Biology Exam 1

Biology the origins of life objective questions

What are the four characteristics of living things

Complexity, the Ability to change in response to environmental stimuli (evolution), the ability to reproduce, and the capacity to evolve

define a cell

it is the simplest self-replicating entity that can exist as an independent unit of life, and it performs all functions necessary for life

Name the three essential features of all cells

They store and transmit information, they have a plasma membrane, and harness energy from the environment

explain the central dogma

transcription: DNA template→ RNA

translation: RNA →protein

Mutations in DNA can change the type of protein produced

Define matter

anything that takes up space and has mass

define an element

substance that cannot be broken down by chemical reactions

what are the four most abundant elements in the human body

carbon, hydrogen, Nitrogen, and oxygen

What is the structure of an atom

an atom has a nucleus that contains protons and neutrons and an electron cloud that contains electrons arranged in orbitals and shells

what are the functions of an atoms subatomic particles

Protons: give an atom a positive charge and add mass

Neutrons: have no charge and add mass to the atom

Electrons: give an atom a negative charge, occupy the orbitals, and determine the chemical reactivity and bonding of an atom

what is the Atomic number of an atom

the number of protons

what is the atomic mass of an atom

the amount of protons plus the amount of neutrons

define an isotope

it is the same element, with a different number of neutrons and the same chemical behavior, but with a different mass

what is an ion

an atom that gains or loses electrons

gain electron→negative

lose an electron→positive

what are electron orbitals

regions where electrons spend most of their time; there is a maximum of two electrons per orbital electrons fill the lowest-energy orbitals first

electron shells

1: shell is one spherical orbital →two electrons

2nd shell has 4 orbitals→8 electrons

locate elements on the periodic table

Rows(periods) have the same number of electron shells

Columns (groups) have the same number of valence electrons; similar chemical behavior

what are the four types of chemical bonds

covalent, polar covalent, hydrogen, and ionic

covalent bond

equal sharing of electrons

polar covalent

unequal sharing of electrons

hydrogen

weak attraction between H and an electronegative atom

Ionic

attraction between charged ions

what is the difference between covalent and polar covalent bonds

covalent bonds have equal sharing of electrons, while polar covalent bonds have unequal sharing due to electronegativity differences

why is water essential for life

it has a high specific heat- stabilizes the ocean temps, moderates the climate, and organisms resist internal temperature changes because of the water in us. Water has a Neutral pH of 7, water is a good solvent, and water is a polar molecule

Interactions within and between water molecules

within the molecule polar covalent bonds form between O and H, between molecules they are connected by hydrogen bonds

Water’s high specific heat and temperature stabilization- Hydrogen bonds allow water to-

absorb or release large amounts of heat with small temp changes, stabilizes ocean temps, limits temp fluctuations on land, and helps organisms resist internal temp changes

Define solution

dissolving agent- usually water

define solute

substance dissolved

define aqueous solution

water is the solvent

what is hydrophobic

water repelling and cannot form hydrogen bonds; also nonpolar

what is Hydrophilic

water attracting and can form hydrogen bonds

Hydrogen ion concentration and pH-acid

Increases H+→pH<7

Hydrogen ion concentration and pH-bases

decreases H+→pH>7

Hydrogen ion concentration and pH-neutral

H+=OH- →pH=7

what are the Carbon bonding properties

forms covalent bonds, creates chains, rings and double bonds, and is the basis of structural diversity in organic molecules

define an isomer

molecules with the same chemical formula but different arrangements of atoms, giving different structures and functions

each amnio acid contains

Amino group- NH2, Carboxyl group COOH, alpha carbon, and an R-group variable that determines its identity

how do amino acids link via peptide bonds

carboxyl carbon of one AA binds to the nitrogen of another, forming a covalent peptide bond, water is lost during bond formation because of the condensation reaction

3 components of nucleic acids

5-carbin sugar; ribose or deoxyribose, nitrogen base, and phosphate groups

what is the difference between deoxyribonucleotide and ribonucleotide

deoxyribonucleotide is a deoxyribose sugar that is formed by the bases A T C G

ribonucleotide is a ribose sugar that is formed by the bases A U C G

what are the five nitrogenous bases

Adenine, Guanine, Cytosine, Thymine, and Uracil

What nitrogenous bases make up purines

Adenine and Guanine

what nitrogenous bases make up pyrimidines

Cytosine, Thymine, and Uracil

Nucleotide joining

adjacent nucleotides join together by phosphodiester bonds, 5’ phosphate binds 3’ OH, and water is lost

describe the structure of DNA

Two antiparallel strands, sugar-phosphate backbone outside, bases inside, right-handed double helix structure, major and minor grooves

define carbohydrates

they are made up of carbon, hydrogen, and oxygen

what are the two classes of sugars in Carbs

Aldose- contains the aldehyde group

Ketose- contains ketone group

what is a Mono- saccharide

one sugar molecule

what is a di- saccharide

two sugar molecules

what are poly-saccharides

many sugars

Cyclization of aldose and ketose

monosaccharides in cells are cyclic, an aldose is an aldehyde bonded to an OH group, ketose is ketone carbon bonded to an OH group

Glycosidic bond formation

this is a covalent bond between sugars where water is lost

what is the major difference between lipids and other biomolecules

lipids are defined by their hydrophobic nature not by their chemical structure

what are the three types of lipids

fatty acids/triacylglycerols, steroids, phospholipids

what is the formation of triacylglycerol

Glycerol+3 fatty acids, the OH groups of glycerol bind to the COOH groups of fatty acids, which are Hydrophobic and are used for energy storage

saturated fats vs unsaturated fats

saturated fats do not have a carbon double bond, they are tightly packed and solid

unsaturated fats have a carbon double bond, which kinks them, and are loosely packed, usually liquid

Van der Waals forces

weak attractions due to electron motion, stabilize fatty acid chains, and are stronger with longer hydrocarbon chains

What is the structure of a phospholipid

glycerol, 2 fatty acids, and a phosphate head group

What is the function of a phospholipid

it is a major component of the cell membrane and it forms bilayers with hydrophobic tails inwards as well as hydrophilic heads outward

Frederick Griffith’s experiment

Virulent strain → mouse dies

Nonvirulent strain → mouse lives

Heat‑killed virulent + live nonvirulent → mouse dies

→ Transformation principle transferred virulence.

Avery, MacLeod, McCarty experiment

Identified DNA as the transforming molecule

Destroying DNA prevented transformation

→ DNA is the genetic material

Regulation of transcription & translation → cell types

Different cell types arise because different genes are turned on/off, producing different proteins.

Transcription & translation locations Prokaryotes:

both are performed in the cytoplasm of the cell

Transcription & translation locations eukaryotes:

Transcription in the nucleus and translation in the cytoplasm of the cell

components of the nucleotide DNA’s negative charges are caused by what

sugar, base, phosphate group,

DNA’s negative charges are caused by what

Phosphate groups have negative charges, giving DNA its overall negative charge

DNA polarity (5’ vs 3’)

5’ end free phosphate

3’ end free OH

DNA is always read 5’→3’

Properties of the double helix

it is a right-handed spiral, antiparallel strands, with major and minor grooves, its bases point inwards, and it is made up of nucleotides connected by hydrogen bonds

what is Chargaff’’s rule

A%=T%

G%=C%

hydrogen bonding with nucleotides

A-T:2 hydrogen bonds

C-G:3 hydrogen bonds

Base stacking

nonpolar surfaces stack tightly, repel water and stabilize the DNA helix

 Chromatin & histone proteins

Eukaryotic DNA is packaged with histones, histones are positively charged, they are bound to negatively charged DNA and allow compaction into chromatin

RNA world hypothesis

RNA likely original genetic material because:

Used in replication, transcription, and translation; can evolve or adapt, can act as a catalyst and is less stable due to the reactive 2’ OH

DNA vs RNA

DNA is made up of deoxyribose sugar, it uses the bases A T C G, has a double strand, is very large, and has a 5’ end monophosphate

RNA is made up of ribose sugar; it uses the bases A U C G, has a single strand, is smaller than DNA; and has a 5’ end triphosphate

template strand vs nontemplate strand

Template strand: used by RNA polymerase to build RNA

RNA sequence is complementary to the template

Matches nontemplate strand except U replaces T

transcription initiation

RNA polymerase binds the promoter, in eukaryotes the TATA box and general transcription factors are vital and the first nucleotide includes 25 bp downstream of the TATA box

 Key features of transcription

RNA grows 5’ → 3’

Template is read 3’ → 5’

U is inserted opposite A

Occurs in the transcription bubble (~14 bp)

Transcription termination

RNA polymerase stops at the terminator sequence.

Promoter recognition: prokaryotes vs eukaryotes

Prokaryotes: sigma factor binds the promoter

Eukaryotes: general transcription factors + mediator recruit RNA polymerase II

Functions of RNA polymerase

Separates DNA, synthesizes RNA, releases transcript, restores DNA double helix, contains channels for DNA entry, RNA exit, nucleotide entry

 RNA polymerization reaction

Nucleotides are added to the 3’ OH, driven by the release of pyrophosphate, which occurs in the transcription bubble

RNA processing: prokaryotes vs eukaryotes

Prokaryotes: no processing, primary transcript = mRNA, translation begins immediately, mRNA often polycistronic

Eukaryotes: 5’ cap (7‑methylguanosine), poly‑A tail (~250 adenines), splicing (introns removed, exons joined)

RNA splicing

Spliceosome binds intron ends, cuts intron → forms lariat, exons joined, lariat degraded, alternative splicing allows multiple proteins from one gene