Biochemistry Exam

Question 1

ionic bond

Answer 1

a chemical bond that forms due to the complete transfer of electrons from one atom to another.

The atom that gains electrons is given a negative charge, while the atom that gives up electrons is given a positive charge.

Question 2

covalent bond

Answer 2

A covalent bond is a chemical bond that forms via the sharing (not complete transfer) of electrons.

When the electrons are shared unequally, the bond is polar covalent.
When the electrons are shared equally, the bond is nonpolar covalent.

Question 3

hydrogen bond

Answer 3

Hydrogen bonds are intermolecular, which means they occur between two or more different molecules.

a weak chemical bond that forms when a hydrogen atom with a partial positive charge of a polar covalent bond in one molecule is attracted to the slightly negative atom of a polar covalent bond in another molecule

Question 4

electronegativity

Answer 4

the attraction of an atom for the electrons of a covalent bond
(i.e. electronegativity of oxygen atom in a water molecule results in polarity)

Question 5

structure of water

Answer 5

Two hydrogen atoms with partial positive charges joined by a single covalent bond to an oxygen atom with a partial negative charge to form H2O

Question 6

Cohesion

Answer 6

the attraction of water molecules to other water molecules through hydrogen bonds
-causes surface tension and helps hold together the column of water being transported upwards within the xylem during transpiration

Question 7

Adhesion

Answer 7

the attraction between water molecules and another substance due to the polarity of the water molecule
-allows water molecules to cling to the cell walls of the xylem during transpiration to resist downward pull of gravity

Question 8

Moderation of Temperature

Answer 8

• Water freezes at 0˚C and boils at 100˚C
• due to high specific heat (1 cal/g/°C), water is a heat bank and resists changes in temperature by absorbing or losing a large quantity of heat for each degree of temperature change
• evaporative cooling allows for the molecules with the most kinetic energy to evaporate and convert to the gaseous state, cooling the surface
• maintain homeostasis in organisms, stabilization of the temperature of land and bodies of water, moderates climate

Question 9

Expansion during Freezing

Answer 9

Water expands as it freezes and becomes less dense due to its crystalline structure formed by hydrogen bonds
- Ice floating at the top of lakes and ponds insulates the water below preventing them from freezing solid as well as allowing life to exist below the frozen surface

Question 10

Solubility

Answer 10

the chemical property of water referring to the ability for a given substance (the solute) to dissolve in the solvent

• based on the polarity (positive and negative charge) of the molecule
  
  • cations (+) are attracted negatively charged oxygen regions of water molecule while anions (-) are attracted to the positively charged hydrogen regions
• as a result, water molecules surround the individual ions and dissolves the solute through the formation of a hydration shell

Question 11

Transport happens on three different scales:

Answer 11

• Transport of water & solutes by individual cells
• Short distance transport at the tissue & organ level
• Long distance transport through the xylem & phloem across the entire plant

Question 12

transport by individual cells

Answer 12

Osmosis
- Water transport across a semi permeable membrane based on solute concentration
Water Potential (Ψ)
- A property that predicts the flow of water based on solute concentration & physical pressure

Question 13

transport at the tissue & organ level

Answer 13

Lateral transport: Short distance movement through
plant tissues
-plasmodesmata are pores in cell walls that allow cytoplasms to fuse together in cells of the same tissue- faster transport and communication

Question 14

transport over long distances

Answer 14

Bulk flow of fluid through the whole plant:

• Water & solutes move through the xylem
• Sugars move through the phloem

Question 15

water’s pathway

Answer 15

Water and mineral salts from the soil enter through the root epidermis with the aid of root hairs and mycorrhizae. Water is then transported to the root cortex and then to the xylem. The transpiration-coheion-tension mechanism is the main source of water’s movement from the xylem to the leaves. Transpiration pull occurs as the oustide air has a lower water potential than the air inside the leaf. This results in diffusion of water vapor from the leaf to the atmosphere (diffusion). Lost water is replaced by water in the xylem due to
cohesion.
- transpiration requires no energy

Question 16

stomata

Answer 16

allows gas exchange to occur, water to evaporate during transpiration
-guard cells regulate the opening and closing of stomata in response to stimuli

Question 17

pH

Answer 17

A scale that compresses the range of H+ and OH concentrations by using logarithms. It is the negative log of hydrogen ion concentration
• pH=-log[H+]

Question 18

acids

Answer 18

a substance that increases the [H+] in a solution by releasing H+ ions

Question 19

base

Answer 19

a substance that reduces the [H+] in a solution by directly accepting H+ ions (weak) or dissociating to release OH- to bond with H+ ions in the solution to form H2O

Question 20

buffer

Answer 20

a substance that minimizes changes in the concentraion of OH- ions and H+ ions in a solution by accepting or releasing H+ ions
- usually composed of weak acid and corresponding base

Question 21

carbon structure

Answer 21

CH4
Carbon’s diversity arises from its ability to bond with four other atoms (covalent)
Tetravalence: carbon with single covalent bonds will form tetrahedrons
Carbons with double covalent bonds will form planar molecules
4 valence electrons; can bond to four other atoms

Question 22

hydrocarbons

Answer 22

– Molecules consisting of only carbon & hydrogen
– Not found often in cells, but rather are organic
molecules have regions that are hydrocarbons
– Ex: hydrocarbon tails found in fats

Question 23

Isomers

Answer 23

molecules with the same molecular formula but different

structures and properties

Question 24

Structural Isomers

Answer 24

changes location of covalent bonds to create new molecules

Question 25

Geometric Isomers

Answer 25

cis - special group on the same side trans - special group on opposite sides covalent bonds remain unchanged, but rather differs in the spatial arrangement and position of atoms and arrangement about a double bonds

Question 26

Enantomers

Answer 26

differ in spatial arrangement around an asymmetric carbon, resulting in molecules that are mirror images

Question 27

Dehydration Synthesis

Answer 27

Monomers are connected by a dehydration reaction: – One monomer provides the hydroxyl group & the other provides a hydrogen to form a water molecule that is removed - this process is repeated continuously

Question 28

Hydrolysis

Answer 28

Monomers are removed from polymers by hydrolysis – Adding water molecules breaks the bonds between monomers – One monomer receive the hydroxyl group & the other gets the hydrogen

Question 29

monomer

Answer 29

the repeating units that serve as the building blocks of a polymer

Question 30

polymer

Answer 30

a long molecule consisting of many similar or identical building blocks linked by covalent bonds

Question 31

general characteristics of carbohydrates

Answer 31

monomer: monosaccharides polymers: disacchardies, polysaccharides bond type: glycosidic linkage - 3-7 carbons with carbonyl group and multiple hydroxyl groups and many structural isomers

Question 32

monosaccharides

Answer 32

• Use multiples of CH2O • Glucose (C6H12O6) is essential for life due to its role in cellular respiration • In solution, glucose & most sugars form rings – The first carbon bonds to the oxygen on carbon 5

Question 33

disaccharides

Answer 33

Two monosaccharides connected by glycosidic linkage | • Sucrose (table sugar) is the most common & is how plants transport carbohydrates

Question 34

polysaccharides

Answer 34

Thousands of monosaccharides – Storage material until hydrolyzed into sugar for cells • Starch: plant storage made of glucose monomers; stored in plastids. • Glycogen: human storage found in the liver and muscles – Building material for protective structures • Cellulose: part of the tough cell wall of plants • Chitin: builds exoskeletons in arthropods & found in fungi cell walls

Question 35

lipids

Answer 35

monomers: fatty acids and glycerol polymers: phospholipids, fats, steroids bond type: ester linkage Little or no affinity for water due to the molecular structure – Mainly hydrocarbons – Smaller than traditional macromolecules

Question 36

Fats

Answer 36

Formed through dehydration reaction of one glycerol and three fatty acids by an ester linkage – Called triacylglycerol (triglyceride)

Question 37

Saturated Fats

Answer 37

- have no double bonds between carbon atoms in the fatty acid chain (saturated with hydrogen). - solid at room temperature due to the ability of molecules to tightly pack together - animal fats (ie butter, lard)

Question 38

Unsaturated Fats

Answer 38

- one or more double bonds formed by the removal of hydrogen atoms from the carbon skeleton - kink in hydrocarbon chain wherever a cis double bond occurs - liquid at room temperature - plants and fish fats (ie olive oil, fish oil)

Question 39

Energy Storage of Fats

Answer 39

adipose in animals | seeds in plants

Question 40

Phospholipids

Answer 40

Glycerol with two fatty acids and a phosphate group – Phosphate head is hydrophilic and fatty acid tail is hydrophobic – Creates double layer in water • Main component of cell membranes (the phospholipid bilayer)

Question 41

Steroids

Answer 41

Carbon skeletons consisting of four fused rings – Differentiation due to attached functional group • Cholesterol is a steroid found in animal cell membranes – High levels in the blood leads to cardiovascular disease • Sex hormones are steroids that acts as messengers – Testosterone & estrogen

Question 42

Proteins

Answer 42

monomers: amino acids polymers: polypeptides bond type: peptide bond One or more polypeptides folded into a specific conformational shape

Question 43

Protein function

Answer 43

``` – Structural support – Storage – Transport – Hormonal – Cellular communication – Movement – Defense against foreign substance – Speed up chemical reactions (enzymes) ```

Question 44

Proteins have • Incredibly diverse structures & functions due to _____________________________

Answer 44

three dimensional shape

Question 45

nonpolar and nonpolar amino acids form

Answer 45

hydrophobic interactions (Van der Waal)

Question 46

polar and polar amino acids form

Answer 46

hydrogen bonds

Question 47

positively charged base and negatively charged acid form

Answer 47

ionic bonds

Question 48

sulfhydryl interacts to form

Answer 48

disulfide bridge

Question 49

amino acid structure

Answer 49

– Amino acids (with an amino & carboxyl group) are the monomers – It is the side group (R) that determines the behavior of the amino acid – All proteins are made from 20 amino acids

Question 50

nonpolar amino acids

Answer 50

carbon and hydrogen | ie methyl

Question 51

polar amino acids

Answer 51

hydroxyl and carbonyl

Question 52

negatively charged acidic

Answer 52

carboxyl group

Question 53

positively charged base

Answer 53

amino group

Question 54

Amino acid polymers

Answer 54

A peptide bond is formed between two amino acids | – Carboxyl group bonds with amino group of the next amino acid

Question 55

Protein Structure: Primary

Answer 55

The unique sequence of amino acids

Question 56

Protein Structure: Secondary

Answer 56

Folds & coils in the polypeptide chain due to hydrogen bonds between repeating sections * α helix * β pleated sheet - due to attraction of negatively charged carboxyl group and positively charged amino group

Question 57

Protein Structure: Tertiary

Answer 57

Overall shape of the polypeptide due to the interactions between side chains (R groups) * Hydrophobic interactions * Disulfide bridges * Ionic bond * Hydrogen bond

Question 58

Protein Structure: Quaternary

Answer 58

-same type of interactions as tertiary structure | Two or more polypeptide chains create one protein

Question 59

Denaturation of Proteins

Answer 59

• The environment can impact the conformation of protein causing denaturation – pH – Salt concentration – Temperature