Cell Structure & Function
What is the basic unit of life in all living organisms?
Cells
Which macromolecule is made up of amino acids?
Proteins
What is the molecule that stores genetic information?
DNA
What do enzymes do to activation energy in chemical reactions?
They lower activation energy
What is contact inhibition?
Contact inhibition is a regulatory mechanism that prevents cells from dividing once they touch neighboring cells.
What structure is made up of a lipid bilayer and controls what enters and exits the cell?
Cell Membrane
What are ionic, covalent, metallic, and hydrogen bonds?
Ionic Bonds = Transfer of electrons ( M and NM )
Covalent Bonds = Sharing of electrons ( Two NM's )
Metallic Bonds = Sea of electrons ( M and M )
Hydrogen Bonds = Bonds with F, O, or N
In the central dogma, what process converts DNA into RNA?
Transcription
What molecule is the universal energy currency in cells?
ATP (adenosine triphosphate)
Tumor suppressor genes are essential for controlling cell growth. Describe how they regulate the cell cycle and what happens when their function is lost.
They produce proteins that monitor DNA damage, slow or stop the cell cycle to allow for repair, or trigger apoptosis if the damage is too severe.
How does the structural diversity of glycoproteins affect the way cells interact with their environment, especially during immune responses?
It allows for cell-specific signaling and recognition, enabling immune cells to distinguish self from non-self.
How can a single amino acid change due to a mutation alter the structure and function of a protein, and what are the consequences at the molecular level?
It can disrupt folding by altering charge, polarity, or size, leading to changes in protein shape, loss of function, or aggregation, which can impair biological processes or cause disease.
Unlike DNA polymerase, RNA polymerase does not require a primer to begin synthesis. Explain the molecular basis for this difference and how it reflects their roles in gene expression.
RNA polymerase can initiate RNA synthesis de novo using promoter sequences, while DNA polymerase requires a pre-existing 3’-OH because it’s designed for high-fidelity replication rather than regulated gene expression.
In a phospholipid bilayer, which part of the phospholipid molecule is hydrophilic and which is hydrophobic, and how does this arrangement contribute to membrane formation?
The phosphate “head” group is hydrophilic (water-attracting), while the fatty acid “tails” are hydrophobic (water-repelling); this causes phospholipids to arrange into bilayers with heads facing outward toward water and tails tucked inward away from water, forming stable cell membranes.
Describe how the amphipathic nature of phospholipids leads to membrane formation and explain the thermodynamic principles behind this self-assembly.
Phospholipids self-assemble into bilayers in aqueous environments to minimize free energy; hydrophobic tails cluster away from water, while hydrophilic heads interact with it, stabilizing the membrane structure.
Both transcriptional regulation and alternative splicing control gene expression. Compare their roles and explain how they contribute to protein diversity in complex organisms.
Transcriptional regulation determines whether a gene is turned on or off, while alternative splicing produces multiple proteins from one gene by rearranging exons; together they enable complex, tissue-specific expression patterns.
How do reversible epigenetic modifications like DNA methylation and histone acetylation regulate gene expression, and why are they significant in development and disease?
These modifications alter chromatin accessibility; methylation typically silences genes, while acetylation promotes transcription. Their reversibility allows dynamic gene control but can lead to disease if dysregulated.