Chapter: The Cell Membrane – Review Questions

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They are all hydrophobic or mostly nonpolar molecules.
They are made of long hydrocarbon chains, which do not interact well with water.
Fats (triglycerides), phospholipids, and steroids.
Energy storage, insulation, and cushioning of organs.
Glycerol and fatty acids; fatty acids are hydrophobic.
A 3-carbon alcohol that forms the backbone of fats and phospholipids.
A long hydrocarbon chain with a carboxyl group at one end.
Butter has mostly saturated fats (straight chains pack tightly); oil has unsaturated fats (kinks prevent tight packing).
Saturated: no double bonds, straight chains.
Unsaturated: one or more double bonds, kinked chains.
Saturated fats pack more densely.
No double bonds, so enzymes act more slowly; tighter packing resists breakdown.
Monounsaturated: 1 double bond.
Polyunsaturated: multiple double bonds.
Cis: hydrogen on same side of double bond (kinked).
Trans: hydrogen on opposite side (linear).
Linear structure allows tight packing, like saturated fats.
Hydrophilic head and hydrophobic tail.
It is made of nonpolar fatty acid chains.
It contains a polar phosphate group that interacts with water.
Micelles, liposomes, and bilayers.
Four fused carbon rings; they vary by functional groups attached.
Cholesterol.
Regulate growth, development, and signaling (hormones).
Only certain molecules can cross freely, others need transport mechanisms.
Phospholipids and proteins.
The hydrophilic heads face the aqueous environment outside and inside the cell.
Passive: no energy, moves down concentration gradient.
Active: requires ATP, moves against gradient.
Active transport.
Active transport.
Diffusion.
Hypertonic: solute higher outside → water leaves.
Isotonic: equal solute → no net movement.
Hypotonic: solute lower outside → water enters.
Hypotonic.
Hypertonic.
Hypertonic (water will leave liposome).
Hypotonic (water will enter liposome).
Isotonic (no net movement).
Simple: directly through lipid bilayer.
Facilitated: via protein channels or carriers.
Small nonpolar molecules (O₂, CO₂, steroids).
Large or polar molecules (ions, glucose).
Facilitated: down gradient, no energy.
Active: against gradient, uses ATP.
Pinocytosis: non-specific uptake of fluids.
Receptor-mediated: specific molecules via receptors (more picky).
Approximately 3.5–4 billion years ago.
Abiogenesis from: 1) primordial soup, 2) hydrothermal vents, 3) RNA world hypothesis.
RNA.
Autotrophs: make own food.
Heterotrophs: consume others.
Thought to be heterotrophs (relied on pre-existing organic molecules).
1. Genetic material (DNA/RNA)
2. Cell membrane to enclose contents.