Lecture 3- Lipid Bilayer/Proteins

Question 1

What are the 3 key features of a phospholipid structure?

Answer 1

1. Modified triglyceride
2. R group (choline, serine, or ethanol-amine)
3. Amphipathic properties

Question 2

What two features make up phospholipids?

Which are hydrophobic/hydrophilic?

Answer 2

Head- hydrophilic
Tail- hydrophobic

Question 3

Which is more stable, micelle or liposome?

Answer 3

Liposome

Question 4

What is a single-layer lipid sphere called? What type of stability does this structure have?

Answer 4

Micelle/unstable

Question 5

What is a lipid-bilayer sphere called? What type of stability does this structure have?

Answer 5

Liposome/stable

Question 6

How do phospholipid heads compare to cell shape in a planar lipid bilayer?

Answer 6

Cell is much larger than phospholipid heads, so many phospholipid heads are required in a curvature style to match the cell size

Question 7

What is the lipid bilayer punctured with?

Answer 7

Proteins

Question 8

What are three integral membrane protein functions?

Answer 8

1. Cellular communication
2. Maintain ion concentrations
3. Protein stability

Question 9

What is the pathway of protein production?

Answer 9

DNA————->RNA———–>Protein
transcription translation

Question 10

What are primary proteins made of?

Answer 10

Sequences of amino acids

Question 11

How are secondary proteins made?

Answer 11

Local folding of the polypeptide chain into helices and sheets

Question 12

What are examples of secondary protein structures?

Answer 12

Helices and sheets

Question 13

How are tertiary protein structures made?

Answer 13

3D folding pattern of protein due to side chain interactions

Question 14

True or false? Both alpha helices and beta sheets are used in tertiary protein structures.

Answer 14

True

Question 15

What are quaternary protein structures made of?

Answer 15

Protein that consists of more than one amino acid chain

Question 16

What are proteins constructed from?

Answer 16

Amino acids

Question 17

What do all amino acids contain? (3 things)

Answer 17

Carboxyl group and an amino group linked by a carbon. R-group attaches to carbon

Question 18

What changes to produce various amino acids?

Answer 18

The R-group

Question 19

True or false? Some R-group are hydrophobic while some are hydrophilic

Answer 19

True

Question 20

How many amino acids are there?

Answer 20

20

Question 21

How are amino acids linked to one another?

Answer 21

Peptide bond

Question 22

How does a peptide bond form?

Answer 22

Carbon on carboxyl group forms covalent bond with nitrogen in the amine group in adjacent amino acid

Question 23

Are alpha helices or beta sheets more common?

Answer 23

Alpha helices

Question 24

What is the alpha helices bonding sequence?

Answer 24

i +4 H bonding
Each peptide bond C-O is hydrogen bonded to the peptide bond N-H, four amino acid residues ahead of it

Question 25

Which way do side chains face from the helix axis in alpha helices?

Answer 25

Outward

Question 26

True or false? Beta sheets are more extended than alpha helices?

Answer 26

True

Question 27

How do polypeptides lay in beta sheets?

Answer 27

Side by side

Question 28

What type of interactions mainly form tertiary structures?

Answer 28

Hydrophobic interactions

Question 29

In the tertiary structures what do non-polar groups form?

Answer 29

Hydrophobic core

Question 30

In the tertiary structures what do polar groups form?

Answer 30

Hydrophilic shell

Question 31

What are quaternary structures defined by?

Answer 31

Interactions between different polypeptides

Question 32

What are 5 examples of proteins?

Answer 32

1. Receptors 2. Hormones 3. Enzymes 4. Transport proteins (protein channels) 5. Antibodies

Question 33

What five things determine protein shape?

Answer 33

1. Type of amino acids 2. Order of amino acids 3. # of amino acids 4. Bonds between amino acids 5. Environmental factors (temperature/pH)

Question 34

What are prions?

Answer 34

Bad proteins Abnormal, pathogenic agents that are transmissible and are able to induce abnormal folding of specific normal cellular proteins called prion proteins that are found most abundantly in the brain

Question 35

What are examples of animal prions?

Answer 35

Scrapie, bovine spongiform encephalopathy SBSE

Question 36

What are examples of human prions?

Answer 36

Creutzfeldt-Jakob Disease (CJB), Kuru

Question 37

What three things determine protein structure?

Answer 37

1. Amino acid sequence 2. Bonds 3. Environment

Question 38

Potassium ions can pass through a biological membrane by moving -Directly across the lipid bilayer -Through transmembrane lipid channels -Through transmembrane protein channels lined with hydrophobic amino acids -Through transmembrane protein channels lined with hydrophilic amino acids -Through transmembrane protein channels lined with uncharged amino acids

Answer 38

Through transmembrane protein channels lined with hydrophilic amino acids

Question 39

In the lipid mosaic model of the membrane, _________ normally form the ion channels. -Amphipathic phosphate head groups -Alpha helices -Beta sheets -Phospholipids -Triglycerides

Answer 39

Alpha helices Alpha helices are proteins embedded in the lipid bilayer. Their R-groups are hydrophobic and interact with hydrophobic phospholipid tails.

Question 40

Hydrogen bonding between the carbonyl oxygen of one amino acid and the hydrogen on the amine of the nearby amino acid is responsible for the ____ structure in proteins. Primary Secondary Alpha helical More than one answer is correct

Answer 40

More than one answer is correct Alpha helices are secondary proteins

Question 41

The charge and orientation of R-groups on amino acids are important in determining all of the following except: -Its 3D shape -Its tertiary structure -The type of ligand or substrate it will bind -The type of ion that will pass through its transmembrane channel -The secondary structure within the protein

Answer 41

The secondary structure within the protein Hydrogen bonds and peptide bonds determine secondary structure. Not R-groups

Question 42

Aquaporins are proteins that span the phospholipid bilayer of cells. What protein structure is most likely associated with the transmembrane portion of the aquaporin channels? -An amino acid chain with hydrogen bonds formed between the peptide bonds -A sequence of amino acids joined by peptide bonds -Multiple protein subunits joined together by non-covalent forces -An amino acid chain with hydrogen bonds between R groups

Answer 42

An amino acid chain with hydrogen bonds formed between the peptide bonds (Alpha helices are embedded in aquaporin channels)