Chapter 10.2

Chapter 3 Study Guide: Cell Structure and Function

1. Cell Theory – Three Main Tenets

• All living organisms are made up of one or more cells.

• The cell is the most basic unit of structure and function in living things.

• All cells originate from pre-existing cells.

2. Universal Features of Cells

All cells (prokaryotic and eukaryotic) share the following features:

• Plasma membrane: Controls what enters and exits the cell.

• Cytoplasm: Jelly-like substance that holds cellular contents.

• Ribosomes: Sites of protein synthesis.

• Genetic material (DNA/RNA): Carries instructions for cellular activities.

3. Eukaryotic Internal Membrane System

Included in the membrane system:

• Nuclear envelope

• Endoplasmic Reticulum (Rough and Smooth)

• Golgi apparatus

• Lysosomes

• Endosomes

• Transport vesicles

• Plasma membrane

• Peroxisomes

• Vacuoles

Not included:

• Mitochondria

• Chloroplasts
  (Note: These have their own membranes and are involved in energy transformation.)

4. Cell Membrane Structure

• Composed of a phospholipid bilayer with embedded proteins, carbohydrates, and cholesterol.

  • Phospholipid bilayer:

    • Hydrophilic heads face outward toward water.

    • Hydrophobic tails face inward, away from water.

• Proteins: Transport, signal reception, cell recognition.

• Carbohydrates: Usually attached to proteins/lipids on the extracellular side for cell recognition.

• Cholesterol: Maintains fluidity and stability of the membrane.

5. Organelle Functions

• Nucleus: Stores genetic material; site of RNA synthesis.

• Rough ER: Studded with ribosomes; produces proteins for secretion or membrane insertion.

• Smooth ER: Lacks ribosomes; synthesizes lipids and detoxifies chemicals.

• Golgi Apparatus: Modifies, sorts, and packages proteins and lipids.

• Lysosomes: Digestive compartments; break down macromolecules and old organelles.

• Mitochondria: Generate ATP through cellular respiration.

• Chloroplasts: Conduct photosynthesis (plant cells).

• Peroxisomes: Detoxify harmful substances; involved in lipid metabolism.

6. Saturated vs. Unsaturated Fats

• Saturated fats: No double bonds; straight chains; solid at room temp.

• Unsaturated fats: One or more double bonds; kinked chains; liquid at room temp.

7. Active Transport

• Primary Active Transport: Uses ATP directly (e.g., sodium-potassium pump).

• Secondary Active Transport: Uses electrochemical gradients created by primary transport to move other substances.

8. Secretory Pathway of a Protein

1. Synthesized in rough ER

2. Packaged into transport vesicles

3. Modified in the Golgi apparatus

4. Packaged into secretory vesicles

5. Released by exocytosis through the plasma membrane

9. Cytoskeleton Components

• Microfilaments (Actin) – Structure, cell movement

• Intermediate Filaments – Strength, mechanical stability 🟠

• Microtubules – Transport, mitosis, cell structure 🟠

(🟠 = Provide structural support and stability)

10. Passive Transport Types

• Simple diffusion: Movement directly through the membrane.

• Facilitated diffusion: Uses channel or carrier proteins.

• Osmosis: Water movement through a semi-permeable membrane.

“Moving down a concentration gradient” means particles move from high to low concentration areas.

11. Dynamic Instability of Microtubules

• Microtubules constantly grow and shrink by adding/removing tubulin subunits, allowing quick cellular reorganization.

12. Role of Liposomes in Drug Delivery

• Liposomes mimic cell membranes and can merge with them to deliver drugs directly into the cytoplasm, often targeting specific cells.

13. Molecules Needing Transport Proteins

• Large, polar, or charged molecules (e.g., glucose, ions) cannot pass freely through the membrane and require channel or carrier proteins.

1. What are the three tenets of the Cell Theory?
• All organisms are made of one or more cells
• The cell is the basic structural and functional unit of life
• All cells originate from other existing cells

2. What components are found in ALL cells?

1. Cell membrane

2. Cytoplasm

3. Ribosomes

4. Genetic material (DNA or RNA)

3. Which organelles are included in the internal membrane system of eukaryotic cells? Which are not included?
Included: Nuclear envelope, endoplasmic reticulum (smooth and rough), Golgi apparatus, lysosomes, endosomes, vesicles, plasma membrane, vacuoles, and peroxisomes
Not included: Mitochondria and chloroplasts

4. Describe the structure of the cell membrane. Include all types of biological molecules and describe their location. Include which parts of the membrane are hydrophobic, and which are hydrophilic:
The cell membrane is made up of a double layer of phospholipids with embedded proteins, carbohydrates, and cholesterol. The phospholipid heads face outward and are hydrophilic, while the tails point inward and are hydrophobic. Proteins can span the membrane or sit on its surface, and carbohydrates are attached to proteins or lipids on the extracellular side, playing a role in cell recognition. Cholesterol is interspersed within the phospholipid bilayer to maintain fluidity.

5. List the functions for each of the following:
Nucleus – Directs cell activities and houses genetic material
Rough Endoplasmic Reticulum – Produces and modifies proteins for secretion or membrane insertion
Smooth Endoplasmic Reticulum – Synthesizes lipids and detoxifies harmful substances
Golgi Apparatus – Processes, packages, and distributes proteins and lipids
Lysosome – Breaks down waste materials and cellular debris
Mitochondrion – Produces energy (ATP) through cellular respiration
Chloroplast – Captures light energy to perform photosynthesis in plant cells
Peroxisome – Breaks down fatty acids and neutralizes toxic substances

6. What is the structural difference between saturated and unsaturated fats?
Saturated fats have no double bonds between carbon atoms, making their structure straight. Unsaturated fats contain one or more double bonds, causing bends or kinks in the fatty acid chains.

7. Describe primary and secondary active transport of the sodium-potassium pump:
Primary active transport uses ATP directly to move sodium out of the cell and potassium into the cell against their concentration gradients. Secondary active transport relies on the gradient created by the pump to move other substances indirectly, without using ATP at that moment.

8. Describe the path of a secretory protein (protein designed for export):
The protein is synthesized in the rough ER, modified and packaged in the Golgi apparatus, then transported in a vesicle to the cell membrane, where it is released outside the cell through exocytosis.

9. Which 3 components make up the cytoskeleton of animal cells? Circle the two of these that function in strength and stability.
• Microfilaments
• Intermediate filaments ⬅
• Microtubules ⬅

10. Describe the three types of passive transport discussed. What is meant by “moving down a concentration gradient”?
• Diffusion – movement of small or nonpolar molecules directly across the membrane
• Facilitated diffusion – uses proteins to help larger or polar molecules cross
• Osmosis – diffusion of water across a semipermeable membrane
“Moving down a concentration gradient” means substances move from an area of higher concentration to an area of lower concentration, without using energy.

11. What is dynamic instability of microtubules?
It refers to the rapid growth and shrinkage of microtubules by adding or removing tubulin subunits, allowing them to reorganize quickly as needed by the cell.

12. How do liposomes help drugs enter the cell?
Liposomes can merge with the cell membrane due to their lipid structure, allowing the enclosed drug to be delivered directly into the cell’s interior.

13. What type of molecules would most likely require a transport protein to get across the cell membrane?
Large, polar, or charged molecules such as glucose, amino acids, and ions typically need help from transport proteins to cross the membrane.