Cell Biology Lecture 3

Front 1

2 Important macromolecule families

Back 1

Nucleic acids
Proteins

Front 2

Macromolecule vs. Small organic molecule

Back 2

Small org. molecules were composed of all covalent bonds. In macromolecules you have covalent andd weak bonds. Weak bonds necessary for flexibility (allow for breakage and reformation). Covalent bonds allow stability.

Front 3

4 Types of weak bonds/ interactions

Back 3

1. Ionic
2. Hydrogen
3. Van der Waal
4. Hydrophobic

Front 4

Weak Bonds (1)

Back 4

IONIC. Attraction between pos/neg charged molecules. Much weaker than covalent bonds in the presence of water. Very strong in absence of water. Are cases in the cell where water is excluded and so have strong ionic bonds, but generally they are present as weak bonds.

Front 5

Weak Bonds (2)

Back 5

Hydrogen atom shared between two electronegative atoms. Very important in DNA and RNA.

Front 6

Weak Bonds (3)

Back 6

VAN DER WAAL. Weakest of the weak. Atoms greatly packed together. Atoms in close proximity with each other. Most of the time there isn't anything going on between them. On occassion, you have positively charged nucleus and negatively charged electrons, sometime they line up so there is an attraction between them. Fleeting attraction. But strong enough to impaort an attraction. So many atoms within cell that this occurs frequently, so you have attraction within.

Front 7

Weak Bonds (4)

Back 7

HYDROPHOBIC. Attraction. Two methyl groups associated with hydrophobic ends of a FA. Those 2 have no attraction. Can't organize cell around methyl groups. Methyl groups will then by default come together. Due to mutual dislike of water.

Front 8

DNA & RNA
Amount

Back 8

DNA & RNA make up 1-3% of the dry weight of the cell. Proteins make up 50%.

Front 9

DNA is found where in the cell?

Back 9

Localized in two regions of the cell, not distributed throughout. Found in the nucleus and in the mitochondria.

Front 10

RNA is found where in the cell?

Back 10

Can be found everywhere; in 7 organelles. Its ubiquitous in its distribution. 3-5 times as much RNA as DNA.

Front 11

DNA Structure

Back 11

Relatively stable in terms of amount within cell, unless it divides. Strucutre is unbranched polymer consisting of only 4 different nucletides. Generally exists as double stranded helix.

No uracil. Combine two nucleotides to form the phosphodiester bond. Breaking & forming of this bond is very important in transcription & translation of DNA. When you add to DNA, you add at the 3' end.

Front 12

Nucleic acids directionality

Back 12

Name based on where phosphate and hydroxyl groups are. Open phosphate; 5' end.

Purine & pyrimidine always bond.

Front 13

Bonding Pairs

Back 13

AT have 2 hydrogen bonds between bases.
CG have 3 hydrogen bonds between bases.

Front 14

Antiparallel

Back 14

5' & 3' ends are opposite on other side

Front 15

Adjacent

Back 15

On same side

Front 16

Complementary

Back 16

A & T.

Due to these pairs ladder will twise and exist as a helix. Each 10 compl. pairs will have one turn.

Front 17

DNA Helix

Back 17

Is 2 nm in diameter. Up to 1m in length.

Front 18

How is DNA typically stored?

Back 18

As chromatin. Cannot exist naked, because it would be chewed apart in the cell (defensive mechanisms of the cell).

Front 19

Which 4 proteins pair up and form a little ball? Histone proteins

Back 19

H2A
H2B
H3
H4

Front 20

What is the little ball composed of 8 histone proteins called?

Back 20

Nucleosome

Front 21

DNA begins to wrap itself around nucleosome...

Back 21

Wrap itself 1.7 turns. Nooks and groves present make it easy to wrap DNA around it and make it easy to hide DNA from enzymes that would destroy it. Nucleosomes; 25 million per cell. DNA double helix wraps around one nucleosome and then wraps around others. Eventually nucleosomes; beads on string, begin to wrap around self. 11 nm in diameter. If you continue to wrap and make it tight enough and coil it so that it forms a chromosome. 1400 nm is the biggest diameter of a chromosome. When wrapping around multiple nucleosomes, there are "open areas", nope the H1 histone protects the linker DNA areas. Not only organized, but protected in the cell.

Front 22

Chromatin

Back 22

Used to represent how DNA is in cell. Histone proteins + DNA; chromatin.

Front 23

Chromatin in most condensed form will make?

Back 23

A chromosome. Most of the time they are in present in interphase and are slightly dispersed.

Front 24

In late telophase chromosome will decondense into?

Back 24

Heterochromatin. So tightly bound to histones you will not replicate or transcribe them. Just there to be organized.

Front 25

Decondensed form of heterochromatin?

Back 25

Euchromatin is the final form of chromatin. This form is the least condensed; most decondensed. It is the euchromatin you transcribe, chromatin must be decondensed into euchromatin.

Front 26

Possible to have DNA on one side and RNA on one side?

Back 26

Yes, during transcription or replication

Front 27

Can you have RNA and DNA next to each other on the same strand?

Back 27

Only is special cases associated with replication, but in GENERAL you won't see that. Ultimately will use DNA to make RNA which will make Proteins

Front 28

Protein

Back 28

Macromolecule. Easy to make. Phosphodiester bond doesn't exist in protein. Here we have the peptide bond; covalent bond just like phosphodiester. Strong bond so little rotation. Strength comes from peptide bond, flexibility from others.

Front 29

Protein
Directionality

Back 29

Open amino and carboxyl end. Carboxy-terminus and Amnio-terminuc. C-terminus & N-terminus. Read from amino to carboxy terminus. DNA read from 5' to 3'. Add to carboxy terminus

Front 30

How many different amino acids exist in cell? Average size?

Back 30

20. Presume we're going to make small protein; 4 amino acids, 160000 diff combinations of a protein. Average protein size in a cell is 300 amino acids and there are 10^309 combinations.

Front 31

Why only 20,000 diff. proteins found in the cell?

Back 31

Stability & flexibility. Protein must be like spaghetti noodle before & after cooked. Only a few combinations that are stable and flexible.

Front 32

Proteins exist in which 2 structural entities?

Back 32

Globular or fiborous. In forming these we have to go to higher order structures. As protein is made it begins to fold and bend into final form, folded while being made. As you fold primary structure you go into secondary strcuture.