Molecular Biology: Enzymes and Ribosomes

In protein synthesis, the amino end (N-terminus) of an amino acid from the A-site tRNA is attached to the free carboxyl group (C-terminus) of the growing polypeptide chain linked to the P-site tRNA.

A type of protein transport that occurs through protein channels or pores in cell membranes, allowing the passage of molecules across the membrane without directly contacting the lipid bilayer.

A type of protein transport that occurs through transmembrane proteins embedded in the cell membrane, directly interacting with the lipid bilayer.

A type of protein transport that involves the movement of molecules within membrane-bound vesicles, which bud off from one organelle and fuse with another.

The movement of proteins from the cytoplasm into the nucleus.

The movement of proteins from the nucleus into the cytoplasm.

The process by which proteins are transported from the cytoplasm into the mitochondria.

Lysosomes are acidic organelles that play a crucial role in cellular digestion. They maintain a low pH (around 2.0 to 2.5), which is essential for the activity of their hydrolytic enzymes.

Different versions of the same gene that code for the same type of RNA or protein but have slightly different sequences.

The point on a chromosome where spindle microtubules attach during cell division.

Cells that have two sets of chromosomes, one set inherited from each parent.

The stage in mitosis where microtubules attach to the kinetochores, which are structures on chromosomes.

In a cross between a pure-breeding yellow plant and a pure-breeding green plant, 50% of the offspring will have green seeds.

A chromosome constitution that would never lead to a viable human baby is YY. Humans need at least one X chromosome for survival.

The possible blood types among the offspring of a couple with blood types AB and A are A, B, and AB.

Two phenotypically normal parents having a child with an autosomal recessive trait indicates that both parents are heterozygous for the trait. This means they each carry one copy of the recessive allele.

DNA polymerase is an enzyme that synthesizes DNA from a DNA template. RNA polymerase synthesizes RNA from a DNA template. The schematic shows the synthesis of RNA (messenger RNA) using a DNA template.

The amino group of the amino acid is NOT modified during the attachment to tRNA by aminoacyl-tRNA synthetase. Instead, the carboxyl group links to the 3' or 2' hydroxyl group of the tRNA.

The mRNA is read from the 5' end to the 3' end. The polypeptide chain is synthesized from the amino (N) terminus to the carboxyl (C) terminus.

The peptidyl transferase activity of the ribosome transfers the polypeptide chain from the P-site tRNA to the amino acid attached to the A-site tRNA.

During translation, the carboxyl end of the polypeptide chain is joined to the free amino group of the amino acid linked to the A-site tRNA, lengthening the polypeptide chain.

Aminoacyl-tRNA synthetases are specific for particular amino acids and their corresponding tRNAs. They charge the tRNA with the correct amino acid.

Reverse transcriptase is an enzyme that synthesizes DNA from an RNA template. The schematic shows RNA synthesis from DNA, not the other way around.

The schematic shows RNA polymerase synthesizing RNA from a DNA template. Topoisomerase is not directly involved in RNA synthesis.

A condition where an affected woman always inherits the disorder from her mother. This suggests a maternal inheritance pattern, often associated with mitochondrial inheritance or X-linked recessive inheritance.

Recombination refers to the exchange of genetic material between homologous chromosomes during meiosis. This process leads to new combinations of alleles on chromosomes, increasing genetic diversity.

Hershey and Chase used radioactive isotopes to label the protein and DNA of bacteriophages, then infected bacteria. They discovered that the radioactive DNA entered the bacteria, while the radioactive protein remained on the outside, proving that DNA was the heritable genetic material.

Telomeres and centromeres are specialized regions of chromosomes characterized by repetitive DNA sequences and heterochromatin. These regions are essential for chromosome stability and proper cell division.

Helicase, single-stranded binding proteins, and topoisomerase all work together to unwind and separate the DNA strands during replication, but primase lays down RNA primers to initiate DNA synthesis.

This is the process of converting a DNA sequence into a RNA sequence. In RNA, Thymine (T) is replaced with Uracil (U). The sequence of the complementary RNA strand is determined by base pairing rules.

Nonsense mutations alter a codon within a gene, changing it into a stop codon. This premature termination of protein synthesis results in a truncated, non-functional protein.

At neutral pH, serine's amino and carboxyl groups ionize, while its unique hydroxyl group remains unchanged.

A specialized enzyme found in human cells that helps maintain telomeres, the protective caps at the ends of chromosomes. It contains an RNA component acting as a template for DNA synthesis.

The leading strand is synthesized continuously 5' to 3' towards the replication fork, while the lagging strand is synthesized discontinuously in short fragments called Okazaki fragments, also in the 5' to 3' direction, but away from the fork.

The restriction point is a critical checkpoint in the G1 phase of the cell cycle where the cell decides whether to commit to cell division or not. It assesses the availability of nutrients and growth factors.

Meiosis II is the second division in meiosis, where sister chromatids separate, much like mitosis. It results in four haploid daughter cells, each with half the number of chromosomes as the parent cell.

The early endosome is a small, membrane-bound vesicle that forms when materials are taken into the cell via endocytosis. It sorts the cargo, preparing it for further processing.

The late endosome is a larger vesicle that matures from an early endosome. Its acidic environment activates enzymes and promotes the degradation of unwanted molecules.

Secretory vesicles are small, membrane-bound sacs that bud off from the trans Golgi network. These vesicles carry proteins and other molecules to the cell surface for secretion outside the cell.

The cis Golgi network (CGN) is a specialized region of the Golgi apparatus where newly synthesized proteins arrive from the endoplasmic reticulum (ER). It sorts and modifies proteins before they move further through the Golgi.