1.
Biology Assignment – Group 3, Set A (DRAFT)
Question 1(b)
Structure R is collagen. 20 related proteins which form triple helices through three
polypeptide chains winding around each other in a rope-like structure. Furthermore, collagen is a
tough, insoluble and fibrous protein. Thus, the functions of collagen are providing structure and
providing strength, support, shape, and elasticity to the tissue. It is also the main building blocks for
bones, skin, hair, muscles, tendons and ligaments. Collagens are characterized by their unique
tertiary structure, called the collagen triple helix, and by their existence in extracellular matrices.
Hydrogen bonds helps collagen to form its tertiary structure. The hydrogen bonds are very strong and
keep the connective tissues in the body together.
Question 2(a)
Firstly, the type of the movement K+
with the aid of Valinomycin is passive
facilitated diffusion. In this type of transportation, 2 types of transport protein involved which are
channel protein and carrier protein. These proteins also known as intrinsic proteins
which attached partially or fully embedded within lipid membrane. Meanwhile, in this following
case, valinomycin transportation is futher specified as mobile ion carrier protein. Mobile ion
carriers have specific site which only allow certain ions to attached to it. As an example,
valinomycin is specific to transport K+
. Valinomycin transporters aren’t dependent on energy sources
in form of ATP to transport K+
across the lipid membrane. Valinomycin transports K+
ion from
higher concentration on one side of membrane across to the lower concentration by forming a
complex with potassium ions until a dynamic equilibrium is achieved both sides.
Question 2(b)
The movement of potassium ions through lipid membrane against the concentration gradient
is active transport. Active transport is the movement of molecules against the concentration gradient,
or from a lower concentration region to a higher concentration region across a selectively permeable
membrane. For example, a phospholipid bilayer. This transport mechanism involves carrier proteins
and requires metabolic energy in the form of ATP.
An example of active transport mechanism is a sodium-potassium pump, or Na-K pump. The
Na-K pump is significant for transmission of nerve impulses. The mechanism of Na-K pump starts
with the binding of three sodium ions, Na+
to a sodium potassium pump which triggers a phosphate
group of an ATP to be transferred to the pump, also known as phosphorylation. The hydrolysis of
ATP provides the energy to change the conformation of the pump. The change in conformation of
the pump allows 3 Na+
to be released outside the cell and two extracellular potassium ions, K+
to
bind to the pump. The binding of K+
triggers the release of the phosphate group from the pump,
causing the pump to assume its original shape. Thus, releasing the 2 K+
into the cell and the cycle is
repeated.