Cell Bio 1

In contrast to yeast or bacterial cells, animal cell cultures are grown on fairly complex media, with added amino acids, vitamins, and/or hormones. This is primarily because animal cells

come from organisms that have specialized cell types.

A disulfide bond is formed between _______ residues.

cysteine

Enzymes act by

decreasing activation energy.

Cholesterol, a membrane lipid in animals, has a chemical structure similar to

estradiol.

A pseudogene is a

gene that arose through gene duplication, but after acquiring mutations became nonfunctional.

Phospholipids consist of a 3-carbon core to which two fatty acids and a phosphate group are linked. The most common 3-carbon core is

glycerol.

In the chromatin around centromeres, nucleosomes are present that have a unique structure in which the core protein _______ is replaced by _______, and this variant of the nucleosome is required for protein assembly at the kinetochore.

histone H3; CENP-A

Lipids with unsaturated fatty acids

increase fluidity of membranes.

Introducing a double bond into a fatty acid puts a(n) _______ into the conformation of the molecule.

kink

The coenzymes NAD+ and NADP+ are structurally related to the vitamin

niacin

The source of the atmospheric oxygen necessary for the development of oxidative metabolism is thought to have been

photosynthesis

Chloroplasts are thought to have originated from endosymbiosis of _______ by a large host cell.

photosynthetic eubacteria such as cyanobacteria

A centromere is a region of the chromosome that

plays a critical role in ensuring the correct distribution of duplicated chromosomes to daughter cells during mitosis.

Proteins must have more than one _______ to have a quaternary structure.

polypeptide chain

The original cell was thought to have arisen from the enclosure of self-replicating _______ by a phospholipid membrane.

protein RNA - correct DNA carbohydrate

Drosophila melanogaster was an organism of choice for the study of

the process of development.

Chymotrypsin, trypsin, elastase, and thrombin are all members of the serine protease family because each

uses the same catalytic mechanism involving the same key amino acids.

Coenzymes are chemically related to

vitamins.

The most abundant molecule in cells is

water

How many amino acids are commonly incorporated into proteins?

20

An E. coli cell under well-defined laboratory conditions divides about every

20 minutes.

The human genome is distributed among _______ chromosomes.

23

The percentage of the average human gene that encodes proteins is approximately

3%

The feature that most clearly separates eukaryotes from prokaryotes is the presence of _______ in eukaryotic cells.

A nucleus

The human genome contains only 20,000 to 25,000 actual gene sequences, yet the human genome can produce up to 100,000 gene products. Which of the following processes accounts for this difference?

Alternative splicing

Which statement about exons is false

An exon may contain sequences for small nucleolar RNAs.

Which transposable element accounts for ~21% of the human genome?

Long interspersed elements (LINEs)

Which of these organisms is not a unicellular eukaryote?

Methanococcus

The ENCODE project revealed that as much as 75% of the genome in humans is actually transcribed into RNA. Most of this is non-protein-coding RNA. Which of the following include two new classes of noncoding RNA discovered by the ENCODE project?

MicroRNA and lncRNA

Which of the following is the most commonly used mammal for genetic studies?

Mouse

Which statement about LINEs is false

Mutations induced by LINEs are exclusively harmful.

Which class of amino acids is buried within the folded structure of the protein?

Nonpolar

Extensive digestion of chromatin with micrococcal nuclease was found to yield particles called nucleosome core particles that appear as beads when viewed by electron microscopy. Which is not found in the nucleosome core particle?

One molecule of H1 protein

The α helix is an example of which level of protein structure?

Secondary

Which statement best describes the mechanism of action of miRNAs in blocking expression of proteins?

Single-stranded miRNA, in association with the RISC complex, binds to the complementary sequence in the 3ʹ UTR of mRNAs, blocking translation and inducing degradation of the mRNA.

What is the major carbohydrate-storage molecule in plants?

Starch

If a human gene is found to contain five introns, the mature mRNA encoded by that gene would have how many exons?

There could be multiple mRNAs that contain between one and six exons.

Which is not true of coenzymes

They are branched amino acids.

Which statement describes centromeric sequences in humans?

They consist of A/T-rich α-satellite DNA, spanning 1-5 million base pairs.

Which statement about introns is true?

Though they are part of a gene, they are absent from the corresponding mRNA.

Which base is not found in DNA?

Uracil

Which of the following is not one of the four major classes of organic molecules in the cell?

Water

The three-dimensional structure of a protein is analyzed most definitively by

X-ray crystallography.

Molecules that are partly water-soluble and partly water-insoluble are called

amphipathic

Enzymes affect the transition state of a chemical reaction by

binding to substrate(s). providing a surface on which reactions converting substrate to product can occur more rapidly. altering the conformation of substrate(s) to approach that of the transition state.

The genome of eukaryotes consists of genes derived from

both archaebacteria and bacteria.

All of the following are ways in which enzyme activity can be regulated except

by modulation of intracellular sucrose concentrations.