bio final flashcards

Central dogma

DNA → RNA → Proteins

DNA

Contains genetic information, has a double-helix structure, made up of nucleotides and deoxyribose

RNA

Aids in translation and transcription of gene expression, made up of ribose, usually single stranded and uses uracil instead of thymine

RNA polymerase

Catalyzes the synthesis of mRNA

Template strand

read by RNA polymerase to synthesize mRNA (3’ to 5’)

Coding strand

the non-template DNA strand that matches the resulting mRNA sequence (5’ to 3’)

Promoter

Where the RNA polymerase binds to during transcription

RNA is always synthesized in a ___

5’ to 3’ direction

Transcription factors

proteins that bind to specific DNA sequences to regulate gene expression and help the RNA polymerase bind to the promoter

TATA box

a sequence commonly found before the promoter and bound by a

transcription factor

Terminator

a specific DNA sequence that marks the end of a gene signaling RNA polymerase to cease transcription and release the newly synthesized RNA molecule

Where does transcription happen?

the nucleus

Where does translation happen?

The cytoplasm

Splicing

Process in eukaryotes where non-coding regions (introns) are removed from the pre-mRNA before it becomes mature mRNA

5’ modified guanine cap structure & 3’ poly-A tail

Features that protect the mRNA, facilitate export from nucleus, and stimulate

translation

Introns

Non-coding regions that are removed during splicing

Extrons

coding regions that are not removed during splicing

Codon

Three nucleotides that encode one amino acid

Transfer RNA (tRNA)

molecule that acts as the physical link between mRNA sequences and amino acids during protein synthesis

Anti codons

three-nucleotide sequence located on a transfer RNA (tRNA) molecule that bonds to a complementary messenger RNA (mRNA) codon during protein synthesis

Ribosome

Major site of protein synthesis, has a channel for mRNA to pass through and a catalytic site for addition of amino acids to the growing protein

P-site

Site in the ribosome that holds the tRNA molecule that is attached to the growing polypeptide chain during protein translation

A site

the first binding site in the ribosome where incoming aminoacyl-tRNAs—charged with amino acids—attach during protein translation, matching their anticodon to the mRNA codon

E site

the final binding site for tRNA in the ribosome during translation, allowing deacylated (empty) tRNA to exit after its amino acid is added to the growing polypeptide chain

Missense mutation

Point mutation that changes one nucleotide which changes the amino acid that is encoded

Nonsense mutation

Point mutation that accidently creates a stop codon

Silent mutation

Point mutation that changes a nucleotide but it doesn’t change the amino acid that is encoded

Insertion mutation

Frameshift mutation that adds an extra nucleotide

Deletion mutation

Frameshift mutation that deletes a nucleotide

Operon

A single promoter serves a set of functionally related genes using an ‘on & off’ switch, found in bacteria

Operator

Switch found in operons that can turn genes on or off by binding repressors or activators.

Repressor

A protein that binds to the operator and blocks the attachment of RNA polymerase

Corepressor

Proteins that bin to a repressor protein to inhibit gene transcription

Lac operon

an inducible operon and contains genes that code for enzymes that function in the metabolism of the sugar, lactose

Inducer

Binds to an operon to help promote it, inactivates the repressor so it can turn on

CRP

acts as an activator of transcription when glucose is scarce. Binds with cAMP (accumulates when glucose is low) and promotes transcription

When glucose and lactose are present in bacteria

Transcription for lac mRNA is off

When glucose is not present at all and lactose is

Transcription for lac mRNA is on

Differential gene expression

the expression of different genes by cells with the same genome

Genes within highly condensed heterochromatin are usually ________

not expressed

Histone acetylation

acetyl groups are attached to amino acids in histone tails. This generally loosens chromatin structure, promoting the initiation of

transcription

Methylation

Addition of methyl groups, can condense chromatin and lead to reduce transcription

Control elements

segments of noncoding DNA serve as binding sites for transcription factors that help regulate transcription

Activator

a protein that binds to an enhancer and stimulates transcription of a gene

Alternate splicing

different mRNA molecules are produced from the same primary transcript, depending on which segments are treated as exons and or introns

Cell differentiation

the process by which cells become specialized in structure and function

Morphogenesis

The physical processes that give an organism its shape

Cytoplasmic determinants

maternal substances in the egg that influence early development

Induction

signal molecules from embryonic cells cause transcriptional changes in nearby target cells

Determination

commits a cell irreversibly to its final fate

Apoptosis

Programmed cell death

Pattern formation

the development of a spatial organization of tissues and organs

Positional Formation

the molecular cues that control pattern formation, tells a cell its location relative to the body axes and to neighboring cells

Proto oncogenes

genes that promote proliferation which promotes cancer

Tumor repressor genes

Genes that reduce proliferation, when there’s reduced activity it can promote cancer

Ras gene mutations

can lead to production of a hyperactive Ras protein and increased cell division which can lead to cancer

p53 mutations

prevent suppression of the cell cycle, so DNA that has mistakes is not stopped and can replicate and cause excessive cell division

Amphipathic molecules

molecules that contain both hydrophobic and hydrophilic, such as phospholipids

Fluid mosaic model

states that the membrane is a mosaic of protein molecules bobbing in a fluid bilayer of phospholipids. More solid at a lower temp and less solid at a higher temp

integral proteins

proteins that penetrate the hydrophobic interior of the lipid bilayer

Peripheral Proteins

Proteins that are loosely bound to the surface of the

membrane

Six major functions of proteins

transport, enzymes, signal transduction, cell to cell recognition, intracellular joining, and extracellular joining to cytoskeleton and extracellular matrix

_____ molecules such as O2 & CO2 can easily cross the lipid bilayer while ___ molecules such as water and sugar

Non-polar/hydrophobic, polar/hydrophilic

Transport proteins

Proteins that allow passage of hydrophilic (polar) substances across the membrane

Channel proteins

proteins that have a hydrophilic channel that certain molecules or ions can use as a tunnel

Aquaporins

Channel proteins that facilitate the passage of water

Carriers

Transport proteins that bind molecules specifically and bring them across the membrane

Diffusion

the tendency for molecules to spread out evenly into the available space

Concentration gradient

Direction where substances move down, typically goes from where it is most concentrated to where it is least concentrated.

Passive diffusion

Type of diffusion where substances move with their concentration gradient, requires no energy

Osmosis

Diffusion of water, moves from lower amount of substances to higher amount of substances

Tonicity

the ability of a surrounding solution to cause a cell to gain or lose water

Isotonic solution

Solute concentration is the same as inside the cell; no net water movement across the plasma membrane

Hypertonic solution

Solute concentration is greater than that inside the cell; cell loses water. Causes cells to shrivel

Hypotonic solution

Solute concentration is less than that inside the cell; cell gains water which can cause it to burst

Facilitated diffusion

a type of passive transport that allows polar, charged, or large molecules (like glucose or ions) to cross cell membranes down their concentration gradient using specific transmembrane proteins

Active Transport

Type of transport that moves substances across membranes against their concentration gradients and requires energy

Electrochemical gradient

the combined force of a chemical concentration gradient and an electrical charge gradient across a membrane, dictating ion movement

Electrogenic Pump

a transport protein that generates voltage across a membrane and helps store energy needed for cellular work

Proton pump

The main electrogenic pump of plants, fungi, and bacteria

Cotransport

the coupled movement of two substances across a cell membrane. It uses the energy from one substance (like sodium) moving down its electrochemical gradient to power the transport of another substance (like glucose) against its gradient.

Exocytosis

transport vesicles migrate to the membrane, fuse with it, and release their contents, used to export contents

Endocytosis

the cell takes in molecules and particulate matter by forming new vesicles from the plasma membrane

Types of endocytosis

Phagocytosis (cellular eating), Pinocytosis (cellular drinking), Receptor-mediated endocytosis

Paracrine signaling

occurs when cells excrete a molecule that acts on nearby cells

G protein-coupled receptors

the largest family of cell-surface receptors that detect extracellular signals like hormones and neurotransmitters to initiate intracellular responses

Catabolic pathways

Pathways that release energy by breaking down complex molecules into simpler compounds

Anabolic/biosynthetic pathways

Pathways consume energy to build complex molecules from simpler ones

First law of thermodynamics

Energy is transformed, not lost or gained

Second law of thermodynamics

Disorder increases as heat is released to the system and large molecules are broken into smaller ones

Kinetic energy

energy associated with motion

thermal energy

kinetic energy associated with random movement of atoms or molecules

Heat

thermal energy in transfer from one object to another, increases disorder of surroundings

Light

another type of energy that can be harnessed to perform work

Potential energy

energy that matter possesses because of its location or structure

Chemical energy

potential energy available for release in a chemical reaction

Entropy

a measure of molecular disorder, or randomness.

Spontaneous

Reactions that have a negative delta G and requires no energy input and increases the entropy of the universe

Free energy

the portion of a system’s energy that can do work when temperature and pressure are uniform throughout, as in a living cell

Exergonic reaction

reaction with a negative delta G, spontaneous, and releases energy that can be used