BIO 111 – Cell Structure, Function, and Energy: Comprehensive Study Notes

Cell Structure and Microscopy

Differences between Light Microscope (LM) and Electron Microscope (EM)

Microscopes are essential tools for visualizing cells and their components. Light and electron microscopes differ in their principles and capabilities.

• Light Microscope (LM): Uses visible light and glass lenses to magnify images. Magnification up to ~1,000–2,000x. Resolution is limited to ~200 nanometers due to the wavelength of light. Advantage: Can observe living cells and processes in real time.

• Electron Microscope (EM): Uses beams of electrons instead of light, and electromagnetic lenses. Resolution is much higher (~0.1–0.2 nanometers); can see subcellular structures like ribosomes or membranes. Limitation: Specimens must be killed, fixed, and placed in a vacuum.

Types of Electron Microscopy

• Transmission Electron Microscopy (TEM): Beam of electrons passes through a thin specimen; reveals internal structures in great detail.

• Scanning Electron Microscopy (SEM): Beam of electrons scans the surface of a specimen; produces detailed 3D images of surface structures.

Surface Area-to-Volume Ratio

The surface area-to-volume ratio affects cell function. As cells grow, volume increases faster than surface area, making it harder for nutrients, oxygen, and waste to diffuse in and out efficiently. Cells often adopt special shapes (long and thin) to maximize this ratio.

Cell Theory and Types of Cells

Main Points of the Cell Theory

• All living organisms are composed of one or more cells.

• Cells are the basic unit of structure and function in organisms, and all cells arise from pre-existing cells by cell division.

Major Types of Cells

• Prokaryotic cells: Small, simple cells without a nucleus or membrane-bound organelles (e.g., bacteria, archaea). DNA is in the nucleoid region.

• Eukaryotic cells: Larger, more complex; have a true nucleus (surrounded by a membrane) and membrane-bound organelles (e.g., animals, plants, fungi, protists).

• Similarities: Both have DNA, ribosomes, cytoplasm, and a plasma membrane.

Cell Structure and Organelles

Parts of a Prokaryotic Cell

• Plasma membrane

• Cytoplasm

• DNA (nucleoid region)

• Ribosomes (make proteins)

• Cell wall (protection/structure; made of peptidoglycan in bacteria)

• Capsule (extra protective layer, in some bacteria)

• Pili (for attachment and DNA transfer)

• Flagella (for movement, in some species)

Parts of a Eukaryotic Cell

• Plasma membrane

• Nucleus (with nucleolus and chromatin)

• Cytoplasm

• Ribosomes

• Endoplasmic reticulum (rough and smooth)

• Golgi apparatus

• Mitochondria

• Lysosomes (animal only)

• Vacuoles (large in plants, small in animals)

• Chloroplasts (plants only)

• Cell wall (plants, fungi, some protists)

• Centrioles (animal only)

Functions of Key Organelles

• Nucleus: Stores DNA, controls cell activities.

• Nucleolus: Makes ribosome components.

• Cytoplasm: Site of reactions and organelles.

• Ribosomes: Protein synthesis.

• Rough ER: Produces proteins (due to ribosomes).

• Smooth ER: Lipid synthesis, detoxification, calcium storage.

• Golgi apparatus: Packages, modifies, and ships proteins and lipids.

• Lysosomes: Digestive enzymes for recycling/breaking down molecules.

• Mitochondria: Powerhouse; makes ATP via cellular respiration.

• Chloroplasts: Photosynthesis; makes ATP via solar energy.

• Vacuoles: Storage of water, nutrients, wastes. Central vacuole in plants maintains turgor pressure.

• Cytoskeleton: Shape, movement, transport inside cell (microtubules, microfilaments, intermediate filaments).

• Cilia/Flagella: Movement (cilia = short, many; flagella = long, few).

• Centrioles: Organize microtubules for cell division in animals.

Organelles Unique to Animal Cells

• Lysosomes

• Centrioles

Organelles Unique to Plant Cells

• Chloroplasts

• Central vacuole

• Cell wall

Cytoskeleton and Its Functions

The cytoskeleton is a network of protein fibers (microtubules, microfilaments, intermediate filaments) that maintains cell shape, provides internal support, helps organelles move, aids in cell movement (cilia/flagella), and assists in cell division.

Plasma Membrane Structure and Function

Terms to Describe Plasma Membrane Structure

• Fluid mosaic model: The membrane is flexible ('fluid') and made up of many different components ('mosaic').

Components of Plasma Membrane

• Phospholipids (bilayer)

• Proteins (integral and peripheral)

• Cholesterol (stabilizes fluidity)

• Carbohydrates (glycoproteins, glycolipids – for recognition/signaling)

Function of Plasma Membrane

• Acts as a barrier, regulates what enters/exits (selectively permeable), communicates with environment, and helps maintain homeostasis.

What Makes Rough ER 'Rough'

• Ribosomes attached to its surface give it a rough appearance.

Cellular Respiration and Energy

Where Does Oxygenated Cellular Respiration Happen?

• In the mitochondria (glycolysis in cytoplasm, Krebs cycle and ETC in mitochondria).

Three Stages of Cellular Respiration

1. Glycolysis (cytoplasm)

2. Citric Acid Cycle / Krebs Cycle (mitochondrial matrix)

3. Electron Transport Chain & Chemiosmosis (inner mitochondrial membrane)

Products of the Three Stages

• Glycolysis: 2 ATP, 2 NADH, 2 pyruvate

• Krebs cycle: CO2, NADH, FADH2, ATP

• ETC: NADH/FADH2 + O2 → ATP, H2O

Energy Molecule for Our Cells

• ATP (adenosine triphosphate): Stores energy in its phosphate bonds and releases energy when converted to ADP + Pi.

Structure of ATP

• Nitrogenous base (adenine) + ribose (sugar) + three phosphate groups.

ATP Cycle

• Energy from food is used to add a phosphate to ADP, making ATP.

• ATP → ADP + Pi when energy is needed for cellular work.

• Continuous cycle of energy capture and release.

Producers/Autotrophs

• Organisms that make their own food (via photosynthesis or chemosynthesis). Examples: plants, algae, some bacteria.

Consumers/Heterotrophs

• Organisms that obtain energy by eating other organisms. Examples: animals, fungi, protozoa.

Aerobic Respiration

• Breakdown of glucose in the presence of oxygen to produce ATP, CO2, and H2O.

How Fermentation Differs from Respiration

• Fermentation (anaerobic) does not yield as much ATP and occurs without oxygen.

• Respiration (aerobic) yields much more ATP and requires oxygen.

Formulas

• Aerobic respiration: $\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 + 6\mathrm{O}_2 \rightarrow 6\mathrm{CO}_2 + 6\mathrm{H}_2\mathrm{O} + \sim36\text{–}38\ \mathrm{ATP}$

• Alcohol fermentation: $\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 \rightarrow 2\ \mathrm{ethanol} + 2\ \mathrm{CO}_2 + 2\ \mathrm{ATP}$

• Lactic acid fermentation: $\mathrm{C}_6\mathrm{H}_{12}\mathrm{O}_6 \rightarrow 2\ \mathrm{lactate} + 2\ \mathrm{ATP}$

Alcohol Fermentation vs Lactic Acid Fermentation

• Alcohol fermentation: Occurs in yeast, produces ethanol and CO2.

• Lactic acid fermentation: Occurs in muscle cells and some bacteria, produces lactate, no CO2.

Cellular Respiration

• The process of extracting energy (ATP) from glucose through glycolysis, Krebs cycle, and ETC.

What Factor Controls Glucose Breakdown?

• Presence or absence of oxygen.

Reactants/Products of Stages

• Glycolysis: Glucose → 2 pyruvate, 2 ATP, 2 NADH

• Krebs cycle: Pyruvate (acetyl-CoA) → CO2, NADH, FADH2, ATP

• ETC: NADH/FADH2 + O2 → ATP, H2O

Final Electron Receptor in ETC

• Oxygen (O2).

NAD+ and FAD

• Coenzymes that carry high-energy electrons to the ETC (NADH and FADH2).

Approximate ATP Yield of Aerobic Respiration

• 36–38 ATP per glucose molecule.

Where Each Stage Occurs

• Glycolysis: Cytoplasm

• Krebs cycle: Mitochondrial matrix

• ETC: Inner mitochondrial membrane (cristae)

Differences Between Anaerobic and Aerobic Organisms

• Anaerobic organisms: Survive without oxygen, rely on fermentation or anaerobic respiration.

• Aerobic organisms: Require oxygen for respiration, more energy-efficient.

Chemiosmosis

• The process in which hydrogen ions (protons) flow back across a membrane through ATP synthase, driving the production of ATP.

Photosynthesis and Plant Cell Structure

Why Are Plants Green?

• Chlorophyll absorbs red and blue wavelengths of light but reflects green light.

Chloroplast

• Plant organelle where photosynthesis occurs. Contains its own DNA and ribosomes.

Parts of a Chloroplast

• Outer membrane

• Inner membrane

• Stroma (fluid)

• Thylakoids (flattened sacs)

• Grana (stacks of thylakoids)

Where Reactions Occur in Chloroplast

• Light-dependent reactions: Thylakoid membranes

• Calvin cycle (light-independent): Stroma

Products of Photosynthesis

• Glucose (C6H12O6) and oxygen (O2).

NADP+

• Electron carrier in photosynthesis; becomes NADPH when it picks up electrons and hydrogen.

Products of Light-Dependent Reactions

• ATP, NADPH, and O2 (from splitting water).

Products of Calvin Cycle

• Glucose (C6H12O6).

Examples of Plants (Different Pathways)

• C3 plants: Rice, wheat, soybeans (most plants).

• C4 plants: Corn, sugarcane, sorghum.

• CAM plants: Cacti, pineapple, succulents (adapted to deserts).

Organelle	Function	Present in
Nucleus	Stores DNA, controls cell activities	All eukaryotes
Chloroplast	Photosynthesis	Plants, algae
Mitochondria	Cellular respiration (ATP production)	All eukaryotes
Lysosome	Digestion, recycling	Animals
Central vacuole	Storage, turgor pressure	Plants

Additional info: These notes expand on the original review sheet by providing definitions, examples, and context for each topic, ensuring a self-contained study guide suitable for exam preparation in General Biology.