Molec Cell: Ch. 2 (pt. 1)

Chapter 2: Molecules and Membranes

What are cells composed of?

Water, inorganic ions, and Carbon-carbon containing (organic) molecules

What do inorganic ions include?

* Sodium (Na+)
* Potassium (K+)
* Magnesium (Mg2+)
* Calcium (Ca2+)
* Phosphate (HPO4 2-)
* Chloride (Cl-)
* Bicarbonate (HCO3-)

What do organic molecules include?

* Carbohydrates
* Lipids
* Proteins
* Nucleic Acids

What is the most abundant molecule in cells?

Water

What is the significance of water?

Water is a **polar molecule:**

* Hydrogen atoms are slightly positive.
* Oxygen is slightly negative.

What type of bonds does water create with each other or with other polar molecules?

Hydrogen bonds

What are some examples of molecules that bond using hydrogen bonds?

Hydrogen bonds form between polar organic molecules, such as amino acids in different parts of a protein.

Water: _____ bond, interact with ___ and ____ ions.

non-covalent, positive, negative

Ions and polar molecules are ____ in water, meaning they are ____.

soluble, hydrophilic

Nonpolar molecules: ___ interact with water; __ soluble, meaning they are hydro___.

cannot, poorly, hydrophobic

Carbohydrates include

simple sugars and polysaccharides

Monosaccharides

* simple sugars
* major nutrients of cells

basic formula of monosaccharides

(CH2O)n

Glucose provides…

the principal source of cellular energy

Formula for glucose

C6H12O6

How to link the monosaccharides?

Dehydration reactions (H2O is removed) / sugars are linked by a **glycosidic bond**

Oligosaccharides

polymers of a few sugars

Polysaccharides

polymers of hundreds or thousands of sugars

What are two common polysaccharides? What do they do?

1. **Glycogen:** storage of glucose in animal cells
2. **Starch:** storage in plant cells

What are glycogen and starch made out of and in what confirmation?

Made completely out of glucose in the *α* configuration.

What type of bonds do glycogen and one other form of starch contain?

Glycogen and amylopectin also contain α configuration.

What do the *α* configuration do?

serve as branch points

Amylopectin

* water soluble polysaccharide
* highly branched polymer of glucose in plants
* one of the two components of starch (other one in Amylose)

Cellulose

* main structural component of plant cell walls
* glucose in *β* configuration
* *β*(1→4) linkages

*β*(1→4) linkages

* great mechanical strength
* cause cellulose to form long extended chains that pack side by side to form fibers of great mechanical strength

What are the three main roles of lipids?

1. Energy storage
2. major component of cell membranes


1. important in cell signaling as steroid horomones and messenger molecules

Fatty acids

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

Unsaturated fatty acids

one or more double bonds

Saturated fatty acids

no double bonds, contains only nonpolar C-H bonds

The hydrocarbon chain is…

hydrophobic

Examples of saturated fatty acids

Palmitate, Stearate

Unsaturated Fatty Acid Example

Oleate

Triacylglycerols/fats strucuture?

three fatty acids linked to a glycerol molecule

Triacylglycerols are ___ in water and accumulate as _________ in the cytoplasm.

insoluble, fat droplets

What happens to Triacylglycerols in _____ reactions?

They are broken down in energy-yielding reactions

What is a more efficient energy storage?

Fats are more efficient energy storage than carbohydrates, yielding more than twice as much energy per weight of material broken down.

Phospholipids

The principal components of cell membranes

Describe the structure of phospholipids.

2 fatty acids joined to a polar head group

* hydrophobic tails: hydrocarbon chains
* hydrophilic head: phosphate group and polar attachment

Amphiatic molecules

part water-soluble / part water-insoluble

Glycerol phospholipids

2 fatty acids bond to two carbons in glycerol

The third carbon of glycerol are bound to a…

Phosphate group

\
frequently attached to polar molecules (choline, serine, inositol, ethanolamine)

Sphingomyelin

the only nonglycerol phospholipid in cell membranes

\
The polar head group is formed from __serine__, instead of __glycerol__

Phosphatidic acid

Many cell membranes also have… (2 things)

1. Glycolipids
2. Cholesterol

Glycolipids

two hydrocarbon chains and a carbohydrate polar head group

Cholesterol

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

The steroid hormones (ex: estrogens and testosterone) are derivatives of ____.

cholesterol

Steroid hormones act as…

chemical messengers

Steroid hormones contain ___ hydrocarbon rings.

4

What is the genetic material?

DNA

Messenger RNA

mRNA carries information from DNA to the ribosomes

Which RNAs are involved in protein synthesis?

Ribosomal RNA and transfer RNA

DNA and RNA are polymers of ____. They consist of__ __*amd*__ _____ bases linked to ______.__

Nucleotides, purine, pyrimidine, phosphorylated sugars

What are the purines and pyrimidines used in DNA?

Purines: adenine and guanine

Pyrimidines: cytosine and thymine

What does RNA have in place of thymine?

Uracil

The bases are linked to ___ to form ____.

sugars, nucleosides

nucleotides

one or more phosphate groups linked to 5’ carbon of sugars

Polymerization of nucleotides

* phosphodiester bonds between the 5’ phosphate of one nucleotide and the 3’ hydroxyl of another

Oligonucleotides

polymers of only a few nucleotides

RNA and DNA are _____ and may contain ___ or ______ of nucleotides.

polynucleotides, thousands or millions

In what direction are polynucleotides synthesized in?

5’ to 3’