MCAT BIO FLASHCARDS

Amino acids consist of a ______, ______ group, and a variable ______ group.

Carbonyl, amino, R

What type of bond links amino acids together?

Peptide bond

The acidic amino acids are ______ and ______.

Glutamate (Glu), Aspartate (Asp)

The basic amino acids are ______, ______, and ______.

Histidine (His), Arginine (Arg), Lysine (Lys)

What type of bond is formed between two cysteine amino acids?

Disulfide bond

A cysteine that forms a disulfide bond is now called a ______.

Cystine

What is the primary structure of a protein?

Linear sequence of amino acids

The two main types of secondary protein structures are ______ and ______.

Alpha-helices, Beta-sheets

A beta-sheet can be arranged in ______ or ______ formation.

Parallel, Anti-parallel

What interactions are involved in tertiary protein structure?

Van der Waals forces, Disulfide bonds, Hydrophobic interactions, Hydrogen bonds

The interactions between different protein subunits make up ______ structure.

Quaternary

What are the five forces involved in quaternary structure?

Non-covalent interactions, Van der Waals forces, Hydrogen bonds, Electrostatic interactions, Disulfide bonds

What are the simplest forms of carbohydrates called?

Monosaccharides

Two monosaccharides linked together form a ______ via a ______ bond.

Disaccharide, Glycosidic

What are carbohydrates composed of more than two monosaccharides called?

Oligosaccharides (few), Polysaccharides (many)

______ uses an alpha-glycosidic linkage, while ______ uses a beta-glycosidic linkage.

Glycogen, Cellulose

The three major functions of lipids are ______, ______, and ______.

Energy storage, Cell membrane barrier, Precursor to steroid hormones

What are the components of a fatty acid?

Carboxyl group, Long hydrocarbon chain

Saturated fatty acids contain ______ double bonds, while unsaturated fatty acids contain ______ double bonds.

No, One or more

What are the components of a triglyceride?

Glycerol backbone, Three fatty acids

Phospholipids are composed of ______, ______, and ______.

Glycerol, Two fatty acids, Phosphate group

What is the function of phospholipids in a membrane?

Form bilayers that serve as the structural basis of cell membranes

______ are the building blocks of steroids.

Cholesterol

What are terpenes composed of?

Isoprene units

A monoterpene consists of ______ isoprene units, a sesquiterpene has ______, and a diterpene has ______.

Two, Three, Four

__________ are modified terpenes with additional functional groups.

Terpenoids

Steroids have a ______ ring structure based on ______.

Tetracyclic, Cholesterol

Phosphate is also known as ______.

Orthophosphate

What do two orthophosphates form when linked together?

Pyrophosphate

The bonds linking phosphates are called ______ and store ______ energy.

Anhydride linkages, High

What are the three components of a nucleotide?

Ribose/deoxyribose sugar, Nitrogenous base, 1-3 phosphate groups

The nitrogenous bases are divided into ______ (double rings) and ______ (single rings).

Purines, Pyrimidines

Which bases are purines?

Adenine (A), Guanine (G)

Which bases are pyrimidines?

Cytosine (C), Thymine (T), Uracil (U)

DNA strands are linked by ______ bonds and run in ______ directions.

Hydrogen, Antiparallel

What is the basic unit of chromatin?

Nucleosome

What are the building blocks of DNA?

Nucleotides

DNA consists of a sugar-phosphate backbone and complementary base pairs held together by ______ bonds.

Hydrogen

What is the difference between a purine and a pyrimidine?

Purines have two rings (Adenine, Guanine), while pyrimidines have one ring (Cytosine, Thymine, Uracil)

DNA strands are always synthesized in the ______ direction.

5’ to 3’

What type of helix does DNA form according to the Watson-Crick model?

Right-handed double helix

In eukaryotes, DNA is stored in ______ chromosomes, while in prokaryotes, DNA is found in ______ chromosomes.

Linear, Circular

What enzyme in prokaryotes supercoils DNA to fit inside the cell?

DNA gyrase

Eukaryotic DNA is wrapped around proteins called ______, forming ______.

Histones, Nucleosomes

What is the difference between heterochromatin and euchromatin?

Heterochromatin is densely packed and transcriptionally inactive, while euchromatin is loosely packed and active

The region of a chromosome where spindle fibers attach during cell division is called the ______.

Centromere

What are telomeres, and what is their function?

Repetitive DNA sequences at chromosome ends that prevent loss of genetic material during replication

A ______ is a single base pair difference in the genome, while a ______ is a variation in the number of copies of a segment of DNA.

SNP (Single Nucleotide Polymorphism), CNV (Copy Number Variation)

What are tandem repeats?

Short sequences of nucleotides repeated one after another, often found in centromeres and telomeres

The central dogma of molecular biology states that ______ is transcribed into ______, which is then translated into ______.

DNA, RNA, Protein

What are the three stop codons, also known as nonsense codons?

UAA, UAG, UGA

The genetic code is ______, meaning multiple codons can code for the same amino acid.

Degenerate

DNA replication occurs during the ______ phase of the cell cycle.

S (Synthesis) phase

What enzyme unwinds the DNA double helix during replication?

Helicase

What is the function of single-strand binding proteins (SSBPs)?

They prevent DNA strands from re-annealing during replication.

The enzyme ______ synthesizes new DNA strands by adding nucleotides in the ______ direction.

DNA Polymerase, 5’ to 3’

What is the role of primase in DNA replication?

It synthesizes short RNA primers to provide a starting point for DNA polymerase.

The leading strand is synthesized ______, while the lagging strand is synthesized in short fragments called ______.

Continuously, Okazaki fragments

What enzyme connects Okazaki fragments on the lagging strand?

DNA Ligase

The enzyme ______ prevents excessive supercoiling by cutting and rejoining the DNA strands.

Topoisomerase

What is the function of telomerase?

It extends the telomeres at the ends of chromosomes to prevent loss of genetic material.

DNA replication is ______, meaning each new DNA molecule consists of one old strand and one new strand.

Semiconservative

What are mutagens?

Agents that cause mutations in DNA.

Ionizing radiation can cause DNA damage by breaking ______.

Both single and double strands of DNA

What type of mutation occurs when a single base pair is substituted?

Point mutation

A ______ mutation results in a codon that codes for a different amino acid.

Missense

What is a nonsense mutation?

A mutation that creates a premature stop codon.

A ______ mutation does not change the amino acid sequence.

Silent

What type of mutation results from the addition or deletion of nucleotides, shifting the reading frame?

Frameshift mutation

______ mutations occur naturally, while ______ mutations are caused by external factors.

Spontaneous, Induced

What are transposons?

Mobile genetic elements that can move within the genome and cause mutations.

A pair of transposons in the same direction can cause a ______, while transposons facing each other can cause an ______.

Deletion, Inversion

What is direct reversal in DNA repair?

A process where damage is directly undone without cutting the DNA, such as UV damage repair.

Homology-dependent repair relies on the fact that DNA is ______ stranded.

Double

What is the function of excision repair?

It removes and replaces defective bases before DNA replication.

Mismatch repair corrects errors in DNA ______ replication.

After

What is homologous recombination in double-strand break repair?

A process that uses a sister chromatid as a template to accurately repair broken DNA.

Nonhomologous end joining directly connects broken DNA ends but is ______ prone.

Error

What enzyme synthesizes RNA from a DNA template?

RNA Polymerase

In prokaryotes, RNA polymerase binds to the ______ box at the promoter region.

Pribnow

What are the three major types of RNA?

mRNA (messenger), rRNA (ribosomal), tRNA (transfer)

In eukaryotes, the process of removing introns from pre-mRNA is called ______.

Splicing

What is the role of the 5’ cap and poly-A tail in eukaryotic mRNA?

They protect mRNA from degradation and help with translation.

What are the three steps of translation?

Initiation, Elongation, Termination

Translation occurs in the ______ of both prokaryotic and eukaryotic cells.

Cytoplasm

What is the role of tRNA in translation?

It carries amino acids to the ribosome and matches them with the correct mRNA codons.

The ribosome has three sites: ______, ______, and ______.

A (Aminoacyl), P (Peptidyl), E (Exit)

What is wobble pairing?

The ability of the third base in a tRNA anticodon to pair flexibly with different codons.

In prokaryotes, translation starts at the ______ sequence, while in eukaryotes it starts at the ______ sequence.

Shine-Dalgarno, Kozak

What is the function of peptidyl transferase in translation?

It forms peptide bonds between amino acids.

Termination of translation occurs when a ______ codon enters the ribosome.

Stop

What energy molecule is required for translation?

GTP

Gene expression can be controlled at the ______, ______, or ______ levels.

DNA, RNA, Protein

How does DNA methylation affect gene expression?

It silences genes by blocking transcription factors.

In female mammals, one X chromosome is randomly inactivated, forming a ______ body.

Barr

What is an operon?

A cluster of genes controlled by a single promoter in prokaryotes.

The lac operon is an ______ system that is activated when ______ is present.

Inducible, Lactose

What is the trp operon?

A repressible operon that is turned off when tryptophan is present.

Eukaryotic transcription factors regulate gene expression by binding to ______ regions.

Promoter or enhancer

What is RNA interference (RNAi)?

A process where small RNA molecules degrade or block mRNA translation.