Unit 1 Learning Objectives

Question 1

•Describe the four characteristics of living things

Answer 1

Complex, change in response to the environment, reproduce, evolve

Question 2

•Define a cell

Answer 2

The simplest self-replicating entity that can exist as an independent unit of life

Question 3

Describe the three essential features of all cells

Answer 3

1. Store & transmit info
2. Plasma membrane
3. Harness energy from the environment

Question 4

Explain the Central Dogma

Answer 4

DNA → (transcription) RNA →(translation) protein

Question 5

•Define matter and element

Answer 5

Matter = anything that takes up space & has mass
Element = fundamental substances in nature; 94 naturally occur; cannot be broken down by chemical reactions

Question 6

Know the four most abundant elements in the human body

Answer 6

Carbon, nitrogen, oxygen, hydrogen

Question 7

Know the structure of an atom and the function of its 3 subatomic particles (protons, neutrons, electrons)

Answer 7

Neutron = neutral charge; contribute to mass
Proton = positive charge; contribute to mass
Electron = negative charge; negligible mass

Question 8

Differentiate between an atom’s atomic number and atomic mass

Answer 8

Atomic number = number of protons
Atomic mass = number of protons and neutrons

Question 9

Define an isotope and an ion and differentiate between the two

Answer 9

Isotope = two atoms of an element that differ in number of neutrons
Ion = Atoms that gain or lose an electron become charged

Question 10

Explain electron orbitals

Answer 10

Regions of space where an electron spends most of its time

Question 11

Describe the 4 types of chemical bonds used to make molecules

Answer 11

Covalent bond = equal sharing of electrons
Polar covalent bond = unequal sharing of electrons; depends on electronegativity of an atom
Hydrogen bond = interaction between Hydrogen and an electronegative atom; partial negative is attracted to partial positive
Ionic bond = interaction between oppositely charged ions; metal + nonmetal

Question 12

Differentiate between covalent and polar covalent bonds

Answer 12

Covalent = equal sharing of electrons
Polar covalent = unequal sharing of electrons

Question 13

Describe the properties of water that make it indispensable to life on earth

Answer 13

Polar molecule
Good solvent
pH of 7

Question 14

Describe the interaction between the atoms of a single molecule of water, and among water molecules

Answer 14

Single molecule → polar covalent bonds
Multiple molecules → hydrogen bonds

Question 15

Correlate water’s high specific heat with its ability to stabilize temperature fluctuations

Answer 15

Water changes its temperature less when it absorbs or releases a given amount of heat
High specific heat → result of hydrogen bonds

Question 16

Define solution, solute, solvent, aqueous solution

Answer 16

Solution = a liquid that is a homogeneous mixture of substances
Solvent = the dissolving agent of a solution
Solute = the substance that is dissolved
Aqueous solution = one in which water is the solvent

Question 17

Differentiate between hydrophilic and hydrophobic substances

Answer 17

Hydrophilic = has an affinity for water; a substance can be hydrophilic without actually dissolving
Example → cotton
Hydrophobic = does not have an affinity for water; cannot form hydrogen bonds
Example → vegetable oil

Question 18

Correlate changes in hydrogen ion concentration (H+) with pH

Answer 18

Acid → increases (H+) and reduces pH
Base → reduces (H+) and increases pH

Question 19

Describe the bonding properties of Carbon that relate to its structural diversity

Answer 19

Carbon atom behaves as if it has 4 unpaired electrons
Forms covalent bonds
Carbon forms a tetrahedron when covalently bound to 4 other atoms

Question 20

Define an isomer

Answer 20

Molecules with the same chemical formula can arrange differently
Different structures
Different functions

Question 21

Describe the basic structure of an amino acid

Answer 21

Amino group
Carbon (alpha)
R group
Carboxyl group

Question 22

Describe how amino acids link together via peptide bonds to form proteins

Answer 22

Carbon of the carboxyl group of one amino acid is linked to the nitrogen in the adjacent amino group by a covalent peptide bond
Water is lost (dehydration reaction)

Question 23

Identify and Define the three components of a nucleic acid

Answer 23

5-Carbon sugar (ribose or deoxyribose)
Ribose = RNA ,Two hydroxyl groups
Deoxyribose = DNA,One hydroxyl group (none on 2’ Carbon)

Base containing nitrogen
Attached to 1’ Carbon
RNA = A,G,U,C
DNA = A,G,T,C

One or more phosphate groups
Makes nucleic acid negative
Attached to 5’ Carbon

Question 24

Describe the difference between a deoxyribonucleotide and a ribonucleotide

Answer 24

Deoxyribonucleotide → has only 1 hydroxyl group on 3’ carbon
Ribonucleotide → has 2 hydroxyl groups; one on 3’ carbon and one on 2’ carbon

Question 25

Identify the five nitrogen-containing bases of nucleic acids and differentiate between the two classes (purines and pyrimidines)

Answer 25

Pyrimidines (one ring structure) Thymine (T) Cytosine (C) Uracil (U) Purines (double ring structure) Adenine (A) Guanine (G)

Question 26

Describe the process of nucleotide joining

Answer 26

Phosphodiester bond 5’ phosphate group of one nucleotide binds to the 3’ OH group on the sugar of another nucleotide Results in the loss of water (dehydration reaction)

Question 27

Describe the structure of DNA

Answer 27

Double helix = 2 strands of nucleotides twisted around each other Sugar phosphate backbone Complementary base-pairing Bases connected by hydrogen bonds

Question 28

Define a carbohydrate and identify/describe the two main classes of sugars

Answer 28

Simple carbohydrates = monosaccharides -Exist as linear or cyclical structures -Composed of Carbon, Hydrogen, & Oxygen -Contain 5 or 6 carbons Two main classes : 1. Ketose = contain ketone group 2. Aldose = contain aldehyde group

Question 29

Define Mono- Di- and Poly- saccharides

Answer 29

Monosaccharides = one sugar Disaccharides = two sugars linked together by glycosidic bond Polysaccharides = many sugars linked together

Question 30

Describe the cyclization process of ketose and aldose sugars

Answer 30

Rearrangement of atoms → NOT loss of atoms Carbon in aldehyde forms a covalent bond w/ the oxygen of the -OH of another carbon in the same molecule

Question 31

Describe the process of glyosidic bond formation

Answer 31

Involves interaction of adjacent hydroxyl groups Loss of water

Question 32

Identify the major difference between lipids and the other three classes of biomolecules

Answer 32

NOT defined by physical structure → defined by hydrophobic nature

Question 33

Describe and compare the three types of lipids

Answer 33

Fatty acids (triacylglycerol) = long carbon chains attached to a hydroxyl group Chains linked by nonpolar covalent bonds Steroids = carbon rings Nonpolar covalent bonds → hydrophobic Phospholipids = glycerol backbone + 2 fatty acid chains + phosphate head group Hydrophobic & hydrophilic

Question 34

Describe the formation of a triacylglycerol

Answer 34

Glycerol’s 3 hydroxyl (-OH) groups covalently bind to the carboxyl group (-COOH) of three fatty acids

Question 35

Compare saturated vs unsaturated fats

Answer 35

Saturated = made up of fatty acids that DO NOT contain C=C bonds (saturated w/ hydrogen atoms) Unsaturated = made up of fatty acids that contain C=C bonds Kinks caused by C=C bonds: Reduce tightness of packing Lower melting temp @ RT

Question 36

Define Van der Waals forces and describe their role in lipid structure

Answer 36

Definition = regions of slight charges caused by constant motion of electrons Role = attract & repel molecules; stabilize molecules

Question 37

Describe the structure and function of a phospholipid

Answer 37

Structure: Glycerol attached to 2 fatty acids and a phosphate-containing head group Function: Major component of cell membrane

Question 38

Describe the RNA world hypothesis and the reasons why RNA is thought to be the original information storage molecule

Answer 38

RNA was the information storage molecule in early life forms Evidence RNA is used in replication, transcription, and translation RNA has evolved over time RNA can act as a catalyst

Question 39

Know the similarities and differences between RNA and DNA

Answer 39

RNA Ribose A,U,C,G 5’ end is triphosphate Smaller Single stranded DNA Deoxyribose A, T, C, G Monophosphate Very large Double stranded

Question 40

Describe template and nontemplate strands of DNA

Answer 40

Template strand → used as a template for RNA transcription Nontemplate strand → other strand NOT used for RNA transcription

Question 41

Know the key features of transcription

Answer 41

RNA Polymerase = enzyme used for RNA synthesis The new RNA stand grows in the 5’ → 3’ direction The template DNA strand is in the 3’ → 5’ direction Uracil containing nucleotides are inserted in RNA when there is an Adenine in the template strand

Question 42

Describe the process of transcription initiation including all factors involved

Answer 42

RNA polymerase & associated proteins bind DNA at promoter sequences Eukaryotic promoters contain a sequence similar to TATAAA: TATA box The first nucleotide to be transcribed is positioned ~25 base pairs from the TATA box

Question 43

Describe the process of transcription termination and all factors involved

Answer 43

RNA polymerase moves along the template strand until it encounters a terminator sequence

Question 44

Know and compare promoter recognition in prokaryotes and eukaryotes

Answer 44

Prokaryotes → Sigma factor proteins Associates with RNA polymerase Facilitates binding of RNA polymerase to promoters to initiate transcription Eukaryotes → General transcription factor proteins General transcription factor proteins recruit RNA polymerase II (Pol II) to the promoter Proteins bound to an Enhancer sequence recruit a Mediator complex that interacts with the Pol II complex to initiate transcription

Question 45

Describe the functions of RNA Polymerase during transcription

Answer 45

Enzyme used for RNA synthesis Steps Separates the DNA Synthesizes the RNA Releases the finished transcript Restores the DNA double helix

Question 46

•Describe the RNA polymerization reaction

Answer 46

Incoming ribonucleotides are accepted if they correctly base pair with the template DNA The 3’ -OH of the growing strand attacks the high-energy phosphate bond of the incoming ribonucleotide, providing the energy to drive the reaction The two phosphates of the incoming ribonucleotide are released as pyrophosphate

Question 47

Know and compare the RNA processing events that occur in prokaryotes and eukaryotes

Answer 47

Prokaryotes The primary transcript is the mRNA mRNA includes info needed to direct the ribosome to produce a protein (translation) Transcription & translation both occur in the cytoplasm Primary transcripts contain the information for more than one gene: Polycistronic mRNA Eukaryotes Nuclear membrane = barrier between transcription and translation RNA processing = the primary transcript undergoes chemical modifications 3 types of chemical modifications occur before an mRNA is translated by the ribosome 5’ cap addition 3’ poly A tail addition Splicing

Question 48

Describe the process of RNA splicing

Answer 48

Excision of introns & joining together of exons Spliceosome: protein complex that catalyzes the intron removal Splicing: binding of Spliceosome to sequences at the ends of introns & subsequent cutting of one end of the introm to form a loop (Lariat) The exon on one end of the intron is joined to the exon at the other end and the intron (lariat) is released and broken down