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Biology 201 > The macromolecules of a cell > Flashcards

The macromolecules of a cell Flashcards

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1
Q

What is synthesized in condensation reactions?

A

polymers in which activated monomers are linked together by the removal of water

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2
Q

What are the nine classes of proteins and what do they do?

A

Enzymes - serve as catalysts, increasing the rates of chemical reactions
Structural - physical support and shape
Motility - contraction and movement
Regulatory - control and coordinate cell function
Transport - move substances into/out of cells
Signalling - communication between cells
Receptor - enable cells to respond to chemical stimuli from environment
Defensive - protect against disease
Storage - reservoirs of amino acids

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3
Q

How many kinds of amino acids are used in protein synthesis?

A

only 20, but some contain additional amino acids due to modification

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4
Q

What is the typical formation of amino acids?

A 
Side chain ( R group)
asymmetric alpha carbon atom ( except glycine)
the specific properties of amino acids depend on their R group
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5
Q

How many amino acids have non polar, hydrophobic R groups?

A

9

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6
Q

Eleven amino acids have what kind of R groups?

A

hydrophilic, these R groups are either polar or charged at cellular pH

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7
Q

What kind of amino acids are negatively charged?

A

Acidic

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8
Q

What kind of amino acids are positively charged?

A

Basic

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9
Q

Where are polar amino acids normally found?

A

on the surfaces of proteins

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10
Q

Amino acids are linked together stepwise into a linear polymer by what kind of reaction?

A

Dehydration (or condensation)

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11
Q

What happens as water is removed in a condensation reaction?

A

a covalent C-N bond (peptide bond) is formed

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12
Q

Do polypeptides have directionality?

A

Yes,

  • the end w/ the amino group is the N- (amino) terminus
  • the end with the carboxyl groups is the C- (carboxyl) terminus
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13
Q

What is protein synthesis?

A

The process of elongating a chain of amino acids - polypeptide

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14
Q

what are covalent disulphide bonds?

A

they form between the sulphur atoms of two cysteine residues - form through the removal of two hydrogens (oxidation) and can be broken only by the addition of tow hydrogens ( reduction)- provide stability to protein conformation

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15
Q

What are intramolecular disulphide bonds?

A

form between cysteine in the same polypeptide

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16
Q

What are intermolecular disulphide bonds?

A

form between cysteine in two different polypeptides

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17
Q

What are the four structures of a protein?

A

Primary - amino acid sequence
Secondary - local folding of polypeptide
Tertiary - 3-dimensional conformation
Quaternary - interactions between monomeric proteins to for a multimeric unit

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18
Q

What is the direction of the amino acid sequence in primary structure? Why is primary structure important?

A

from the N-terminus to the C-terminus, the direction in which the polypeptide was synthesized.
It is important genetically ( sequence specified by the order of nucleotides in mRNA) as well as it directs the formation of higher order structures

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19
Q

What did Sanger win the Nobel prize for?

A

he cleaved the insulin protein into smaller fragments and analyzed the amino acid order within individual overlapping fragments.

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20
Q

What does the secondary structure do?

A

describes local regions of structure that result from hydrogen boding between the NH and CO groups along the polypeptide backbone - results in the alpha helix and the beta pleated sheet

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21
Q

What is the alpha helix?

A

spiral shape, consists of the peptide backbone, with R groups jutting out from the spill. there are 3.6 amino acids per turn of the helix.

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22
Q

what is the beta pleated sheet?

A

an extended sheetlike conformation with successive atoms of the polypeptide chain located at “peaks” or “troughs”. R groups jut out on alternating sides of the sheet. It is characterized by a max of hydrogen bonding, but formation may involve different polypeptides or different regions of a single polypeptide

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23
Q

What are motifs?

A

short stretches of alpha helices and beta sheets

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24
Q

What is the tertiary structure?

A

reflects unique aspect of amino acid sequence because it depends on interactions of the R groups. Not repetitive nor predictable. Results from the summer of hydrophobic residues avoiding water.

25
Q

What is a native conformation?

A

the most stable 3- dimensional structure of a particular polypeptide

26
Q

What are fibrous proteins?

A

have extensive regions of secondary structure, giving them a highly ordered, repetitive structure (ex. keratin proteins of hair and wool)

27
Q

What are globular proteins?

A

majority of proteins, they are folded into compact structures. Each type has its own unique tertiary structure. Most enzymes are gobbler proteins.
Can be mainly alpha helical, beta sheet, or a mix of both.
Many consist of a number of segments called domains

28
Q

What is a protein domain?

A

a discrete, locally folded unit of tertiary structure, usually with a specific function.
typically 50-350 amino acids long, with regions of alpha helices and beta sheets packed together
Proteins with similar functions usually share a domain, while proteins with multiple functions usually have separate domains for each function

29
Q

What is the quaternary structure?

A

the level of organization concerned with subunit interactions and assembly.
applies specifically to multimeric proteins
bonds and forces maintaining this structure are the same as those for tertiary.
the process for subunit formation is usually spontaneous and sometimes requires molecular chaperones

30
Q

When is a higher level assembly possible?

A

in the case of proteins (usually enzymes) that are organized into multi protein complexes. each protein in the complex may be involved sequentially in a common multistep process.

31
Q

What do nucleic acids do?

A

store, transmit and express genetic info.

they are linear polymers of nucleotides

32
Q

What are the proper names for DNA and RNA?

A

deoxyribonucleic acid an ribonucleic acid

33
Q

What are the differences between DNA and RNA?

A

RNA - 5 carbon sugar = ribose
DNA - sugar = deoxyribose
DNA - repository of genetic info
RNA - plays several roles in expressing genetic info

34
Q

What are the purines?

A

adenine (A) and guanine (G)

35
Q

What are the pyrimidines?

A

thymine (T) and cytosine (C) and in RNA, uracil (U)

36
Q

What is the sugar-base portion without the phosphate group called?

A

nucleoside

37
Q

What are nucleic acids?

A

linear polymers of nucleotides linked by a 3’,5’ phosphodiester bridge, a phosphate group linked to two adjacent nucleotides via two phosphodiester bonds
the polynucleotide formed by this process has a directionality with a 5’ phosphate group at one end and a 3’ hydroxyl group at the other

38
Q

What direction are nucleotide sequences written in?

A

the 5’ to 3’ direction

39
Q

What are the complimentary base pairs?

A

A -T ( or U in RNA)

C-G

40
Q

Who came up with the double helix structure?

A

Crick and Watson in 1953 - the structure accounted for the known physical and chemical properties of DNA - also suggested a mechanism for DNA replication.
2 antiparallel and complementary strands of DNA twist around a common axis to form a right handed spiral structure

41
Q

What is RNA’s structure?

A

single stranded

42
Q

What are polysaccharides?

A

long chain polymers of sugar and sugar derivatives - serve primarily in structure and storage - consist of a single kind of repeating unit or sometimes an alternating pattern of 2 kinds.
Short polymers are sometimes attached to cell surface proteins

43
Q

What are repeating units of polysaccharides called?

A

monosaccharides

44
Q

What are the classifications of sugars?

A
  • trioses (3 C)
  • tetroses (4 C)
  • pentoses (5 C)
  • hexoses (6 C)
  • heptoses (7 C)
45
Q

What is the structure of glucose?

A

D-glucose is the most stable form of glucose -in the cell, it exists in a dynamic equilibrium between the linear and ring form

46
Q

What are the two forms of D- glucose?

A

Alpha (hydroxyl group downward)

Beta (hydroxyl group upward)

47
Q

What is a glycosidic bond?

A

the linkage of disaccharides, formed between two monosaccharides by the elimination of water

48
Q

What are the most familiar storage polysaccharides in plant and animals?

A

plant cells - starch
animal cells and bacteria - glycogen
both consist of alpha D-glucose unties linked by alpha glycosidic bonds, involving carbons 1 and 4. Sometimes alpha (1-6) bonds may form, allowing for the formation of side chains (branching)

49
Q

Structure and storage of glycogen?

A

highly branched, occurring every 8-10 glucose units along the backbone
stored mainly in the liver and muscle tissues of animals

50
Q

What is starch?

A

the glucose reserve commonly found in plant tissue
It is both:
unbranched amylose (10 - 30%)
branched amylopectin (70-90%)
it is stored as starch grains within the plastids
- chloroplasts, the sites of carbon fixation and sugar synthesis
- amyloplasts - which are specialized for starch storage

51
Q

What is the structural polysaccharides found in plant cell walls?

A

cellulose - composed of repeating monomers of beta D-glucose

-hard to digest for mammals

52
Q

What are lipids?

A

regarded as macromolecules because of their high molecular weight and their importance in cellular structures (membranes)
all have hydrophobic nature - readily soluble in non polar solvents
some are amphipathic
functions - energy storage, membrane structure, specific biological functions

53
Q

What are the 6 classes of lipids?

A
  • fatty acids- long amphipathic, unbranched hydrocarbon chain with a carboxyl group at one end
  • triaclyglycerols -consist of a glycerol molecule with 3 fatty acids attached
  • phospholipids - membrane structure
  • glycolipids - lipid containing a carbohydrate, often a derivative of sphingosine and glycerol
  • steroids -derivatives of a 4-ringed hydrocarbon skeleton, non polar therefore hydrophobic
  • terpines
54
Q

what is a glycerol?

A

3 carbon alcohol with a hydroxyl group on each end

55
Q

what is the function of triclyglycerols?

A

energy storage

56
Q

what are phosphoglycerides?

A

the predominant phospholipid in most membranes

consists of a phosphatidic acid, which has 2 fatty acids and a phosphate group attached to a glycerol

57
Q

What are sphingolipids?

A

based on the amine sphingosine, which has a long hydrocarbon chain with a single site of unsaturation near the polar end
mainly found in the outer leaflet of the plasma membrane bilayer, often in lipid rafts (important in communication between cell and its external environment), localized domains within a membrane

58
Q

Why is cholesterol important?

A

starting material for synthesis of steroid hormones

59
Q

What are terpenes formed from?

A

Isoprene

Biology 201 (3 decks)

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