong adhesion between cells, resisting mechanical stress. 3. **Gap junctions**: Allow direct communication and passage of small molecules between adjacent cells.

Question 23

Describe the fluid mosaic model of the cell membrane.

Accepted Answer

The fluid mosaic model states that the cell membrane is a dynamic structure composed of a phospholipid bilayer with embedded and associated proteins. The phospholipids and proteins can move laterally, giving the membrane a "fluid" quality, while the "mosaic" refers to the diverse array of proteins.

Question 24

What is the function of ribosomes?

Accepted Answer

Ribosomes are cellular structures responsible for protein synthesis (translation). They read messenger RNA (mRNA) sequences and use transfer RNA (tRNA) to assemble amino acids into polypeptide chains. They can be free in the cytoplasm or bound to the RER.

Question 25

What are the three main components of the cytoskeleton and their general roles?

Accepted Answer

The cytoskeleton is a network of protein filaments that provides structural support, facilitates cell movement, and aids in intracellular transport. Its three main components are: 1. **Microtubules**: Involved in cell shape, organelle movement, cilia/flagella. 2. **Microfilaments (Actin filaments)**: Involved in muscle contraction, cell division, cell shape. 3. **Intermediate filaments**: Provide tensile strength, anchor organelles.

Cell Biology - Cellular Structure & Function

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