BIO 181 - Cells Exam 2

What are the three core principles of Cell Theory?

1. All living things are made of cells. 2. The cell is the basic unit of life. 3. New cells come from existing cells.

What is the main structural difference between Prokaryotes and Eukaryotes?

Eukaryotes have a membrane-bound nucleus and organelles; prokaryotes do not.

What four structures do ALL cells share?

Plasma membrane, cytoplasm, DNA, and ribosomes.

What three structures do plant cells have that animal cells lack?

Cell wall, large central vacuole, and chloroplasts.

Why are cells microscopic?

As a cell grows, its volume increases faster than its surface area, making diffusion inefficient.

What is the Endosymbiotic Theory?

Mitochondria and chloroplasts evolved from independent bacteria engulfed by an ancestral cell.

What are the primary differences between prokaryotic and eukaryotic cells?

Prokaryotic cells lack a membrane-bound nucleus and organelles; eukaryotic cells have a true membrane-bound nucleus.

How are cells organized hierarchically in multicellular organisms?

Cells form tissues, tissues form organs, and organs create organ systems.

Why is the surface-area-to-volume ratio a critical size limitation for cells?

If a cell gets too large, its plasma membrane won't support the rate of diffusion needed for its volume.

What is the difference between inductive and deductive reasoning?

Inductive reasoning uses specific observations to form a general conclusion; deductive reasoning uses general principles to predict specific results.

How are variables grouped during experimental data collection?

Independent variable is manipulated; dependent variable is measured; control group remains unaltered.

What is the role of Ribosomes?

They synthesize proteins.

What is the function of Lysosomes?

They digest waste and worn-out organelles using acidic enzymes.

What do Mitochondria and Chloroplasts do?

Mitochondria make ATP; Chloroplasts make glucose.

What happens to a human cell in a Hypertonic vs. Hypotonic solution?

In hypertonic, it shrivels; in hypotonic, it swells and bursts.

What are Aquaporins?

Specialized channel proteins that allow water to cross the membrane quickly.

What are the major components of cell theory?

All living organisms are composed of one or more cells. The cell is the basic unit of life. New cells arise from existing cells.

What are the similarities between prokaryotic and eukaryotic cells?

Both contain a plasma membrane, cytoplasm, double-stranded DNA, and ribosomes.

What are the differences between prokaryotic and eukaryotic cells?

Prokaryotes lack a nucleus and membrane-bound organelles; eukaryotes have a membrane-bound nucleus and specialized organelles.

What characteristics do all cells share?

Plasma membrane, cytoplasm, DNA, and ribosomes.

What are lysosomes and their function?

Membrane-bound spheres containing digestive enzymes that break down foreign pathogens and worn-out organelles.

What is the function of the rough endoplasmic reticulum (RER)?

Synthesis, folding, and structural modification of proteins.

What is the function of the smooth endoplasmic reticulum (SER)?

Synthesis of carbohydrates and lipids, detoxification, and calcium ion storage.

What are the major functions of mitochondria?

Perform cellular respiration, converting glucose into ATP and releasing carbon dioxide.

What are the major functions of chloroplasts?

Perform photosynthesis, capturing light energy to synthesize glucose and releasing oxygen.

What is the role of vacuoles in plant cells?

Regulate water concentration and maintain turgor pressure.

What is the function of peroxisomes?

Break down fatty acids and amino acids, and detoxify harmful substances.

What are the three types of fibers in the cytoskeleton?

Microfilaments, intermediate filaments, and microtubules.

What limits cell size?

Cells are limited by their surface-area-to-volume ratio.

What happens when a cell becomes too large?

Its surface area will lack the capacity to import nutrients and export wastes quickly enough.

What is the structure of the plasma membrane?

It consists of a phospholipid bilayer with hydrophilic heads facing outward and hydrophobic tails facing inward.

What role do phospholipids play in the plasma membrane?

They create a self-sealing barrier that separates the inside of the cell from the outside.

What is the glycocalyx?

It is a carbohydrate structure on the extracellular surface of the membrane, important for cell recognition.

What is the function of cholesterol in the plasma membrane?

Cholesterol acts as a fluidity buffer, preventing the membrane from becoming too stiff or too fluid.

What are the functions of membrane proteins?

They serve as transport channels, receptors, enzymes, and structural anchors.

What factors affect membrane permeability?

Size and polarity/charge of molecules influence their ability to cross the membrane.

What is osmosis?

It is the diffusion of water through a semipermeable membrane.

What happens to cells in hypotonic solutions?

Cells swell and may burst due to water influx.

What happens to cells in hypertonic solutions?

Cells shrink as water moves out into the surroundings.

What is the difference between a hypothesis and a theory?

A hypothesis is a testable explanation for a specific observation; a theory is a comprehensive explanation for a broad set of observations.

What is the purpose of a positive control in an experiment?

It confirms that the experimental setup is functioning correctly by expecting a known response.

What is the purpose of a negative control in an experiment?

It shows that the experiment does not produce false-positive results.

What do Ribosomes do?

They synthesize proteins.

Contrast Rough ER vs. Smooth ER functions.

Rough ER modifies proteins; Smooth ER makes lipids and detoxifies toxins.

What is the role of the Golgi Apparatus?

It sorts, tags, and packages proteins for transport.

What is the role of a Peroxisome?

It breaks down fatty acids and uses catalase to neutralize toxic hydrogen peroxide.

Describe the polarity of the Phospholipid Bilayer.

Phosphate heads are hydrophilic (face water); fatty acid tails are hydrophobic (hide inside).

What do Cholesterol and Carbohydrates do in the membrane?

Cholesterol buffers membrane fluidity; carbohydrates handle cell-to-cell recognition.

How do Saturated vs. Unsaturated fatty acid tails affect fluidity?

Saturated tails pack tightly (rigid); unsaturated kinks push apart (fluid).

What molecules cross the membrane by Simple Diffusion?

Small, nonpolar molecules (like O₂ and CO₂) that dissolve straight through.

How do Facilitated Diffusion and Active Transport differ?

Facilitated diffusion moves with the gradient using no ATP; active transport pumps against it using ATP.

Define Osmosis.

The diffusion of water through a semipermeable membrane toward higher solute concentrations.

Hypothesis vs. Scientific Theory.

A hypothesis is a specific, testable guess; a theory is a broad, heavily tested explanation.

Independent vs. Dependent variable.

Independent is what you manipulate; dependent is what you measure as a result.

Negative vs. Positive control.

Negative expects no result (prevents false positives); positive expects a known result (proves setup works).