Molecules (proteins)- topic 1

Question 1

what elements do protein molecules contain?

Answer 1

-carbon
-hydrogen
-oxygen
-nitrogen
-sulfur (sometimes)

Question 2

are proteins polymers?

Answer 2

-yes and they are formed from amino acid sub units

Question 3

how many amino acids are there and what is the effect of this?

Answer 3

-there are 20
-this allows for infinite amino acid arrangements in a protein

Question 4

how is the shape of a protein determined?

Answer 4

-through the sequence of amino acids

Question 5

what is the general structure of a protein look in book and learn

Answer 5

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Question 6

how do amino acids differ?

Answer 6

-through their R groups which can range anywhere between a single hydrogen to a CH3 group

Question 7

what happens to the R group if sulfur is present in the amino acid?

Answer 7

-the sulfur atom will be contained inside the R group

Question 8

how are amino acids linked together? what reaction occur and where does it take place?

Answer 8

-by peptide bonds
-condensation reactions take place which involve the loss of water
-condensation reactions take place between the amino group of one amino acid and the carboxyl group of another amino acid

Question 9

what is it called when two amino acids join?

Answer 9

-dipeptide

Question 10

what elements are in an amino group?

Answer 10

-nitrogen bonded to two hydrogens

Question 11

what elements are present in a carboxyl group?

Answer 11

-carbon single bonded to hydroxyl group and the carbon is double bonded to an oxygen

Question 12

how can a peptide bond between two amino acids be broken?

Answer 12

-via a hydrolysis reaction, the release of the two amino acids with the addition of water

Question 13

what is is called when many amino acids are joined in a chain?

Answer 13

-many can be joined in a chain through peptide bonds to form a polypeptide chain

Question 14

what is the primary structure of protein?

Answer 14

-the primary structure of a polypeptide chain is the sequence of amino acids in the chain in which the amino acids are linked together by peptide bonds

Question 15

look at the diagrams of each stage of protein and memorize them

Answer 15

-bdhgdgh

Question 16

what is the secondary structure of protein? what does the ends of the polypeptide chains contain?

Answer 16

-at either end of the polypeptide chain the amino acids contain an -NH (amino group) and a -C=O (carboxyl group)
-the O of the carboxyl group has a negative charge and the H of the amino group has a positive charge, this allows the formation of hydrogen bonds that allow the secondary structures to be formed

Question 17

what are the two secondary structures of protein?

Answer 17

-a- helix
-b-pleated sheets

Question 18

what is the a-helix secondary structure of protein consist of?

Answer 18

-in a-helix the hydrogen bonds are formed between amino acids are regular intervals in the sequence
-the bond twist the chain of amino acids cause it to spiral into a helical shape

Question 19

what does the b-pleated sheet secondary structure of protein consist of?

Answer 19

-these are more rigid and less flexible than a-helix
-they are formed by small sections of the polypeptide chain, orientated in opposite directions lying adjacent to each other
-hydrogen bond are formed between the carboxyl and amino groups

Question 20

what is the tertiary structure of amino acids?

Answer 20

-further folding of the secondary structure
-this additional folding gives protein its unique 3D shape and is consequence of the range of bonds formed between the R groups of amino acids in the chain

Question 21

what is the effect of using hydrogen bonds in the tertiary structure of protein??

Answer 21

-are numerous but are relatively weak and are easily broken

Question 21

what are the three bonds involved in the tertiary structure of protien?

Answer 21

-hydrogen bonds
-ionic bonds
-disulfide bridges

Question 22

what is the effect of using ionic bonds in the tertiary structure of protein?

Answer 22

-formed between the amino and carboxyl group in some amino acids
-they are stronger than hydrogen bonds but they are damaged by changes in pH

Question 23

what is the effect of using disulfide bridges in the tertiary structure of protein?

Answer 23

-they are covalent bonds formed between the R groups of sulfur containing amino acids
-they are very strong bond and are important to give strength to structural proteins such as collagen

Question 24

how do hydrophobic interactions further influence the tertiary structure?

Answer 24

-hydrophobic interactions involve amino acids with hydrophobic R groups which usually take position within the molecule surrounded by other parts of the polypeptide as opposed to water

Question 25

what is the quaternary structure of protein?

Answer 25

-some proteins consist of two or more polypeptide chains bonded together usually by disulfide bridges
-some quaternary proteins contain non protein groups known as prosthetic groups that are important in their function, the name of these proteins are conjugated proteins

Question 26

what are two examples of these conjugated proteins?

Answer 26

-glycoproteins which are important in membrane functions
-hemoglobin is a conjugated protein that contains four polypeptide chains an each chain is attached to an iron rich haem group which essential in the blood for the transport of oxygen

Question 27

what are the types of groups protein can be grouped into?

Answer 27

-fibrous proteins and globular proteins

Question 28

what are fibrous proteins?

Answer 28

-consist of polypeptide chains that form fibers or sheets
-the parallel chains are linked by cross bridges to form strong stable molecules and so their job is primarily structural support

Question 29

what is one example of a fibrous protein? where is it found?

Answer 29

-collagen
-each collagen ,molecule contains 3 identical a-helix polypeptide chains intertwined and held together by hydrogen bonds
-collagen is found in tendons that link muscle to bones and it is very important that is is a strong molecule so that it does not stretch when tension is applied

Question 30

what are globular proteins and what is one example of a globular protein?

Answer 30

-have metabolic role and include enzymes and antibodies which are important in the formation of proteins 3D shape
-hemoglobin is a globular protein

Question 31

what are prions?

Answer 31

-particular type of protein found in mammals in the nervous system that is involved in synaptic transmission

Question 32

what is the normal form of prions?

Answer 32

-PrP

Question 33

what happens if the normal form of prions convert?

Answer 33

-they can convert to the disease causing form (PrPsc)
-if the disease causing form is present it can act as a template causing other normal prions to convert to the disease causing prions

Question 34

how does the disease causing prions differ structurally to normal prions?

Answer 34

-the disease causing form contains more beta sheets

Question 35

what happens when the disease causing form is present in the body?

Answer 35

-it leads to a chain reaction causing the number of disease causing prions to increase meaning the prions proteins become more misfolded and changes form the PrP to the PrPsc
-over time the number pf harmful prions with tightly packed beta sheets increases to reach threshold

Question 36

what happens when the number of disease causing prions reaches the threshold?

Answer 36

-it can cause neurodegenerative disorders in the brain and eventually death

Question 37

what are the two key features of disease causing prions?

Answer 37

-they can replicate and infect

Question 38

how long does the incubation period last for disease causing pirons?

Answer 38

-5 to 20 years

Question 39

what are the three ways that the disease causing form can arise?

Answer 39

-normal form can spontaneously adopt the PrPsc form
-mutations in the DNA that codes for the prions meaning the disease form is passed from parent to offspring
-through eating prion rich contaminated foods that contain the disease causing form

Question 40

what are the three prion diseases?

Answer 40

-scrapie in sheep
-BSE or Bovine Spongiform Encephalopathy or mad cows disease that affects cattle through eating contaminated foods
-vCJD or variant Creutzfeldt- Jakob disease which is a human form of mad cows disease that is acquired by humans through eating contaminated beef products containing the disease causing form