Biology Unit 4: Cell Communication and Cycle

Study Notes

Unit 4: Cell Communication and Cell Cycle

Cell Membrane Components: The phospholipid bilayer forms a semi-permeable barrier. Proteins like channels/carriers facilitate molecule movement, while receptors enable cell signalling. Cholesterol maintains membrane fluidity. Carbohydrates act as cell identifiers (glycoproteins, glycolipids).

Fluid Mosaic Model

The cell membrane is a fluid structure with embedded proteins, allowing lipids and proteins to move laterally.

Selective Permeability

Small nonpolar molecules (oxygen, carbon dioxide) easily cross the membrane. Large, polar molecules need proteins or vesicles for transport.

Cell Wall Structure and Function

Plant cell walls are rigid due to cellulose. Fungi cell walls are strengthened by chitin. Bacterial cell walls are protected from osmotic pressure by peptidoglycan.

Maintaining Solute and Water Balance

Osmosis governs water movement. Aquaporins (proteins) facilitate water transport.

Molecule Size and Membrane Passage

Small molecules diffuse readily across membranes. Larger molecules require active transport or endocytosis.

Concentration Gradients

Passive transport (diffusion, facilitated diffusion) depends on concentration gradients. Active transport (sodium-potassium pump) goes against gradients, using ATP.

Ion and Molecule Transport

Channels and pumps maintain proper transport across membranes, e.g., proton pumps in mitochondria for ATP synthesis.

Prokaryotic vs. Eukaryotic Compartmentalization

Prokaryotes have little internal structure. Eukaryotes have specialized organelles for efficient cellular functions.

Organelle Structure and Function

Nucleus: DNA storage. Mitochondria: ATP production. Golgi Apparatus: protein modification and transport.

Subcellular Components and Functionality

Ribosomes: protein synthesis. Lysosomes: intracellular digestion.

Molecular Variations in Different Environments

Cells adapt to environmental needs, e.g., kidney cells have more aquaporins to reabsorb water.

Unit 5: Heredity

Surface Area-to-Volume Ratio: High ratios improve exchange efficiency; think gas exchange in the alveoli.
Specialized Exchange Structures: Microvilli increase intestinal absorption. Stomata facilitate gas exchange in leaves.
Enzyme Properties: Enzymes speed up reactions by lowering activation energy. They are affected by temperature, pH, and inhibitors.
Enzyme Roles: Enzymes break down substrates (e.g., amylase digests starch) and join substrates (e.g., DNA polymerase forms nucleotides).
Enzyme Function and Environment: High temperature denatures enzymes. pH changes alter enzyme active sites. Environmental factors impact enzyme function, for instance, pepsin functions in the acidic stomach.

Unit 6: Gene Expression and Regulation

Energy in Organisms: ATP is the primary energy currency for cells, driving muscle contraction and active transport.
Photosynthesis: Converts light energy into chemical energy (glucose), occurring in the chloroplast.
Light Capture: Light excites electrons in chlorophyll, storing energy as ATP and NADPH.
Energy Use from Biomolecules: Carbohydrates provide short-term energy, while lipids store energy long-term.
Membrane-Bound Organelles: Endoplasmic reticulum is involved in protein/lipid synthesis. Mitochondria facilitate cellular respiration.
Negative Feedback: Maintains homeostasis, like blood glucose regulation.
Energy Capture, Storage, and Use: ATP is generated during cellular respiration.
Molecular Variations: Different environments cause specific cellular adaptations.

Description

Explore crucial concepts in cell communication and the cell cycle through this quiz. Understand the structure and function of cell membranes, including the fluid mosaic model and selective permeability. Additionally, delve into the significance of cell walls in various organisms and the processes maintaining solute and water balance.