Basic Chemistry
Why do atoms with incomplete outer shells tend to form chemical bonds?
To achieve stability by filling their valence shell to the full outer shell
Why does water stick to itself and climb the sides of a tube (cohesion and adhesion)?
Cohesion comes from hydrogen bonds between water molecules; adhesion comes from hydrogen bonds with other surfaces.
Why are condensation reactions necessary for building proteins and nucleic acids?
hey form covalent bonds between monomers by releasing water, creating polymers.
What structures are found in all cells, no matter what type?
Plasma membrane, ribosomes, cytoplasm, DNA.
What’s the basic structure of a cell membrane?
Phospholipid bilayer with embedded proteins and carbohydrates.
Why does oxygen form polar covalent bonds with hydrogen in water molecules?
Oxygen is more electronegative, pulling electrons closer and creating partial charges.
Why is ice less dense than liquid water at the molecular level?
Hydrogen bonds lock molecules in an open crystal structure, spacing them farther apart.
Why does protein folding depend on R group interactions?
R groups form hydrogen bonds, ionic bonds, and hydrophobic interactions that shape the protein.
Why do eukaryotes benefit from having organelles, while prokaryotes do not?
Organelles create specialized compartments for efficiency, which supports larger, more complex cells.
Which end of a phospholipid is hydrophilic, and which is hydrophobic?
Head = hydrophilic, tails = hydrophobic.
Why are ionic bonds weaker in water than in a dry crystal of salt?
Water’s polarity separates and stabilizes the ions, reducing attraction.
Why does water require more heat to change temperature compared to alcohol?
Hydrogen bonds must absorb energy before water molecules move faster.
Why can humans digest starch but not cellulose, even though both are made of glucose?
Starch has alpha-glucose linkages, which human enzymes can break, but cellulose has beta-glucose linkages, which they cannot.
What does the Golgi apparatus actually do for the cell?
Modifies, sorts, and ships proteins and lipid
How are passive diffusion, facilitated diffusion, and active transport similar and different?
Passive & facilitated move down gradients (facilitated uses proteins); active requires ATP to move against gradient.
Why does polarity determine whether a molecule can form hydrogen bonds?
Hydrogen bonds require partial charges from unequal electron sharing.
Why is water’s solvent property essential for biochemical reactions?
It dissolves ions and polar molecules, allowing collisions and reactions to occur inside cells.
Why do double bonds in unsaturated fatty acids make oils liquid at room temperature?
Double bonds create kinks that prevent fatty acid chains from packing tightly.
Which organelles (besides the nucleus) have their own DNA, and what does that tell us about their origin?
Mitochondria and chloroplasts, it supports endosymbiosis theory. .
Why does water move into a cell placed in a hypotonic solution?
Water moves toward higher solute concentration inside the cell to balance osmotic pressure.
Compare how ionic, polar covalent, and non-polar covalent bonds influence solubility in water.
Ionic and polar covalent compounds dissolve due to charge interactions; non-polar covalent compounds do not dissolve because they lack charges.
How does carbonic acid work as a buffer in the body?
It releases H⁺ when pH rises and binds H⁺ when pH drops, stabilizing blood pH.
What’s the difference between DNA nucleotides and RNA nucleotides?
DNA has deoxyribose and thymine, double-stranded; RNA has ribose and uracil, single-stranded.
What are the three types of cytoskeleton fibers, ranked by size, and what does each one do?
Microfilaments (smallest, shape/movement), Intermediate filaments (medium, structural support), Microtubules (largest, transport/division).
Why does active transport like the sodium-potassium pump, require ATP input?
It moves ions against their electrochemical gradient, which cannot occur without energy input.