Chapter 3 - Cell Protein Production

Question 0

Why do synthesis require both matter and energy?

Answer 0

Matter - small molecules to be joined.

Energy - to form the chemical bonds that hold the smaller units together.

Question 1

What is protein synthesis?

Answer 1

It is the combining of small molecules to make large molecules.

Question 2

What is a base triplet?

Answer 2

It is a sequence of three bases.

Eg.
CAG - Valine
TTA - Leucine
CCC - Proline

Question 3

Where are the amino acids joined together?

Answer 3

Ribosomes

Question 4

Explain the function if the messenger RNA (mRNA) ?

Answer 4

The RNA molecule takes the code from the DNA in the nucleus to the ribosomes in the cytoplasm. mRNA is small enough to pass through the pores in the membrane around the nucleus. (Nuclear pores)

Question 5

What is the function of Helicases?

Answer 5

They are enzymes that make the double-stranded DNA molecule come apart, usually about 17 base pair at a time.

Question 6

What happens at the end of the gene?

Answer 6

A sequence of bases tell the RNA polymerase to stop copying and as a result the mRNA molecules is released. Often other RNA polymerases will follow the first one so that many copies of the same mRNA are made.

Question 7

Which strand of the DNA molecule is copied during transcription?

Answer 7

The Template Strand because it is the template from which the mRNA is made.

Question 8

What is the Coding Strand?

Answer 8

One of the 2 strands of the DNA molecule that contains the triplets for a particular protein.

Question 9

What is an intron?

Answer 9

Nonsense regions in a newly formed mRNA molecule. Nucleotides that have no meaning are removed before the mRNA leaves the nucleus.

Question 10

What is an exon?

Answer 10

Segments in the newly formed mRNA molecule that contain the code for a protein. Each exon will contain many codons. After the introns have been removed the mRNA will consist only of exons.

Question 11

What happens after the introns have been removed?

Answer 11

After the introns have been removed the mRNA will consist only of codons. This shortened, functional mRNA is ready to leave the nucleus and direct protein synthesis in the cytoplasm.

Question 12

What is a Codon?

Answer 12

A group do three bases which is the code for an amino acid.

Question 13

What is the Start Codon?

Answer 13

The codon AUG (adenine, uracil, guanine)

Question 14

AUG is the codon for the amino acid Methionine. What does this mean?

Answer 14

This means that every protein begins with methionine when it is first made. The methionine may be removed later.

Question 15

Step by step process of Transcription.

Answer 15

1. The two strands of the DNA in a gene separate. (RNA polymerase)
2. mRNA forms with bases that are complementary to those on the template strand of the DNA.
3. The mRNA molecule that is formed undergoes modification - the introns are removed, leaving just exons.
4. mRNA travels from the nucleus to the cytoplasm.

Question 16

Step by step process of Translation.

Answer 16

5. mRNA attaches to a ribosome.
6. The ribosome moves along the mRNA, reading the code. At the start codon it begins making the protein.
7. For each codon on the mRNA, a tRNA with a matching anticodon brings the correct amino acid.
8. The amino acids are bonded together to form the protein.

Question 17

What is Translation?

Answer 17

Translation is the production of protein using the information that is coded in the mRNA molecule.

Question 18

Explain the role of the tRNA.

Answer 18

Transfer RNA; a small RNA molecule that carries amino acid to the ribosome and places It in the correct position determined by the mRNA.

Question 19

Explain the role of an Anticodon.

Answer 19

An Anticodon can bind with the complementary bases of a codon on the mRNA molecule. The anticodon determines the type of amino acid carried by the tRNA.

The three bases in a tRNA molecule that are the ‘mirror image’ of a codon.

Question 20

How do antibiotics work?

Answer 20

They work by blocking translation during the process of protein synthesis. This is because bacteria are unable to reproduce if they cannot make new protein. Such antibiotics include tetracycline, streptomycin and erythromycin.

Question 21

What is a triplet?

Answer 21

A sequence of three bases in DNA that specifies a particular amino acid ( aka base triplet).

Question 22

What is a Gene Expression?

Answer 22

It is where information is transcribed from DNA to produce mRNA and then translated into a chain of amino acids to form a protein.

Question 23

What is the difference between Protein Synthesis and Gene Expression?

Answer 23

Protein synthesis is one of the possible outcomes of expression of genes that codes for protein segments. However, DNA also code for RNA that is not involved in protein synthesis directly. These pieces of RNA act to regulate the expression of genes.

Question 24

What is a structural gene?

Answer 24

It is the portion of a DNA molecule that contains the code for manufacture of a protein. Other parts of the DNA act as promoters or regulators.

Question 25

What is gene regulation?

Answer 25

The is the cell’s control over when a particular protein is made and the quantity that is made is known as the regulation of gene expression.

Question 26

Explain the process of Gene Expression.

Answer 26

It is a two-stage process.

1. Transcription, an mRNA molecule is synthesized using the DNA as a template.
2. Translation, the info contained in the mRNA is used to determine the sequence of amino acids in the protein.

Gene expression can be regulated at the transcription stage, at the translation stage or by the later modification of the protein that is formed.

Question 27

Explain the role of Promoters.

Answer 27

Promoter genes are controlled so that they indicate which structural genes should be in use for the production of a particular mRNA at a give time. In this way they control which proteins a cell manufacture.

Question 28

Explain the role of Regulator Genes.

Answer 28

These regulate the activity of structural genes by controlling production of a protein that controls the rate of transcription from the structural gene. Control of the rate of transcription from the structural gene determines the amount of the particular protein that is made at any given time.

Question 29

Does protein synthesis stop after the production of an amino acid chain as a result of translation?

Answer 29

No, the chain of amino acids must also be organized into a particular shape. Protein molecule shape is critical for the correct functioning of the protein. Even a very slight change in structure can prevent the protein from functioning normally.

Question 30

List the types of protein structures.

Answer 30

1. Primary Structure - chain of AA joined by peptides
2. Secondary Structure - AA chain forms sheets or spirals due to bonding between the different parts of the chain
3. Tertiary Structure - formed by further bending and folding of the protein info globular or fibrous shapes.
4. Quaternary Structure - when 2+ chains interact

Question 31

What happens if proteins are to be used outside the cell?

Answer 31

1. After they are made at the ribosomes, such proteins pass through the channels of the endoplasmic reticulum and into the Golgi apparatus.
2. Inside the Golgi apparatus the proteins are modified by the addition of sugar, sulfate, phosphate, fatty acid or other molecules.
3. At the edges of the Golgi apparatus the membrane pinches off to form an vesicle containing some of the modified proteins.
4. Some of these vesicles will make their way to the cell membrane, where the contents are secreted from the cell by exocytosis.

Question 32

Are all vesicles contains proteins go through exocytosis?

Answer 32

No, other vesicles containing digestive enzymes remain within the cytoplasm as lysosomes.

Question 33

Does a cell’s DNA control the process of lipid and carbohydrate synthesis?

Answer 33

A cell’s DNA only has code for the manufacture of proteins. However, the synthesis if these compounds require enzymes and enzymes are proteins. Since DNA in the genes carries the code for protein manufacture, the genes indirectly control the synthesis of lipids and carbohydrates.

Question 34

Explain how lipid and carbohydrate synthesis takes place.

Answer 34

Lipid and carbohydrates are synthesized from the products of digestion. During digestion, complex carbohydrates are broken down into glucose and lipids are broken down into fatty acids and glycerol. A cell can then use enzymes to join these small molecules together into carbohydrates and lipids again.

Question 35

Interesting facts.

Answer 35

Liver cells and fat storage cells can synthesis lipids from CHO and AA. This is evident when a diet high in sugars (CHO) causes us to put on weight by storing the excess energy as fat.

Glucose can be made, mainly in the liver, from fats and amino acids. The glucose molecules can then be joined together to make glycogen, which is used to store energy in the liver and muscles.

Question 36

What is a gene?

Answer 36

A gene is a unit of heredity which is transferred from a parent to offspring and is held to determine some characteristic of the offspring.

Question 37

What is a mRNA ?

Answer 37

Messenger RNA; an RNA molecule that carries the genetic information from the DNA in the nucleus to the ribosomes in the cytoplasm of the cell.