Molecular cell biology: Chapter 2: Molecules and Membranes

What is the most abundant molecule in cells?

Water

Describe how water is polar?

The hydrogen atoms have a slight positive charge and the oxygen has a slight negative charge

Describe the bonds that water forms?

hydrogen bonds

Describe the solubility of water and polar molecules

They are readily soluble in water (hydrophillic)

Describe the solubility of non-polar molecules in water?

they cannot interact with water and are poorly soluble (hydrophobic)

How much of the mass do inorganic molecules contribute to of a cell?

List examples of ionorganic molecules

1% or less; sodium, potassium, magnesium, calcium, phosphate, chloride, and bicarbonate

List the type of organic molecules

carbohydrates, lipids, proteins, and nucleic acids

What are included by carbohydrates?

simple sugars and polysaccharides

What are monosaccharides?

(simple sugars) major nutrients of cells.

What is the basic formula for monosaccharides?

(CH2O)n

What proves as the principal source of cellular energy?

glucose

What reaction helps with the formation of a glycosidic bond?

Dehydration reactions (H2O is removed); sugars get linked by a glycosidic bond

Define oligosaccharides

polymers of a few sugars

Define Polysaccharides

polymers of hundreds or thousands of sugars

Describe the configuration of a glycosidic bond for monosaccharides and polysaccharides

Alpha 1-->4 glycosidic bond

List the common polysaccarides

Glycogen and Starch

Define Glycogen

storage of glucose in animal cells

Define starch

Storage in plant cells

What are polysaccharides composed of?

glucose molecules in the alpha configuration

What do glycogen and amylopectin also contain?

alpha (1-->6) bonds

What do the alpha 1-->4 bonds and alpha 1-->6 bonds serve as?

branch points

What is cellulose?

main structural component of plant cell walls

What is cellulose composed of?

glucose molecules in the beta configuration

What does the beta 1 -->4 linkage result in?

Great mechanical strength of plant cell walls

List the main roles of lipids?

1. Energy storage

2. Major component of cell membranes

3. Important in cell signaling as a steroid hormone and messenger molecule

What are fatty acids?

long hydrocarbon chains (16 or 18 carbons) with a carboxyl group (COO-) at one end

What makes an unsaturated fatty acid?

it has one or more double bonds

What makes a saturated fatty acid?

It has No double bonds

List an unsaturated fatty acid.

Oleate

List saturated fatty acids.

Palmitate, stearate

The hydrocarbon chain in fatty acids is hydrophobic/hydrophillic/amphipathic.

hydrophobic

What are fatty acids stored as?

Triacylglycerols or fats.

Describe the configuration of Triaclyglycerols.

3 fatty acids linked to a glycerol molecule

Describe the solubility of fatty acids, and what do they accumulate as in the cytoplasm.

not soluble in water, and accumulate as fat droplets in the cytoplasm

Fats are more/less efficient energy storage than carbohydrates. Why?

more; it yields more than twice as much energy per weight of the material broken down.

What are phospholipids?

principle component of cell membranes

Describe the composition of phospholipids.

2 fatty acids joined to a polar head group

Describe the structure of phospholipids

hydrophobic tail made with hydrocarbon chains and a hydrophillic head made of phosphate group and polar attachment

Phospholipids are hydrophobic/hydrophillic/amphipathic.

ampiphatic

Describe the structure of glycerol phospholipids

2 fatty acids are bound to carbon in glycerol. The third carbon of glycerol is bound to a phosphate group, which in turn, frequently attached to another small polar molecule.

List the glycerol phospholipids

choline, serine, inositol, and ethanolamiae

What is special about sphingomyelin?

Only nonglycerol phospholipid in cell membranes. The polar head is formed from serine instead of glycerol

Define glycolipids

two hydrocarbon chains and a carbohydrate polar head group (ampipathic)

Define cholesterol

four hydrophobic hydrocarbon rings and a polar hydroxyl (OH) group (amphipathic)

What do many cell membranes also have (excluding phospholipids)?

glycolipids and cholesterol

List the steroid hormones

estrogen and testosterone

What are steroid hormones

derivatives of cholesterol and act as chemical messenger

What is the genetic material?

Deoxyribonucleic acid (DNA)

What does messenger RNA (mRNA) do?

carries information from DNA to ribosomes

What does ribosomal RNA (rRNA) and transfer RNA (tRNA) do?

involved in protein synthesis

What are the other RNAs involved to (excluding mRNA, rRNA, and tRNA)?

regulation of gene expression and processing and transport of RNAs and proteins

What are DNA and RNA?

polymers of nucleotides

What do DNA and RNA consist of?

two purines and two pyrimidine bases linked to phosphorylation sugars

What does DNA contain?

two purines (adenine and guanine) and two pyrimidines (cytosine and thymine)

What is the difference of RNA to DNA?

RNA has uracil in place of thymine

In nucleic acids, what are the bases linked to and what is formed?

sugars to form nucleosides

What is the sugar that DNA has?

2'-doxyribose

What sugar does RNA have?

ribose

Describe the linkage that nucleotides have?

They have one or more phosphate groups linked to the 5' Carbon of the sugars

Describe the bonds of the polymerization of nucleotides

phosphodiester bonds between the 5' phosphate of one nucleotide and to 3' hydroxyl of another

What are oligonucleotides?

polymers of only a few nucleotides

DNA and RNA are oligonucleotides/polynucleotides and may contain thousands or millions of nucleotides.

polynucleotides

Describe a polynucleotide chain

It has a sense of direction with one end terminating in a 5' phosphate group and the other in a 3' hydroxyl group

How are polypetides synthesized?

from the 5' to 3' direction

a. What is the Information in DNA and RNA conveyed by?

b. Where are the bases at?

a. the order of the bases

b. on the inside joined by hydrogen bonds between complementary base pairs.

What bond brings complementary base pairs together?

hydrogen bonds

What are the complementary base pairs in DNA?

Guanine (G) with Cytosine (C) and Adenine (A) with Thymine (T)

What are the complementary base pairs in RNA?

Guanine with Cytosine and adenine and Uracil

Describe the contents of chromosome.

There are supercoils that have coils inside that have a nucleosome. Nucleosome has histones that contains DNA

What does complementary base pairing allow?

It allows one strand of DNA (or RNA) to act as a template for synthesis of a complementary strand

Why are nucleic acids capable of self-replication?

complement base pairing

What does the information carried by DNA and RNA do?

It directs synthesis of specific proteins which control most cellular activities

What is Adenosine 5'-triphoshate?

the principal form of chemical energy within cells

What does cyclic AMP do?

acts as signaling molecule within cells

Which macromolecule is the most diverse?

proteins

How many proteins are in each cell?

thousands

What do proteins do (in a general sense)

direct virtually all activities of a cell

What are specific functions of proteins? (Hint 5)

1. structural components

2. transport and storage of small molecules. ex: o2

3. Transport information between cells (protein hormones)

4. Defense against infection (antibodies)

5. enzymes

What are proteins?

Polymers of about 20 different amino acids

What does each amino acid consist of (chemical structure)?

an alpha carbon bonded to a carboxyl group (COO-), an amino group (NH3+), a hydrogen, ad a distinctive side chain.

1. What criteria are amino acid grouped upon?

2. What are the 4 categories?

1. Based on their characteristics of their side chains.

2. Non-polar side chains, polar side chains, side chains with charged basic groups, acidic side chains terminating in carboxyl groups

How are the amino acids joined?

Peptide bonds

Define polypeptides

chains of amino acids, hundreds or thousands of amino acids.

Describe how polypeptides terminate.

One end of a polypeptide terminates in an alpha amino group (N terminus) and the other in an alpha Carboxyl group (C terminus)

What does the amino acid sequence do?

defines the characteristics of proteins

Who and when was the sequence of insulin worked out

Fredrick Sanger in 1953

What are protein sequences deduced from?

sequences of mRNA.

What does insulin consist of?

two polypeptide chains

Describe the interactions of side chains in insulin.

The side chains of three pairs of cysteine residue are joined by disulfide bonds

What is the sequence of amino acids in a protein determined by?

the order of nucleotide bases in a gene

Why do proteins have a 3-dimensional structure?

interactions between the amino acids so the shape of amino acids is determined by their amino acid sequences

Describe what Christian Anfisen did.

-He disrupted proteins with treatments such as heating which broke non-covalent bonds (desaturation).

-If the treatment was mild, then the proteins would return to their original shape.

Therefore, he showed that all the information required to specify the correct 3-D conformation of a protein is contained in its primary amino sequence.

What is desaturation?

A treatment in which proteins are disrupted by heating and non-covalent bonds are broken.

List the four levels of Protein structure

Primary, secondary, tertiary, and quaternary

Define primary structure

The sequence of amino acids in the polypeptide chain

Define secondary structure.

regular arrangement of amino acids within localized regions

What are the two common types of secondary structure?

alpha helix and beta sheets

What are the alpha helix and beta sheet held together by?

hydrogen bond between the CO and NH groups of peptide bonds

Define tertiary structure

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

In most proteins, what does tertiary structure result in?

domains