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Flashcards in Chapter 2 Deck (68):
1

What is the most abundant molecule in cells?

water

2

Is water polar or nonpolar?

polar due to slightly positive charge on hydrogen atoms and slightly negative charge on oxygen atoms

3

Four classes of organic molecules

carbohydrates
lipids
proteins
nucleic acids

4

Glycosidic bonds

result of dehydration reactions that join together monosaccharides

5

Oligosaccharides

polymers of a few sugars

6

Polysaccharides

macromolecules; polymers of hundreds or thousands of sugars

7

Glycogen

stores glucose in animal cells

8

Starch

stores glucose in plant cells

9

Glycogen and Starch

both composed entirely of glucose molecules in alpha configuration

10

Lipids have three main roles

-energy storage
-major component of cell membranes
-cell signaling as steroid hormones and messenger molecules

11

What is the only nonglycerol phospholipid in cell membranes?

sphingomyelin

12

amphipathic molecule

part water-soluble and part water-insoluble

13

Nucleic acids

principal informational molecules of the cell

14

Deoxyribonucleic acid

the genetic material

15

Ribonucleic acid

several types

16

Messenger RNA

carries information from DNA to ribosomes

17

Ribosomal RNA and transfer RNA

involved in protein synthesis

18

DNA

double helix with two stands of the helix running antiparallel to one another

19

External of the DNA helix

sugar and phosphate groups

20

Internal of DNA helix

bases

21

Adenine base pairs with

thymine via two hydrogen bonds

22

Cytosine base pairs

guanine sharing three hydrogen bonds

23

How many base pairs per turn of the helix?

10 base pairs

24

Bases are separated by how much?

.34 nm

25

What do the bases exhibit?

propeller twist around the axis of the double helix

26

Plectonemically coiled

two strands of the helix

27

What contribute to the chemical stability of the double helix?

hydrogen bonding and base stacking interaction

28

The two strands of the helix

are complimentary not identical

29

The most diverse of all macromolecules

proteins

30

What virtually directs all activities of the cell?

proteins

31

Proteins

are polymers of 20 different amino acids
have distinct 3-D conformations that are critical to their function

32

amino acids with nonpolar side chains

do not interact with water-hydrophobic

33

amino acids with polar side chains

uncharged but can interact with water-moderately hydrophilic

34

amino acids with side chains with charged basic groups

very hydrophilic

35

amino acids with acidic side chains terminating in carboxyl groups

very hydrophilic

36

What is x-ray crystallography used for?

analyze protein structure

37

John Kendrew

first to determine the 3-D structure of a protein myoglobin which is 153 amino acids

38

Two common types of secondary structure

alpha helix and beta sheet

39

Alpha helix and beta sheet held together by what?

bonds between the CO and NH groups of peptide bonds

40

Tertiary structure

the polypeptide chain folds due to interactions between side chains of amino acids in different regions of the chain

41

domains

the basic units of tertiary structure

42

Quaternary structure

interactions between different polypeptide chains in proteins composed of more than one polypeptide

43

Hemoglobin

is composed of four polypeptide chains

44

enzymes

catalysts that increase the rate of all chemical reactions in cells

45

fundamental properties of enzymes

-increase rate of chemical reactions without themselves being consumed or permanently altered
-increase reaction rates without altering the chemical equilibrium between reactants and products

46

active site

the site where a substrate binds to a specific region

47

lock and key model

the substrate fits precisely into the active site

48

induced fit

conformation of both enzyme and substrate is modified

49

prosthetic groups

small molecules bound to proteins that have critical functional roles

50

coenzymes

small organic molecules that work together with enzymes to enhance reaction rates

51

nicotinamide adenine dinucleotide (NAD+)

a coenzyme that carries electrons in oxidation-reduction reactions

52

feedback inhibition

the product of a metabolic pathway inhibits an enzyme involved in its synthesis

53

allosteric regulations

enzyme activity is controlled by the binding of small molecules to regulatory sites on the enzyme

54

phosphorylation

a common mechanism of enzyme regulations
can either stimulate or inhibit the activities of many enzymes

55

cell membranes

phospholipid bilayers with associated proteins

56

phospholipid bilayers

form a stable barrier between two aqueous compartments

57

lipid bilayers

are 2-dimensional fluids in which molecules are free to rotate and move laterally

58

cholesterol

reduces interaction between fatty acids, maintaining membrane fluidity at lower temperatures

59

fluid mosaic model

proposed by Singer and Nicolson that integral membrane proteins inserted into a phospholipid bilayer, with nonpolar regions in the lipid bilayer and polar regions exposed to the aqueous environment

60

integral membrane proteins

embedded directly in the lipid bilayer

61

peripheral membrane proteins

associated with membrane indirectly, generally by interactions with integral membrane proteins

62

transmembrane proteins

span the lipid bilayer, with portions exposed on both sides

63

alpha helical regions

20 to 25 nonpolar amino acids

64

beta barrel

formed by folding of beta sheets into a barrel-like structure
found in some bacteria, chloroplasts, and mitochondria

65

channel proteins

form open pores across the membrane and they can be selectively opened and closed in response to extracellular signals

66

carrier proteins

selectively bind and transport small molecules, such as glucose

67

passive transport

molecule movement across the membrane is determined by concentration and electrochemical gradients

68

active transport

molecules can be transport against a concentration gradient if coupled to ATP hydrolysis as a source of energy