Zadanie 7, Paper 2, maj 2023, TZ2, Biologia IB HL
Wzorowane na: Biology HL Paper 2, May 2023, TZ2, pytanie 7. Treść, dane i kontekst są zmienione; sprawdzane umiejętności, format i punktacja jak w oryginale.
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Zadanie
Polecenie
(a) Describe protein structure, distinguishing shared features from features that can vary.
(b) Explain how proteins enable substances to move across cell membranes.
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Odpowiedź z klucza
(a)
Each protein contains at least one polypeptide; some contain several. ✔
Polypeptides are chains of amino acids. ✔
Peptide bonds link the amino acids. ✔
Twenty amino acids are commonly encoded OR amino acids have different R groups OR include polar and non-polar groups. ✔
Primary structure is the sequence of amino acids (their number may also vary). ✔
Many possible sequences produce a huge variety of proteins. ✔
Secondary structure includes alpha helices and beta sheets. ✔
Hydrogen bonding stabilizes these secondary arrangements. ✔
Tertiary structure is the overall three-dimensional fold of a polypeptide. ✔
Side-chain interactions, including ionic attractions, hydrogen bonding or disulfide links, stabilize that fold. ✔
Proteins can have fibrous or globular forms. ✔
Amino-acid sequence influences the conformation. ✔
Association of two or more polypeptides produces quaternary structure. ✔
(b)
Pumps perform active transport. ✔
Active transport moves a substance against its concentration gradient. ✔
Energy, often supplied by ATP, powers this movement. ✔
Channels permit facilitated diffusion. ✔
Diffusion follows the concentration gradient. ✔
Channels provide routes for ions or other hydrophilic solutes that cannot readily cross the hydrophobic core. ✔
Aquaporins enable water movement (by osmosis). ✔
More aquaporins increase water permeability. ✔
Transport proteins are embedded in or span the lipid bilayer. ✔
Quality of communication: The complete response is clear on a first reading and concise, with little repetition or irrelevant material. ✔
Schemat punktowania
Part (a): Award any 7 of the listed points; maximum 7 marks. Part (b): Award any 5 of the listed points; maximum 5 marks. Award 1 independent communication mark across all retained parts. Maximum 13 marks. Scientifically equivalent alternatives and clearly annotated diagrams may be accepted where appropriate.