Cell Biology Exam 1

True or False? During the cell cycle, most cell growth occurs during interphase.

true

True or False? Eukaryotic cells have both nuclear and non-nuclear DNA.

true

True or False? Endocytosis is commonly used to add new membrane at cellular wound sites.

false

True or False? Truncating mutations (i.e., mutations that cause an early stop codon) are more likely to lead to a gain of function than a loss of function.

false

A DNA replication fork is shown below. The strand labeled ‘1’ is called the … strand.

lagging. It’s 3’ end is on the left, and the 5’ end is at the fork. So it polymerizes (5’ to 3’) in a direction opposite to the fork.

Using genetic engineering, a student has fused an ER signal sequence to a toxic protein whose cytosolic expression leads to cell lysis but is harmless when in the ER. This student has also fused a mitochondrial signal sequence to another protein that is required in the cytosol for cell viability but is inactive when in mitochondria. Whereas wild-type cells die upon the expression of these fusion proteins, she has been able to identify viable mutants, which have a loss-of-function mutation in a gene encoding a protein involved in transmembrane transport. The products of these genes are probably ...

B. involved in the transport of proteins into mitochondria, but not in the transport of proteins into the ER.

• The mutation would need to stop mitochondrial import for the cell to live. Import of the protein into the ER should remain intact because cytosolic expression of this protein causes cell lysis but it is harmless in the ER.

Fundamental unit of life. Small, membrane-enclosed units filled with a concentrated aqueous solution of chemicals and endowed with the extraordinary ability to create copies of themselves by growing and then dividing in two.

Cell

America's first cell biologist. He said “the key to every biological problem must finally be sought in the cell; for every living organism is, or at some time has been, a cell.”

E.B. Wilson

Deoxyribonucleic acid. Has sugar-phosphate backbone & hydrogen-bonded base pairs = nucleotide.

AT (double bonded) and CG (triple bonded).

DNA

Single strand of DNA or RNA whose nucleotide sequence acts as a guide for the synthesis of a complementary strand.

Template

This requires transcription of DNA to RNA and translation of RNA to protein.

Gene Expression

Uses ribose. Uses C, G, and A, but replaces T with U (uracil). Single-stranded. Can exert functions itself (like ribosomal RNA, tRNA, microRNA) or serve as messengers (mRNA) that code for protein production.

RNA

The major macromolecular constituent of cells. A linear polymer of amino acids linked together by peptide bonds in a specific sequence.

Protein

Copying of one strand of DNA into a complementary RNA sequence by the enzyme RNA polymerase.

Transcription

Process by which the sequence of nucleotides in an mRNA molecule directs the incorporation of amino acids into protein. Occurs on a ribosome.

Translation

The segment of DNA sequence corresponding to a single protein, a set of protein variants, or a single catalytic, regulatory, or structural RNA

gene

The membrane that surrounds a living cell.

plasma membrane

The passing on of characteristics from one generation to the next.

heredity

A molecule that can be bonded to other identical molecules to form a polymer.

monomer

A large molecule made of monomers

polymer

a sugar molecule (monosaccharide) with at least one phosphate group attached

sugar phosphate

the fundamental building block of nucleic acids like DNA and RNA, composed of three parts: a phosphate group, a five-carbon sugar (ribose or deoxyribose), and a nitrogenous base (Adenine, Guanine, Cytosine, Thymine, or Uracil)

nucleotide

the linkage of monomers into a polymer

polymerization

sugar in RNA

ribose

sugar in DNA

deoxyribose

One way RNA differs from DNA. RNA is primarily single-stranded. The term is…

strandedness

Nucleotide bases

Cytosine, guanine, thymine, uracil, adenine

nucleotide triplets that specify amino acids

codon

free-energy carriers

adenosine triphosphate (ATP)

Cellular membranes are composed of ______ molecules – they have one part that is hydrophilic (water-soluble), and another that is hydrophobic

amphiphilic

water soluble

hydrophilic

water insoluble

hydrophobic

An organic compound made entirely of hydrogen (H) and carbon (C) atoms

hydrocarbon

____have a membrane-enclosed nucleus that houses DNA. Single-celled or multicellular. Larger genomes (in humans: ~25000 genes). Also have more non-coding DNA.

Eukaryotes

__have no distinct nucleus (bacteria & archaea). Predominantly single-celled. Simple genomes (1000-6000 genes). Smallest is M. genitalium (~500 genes). Little internal compartmentalization.

prokaryotes

A single, organized layer of amphiphilic (water-loving head, water-fearing tail) phospholipid molecules that spontaneously forms at an interface, like air and water, with hydrophilic heads in the water and hydrophobic tails pointing out, acting as a simplified model for studying cell membrane components and interactions

phospholipid monolayer

the fundamental structure of cell membranes, consisting of two layers of phospholipid molecules arranged with their water-loving (hydrophilic) heads facing outward and water-fearing (hydrophobic) tails facing inward, creating a semipermeable barrier that controls substance movement in and out of the cell

phospholipid bilayer

Help get things in and out. They are embedded in the phospholipid bilayer.

transporters

What are the three domains of life?

bacteria, archaea, eukaryotes

Heritable change in the nucleotide sequence of a chromosome.

mutation

a genetic event where a segment of DNA, containing one or more genes, gets copied, creating extra identical or similar gene copies within a genome

gene duplication

The acquisition by an organism of genetic information by transfer, for example via the agency of a virus, from an organism that is not its parent and is typically a member of a different species.

horizontal gene transfer

Genes that are related by descent. There are two types. Disrupting homologous genes in different species often causes similar phenotypes (observable traits)

Homologs / homologous genes

genes in two separate species that derived from the same ancestral gene

orthologs

Related genes in the same genome that resulted from gene duplication

paralogs

the membrane-bound organelle in eukaryotic cells that acts as the cell's control center, housing the cell's genetic material (DNA) organized into chromosomes, and directing crucial activities like growth, metabolism, and reproduction

nucleus

degradation center

lysosome

energy hub ; Membrane-bounded organelle, about the size of a bacterium, that carries out oxidative phosphorylation and produces most of the ATP in eukaryotic cells.

mitochondria

sorting organelle ; Extensive, net-like membrane-bounded compartment in the cytoplasm of eukaryotic cells, where lipids are synthesized and membrane-bound proteins and secretory proteins are made.

ER

cytoskeleton components ; dynamic protein fibers made of actin monomers, forming a crucial part of the eukaryotic cytoskeleton that dictates cell shape, enables movement (like crawling or muscle contraction), and facilitates intracellular transport and division, working with motor proteins like myosin to create force and movement.

actin

Mechanism in which a cell engulfs and internalizes an external particle

phagocytosis

organelles which perform photosynthesis may have originated by a similar mechanism

chloroplast

examples of prokaryotes?

E. coli

examples of eukaryotes?

yeasts like S.cerevisiae and S.pombe

examples of plants?

Arabidopsis

examples of invertebrates?

c.elegans and Drosophila

essential cell division cycle regulator ; acting as master regulators by phosphorylating other proteins to drive transitions between cell cycle phases

CDK (Cyclin-Dependent Kinase)