Cell Membrane Structure and Function in Biology

Saturated Fat

No double bonds; maximum hydrogen content.

Unsaturated Fat

Contains one or more double bonds; forms kinks.

Fluid Mosaic Model

Membrane structure with embedded proteins in bilayer.

Cholesterol

Stabilizes animal cell membranes at varying temperatures.

Phospholipid Bilayer

Two layers of phospholipids forming cell membranes.

Freeze-Fracture Microscopy

Technique revealing protein distribution in membranes.

Peripheral Membrane Proteins

Located on membrane surface; isolated with detergents.

Integral Membrane Proteins

Span the membrane; isolated with high salt buffers.

Diffusion

Molecules move along concentration gradient directly.

Facilitated Diffusion

Transport via carrier and channel proteins.

Active Transport

Molecules move against gradient using ATP.

Secondary Active Transport

Cotransport driven by primary active transport.

Hydrophobic Tails

Fatty acid chains that affect membrane fluidity.

Temperature Effects

Lower temps reduce membrane fluidity and permeability.

Concentration Gradient

Difference in concentration across a membrane.

Carrier Proteins

Bind solutes, change shape to transport them.

Channel Proteins

Form hydrophilic channels for molecule passage.

Phospholipid Mobility

Lateral movement contributes to membrane fluidity.

Hydrogen Bonds

Interactions that stabilize membrane structure.

Kinks in Chains

Result from double bonds in unsaturated fats.

Animal Cell Membrane

Contains cholesterol for stability and fluidity.

Plant Cell Membrane

Contains phytosterols instead of cholesterol.

Fungal Cell Membrane

Contains ergosterols instead of cholesterol.

Osmotic Conditions

Effects on cells vary with solute concentration.

Solids at Room Temperature

Saturated fats typically remain solid at room temp.

Fluidity and Permeability

Affected by fatty acid chain length and saturation.

Homogenization

Process to isolate membrane proteins using buffers.

Hypotonic

Water rushes into the cell, causing lysis.

Isotonic

Cell maintains normal conditions, balanced water movement.

Hypertonic

Free water leaves cell, causing it to shrivel.

Turgor Pressure

Pressure from water in plant cells, maintaining structure.

Lysed Cell

Cell that bursts due to excess water intake.

Wilted Cell

Cell lacking turgor pressure, appears shriveled.

Plasmolysis

Cell membrane pulls away from cell wall in plants.

Ion Channels

Facilitated diffusion without conformational change.

Carrier Proteins

Facilitated diffusion with conformational change.

Sodium-Potassium Pump

Transports sodium out, potassium into animal cells.

Phagocytosis

Cell engulfs particles, forming vacuoles.

Pinocytosis

Cell takes in liquids via coated vesicles.

Receptor Mediated Endocytosis

Specific macromolecules bind to receptors for uptake.

Exocytosis

Secretion of molecules from the cell.

LUCA

Hypothetical ancestor of all life forms.

Central Dogma

Process of DNA to RNA to protein.

Ribosomes

Cell structures that synthesize proteins.

ATP

Energy currency used by all cells.

Surface Area to Volume Ratio

Critical for efficient material exchange in cells.

Prokaryotic Cells

Cells without a nucleus, includes Bacteria and Archaea.

Eukaryotic Cells

Cells with a nucleus and membrane-bound organelles.

Bacteria

Domain of prokaryotic cells with unique features.

Archaea

Domain of prokaryotic cells, often extremophiles.

Metabolic Activity

Biochemical processes essential for cell survival.

Cell Membrane

Regulates material passage in and out of cells.

Bacteria

Single-celled prokaryotic microorganisms.

Archaea

Prokaryotes distinct from bacteria, often extremophiles.

Cell Wall

Rigid outer layer providing structural support.

Peptidoglycan

Polymer forming bacterial cell walls.

Pseudopeptidoglycan

Similar to peptidoglycan, found in Archaea.

Cell Membrane

Phospholipid bilayer controlling substance entry.

Linear fatty acids

Fatty acids with straight chains in membranes.

Branched fatty acids

Fatty acids with branched chains in membranes.

RNA Polymerase

Enzyme synthesizing RNA from DNA template.

Translation

Process of synthesizing proteins from mRNA.

N-formylmethionine

First amino acid in bacterial protein synthesis.

Methionine

First amino acid in eukaryotic protein synthesis.

Prokaryotes

Organisms without a membrane-bound nucleus.

Eukaryotes

Organisms with a membrane-bound nucleus.

Nucleoid

Region containing prokaryotic DNA, not membrane-bound.

Plasmids

Small DNA molecules independent of chromosomal DNA.

Cytoskeleton

Network providing structural support in cells.

Nucleus

Membrane-bound organelle containing genetic material.

Nucleolus

Site of ribosome subunit production within nucleus.

Ribosomes

Non-membrane structures for protein synthesis.

Smooth Endoplasmic Reticulum

Site for lipid synthesis and detoxification.

Rough Endoplasmic Reticulum

Studded with ribosomes; synthesizes secretory proteins.

Golgi Apparatus

Modifies and sorts proteins from the ER.

Peroxisome

Organelle for fat breakdown and detoxification.

Lysosome

Digestion and recycling center in animal cells.

Mitochondria

Powerhouse of the cell; ATP synthesis.

Chloroplasts

Site of photosynthesis in plant cells.

Vacuole

Storage organelle, large in plant cells.

Cytosol

Fluid component of the cytoplasm, site of glycolysis.

Endosymbiotic Theory

Theory explaining origin of mitochondria and chloroplasts.

Signal Sequences

Short amino acid chains directing protein transport.

Signal Sequence

Directs protein import into cellular organelles.

Co-Translational Import

Simultaneous protein synthesis and ER transport.

Signal Recognition Particle (SRP)

Binds signal sequence, guiding proteins to ER.

Golgi Apparatus

Sorts and tags proteins for cellular destinations.

Cis Face

Entry point for proteins in the Golgi.

Mannose-6-Phosphate

Tag for lysosomal protein delivery.

Pulse-Chase Experiment

Tracks protein movement using isotopic labeling.

14C Leucine

Isotope used in pulse phase of experiment.

Photographic Emulsions

Reveal protein locations as black or silver dots.

Microfilaments

7 nm wide, made of actin, support cell shape.

Intermediate Filaments

8-12 nm wide, provide structural support.

Microtubules

25 nm wide, hollow tubes of tubulin dimers.

Myosin

Motor protein that interacts with actin filaments.

Dynein

Moves cilia/flagella by walking on microtubules.

Kinesin

Transports vesicles along microtubules using ATP.

Centrosome

Microtubule organizing center in animal cells.

Cell Shape Maintenance

Cytoskeleton resists tension and compression forces.