Cellular Processes
(Biology AAC 25-26)
About the Cell Membrane
Provides protection and support
Controls entries and exits
This maintains internal balance
Selectively Permeable Membrane
Has pores that act as tunnels for particles to go through
Composed of a Lipid Bilayer: 2 layers of phospholipid proteins embedded in the membrane
Homeostasis: Balance of a state in an organism (e.g. body heat)
Cellular Transport
Passive Transport
Cell does not use energy
→There are three types:
Diffusion: Random Movement from High Conc. to Low Conc. until equilibrium is reached
Facilitated Diffusion: Particles move through the cell membrane through the help of proteins as transport
Transport proteins are selective
(Key term: Channel Protein)
Transports larger/bulkier molecules
Osmosis: Diffusion of water
Exclusively water
Moves through pores
*MOVES FROM HIGH → LOW
Active Transport
Cell uses energy
→There are three types:
Exocytosis
Forces material out of the cell in bulk
Endocytosis
Taking bulky material into a cell
Protein pumps
Transport proteins that require energy to do work
*MOVES FROM LOW → HIGH
Key Terms of this Topic
Hypotonic: Cell has lower concentrate of water in the solution; Cell expands through osmosis
Cytolysis: When Cell swells and bursts open.
Hypertonic: Cell has higher concentration of water than in the solution; Cell shrinks through osmosis
Plasmolysis: When Cell shrinks.
Isotonic: Cell and solution have an equal amount of concentration; No net change in Cell
Dynamic Equilibrium: Cell remains the same size; Water moves equally in both directions
Extra Information: How Organisms deal with Osmotic Pressure
Turgor Pressure: Pressure against Cell Walls due to Osmosis
Protists: Contractile Vacuoles collecting water coming in and pumps it out to prevent over-expanding
Salt-Water Fish: Use specialized gills to pump out salt and to not dehydrate.
Animal cells bathed in blood; Kidneys keep blood isotonic by removing excess salt/water.
Cell membrane model
Photosynthesis
Light Dependent Reaction
Formula: H2O + CO2 ——-Sun——→ C6 H12 O6
Chloroplasts in top side of leaves
Sun particles are called Photons
Summary
🔬 CELL MEMBRANE
Structure: Phospholipid bilayer + proteins
Function: Protects, supports, controls entry/exit
Selectively permeable: Only allows certain substances
🔁 CELLULAR TRANSPORT
Type | Subtype | Energy? | Direction | Protein Involved? | Notes |
|---|---|---|---|---|---|
Passive | Diffusion | ❌ | High → Low | No | Random movement |
Facilitated Diffusion | ❌ | High → Low | ✅ Channel Protein | For larger molecules | |
Osmosis | ❌ | High → Low (Water) | Sometimes | Water only | |
Active | Protein Pumps | ✅ | Low → High | ✅ Pump protein | Needs ATP |
Endocytosis | ✅ | Bulk In | ❌ | Cell engulfs material | |
Exocytosis | ✅ | Bulk Out | ❌ | Cell expels material |
💧 OSMOSIS TERMS
Solution Type | Water Movement | Cell Result |
|---|---|---|
Hypotonic | Into cell | Cell swells (cytolysis) |
Hypertonic | Out of cell | Cell shrinks (plasmolysis) |
Isotonic | Equal both ways | No size change (dynamic equilibrium) |
🌿 PHOTOSYNTHESIS
Formula:
CO₂ + H₂O + Light → C₆H₁₂O₆ + O₂Location: Chloroplast (leaves)
Light particles: Photons
🌊 HOW ORGANISMS HANDLE OSMOTIC PRESSURE
Organism / System | How It Manages Osmosis |
|---|---|
Plant Cells | Use turgor pressure (cell wall prevents bursting) |
Protists | Use contractile vacuoles to pump water out |
Saltwater Fish | Pump out salt via specialized gills |
Humans/Animals | Kidneys regulate water/salt to keep blood isotonic |
🧠 EXAM TIPS
Hypo = Hippo = Swell
Hyper = Shrink
Iso = Equal = No change
Osmosis = Water ONLY
Facilitated = Needs a channel
Active = Needs energy (ATP!)