Unit 1
What type of bond forms when electrons are shared between atoms?
Covalent bond
What type of cell lacks membrane-bound organelles?
Prokaryotic cell
What type of molecule speeds up chemical reactions without being consumed?
Enzyme
What is the first step of a signal transduction pathway?
Reception
What term describes different versions of the same gene?
Alleles
Why is water considered a polar molecule?
Oxygen is more electronegative than hydrogen, causing unequal electron sharing
Which organelle is responsible for ATP production in eukaryotic cells?
Mitochondrion
What is the term for the minimum energy required to start a reaction?
Activation energy
During which phase of the cell cycle is DNA replicated?
S phase
What law states that allele pairs separate during gamete formation?
Law of Segregation
What property of water allows it to resist rapid temperature changes?
High specific heat
What is the primary function of the phospholipid bilayer in the cell membrane?
It creates a selectively permeable barrier
Where do the light-dependent reactions of photosynthesis occur?
Thylakoid membranes of the chloroplast
How do phosphorylation cascades amplify a signal inside a cell?
Each activated kinase activates multiple downstream proteins, increasing the response
What is the genotype of an organism that has two different alleles for a trait?
Heterozygous
How do buffers help maintain homeostasis in living organisms?
They resist changes in pH by absorbing or releasing H⁺ ions
Why do cells rely on membrane-bound compartments to increase efficiency?
Compartmentalization separates incompatible reactions and increases surface area for metabolic processes
Explain how the electron transport chain produces ATP during cellular respiration.
Electrons release energy as they move through the chain, pumping protons across the membrane; the resulting proton gradient drives ATP synthase to produce ATP
Explain how checkpoints regulate the cell cycle and prevent uncontrolled cell division.
Checkpoints monitor DNA integrity, cell size, and spindle attachment; if conditions are unfavorable, the cycle is halted or apoptosis is triggered
How does independent assortment increase genetic variation?
Alleles of different genes segregate independently during meiosis, creating new allele combinations
Explain how hydrogen bonding in water contributes to ice floating and the survival of aquatic life.
Hydrogen bonds space water molecules farther apart in ice, making it less dense than liquid water, which insulates aquatic environments
Explain how the surface-area-to-volume ratio limits cell size.
As a cell grows, volume increases faster than surface area, reducing efficiency of material exchange across the membrane
Compare the role of proton gradients in photosynthesis and cellular respiration.
Both processes use proton gradients across membranes to drive ATP synthesis via ATP synthase, though they occur in different organelles and use different energy sources
Describe how a G-protein–coupled receptor transmits a signal from outside to inside the cell.
Ligand binding activates the receptor, which activates a G protein, triggering a second messenger pathway that leads to a cellular response
Predict the phenotypic ratio of a monohybrid cross between two heterozygous organisms and explain why it occurs.
3:1 dominant to recessive, because alleles segregate equally during gamete formation