Ch.1/2 - Intro & Chem Components of Cells

Question 1

________ is the amount of energy required to break a bond.

Answer 1

Bond strength is the amount of energy required to break a bond.

• Typ expressed as [kcal/mole] or [kJ/mole]
  
  • 1 kcal = ~4.2 kJ
  • kcal: amount of energy to raise temp of 1 liter of water by 1C.

Question 2

T/F: The presence of water signif increases covalent bond strength relative to ionic bond strength.

Answer 2

True

The presence of water signif increases covalent bond strength relative to ionic bond strength.

• In aq soln, ionic bonds 10–100x weaker than covalent bonds.

Question 3

T/F: Small organic molecules are much less abundant than organic macromolecules.

Answer 3

True

Small organic molecules are much less abundant than organic macromolecules.

• Small org molecules account for only ~1/10 total mass of organic matter in cell.

Question 4

What are the four major families of small organic molecules?

Answer 4

Small organic molecules: sugars, fatty acids, amino acids, and nucleotides.

• Account for most, but not all, of cell’s mass.

Question 5

Monosaccharides can be converted into diff sugars (e.g. glucose, mannose, or galactose) simply by switching orientations of specific ________ groups.

Answer 5

Monosaccharides can be converted into diff sugars (e.g. glucose, mannose, or galactose) simply by switching orientations of specific –OH (hydroxyl) groups.

• Two forms: D-form and L-form; mirror images of ea/o, i.e. optical isomers.

Question 6

Two monosaccharides can be linked by a covalent _________ bond to form a __________.

Answer 6

Two monosaccharides can be linked by a covalent glycosidic bond to form a disaccharide.

Question 7

What feature of sugars makes branched polysaccharides possible?

Answer 7

Each mono has several free hydroxyl groups that can form glycosidic bond (or link w some other compound) → can be branched → large # of possible poly structures.

Question 8

Fatty acid chains are formed by what two chemically distinct regions?

Answer 8

Fatty acid chains are formed by a long HC chain tail and a carboxyl group (-COOH) head.

Question 9

What feature of fatty acid chains cause them to behave like an acid in aq soln?

Answer 9

The carboxyl group (head) behaves as an acid (carboxylic acid), i.e. donates H+ in aq soln (–COO^–) → extremely hphilic → chemically reactive.

• Almost all FAs in cell are covalently linked to other molecules by carboxylic acid group.

Question 10

Fatty acids are a rich energy source and are stored as ________ in the cytoplasm.

Answer 10

Fatty acids are a rich energy source and are stored as triacylglycerols in the cytoplasm.

• Can be broken down to produce ~6x as much usable energy, weight for weight, as glucose.
• Stored in cytoplasm in form of fat droplets composed of triacylglycerols—3 FA chains covalently joined to a glycerol.

Question 11

When cells need energy, ________ are released from triacylglycerols and broken into ____ units.

Answer 11

When cells need energy, fatty acid chains are released from triacylglycerols and broken into 2-C units.

• These 2-C units are identical to those derived fr breakdown of glucose → enter same energy-yielding rxn pathways.

Question 12

Loosely defined as insoluble in water but soluble in fat/organic solvents (e.g. benzene), ______ include fatty acid chains and its derivatives (e.g. triacylclycerols.

Answer 12

Loosely defined as insoluble in water but soluble in fat/organic solvents (e.g. benzene), lipids include fatty acid chains and its derivatives (e.g. triacylclycerols.

• May contain multiple linked aromatic rings instead of FA chains; e.g. steroids.

Question 13

Describe the structure of phospholipids.

Answer 13

Phospholipids:

• Most constructed mainly fr FAs and glycerol.
  
  • Glycerol is joined to two FA chains (rather than 3 in triacylglycerols).
• Remaining –OH group on glycerol is linked to a hphilic P group → attached to small hphilic comp, typ choline.
• Strongly amphipathic → diff chem/phys props fr triacylglycerols (predom hphobic).
• Spontaneous arrangement - readily form lipid bilayer/other strucs in aq soln (water).

Question 14

What is the one defining property of all amino acids?

Answer 14

Amino acids - one defining property: all possess carboxylic acid group and an amino group, both linked to their α-carbon atom.

• side chain attached to α-C → identity distinguishes AAs.

Question 15

All AAs (except glycine) exist as _________ in D and L-forms (like sugars), of which the __-form is signif more common.

Answer 15

All AAs (except glycine) exist as optical isomers in D and L-forms (like sugars), of which the L-form is signif more common.

Question 16

_________ are composed of a N-containing ring linked to a pentose sugar, like ribose or deoxyribose.

Answer 16

Nucleosides are composed of a N-containing ring linked to a pentose sugar, like ribose or deoxyribose.

Question 17

Nucleotides are the subunits of DNA and RNA. What differentiates nucleotides fr nucleosides?

Answer 17

Nucleotides are nucleosides w 1+ P groups attached to sugar (at 5’C).

Question 18

Adenosine triphosphate (ATP) is a ribonucleotide w three P groups linked in series by two _________ bonds.

Answer 18

Adenosine triphosphate (ATP) is a ribonucleotide w three P groups linked in series by two phosphoanhydride bonds.

• Rupture of these P bonds releases large amounts of useful energy.
• Terminal P group frequently split off by hydrolysis → often transferred to another molecule → releases energy that drives energy-req biosynth rxns.

Question 19

Each macromolecule contains a specific sequence of subunits formed via _________ reactions.

Answer 19

Each macromolecule contains a specific sequence of subunits formed via polymerization reactions.

• Grow via condensation (dehydration) rxn
• Catalyzed by specific enzymes in repeated process.
• Subunits are added in particular sequence, not random.

Question 20

Animal and plant cells are typ __to __ µm in diam and can be seen w a ______ microscope, wh also reveals some of their internal components, incl larger organelles.

Answer 20

Animal and plant cells are typ 5-20 µm in diam and can be seen w a light microscope, wh also reveals some of their internal components, incl larger organelles.

• Cannot resolve structures < 0.2 µm (half wavelength of visible light).
• Tissue must be fixed and often stained.

Question 21

________ microscopes are a recent development which utilizes sophisticate methods of illumination and processing to resolve structures as small as a ~20 nm, e.g. a single ribosome.

Answer 21

Fluorescence microscopes are a recent development which utilizes sophisticate methods of illumination and processing to resolve structures as small as a ~20 nm, e.g. a single ribosome.

Question 22

_______ microscopes provide the highest magnification and best resolution (0.2-2nm, e.g. some larger atoms), but requires painstaking preparations.

Answer 22

Electron microscopes provide the highest magnification and best resolution (0.2-2nm, e.g. some larger molecules), but requires painstaking preparations.

• Cannot view living, wet cells.

Question 23

Electron microscopes cannot resolve individual atoms (< 0.2nm). What method might be used to observe the precise 3D structure of proteins?

Answer 23

Electron microscopes cannot resolve individual atoms (< 0.2nm). What method might be used to observe the precise 3D structure of proteins?

X-ray crystallography

Question 24

__________ are a free-living, non-photosynthetic, single-celled, motile euk (microorganism).

Answer 24

Protozoans (plural: protozoa) are a free-living, non-photosynthetic, single-celled, motile euk (microorganism).