Top1-Ch1-P7-13

Question 1

Plasmid?

Answer 1

It is a small DNA molecule that is physically separate from, and can replicate independently of, chromosomal DNA within a cell. Most commonly found as small circular, double-stranded DNA molecules in bacteria, plasmids are sometimes present in archaea and eukaryotic organisms. (wikipedia) They are not essential but may confer a selective advantage.

Question 2

How is the cytoskeleton structured in the eukaryotic cell?

Answer 2

The cytoplasmic filaments criss cross the cell forming an interlocking three dimensional network.

Question 3

Name the three general types of cytoplasmic filaments?

Answer 3

Actin filaments, microtubules, and intermediate filaments.

See picture below: The eukaryotic cytoskeleton. Actin filaments are shown in red, microtubules in green, and the nuclei are in blue.

Question 4

Proteins?

Answer 4

Are large biological molecules consisting of one or more chains of amino acids. Proteins perform a vast array of functions within living organisms, including catalyzing metabolic reactions, replicating DNA, responding to stimuli, and transporting molecules from one location to another.

Question 5

Amino acids?

Answer 5

Are biologically important organic compounds made from amine (-NH2) and carboxylic acid (-COOH) functional groups, along with a side-chain specific to each amino acid. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen, though other elements are found in the side-chains of certain amino acids. About 500 amino acids are known which can be classified in many ways.

Question 6

Peptides?

Answer 6

Are short chains of amino acid monomers linked by peptide (amide) bonds, the covalent chemical bonds formed when the carboxyl group of one amino acid reacts with the amino group of another. Peptides are distinguished from proteins on the basis of size, and as a benchmark can be understood to contain approximately 50 amino acids or less.

Question 7

Organelle?

Answer 7

Is a specialized subunit within a cell that has a specific function. Ie nucleus, mitochondria etc.

Question 8

Endomembrane system?

Answer 8

The different membranes suspended in cytoplasm of a eukaryotic cell, which divide cell into organelles.

The organelles of the endomembrane system include: the nuclear envelope, the endoplasmic reticulum, the Golgi apparatus, lysosomes, vacuoles, vesicles, endosomes and the cell membrane. Importantly, the endomembrane system does not include the membranes of mitochondria and chloroplasts.

Question 9

Exocytosis

Answer 9

Transport out of the cell that involves membrane fusion.

It is the durable process by which a cell directs the contents of secretory vesicles out of the cell membrane and into the extracellular space. These membrane-bound vesicles contain soluble proteins to be secreted to the extracellular environment, as well as membrane proteins and lipids that are sent to become components of the cell membrane.

Question 10

Endocytosis

Answer 10

Iis a process by which cells absorb molecules (such as proteins) by engulfing them. It is used by all cells of the body because most substances important to them are large polar molecules that cannot pass through the hydrophobic plasma or cell membrane. The process which is the opposite to endocytosis is exocytosis.

Question 11

Cell size hierarchy?

Answer 11

• *Level 4:** The cell and its organelles
• *Level 3:** Supramolecular complexes (ie chromatin, plasma membrane, cell wall)
• *Level 2:** Macromolecules (ie DNA, protein, cellulose)
• *Level 1:** Monomeric units (ie nucleotides, amino acids, sugars)

Question 12

How are monomeric units of proteins, nucleic acids and polysaccharides joined. Ie what forces?

Answer 12

Covalent bonds

Question 13

Name the forces holding macromolecules together?

Answer 13

They are non-covalent interactions which follow:

• *Hydrogen bonds** (between polar groups) - electromagnetic attractive interaction of a polar hydrogen atom in a molecule or group and an electronegative atom like N, O etc.
• *Ionic interactions** (between charged groups)
• *Hydrophobic interactions** (among non-polar groups in aqueous solution)
• *Van der Waals interactions** (London forces) - the sum of the attractive or repulsive forces between molecules (or between parts of the same molecule) other than those due to covalent bonds, the hydrogen bonds, or the electrostatic interaction of ions.

Question 14

In vitro

Answer 14

In the glass, in the test tube

Question 15

In vivo

Answer 15

in the living

Question 16

How many of the 90 naturally occurring chemical elements are essential to organisms?

Answer 16

Fewer than 30

Question 17

What are the four most abundant elements in living organisms in terms of percent of total number of atoms? How much of the mass of cells do they comprise?

Answer 17

Hydrogen, Oxygen, Nitrogen, and Carbon. They make up 99% of the mass of most cells.

Question 18

How much does carbon account for the dry weight of cells?

Answer 18

More than half the dry weight.

Question 19

What is the angle formed for a carbon atom when it has four single bonds, what is the shape name, and what is the average bond length?

Answer 19

109.5 degrees

Tetrahedron

0.154nm (nano metre or 10^-9)

Question 20

How many different types of small organic molecules are in the cytosol?

Answer 20

About a 1,000.

Question 21

What are secondary metabolites?

Answer 21

Found in vascular plants. An organic compound that is not directly involved in the normal growth, development, or reproduction of an organism. Unlike primary metabolites, absence of secondary metabolites does not result in immediate death, but rather in long-term impairment of the organism’s survivability, fecundity, or aesthetics, or perhaps in no significant change at all. Secondary metabolites often play an important role in plant defense against herbivory and other interspecies defenses.