Learn: mcdb 6 midterm 1

order of life

Atoms → molecules → macromolecules → organelles → cells → tissues → organs → populations → communities → ecosystems → biosphere

characteristics that prokaryotes & eukaryote cells share

DNA, enclosed by membrane, cytoplasm, ribosomes

3 major differences between plants and animal cells

cell wall, chloroplasts, vacuole

3 domains of life

Bacteria, Archaea, Eukarya

big 4 elements

carbon, hydrogen, oxygen, nitrogen

how many natural elements are there, and what percentage are essential elements?

94, 25%

The reactivity of an atom is due to

the presence of one or more unpaired electrons in the valence shell

Atoms with completed valence shells are

nonreactive (inert gases)

Bonding capacity (valence)

the number of bonds that the atom can form

covalent bond

the sharing of a pair of valence electrons by two atoms

Non-polar covalent bond

equal sharing of electrons

Polar covalent bond

electrons are not shared equally, causes a positive or negative partial charge

ionic bond

both atoms have charges (ions)

What is a hydrogen bond?

A hydrogen bond is an attraction between a hydrogen atom covalently bonded to one electronegative atom and another electronegative atom.

Which atoms are commonly involved in hydrogen bonds?

Oxygen and nitrogen

Van der Waals interaction

electrons are distributed asymmetrically in molecules or atoms resulting in regions of positive or negative charge, enabling all atoms to stick together

What is the strongest bond?

covalent, ionic as a dry salt

Which bonds are weak?

ionic (salts dissolved in water), hydrogen, van der waals

1 water molecule can form a maximum of

4 hydrogen bonds

Why does ice float?

hydrogen bonds are stable in ice, ice has a lower density than liquid water

4 properties of water

cohesion (surface tension), ability to moderate temperature (high specific heat), expansion upon freezing, versatility as a solvent

Oil is hydrophobic because

it is nonpolar

Valencies of the major elements of organic molecules:

H = 1, O = 2, N = 3, C = 4

3 polymeric macromolecule types

carbs, proteins, nucleic acids

why are lipids not true polymers?

lipids are not composed of repeating units of the same molecules or atoms

A carbon atom can form covalent bonds to other carbon atoms, linking the atoms into

chains

ok cool

Functional groups

the chemical groups that affect molecular function by being directly involved in chemical reactions

ATP

(adenosine triphosphate) main energy source that cells use for most of their work

polymers

long molecules consisting of many similar building blocks, called monomers

Dehydration reaction

2 monomers bond together through the loss of water

Hydrolysis

polymers are disassembled to monomers (reverse of dehydration)

Enzymes

speed up/facilitate chemical reactions

Carbohydrates

serve as fuel and building material

Monosaccharides (sugars)

molecular formulas that are multiples of CH2O (Triose, Pentose, Hexose)

Disaccharide (sugars)

formed when a dehydration reaction joins two

monosaccharides (also called glycosidic linkage)

Polysaccharides

polymers of sugars, have storage and structural roles (starch, glycogen, cellulose, chitin)

Starch

storage polysaccharide of plants (consists entirely of glucose)

Glycogen

storage polysaccharide in animals (stored in liver and muscle cells)

Cellulose

structural polysaccharide, major component of the tough wall of plant cells

Chitin

structural polysaccharide, support for the cell walls of many fungi, Enzymes that digest starch by hydrolyzing alpha glucose linkages can't hydrolyze beta linkages in cellulose.

Lipids

hydrophobic molecules, consisting mostly of hydrocarbons

3 different types of lipids

triglycerides (fats), phospholipids, steroids

triglycerides

formed by glycerol, a three-carbon alcohol with a hydroxyl group attached to each carbon, and 3 fatty acids, which consist of a carboxyl group attached to a long carbon skeleton

saturated fat

fatty acid chain has max number of hydrogen atoms (no double bonds)

Unsaturated fat

has one or more carbon=carbon double bonds (bent)

Hydrogenation

conversion of some C=C double bonds into trans configuration, produces trans fat for unsaturated fatty acids

Phospholipids

major constituents of cell membranes, hydrophilic head and hydrophobic tail. When added to water, they self assemble into a bilayer, with the hydrophobic tails pointing toward the interior

Steroids

characterized by a carbon skeleton consisting of 4 fused rings (cholesterol, sex hormones)

Cholesterol

important component of animal cell membranes

Sex hormones

estradiol and testosterone

DNA monomers are called

nucleotides

structure of a nucleotide

phosphate group, pentose sugar, nitrogenous base

bonds between nitrogenous bases

double bond between A and T, triple bond between G and C

Watson and Crick contribution

discovered the DNA double helix, the width of the helix, the spacing between the bases and that the sugar-phosphate backbones run antiparallel (subunits run in opposite directions)

Miescher contribution

discovered "nuclein" a substance found in the nuclei of white blood cells which was eventually found to be nucleic acids

Levene contribution

1. The order of the three major components of a single nucleotide

(phosphate-sugar-base)

2. The carbohydrate component of RNA (ribose)

3. The carbohydrate component of DNA (deoxyribose)

4. The correct way to identify the way RNA and DNA are put

together (polynucleotide model)

Morgan contribution

genes are located on chromosomes

What were the candidates for genetic material?

DNA and protein

Griffith contribution

discovered the genetic role of DNA and transformation

○ The transforming substance (aka the genetic material)= DNA

○ Studies on viruses that infect bacteria further supported that the

genetic material was DNA

The Hershey and Chase experiment

used T2 phage to show that DNA is the genetic material by showing that only the DNA of the T2 phage and not the protein enters E. coli during infection

Transformation

the change in genotype and phenotype due to the assimilation of foreign DNA

how was transformation discovered

Was discovered when he mixed heat killed pathogenic bacteria with harmless bacteria and found that some of the living cells became pathogenic

Virus

DNA (or RNA) enclosed by a protective coat, usually made by protein which need to take over the host metabolic machinery in order to reproduce

Chargaff’s rules

A = T, G = C. (A + G) = (T + C)

Wilkins and Rosalind Franklin

used X- ray crystallography to study molecular structure and she was able to produce a picture of a DNA molecule using this technique. Also found the sugar-phosphate backbone was on the outside of the helix and the nitrogenous bases were base paired in the middle

Purines

A or G (pure as gold)

Pyrimidines

C or T, and U for RNA. (the tip of the pyramid CUTs)

How did structure imply function for DNA?

Because of specific base pairing, Watson and Crick thought that there was a copying mechanism for genetic material

Why were experiments done using viruses and bacteria?

Their small genomes, simple structure of chromosomes, short generation times, can interact with one another

Semiconservative model of replication

predicts that when one double helix replicates, each daughter molecule will have one old strand (conserved from the parent) and one newly made complementary strand

Conservative model of replication

the two parent strands rejoin

Dispersive model of replication

each strand is a mix of old and new

DNA replication

Fast and accurate, utilizes more than a dozen enzymes and other proteins, we know more about this mechanism in bacteria than in eukaryotes, the process is similar between prokaryotes and eukaryotes

DNA replication begins how?

The two DNA strands are separated at the origin of replication which opens up a replication bubble

Each end of the replication bubble has what?

A replication fork

Replication fork

Y shaped region where the parental strands of DNA are being unwound

Helicases

enzymes that untwist the double helix at the replication fork

Single strand binding proteins (SBP)

bind to and stabilize the single-stranded DNA

Topoisomerases

relieve the strain caused by tight twisting ahead of the replication fork by breaking, swiveling and rejoining DNA strands

Primase

creates the RNA primer to start DNA synthesis

DNA polymerase I

removes RNA primers and replaces them with DNA

DNA ligase

joins together the gaps