MCAT Bio Terms

cyclins

proteins that regulate the cell cycle that activate CDKs to phosphorylate proteins that promote the cell cycle phases

rough endoplasmic reticulum

organelle that is covered in ribosomes in order to fold and modify proteins

smooth endoplasmic reticulum

organelle that is responsible for lipid metabolism, steroid hormone synthesis, and detoxification

golgi apparatus

organelle responsible for modifying vesicles and sending them to their final destination in the cell

lysosomes

organelles responsible for breaking down materials in vesicles using hydrolytic enzymes and autophagy

peroxisomes

organelles responsible for neutralizing peroxides and breaking down fatty acids via beta oxidation

prophase

phase of mitosis in which the nuclear membrane disappears, the mitotic spindle forms, and chromosomes condense

metaphase

phase of mitosis in which spindle fibers line up the chromosomes along the middle of the cell

anaphase

phase of mitosis in which microtubules pull chromosomes apart

telophase

phase of mitosis in which the nuclear envelope and nucleoli reappear

cytokinesis

phase of mitosis in which the cytoplasm splits and the cell divides

mitosis

cell cycle in somatic cells in which identical diploid cells are made from one diploid parent cell

meiosis

cell cycle in germ cells in which different haploid cells are made from one diploid parent cell

coccus

sphere-shaped bacterium

bacillus

rod-shaped bacterium

spirillum

spiral-shaped bacterium

plasmids

circular DNA fragments in bacteria that contain non-essential genes such as resistance, virulence factors, etc.

gram positive cells

bacterial cells with cell walls containing a thick peptidoglycan layer that results in purple staining

gram negative cells

bacterial cells with cell walls containing a thin peptidoglycan later that results in pink staining and more resistance

transformation

method of gene transfer in which bacteria absorb DNA from the environment

transduction

method of gene transfer in which bacteria receive DNA from a viral infection

conjugation

method of gene transfer in which a plasmid is transferred between cells using a pilus

virion

fully assembled, infectious virus

positive sense RNA viruses

single-stranded RNA viruses that contain mRNA that can be directly translated into a protein upon infection

negative sense RNA viruses

single-stranded RNA viruses that contain RNA that is made into mRNA via RNA replicase before a viral protein can be made

retroviruses

RNA viruses that contain reverse transcriptase so that they can turn viral RNA into DNA that can be integrated into the host genome

lytic cycle

viral life cycle in which the virus rapidly replicates using the host cell’s machinery until a large amount of virions is made that can lyse the cell

lysogenic cycle

viral life cycle in which the viral DNA is integrated into the host DNA (now called a prophase/provirus) → can stop being dormant at any point and lyse the cell

viroids

RNA viruses that infect plants and bind complementary host RNA to silence gene expression

prions

misfolded proteins that cause other proteins to misfold and group together

nucleotides

nucleic acid monomers that are made up of a pentose sugar, a phosphate group, and a nitrogenous base

purines

nitrogenous bases that contain two rings

pyrimidines

nitrogenous bases that contain one ring

silent mutations

point mutations that involve the exact same amino acid being coded for

missense mutations

point mutations that involve a different amino acid being coded for

conservative mutations

missense mutations in which a similar amino acid is coded for, so protein folding isn’t impacted

nonconservative mutations

missense mutations in which a different amino acid is coded for, so protein folding is impacted

nonsense mutations

point mutations in which a codon is changed into a premature stop codon

aneuploidy

having an abnormal number of chromosomes due to nondisjunction during cell division

base excision repair

mechanism of DNA repair for single base, small-scale mutations

nucleotide excision repair

mechanism of DNA repair for larger mutations

penetrance

percent of individuals with a given genotype who display the corresponding phenotype

law of segregation

law that allele pairs segregate randomly from each other into gametes

law of independent assortment

law that alleles for separate traits are independently inherited

stabilizing selection

selection that favours the intermediate phenotype

directional selection

selection that favours one of the extreme phenotypes

disruptive selection

selection that favours the extreme phenotypes over the intermediate one

genetic drift

change in a gene pool due to random chance → population bottleneck and founder effect

divergent evolution

evolution of two species from a common ancestor

convergent evolution

evolution of two un-related species to get the same trait

totipotent cells

stem cells that can differentiate into any type of cell (in early embryos only)

pluripotent cells

stem cells that are limited to differentiating into endoderm, mesoderm, or ectoderm cells

multipotent cells

stem cells that are limited to differentiating into cells within one type of germ layer (endoderm, mesoderm, or ectoderm)

apoptosis

programmed cell death

positive control

gene expression control in prokaryotes in which the gene isn’t expressed unless an activator binds to the regulator

negative control

gene expression control in prokaryotes in which the gene is expressed unless a repressor is bound to the operator

promoters

upstream DNA sequences that initiate transcription in eukaryotes

enhancers

DNA sequences that increase transcription in eukaryotes when bound by activators

silencers

DNA sequences that decrease transcription in eukaryotes when bound by repressors

oncogenes

mutated genes that promote division and oncogenesis

tumor suppressor genes

genes that restrict division and suppress oncogenesis

endocrine cells

cells that release signalling products to other organs using the circulatory system

exocrine cells

cells that release signalling products into ducts to communicate with local cells

merocrine cells

exocrine cells that release signalling products via exocytosis (also called eccrine cells)

apocrine cells

exocrine cells that release signalling products via membrane budding

holocrine cells

exocrine cells that release signalling products via membrane rupture and cell lysis

tropic hormones

signalling molecules that act of endocrine glands to signal the release of other signalling molecules

non-tropic hormones

signalling molecules that are direct and act on the target tissue to induce change

peptide hormones

hormones that are hydrophilic, made of amino acid chains, and have rapid but short term effects

steroid hormones

hormones that are lipophilic, made of the 4 ring structure of cholesterol, and have late onset but long term effects

anterior pituitary

endocrine gland that receives hormonal input from the hypothalamus via the hypophyseal portal and releases LH, FSH, GH, ACTH, TSH, prolactin, and endorphins

posterior pituitary

endocrine gland that receives neural input from the hypothalamus and releases ADH and oxytocin

insulin

hormone released by the pancreas that lowers blood glucose levels

glucagon

hormone released by the pancreas that raises blood glucose levels

cortisol

hormone released by the adrenal cortex that increases blood glucose levels and is associated with the long term stress response

epinephrine

hormone released by the adrenal medulla that increases blood glucose levels and is associated with the short term stress response

Sertoli cells

cells that do spermatogenesis

Leydig cells

cells that produce testosterone

morula

what is made when the zygote does cleavage and becomes a 16 cell mass

blasocyst

develops from the morula and contains a fluid-filled sac → implants itself into the uterine wall

gastrula

develops from the blastocyst once the three germ cell layers have developed

ectoderm

germ cell layer of the gastrula that later forms the skin, hair, nails, sweat glands, and the nervous system

mesoderm

germ cell layer of the gastrula that later forms the connective tissue (blood & bone), muscles, and gonads

endoderm

germ cell layer of the gastrula that later forms the lining of the gastrointestinal tract, the lungs, and the bladder

Mullerian duct

structure that forms the uterus and cervix over development

Wolffian duct

structure that later forms the male reproductive organs

ovarian cycle

cycle in females the involves releasing an ovum

follicular, ovulation, luteal

phases of the ovarian cycle

follicular phase

phase of the ovarian cycle in which the follicle develops as FSH levels gradually rise

ovulation

phase of the ovarian cycle in which the egg is released due to estrogen peaking, triggering LH levels to spike

luteal phase

phase of the ovarian cycle in which the follicle becomes the corpus luteum, which secretes estrogen and progesterone

uterine cycle

cycle in females that prepares the uterus for fertilization

menstruation, proliferative, secretory

three phases of the uterine cycle

menstruation

phase of the uterine cycle in which the uterine endometrium is shed

proliferative phase

phase of the uterine cycle in which a new uterine endometrium forms due to rising estrogen levels

secretory phase

phase of the uterine cycle in which the endometrium is ready for implantation due to progesterone released by the corpus luteum

hCG

hormone released by the embryo that maintains the corpus luteum so that it can continue releasing progesterone to keep the endometrium from shedding

surfactant

fluid covering the alveoli to decrease surface tension and prevent the lungs from collapsing

negative pressure respiration

respiration mechanism by which we inhale when our diaphragm contracts, which expands the thoracic cavity and the lungs, so the increase in volume decreases the pressure and brings air in

hemoglobin

four-subunit molecule in erythrocytes that use iron ions to bind oxygen (cooperative binding!)