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Biology CH 4
Chapter 4 Study Questions
| Question | Answer |
|---|---|
| How old is Earth? | About 4.8 billion years old. |
| What were early Earth conditions like? | High heat, volcanic activity, deep‑sea vents, dense clouds, almost no oxygen. |
| What event allowed the first oceans to form? | Earth cooled ~3.5 billion years ago, allowing condensation and rainfall. |
| What did the Stanley Miller experiment in the 1950s demonstrate? | Organic molecules (amino acids, sugars) can form from early Earth gases + electricity |
| Can polymers form in water without constant hydrolysis destroying them? | Yes — experiments show polymers can form in aqueous solutions. |
| Why is the extraterrestrial origin hypothesis disputed? | Heat on entry and extreme cold would destroy most organic molecules. |
| Where might life have originated according to the vent hypothesis? | Deep‑sea hydrothermal vents protected from UV radiation |
| What environment did LUCA live in? | Hot, oxygen‑free, energy from chemical gradients. |
| Why are black smokers unlikely origins of life? | Too hot and acidic |
| Why are white smokers a strong candidate? | Alkaline, methane‑rich, lower temperature (Lost City vent field). |
| What organisms live in deep‑sea vents today? | Archaeans that use chemical gradients for energy |
| White Smokers | Alkaline vents rich in methane, lacking carbon dioxide, and operating at lower temperatures. The Lost City vent field on the Mid-Atlantic Ridge is a leading candidate cradle of life. |
| Black Smokers | Deep-sea vents discharging acidic, carbon dioxide-rich water heated to hundreds of degrees Celsius with sulfur, iron, and copper; deemed too hot for LUCA. |
| Extremophiles | Archaeans currently inhabit deep-sea thermal vents, deriving energy entirely from chemical gradients without sunlight. |
| What were protobionts? | Pre‑cellular aggregates with membranes that could catalyze reactions and self‑replicate. |
| What do phospholipids form spontaneously in water? | Liposomes (hollow spheres). |
| What helps liposomes encapsulate RNA? | Charged clay particles. |
| Why is RNA thought to precede DNA? | It stores info, self‑replicates, and acts as a catalyst (ribozymes). |
| What RNA variants were favored? | Faster‑replicating, more catalytic RNA. |
| What is the central dogma? | DNA → RNA → Protein |
| DNA | functions as stable information storage |
| RNA | carries instructions |
| Proteins | serve as primary catalysts and structural components |
| Who named “cells”? | Robert Hooke |
| Who first observed living microbes? | Anton van Leeuwenhoek |
| What did Matthijs Schleiden conclude? | All plants are made of cells |
| What did Theodore Schwann conclude? | All animals are made of cells |
| What are the three tenets of cell theory? | All organisms are cells; cells are smallest living units; cells arise from pre‑existing cells |
| Robert Hook examined | examined wine cork under an early microscope, observed box-like compartments, and named them "cellulite" (Latin for tiny rooms) |
| Anton von Leewinhoek examined | examined tooth tartar and observed living microscopic organisms swimming around |
| Peter Birchow and Louis Pasteur | contributed to formulating the unified cell theory. |
| What is resolution | is the ability to distinguish between two separate points. |
| What is the max magnification of a light microscope? | ~1,000× |
| What does Transmission Electron Microscopes(TEM) allow? | Viewing internal structures of dead specimens at 0.2 nm resolution. |
| What does Scanning Electron Microscopes (SEM) show? | 3D surface images of metal‑coated dead specimens. |
| Why are cells small? | High surface area: volume ratio speeds communication and transport |
| What features do all cells share? | DNA/RNA, ribosomes, cytoplasm, plasma membrane |
| Compound Light Microscopes: | Utilize glass lenses with four objective intervals, offering up to 1,000 times magnification; Provide total resolving power approximately 500 times greater than the human eye; Allow observation of living specimens, such as Euglena or pond scum. |
| What is Transmission Electron Microscopes(TEM) | Utilize magnetic lenses and electron beams to photograph dead specimens on a screen |
| What domains contain prokaryotes? | Bacteria and Archaea |
| Where is DNA located in prokaryotes? | Nucleoid region |
| Name three bacterial shapes. | Cocci, bacilli, spirillum/spirochete |
| What does the bacterial cell wall do? | Maintains shape; target of antibiotics-- present in certain species like streptococcal bacteria. |
| What is a capsule? | Protective outer layer present in certain species like streptococcal bacteria. |
| What is the function of flagella? | Movement |
| What do pili do? | Surface adhesion and horizontal gene transfer |
| What is the nucleus? | Control center containing DNA and houses the nucleolus where ribosomes are produced; enclosed by a regulated nuclear envelope. |
| What is the function of the rough Endoplasmic Reticulum(Rough ER)? | Protein synthesis |
| What does the smooth Endoplasmic Reticulum (Smooth ER) do? | Lipid synthesis, carbohydrate synthesis, detoxification |
| What is the Golgi apparatus? | Modifies, packages, and ships molecules (e.g., packaging breast milk droplets in mammary glands). |
| What is the function of mitochondria? | Cellular powerhouses that convert sugars into usable energy (ATP) production |
| Flagella: | External protein tails used for locomotion or ingestive phagocytosis. -- Long, whip-like tails used for propulsion (found in bacteria and human sperm cells). |
| Pili: | Short hair-like projections used for surface adherence and horizontal transfer of genetic material (antibiotic resistance). |
| Rough Endoplasmic Reticulum (Rough ER) | Studded with ribosomes; primary site for protein synthesis -- Covered in ribosomes; synthesizes and processes proteins before packaging them into vesicles. |
| Smooth Endoplasmic Reticulum (Smooth ER): | Lacks ribosomes; synthesizes lipids and carbohydrates, and detoxifies drugs/alcohol (abundant in liver cells) |
| What do lysosomes do? | Digest worn‑out cell parts |
| What do peroxisomes break down? | Hydrogen peroxide → water + oxygen. |
| What does the cytoskeleton provide? | Structure, shape, transport - - Internal protein scaffolding that maintains cell shape and provides transport tracks |
| Rough ER | Rough Endoplasmic Reticulum |
| Smooth ER | Smooth Endoplasmic Reticulum |
| What is the plant cell wall made of? | Cellulose |
| What do chloroplasts do? | Photosynthesis |
| What is the function of the central vacuole? | Water storage and turgor pressure. |
| Why do Red Blood Cells (RBCs) lack nuclei? | To maximize oxygen transport. |
| What is the fluid mosaic model? | Flexible phospholipid bilayer with embedded proteins and cholesterol. |
| What passes freely through the membrane? | Small nonpolar molecules and hydrophobic substances. |
| What do MHC proteins do? | Help immune cells recognize self vs non‑self |
| Sperm Cells: | Feature an extensive flagellum powered by a surrounding battery of mitochondria |
| Cell Wall: | Rigid carbohydrate boundary containing plasmodesmata channels for communication |
| Chloroplasts: | Photosynthetic organelles containing green pigment to convert solar energy into sugars. Note: Plants contain both chloroplasts and mitochondria. |
| Central Vacuole: | Large fluid-filled organelle that stores water and maintains cellular turgor pressure. |
| Why are cristae folded? | Increase surface area for ATP production. |
| What are thylakoids? | Chloroplast membranes where photosynthesis occurs |
| What evidence supports endosymbiosis? | Double membranes, circular DNA, bacterial ribosomes, binary fission |
| What do intermediate filaments provide? | Strong structural support |
| What do microtubules act as? | Transport tracks |
| What do microfilaments do? | Provide shape and flexibility |
| What do centrioles organize? | Spindle fibers during cell division |
| What is the function of cilia? | Sweep particles/mucus |
| What is the function of flagella? | Propulsion |
| Phospholipid Bilayer: | Composed of polar, hydrophilic phosphate heads facing outward and nonpolar, hydrophobic fatty acid tails pointing inward. |
| Selective Permeability: | Allows small nonpolar molecules (such as dissolved gases) and hydrophobic substances to pass freely, while blocking hydrophilic and polar compounds. |
| Cholesterol: | Embedded within the bilayer to regulate fluidity and add structural stability |
| Membrane Proteins: | Transmembrane proteins form channels/tunnels for polar molecules and ions; cell surface proteins such as Major Histocompatibility Complex (MHC) aid in self versus non-self recognition by T cells |
| Ribosomes: | Non-membrane-bound complexes of ribosomal RNA (r RN A) and proteins that synthesize proteins; float freely in cytoplasm or attach to the rough ER. |
| Vacuoles: | Storage compartments enclosed by membrane. |
| Central Vacuole | Occupies most space in plant cells, storing water and dissolved solutes. |
| Contractile Vacuole: | Found in certain protists to pump out water and propel the cell. |
| Cilia: | Short, hair-like projections that move in waves to sweep trapped particles and mucus (e.g., lining the human trachea). |
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jsminnie118
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