Practise IB Biology HL B Form and Function through questions on biological structures, cells, transport, physiology and body systems, including the wider HL evidence set.
Syllabus
First assessment 2025
Course
Biology HL
Level
HL
Exam points
Relate carbohydrate, lipid and protein structures to condensation, hydrolysis, properties and function.
Explain membrane transport and compartmentalization using bilayers, proteins, gradients and ATP.
Link cell specialization, stem-cell potency and surface-area-to-volume ratio to function.
Interpret gas-exchange, transport and ventilation data using diffusion gradients and vessel adaptations.
Explain muscle movement, ecological adaptation and niche separation from structure and environmental evidence.
What feature of carbon makes it most suitable as a basis for life?
A
Its abundance in nature
B
Its bonding properties
C
Its reactivity to light
D
Its presence in the early atmosphere of the Earth
B
Question 2
[Maximum number: 7]
Question (a)
(a)
Some of the twenty amino acids that are linked together to make polypeptides in human cells are essential in the diet and others are not. Distinguish between essential and non-essential amino acids.
[ 2 ]
a. essential amino acids cannot be synthesized (by human cells) OR essential amino acids are required to be obtained by diet / OWTTE; b. non-essential amino acids can be made (from other amino acids);
Question (b)
(b)
The molecules of all amino acids include an amine group, a carboxyl group and an R-group. Draw a diagram to show the structure of an amino acid molecule.
[ 3 ]
a.
b.
and bonded to C ;
c.
Allow a specific amino acid R - group in marking point c, such as CH3 (in alanine).
Question (c)
(c)
The R-groups of amino acids are very diverse chemically. Interaction between R-groups in different parts of a polypeptide helps to determine the tertiary structure of a protein. List two types of interaction between R-groups.
Outline how the amphipathic properties of phospholipids play a role in membrane structure.
[ 2 ]
a part hydrophobic/not attracted to water/non-polar AND part hydrophilic/attracted to water/polar b bilayer formed (formed naturally by phospholipids in water) c hydrophilic heads/parts face outwards and hydrophobic tails/parts face inwards
Question (b)
(b)
State the role of cholesterol in animal cell membranes.
[ 1 ]
a controls/regulates/reduces fluidity of membrane/ prevents crystallization of phospholipids
b reduces permeability to some substances
Question 4
[Maximum number: 4]
Testis cells are eukaryotic cells. Identify the structures seen under the electron microscope in testis cells that are not present in prokaryotic cells.
a
nucleus/nuclear membrane
b
membrane bound organelles
c
mitochondria
d
rough ER/smooth ER/golgi apparatus
e
lysosomes / centrioles /
f
large/80S ribosomes / ribosomes attached to a membrane