heredity - DNA and polypeptide synthesis

Question 1

why is polypeptide synthesis important?

Answer 1

• The role of DNA is to code for specific polypeptides (proteins).
• All organisms produce proteins.
• These proteins have specific functions: transport, enzymes, structural, hormones, and antibodies.
• Without these proteins, these functions would not occur.
• Life would cease to exist.

Question 2

prokaryote structure

Answer 2

• lack distinct nucleus and no membrane enclosed organelles
• contain free floating ribosomes
• generally small 1-10 micrometres
• unicellular

Question 3

eukaryote structure

Answer 3

• distinct nucleus and contain membrane enclosed organelles
• contain ribosomes
• generally larger in size 10-100 micrometres
• unicellular or multicellular

Question 4

DNA in prokaryotes

Answer 4

DNA in prokaryotes are usually a single circular chromosome and plasmids. DNA contains no histones and is found in the cytoplasm (nucleoid). The DNA does not contain introns.

Question 5

plasmid

Answer 5

Small circular, independent double stranded DNA molecule. Plasmids can frequently be transmitted from one bacterium to another.

Question 6

intron

Answer 6

A segment of a DNA or RNA molecule which does not code for proteins and interrupts the sequence of genes

Question 7

intron

Answer 7

A segment of a DNA or RNA molecule which does not code for proteins and interrupts the sequence of genes

Question 8

DNA in eukaryotes

Answer 8

DNA in eukaryotes is linear, associated with histones and is found in the nucleus. The genes contain introns.

Question 9

mitochondrial DNA

Answer 9

Both mitochondria and chloroplasts have their own DNA separate to the nucleic DNA.

Mitochondrial DNA (mtDNA) is a double stranded, circular molecule with no introns (similar to prokaryotes).

Question 10

endosymbiosis

Answer 10

A relationship in which one organism lives inside the other, the two typically behaving as a single organism. It is believed to be the means by which such organelles as mitochondria and chloroplasts arose
within eukaryotic cells.

Question 11

chloroplast DNA (cpDNA)

Answer 11

a double-stranded, circular molecule with no introns.

Question 12

peptide

Answer 12

short chain of 2-50 amino acids

Question 13

polypeptide

Answer 13

linear molecules made up of multiple peptides

Question 14

polypeptide

Answer 14

linear molecules made up of multiple peptides

Question 15

proteins

Answer 15

proteins are the functional unit, made up of one or more polypeptides

Question 16

amino acids

Answer 16

Amino acids are simple organic compound containing a carboxyl (— COOH) and an amino (— NH2) group. They are the building blocks of proteins.

Question 17

essential amino acids

Answer 17

• must be obtained from food
• histide, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine

Question 18

non-essential amino acids

Answer 18

• produced by our bodies
• arginine, alanine, asparagine, aspartic acid, cysteine, glutamine, glutamic acid, glycine, proline, serine and tyrosine

Question 19

advantages of models

Answer 19

• simplifies complex concepts
• predictive power
• leads to increased understanding and future research

Question 20

disadvantages of models

Answer 20

• over-simplification can be misleading
• may not be accurate
• lack detail

Question 21

transcription

Answer 21

the process by which a complementary copy (mRNA) of a gene (DNA) is made in the nucleus

Question 22

translation

Answer 22

the process by which mRNA sequence is converted into a specific sequence of amino acids (carried by tRNA) in the ribosomes

Question 23

mRNA

Answer 23

single stranded nucleic acid, consisting of ribose sugar, phosphate backbone and nitrogen bases (A, U, G, C)

Question 24

tRNA

Answer 24

small RNA molecule that transfers specific amino acids to the ribosome during formation polypeptides

Question 25

codon

Answer 25

set of three nitrogen bases in mRNA

Question 26

anti-codon

Answer 26

complementary set of three nitrogen bases on tRNA

Question 27

the importance of mRNA and tRNA in transcription and translation

Answer 27

explain - DNA does not leave the nucleus. As a result, a message must be sent from the nucleus to the ribosomes where protein synthesis occurs. This message is sent in the form of mRNA

assess - protein synthesis would therefore not be possible without mRNA

Question 28

the function and importance of polypeptide synthesis

Answer 28

As a result of the complementary nature of the mRNA and tRNA codon-anticodon complex the
specific sequence of amino acids required for protein synthesis occurs. Protein synthesis would therefore not be possible without tRNA.

Question 28

the function and importance of polypeptide synthesis

Answer 28

every organism makes proteins which are vital for key functions meaning that without proteins, life would cease to exist, hence why the process of making proteins is a significant one

Question 29

primary protein structure

Answer 29

The primary structure is the specific linear sequence of amino acids that make up a polypeptide chain.

Question 30

secondary protein structure

Answer 30

Regular, repeated patterns of folding of the protein backbone.

Question 31

tertiary protein structure

Answer 31

The overall folding of the entire polypeptide chain into a specific 3D shape.This final shape is determined by disulphide and ionic bonds between the “side chains” on the amino acids in the alpha helices and beta sheets.

Question 32

quaternary protein structure

Answer 32

Occurs when a protein is made up of two or more polypeptides. Quaternary structure describes the way in which the different polypeptide subunits are arranged together to form the overall structure of the protein.

Question 33

transport proteins

Answer 33

involved in either the active or passive movement of substances across cellular membranes or between cells (an example is haemoglobin).

Question 34

structural proteins

Answer 34

the largest of the protein groups. They are typically found in body tissues that require tensile strength which is provided by the long and fibrous structural proteins. Some examples are collagen and keratin.

Question 35

enzymes

Answer 35

Enzymes speed up reactions by lowering the activation energy required for the reaction to occur. They hold substrate molecules in a way that makes the reaction more likely to occur. Without enzymes, metabolism would be too slow to support life.

Question 36

protein hormones

Answer 36

Protein hormones are typically globular in shape and water soluble. They function by binding to receptors on the outside of a cell and causing a change to occur inside the cell. Some examples are insulin, glucagon.

Question 37

genotype

Answer 37

the set of genes in the DNA responsible for a particular phenotypic trait

Question 38

phenotype

Answer 38

the physical expression of that trait, as a protein or physically observable characteristic

Question 39

effect of temperature on reptile gender

Answer 39

During a thermosensitive period (TSP) of reptile egg incubation, gonadal tissue is responsive to temperature. This influences the gender of the offspring.

Question 40

effect of soil on pH on hydrangea

Answer 40

Flower colour is determined by soil pH. The pH effects the availability of other ions in the soil and these ions are responsible for the colour change.