Questions

There are approximately 6 trillion miles in a light-year, so the distance we need to go is 6 trillion miles / light-year times. 4 light-years is equal to 24 trillion miles. So, this whole would take 1.2 billion hours. There are 24 hours a day and 365.25 days per year, so this time in years is 137 thousand years.

Amino acids are a crucial, yet basic unit of protein, and they contain an amino group and a carboxylic group. They play an extensive role in gene expression processes.

Amino acids become proteins when 50 or more are bonded together in a chain. All the millions of different proteins in living things are formed by the bonding of only 20 amino acids.

Eight of these amino acids are essential and cannot be produced by the body.

They are:

• Leucine

• Isoleucine

• Lysine

• Threonine

• Methionine

• Phenylalanine

• Valine

• Tryptophan

•  Histidine is an amino acid that is categorized as semi-essential since the human body doesn't always need it to properly function

Nonessential amino acids are produced by the human body either from essential amino acids or from normal protein breakdowns. Nonessential amino acids include:

• Asparagine

• Alanine

• Arginine

• Aspartic acid

• Cysteine

• Glutamic acid

• Glutamine

• Proline

• Glycine

• Tyrosine

• Serine.

The number of cell layers and cell types together give rise to 6 different types of epithelial tissue.

1. Simple squamous epithelia

2. Simple cuboidal epithelia

3. Simple columnar epithelia

4. Stratified squamous epithelia

5. Stratified cuboidal epithelia

6. Stratified columnar epithelia

Stratified squamous epithelia is best suited for areas subject to friction.