Transcript Proteins - churchillcollegebiblio

STARTER. You are about to see an animation on protein structure
Try and match the
following key
terms with the
definitions given
-primary structure
-secondary
structure
-tertiary structure
-quaternary
structure
-alpha helix
-beta pleated sheet
Learning Objectives
Everyone should
• State four functions of proteins, giving a named example of each
Most will
• Outline the difference between fibrous and globular proteins, with
reference to two examples of each protein type.
Some might
• Explain the significance of polar and non-polar amino acids.
• Explain the four levels of protein structure, indicating the
significance of each level.
Starter – Team Activity
You have 5 min to complete Steps A and B of
Protein modelling handout on your bench in teams
• Alina and Lucia
• Andrea , JP and Natalia
• Work in a team BUT complete your own
handout INDIVIDUALLY
Learning Objectives
Everyone should
• State the four levels of protein structure
Most will
• Describe the four levels of protein structure, indicating
the features of each level.
Some might
• Explain how polar and non-polar amino acids
determine the folding of a polypeptide to produce a
functional protein
Primary structure of a protein
• To simulate a protein, you will make a model of your protein using
plasticine beads
• Refer to the sequence of 15 amino acids (the colored circles on Step
C of your worksheet)
Complete Step C first if you haven’t already using the amino
acid chart provided
• Arrange beads of the appropriate colors on the pipe cleaner.
(substitute yellow for green)
• The beads should be approximately evenly spaced the along the
pipe cleaner.
Secondary structure of a protein
• Twist one half of your protein model around a pencil to
make a spiral.
• Bend the other half of your protein molecule into a zig-zag
shape by making a bend in the opposite direction at each
bead.
• Make a drawing to show the secondary structure of your
protein model (Step D of your worksheet).
• Label the alpha helix region and the beta-pleated sheet
region on your drawing.
Tertiary Structure
• Twist your protein into a 3-D shape according to
the protein folding rules on the chart
• Make a drawing to show the tertiary structure of
your protein model (Step D of your worksheet).
• Note: Do the best you can to make your 2dimensional drawing look like your 3D model.
Quarternary Structure
• Some protein chains are attracted to other
protein chains.
• Work with the other team and try putting your
protein model next to their protein model in a
way that still follows the rules of protein folding.
• Make a drawing to show the quaternary
structure of your protein model (Step D of your
worksheet).
Plenary – Ticket to Exit!
• Fill out your table without using your
notes
• Try and incorporate as many key terms
from the topic as you can
PLENARY
Explain the four levels of protein structure (10)
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primary structure is sequence / number of amino acids;
determined by base sequence in the gene;
(largely) determines higher level structures/secondary structure/tertiary
structure;
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secondary structure is regular repeating patterns;
such as alpha/α helix and beta/β (pleated) sheet;
determined by H bonds (within chain);
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tertiary structure refers to overall 3-D shape;
conformation can determine function;
tertiary structure determined by R-group interactions / ionic interactions
/hydrophobic interactions / disulfide bridges / H-bonds;
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quaternary structure is only found in proteins formed from more than one
polypeptide;
e.g. hemoglobin; (accept other suitable example)
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Starter– sort the statements into your
table (q7)
Learning Objectives
Everyone should
• State four functions of proteins, giving a named example of
each
Most will
• Outline the difference between fibrous and globular
proteins, with reference to two examples of each protein
type.
Some might
• Explain the significance of polar and non-polar amino acids
in biological molecules
GROUP ACTIVITY:
Using your whiteboards – can you draw a diagram to explain how they do this?
Now lets try some PPQs (Q9-11)
For question 11.c – please change the
word CHANNEL to the word MEMBRNE
Mark scheme
9.
Describe a polar molecule.
Has charge
10. In the space below, draw and annotate a simple diagram to explain
how polar molecules aid enzyme function.
11. a) The hydrophobic tails of the plasma membrane reject polar
molecules: they do not allow them to pass through the membrane into
or out of the cell.
Define hydrophobic.
Lacks an affinity for water
b) Identify labels I to IV as being polar or non-polar.
polar
Non polar
polar
Non-polar
c) Using the diagram, explain the significance of
polar molecules in MEMBRANE proteins. (8)
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membrane is a lipid bi-layer;
membrane has hydrophobic interior / lipid hydrophobic tails oriented inward;
hydrophilic on cytoplasmic and extracellular side / lipid hydrophilic heads oriented
outward;
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polar amino acids are hydrophilic/water soluble/attracted to outside of
membrane;
non-polar amino acids are hydrophobic/attracted to inside of membrane;
integral proteins embedded in the membrane;
peripheral proteins associated with surface of membrane;
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non-polar amino acids cause proteins to be embedded in membrane;
polar amino acids cause parts of proteins to protrude from membrane;
transmembrane proteins have both polar and non-polar amino acids;
polar amino acids create channels through which (hydrophilic) substances/ions
can diffuse;