Biology 2

Prokaryotic Cells

Simple single-celled organisms lacking a membrane-bound nucleus; DNA in nucleoid with 70S ribosomes and peptidoglycan cell walls.

Eukaryotic Cells

Complex single-celled or multicellular organisms with a membrane-bound nucleus linear DNA and 80S ribosomes.

Plant Cells

Rigid cellulose cell wall large central vacuole and chloroplasts for photosynthesis; fixed rectangular shape.

Animal Cells

Flexible shape lacking cell walls and chloroplasts; contain small temporary vacuoles centrioles and lysosomes.

Endosymbiotic Theory

Host cell engulfed aerobic bacteria that evolved into mitochondria forming a mutually beneficial relationship.

Fluid Mosaic Model

Plasma membrane is a dynamic fluid bilayer of phospholipids embedded with proteins carbohydrates and cholesterol.

Phospholipid Bilayer

Hydrophilic phosphate heads face outward; hydrophobic fatty acid tails face inward to form a non-polar core.

Integral Proteins

Transmembrane proteins spanning the lipid bilayer to function as channels or carriers.

Peripheral Proteins

Surface-attached proteins functioning in cell signalling and structural support.

Cholesterol (Membrane)

Regulates membrane fluidity

Glycoproteins & Glycolipids

Surface carbohydrates that function in cell recognition adhesion and immune responses.

Passive Transport

Movement of substances down their concentration gradient (high to low) without cellular energy (ATP).

Simple Diffusion

Direct movement of small non-polar molecules through the phospholipid bilayer.

Facilitated Diffusion

Movement of large or polar molecules (glucose ions) across the membrane using specific protein channels or carriers.

Osmosis

Net movement of water across a semi-permeable membrane from low solute concentration to high solute concentration.

Active Transport

Movement of substances against their concentration gradient (low to high) requiring ATP and carrier proteins.

Isotonic Solution

Equal solute concentration inside and outside cell; results in no net water movement.

Hypertonic Solution

Higher solute concentration outside cell; water leaves cell causing animal cells to crenate (shrivel) and plant cells to plasmolyse.

Hypotonic Solution

Lower solute concentration outside cell; water enters cell causing animal cells to lyse (burst) and plant cells to become turgid.