Chp.8 Cells 2B Summary & Study Notes

• Topic: cell structure, function, and how substances move across cell boundaries.
• Purpose: build from the tiniest ideas (what a cell is) to full systems (organelles, membrane architecture, transport, and levels of organization).
• How to use these notes: read top → down; stop at any section and quiz yourself with the practice problems at the end.

Discovery & Cell Theory 🔬

• Start small: a cell is the smallest living unit that can carry out life processes.
• Early tools: microscopes let scientists see cells for the first time.
  • Anton van Leeuwenhoek: invented an improved single-lens microscope and saw microscopic life.
  • Robert Hooke: viewed cork slices and coined the word “cell” for the box-like structures.
• The Cell Theory — three core ideas, each simple:
  1. All living things are made of one or more cells.
  2. Cells are the basic units of structure and function in living things.
  3. New cells come from existing cells (cells divide to produce new cells).
• Key terms (memorize 2–3): cell, cell theory

Cell Types: Prokaryotes vs Eukaryotes 🧬

• Smallest pieces: presence/absence of a nucleus separates the two major cell types.
• Prokaryotes (simple):
  • No nucleus; DNA is not enclosed by a membrane.
  • Small and generally single-celled (all bacteria).
  • Contain: cell membrane, cytoplasm, ribosomes, often a cell wall.
  • Key term: prokaryote
• Eukaryotes (complex):
  • Have a true nucleus that contains DNA.
  • Larger, can be single-celled or multicellular (plants, animals, fungi, protists).
  • Contain organelles (specialized internal structures).
  • Key term: eukaryote
• Things both share: cell membrane, cytoplasm, ribosomes, DNA.

Eukaryotic Cell Structure & Organelles 🧫

• Organelles = “tiny organs” inside eukaryotic cells; each has a specific job.
• Nucleus:
  • Function: controls cell activities and stores DNA.
  • Parts: chromatin (DNA + proteins), chromosomes (condensed chromatin), nucleolus (makes ribosomes), nuclear envelope with nuclear pores (lets materials in/out).
  • Key term: nucleus
• Ribosomes:
  • Function: synthesize proteins.
  • Location: free in cytoplasm or attached to rough ER.
• Endoplasmic Reticulum (ER):
  • Rough ER: has ribosomes; makes proteins for export or membrane use.
  • Smooth ER: makes lipids and detoxifies (e.g., liver cells).
• Golgi apparatus:
  • Function: modifies, sorts, and packages proteins and lipids for storage or export.
• Lysosomes:
  • Function: contain enzymes to break down macromolecules and clean up the cell.
• Vacuoles:
  • Function: storage of water, salts, proteins, carbohydrates. Large central vacuole common in plant cells.
• Mitochondria:
  • Function: produce ATP (cellular energy) via cellular respiration.
  • Key term: mitochondrion
• Chloroplasts:
  • Function: perform photosynthesis (convert sunlight into chemical energy) in plants and some protists.
  • Key term: chloroplast
• Quick location rule: animal cells have lysosomes and centrioles; plant cells have cell walls, chloroplasts, and large central vacuoles.

Cytoskeleton & Movement 🦴

• Purpose: gives cells shape, internal organization, and the ability to move parts.
• Two main fibers:
  • Microtubules:
    • Provide shape and tracks for organelle movement.
    • Make cilia (short, hair-like projections) and flagella (long, whip-like) for cell movement.
    • Form centrioles (help organize cell division in animal cells).
  • Microfilaments:
    • Thin fibers used for cell movement and structural support.

Cell Membrane: Structure & Proteins 🧩

• Basic idea: cell membrane separates the internal cell from the environment and controls traffic.
• Built from a double layer of phospholipids:
  • Each phospholipid: polar (water-attracting) head and nonpolar (water-repelling) tails.
  • Tails face inward; heads face the watery inside and outside.
  • Key term: phospholipid bilayer
• Fluid Mosaic Model:
  • Membrane is fluid (molecules move laterally) and mosaic (many components: lipids, proteins, carbohydrates).
  • Key term: fluid mosaic model
• Membrane proteins and roles:
  • Channel proteins: allow specific molecules to cross.
  • Receptor proteins: detect signals and transmit information into the cell.
    • Key term: receptor proteins
  • Surface marker proteins with attached carbohydrates: identify the cell (cell “name tags”).
  • Structural/anchor proteins: attach to cytoskeleton for shape and support.
• Other components:
  • Cholesterol: stabilizes membrane fluidity, especially at low temperatures.
  • Carbohydrates: often attached to proteins (glycoproteins) for recognition.

Transport Across Membranes 🚰

• Two broad categories:
  • Passive transport: no energy required; molecules move from high concentration to low concentration.
    • Diffusion: general movement of molecules down a concentration gradient.
      • Key term: diffusion
    • Osmosis: diffusion of water across a selectively permeable membrane.
      • Key term: osmosis
    • Facilitated diffusion: diffusion of larger or charged molecules through protein channels.
  • Active transport: requires cellular energy (ATP); moves substances from low concentration to high concentration (against gradient).
    • Key term: active transport
• Osmotic solutions (how water moves):
  • Isotonic: equal solute concentration inside and out → no net water movement.
  • Hypotonic: lower solute concentration outside → water moves into cell → cell swells; plant cells gain turgor pressure.
  • Hypertonic: higher solute concentration outside → water moves out → cell shrinks.
• Bulk transport mechanisms (large materials):
  • Endocytosis: cell takes in material by forming vesicles from the membrane.
    • Phagocytosis: “cell eating” — engulfs large particles or cells.
    • Pinocytosis: “cell drinking” — takes in liquids or dissolved substances.
  • Exocytosis: vesicles fuse with membrane to export materials (secretion of hormones, waste removal).

Specialization & Levels of Organization 🧩

• Unicellular vs multicellular:
  • Unicellular: single cell performs all life functions (many prokaryotes; some eukaryotes like yeast).
  • Multicellular: many specialized cells that depend on each other (plants, animals).
• Cell specialization:
  • Cells differentiate to perform a specific job (e.g., muscle cells contract; red blood cells carry oxygen).
• Levels of organization (simplest → most complex):
  1. Cell
  2. Tissue (group of similar cells working together)
  3. Organ (groups of tissues performing specific functions)
  4. Organ system (groups of organs working together)
  5. Organism

Practice Problems: Multiple-choice + step-by-step solutions ✅

• Instructions: read the question, identify the key fact, eliminate wrong answers, choose best answer.

Problem 1 (Slide 33)

Which states that new cells are produced from?

• a. nonliving material. b. existing cells. c. cytoplasm. d. animals. Solution:

1. Cell theory says new cells arise from existing cells.
2. That matches answer (b).
3. Therefore, correct answer: b.

Problem 2 (Slide 34)

Who first used the term "cell"?

• a. Schleiden b. Margulis c. Leeuwenhoek d. Hooke Solution:

1. Robert Hooke observed cork and called the structures "cells".
2. Therefore, correct answer: d.

Problem 3 (Slide 35 / 55)

Why do electron microscopes show more detail than light microscopes?

• a. can be used with live organisms. b. light microscopes can't examine thin tissues. c. electron wavelengths are longer. d. electron wavelengths are shorter. Solution:

1. Resolution improves with shorter wavelengths.
2. Electrons have much shorter wavelengths than visible light.
3. Therefore, correct answer: d.

Problem 4 (Slide 36)

Which organism is a prokaryote?

• a. protist b. bacterium c. fungus d. plant Solution:

1. Prokaryotes = bacteria (no nucleus).
2. Bacterium is the only prokaryote listed.
3. Therefore, correct answer: b.

Problem 5 (Slide 37)

One way prokaryotes differ from eukaryotes is:

• a. contain DNA b. have cell membrane c. do not have membrane separating DNA d. are usually larger and more complex Solution:

1. Both types contain DNA and have membranes; prokaryotes lack a nucleus.
2. Prokaryotes do not have a membrane separating DNA from the rest of the cell.
3. Therefore, correct answer: c.

Problem 6 (Slide 38 / 58)

In the nucleus, DNA is usually visible as:

• a. nucleolus b. nuclear envelope c. chromatin d. chloroplasts Solution:

1. DNA bound to proteins in nucleus appears as chromatin (granular).
2. Chromatin condenses into chromosomes during division.
3. Therefore, correct answer: c.

Problem 7 (Slide 39)

Two functions of vacuoles: storing materials and helping to:

• a. break down organelles b. assemble proteins c. maintain homeostasis d. make new organelles Solution:

1. Vacuoles store water and solutes and help regulate cell's internal environment.
2. That is maintaining homeostasis.
3. Therefore, correct answer: c.

Problem 8 (Slide 40)

Chloroplasts are found in:

• a. plants only b. plants and some other organisms c. all eukaryotes d. most prokaryotes Solution:

1. Chloroplasts occur in plants and some protists (e.g., algae).
2. Therefore, correct answer: b.

Problem 9 (Slide 41)

Which is NOT a function of the Golgi apparatus?

• a. synthesize proteins b. modify proteins c. sort proteins d. package proteins Solution:

1. Golgi modifies, sorts, and packages proteins; it does not synthesize proteins (ribosomes do).
2. Therefore, correct answer: a.

Problem 10 (Slide 42)

A function of the cytoskeleton is:

• a. manufacture organelles b. assist in movement of some cells c. release energy d. modify/sort/package proteins Solution:

1. Cytoskeleton provides shape and assists in movement.
2. Therefore, correct answer: b.

Problem 11 (Slide 43)

Unlike a cell wall, a cell membrane:

• a. is composed of lipid bilayer b. provides rigid support c. allows most small molecules easily d. is found only in plants/fungi/prokaryotes Solution:

1. Cell membrane is a lipid bilayer and is flexible; cell wall gives rigid support.
2. Statement (a) correctly describes membrane vs wall.
3. Therefore, correct answer: a.

Problem 12 (Slide 44)

Concentration of a solution is defined as:

• a. volume of solute in mass of solution b. mass of solute in volume of solution c. mass of solution in volume of solute d. volume of solution in mass of solute Solution:

1. Concentration = amount (mass or moles) of solute per unit volume of solution.
2. That is “mass of solute in a given volume of solution.”
3. Therefore, correct answer: b.

Problem 13 (Slide 45)

If substance more concentrated outside than inside and can move through membrane, it will:

• a. move from inside to outside b. remain outside c. move from outside to inside d. cause water to enter by osmosis Solution:

1. Diffusion moves substances from high → low concentration.
2. Substance is higher outside → it will move into the cell.
3. Therefore, correct answer: c.

Problem 14 (Slide 46)

Movement of materials against concentration difference is called:

• a. facilitated diffusion b. active transport c. osmosis d. diffusion Solution:

1. Against concentration gradient requires energy — this is active transport.
2. Therefore, correct answer: b.

Problem 15 (Slide 47)

Molecules diffuse across a membrane through protein channels is called:

• a. active transport b. endocytosis c. facilitated diffusion d. osmosis Solution:

1. Movement through protein channels without energy = facilitated diffusion.
2. Therefore, correct answer: c.

Problem 16 (Slide 48)

Cell specialization is characteristic of:

• a. bacteria b. all unicellular organisms c. yeasts d. multicellular organisms Solution:

1. Multicellular organisms have specialized cell types.
2. Therefore, correct answer: d.

Problem 17 (Slide 49)

Which cell is specialized for contraction?

• a. muscle cell b. red blood cell c. pancreatic cell d. nerve cell Solution:

1. Muscle cells contract to produce force and movement.
2. Therefore, correct answer: a.

Problem 18 (Slide 50)

The stomach is an example of a:

• a. tissue b. organ c. organ system d. organism Solution:

1. Stomach is made of multiple tissues and performs a specific function → organ.
2. Therefore, correct answer: b.

Problem 19 (Slide 51)

Order simplest → most complex:

• a. organ system, organ, cell, tissue b. tissue, cell, organ, organ system c. cell, tissue, organ, organ system d. cell, organ, tissue, organ system Solution:

1. Correct biological order: cell → tissue → organ → organ system.
2. Therefore, correct answer: c.

Problem 20 (Slide 52)

Which would contain greatest variety of specialized cells?

• a. an organ system b. a tissue c. an organ d. a multicellular organism Solution:

1. A multicellular organism contains many organs and systems and thus the greatest variety of specialized cells.
2. Therefore, correct answer: d.

• Final quick-check questions for study:

  • What are the three parts of the cell theory?
  • How do prokaryotic and eukaryotic cells differ in DNA location?
  • Which organelle produces ATP and which makes proteins?
  • Describe the phospholipid bilayer (head vs tail) in one sentence.
  • Give one example each of passive and active transport.

• Use these notes to quiz yourself aloud or draw a cell and label organelles; practice the multiple-choice problems until you can explain each answer in two sentences.