This is an IB Biology IA that achieved 22/24 marks. The practical done regards osmosis, how temperature affects membrane permeability by measuring the concentration of pigments found in the solution. This IA is a good exemplar for science IAs which can be used as an example for both Standard and Hi...
How does the temperature (30, 40, 50, 60, 70, 80, 90 °C) of 5 mL of distilled water affect the
cell membrane permeability of a 2 cm3 Beta vulgaris cube as measured by the concentration
of the pigment, Betalain, in the solution?
Biology IA
Session: May 2020
1
,Research Question
How does the temperature (30, 40, 50, 60, 70, 80, 90 °C) of 5 mL of distilled water
affect the cell membrane permeability of a 2 cm3 Beta vulgaris cube as measured by the
concentration of the pigment, Betalain, in the solution?
Personal Engagement
My personal interest in this topic is deeprooted in a family history of heart
conditions. My father was given advice by his doctor to increase his intake of beetroot and
other vegetables that have a high concentration of natural nitrates such as nitric oxide which
regulates blood flow and heart contractions. I wanted to understand how this nutrient content
will vary in the different styles of cooking in my household. If high or low temperatures are
more beneficial and how they will affect the nitrate concentration of the beetroot.
Background Information
A Beetroot (Beta vulgaris) is known for its vibrant red-violet pigments which are
found in the vacuole of the cell, the pigments are called Betalain and can be extracted when
the cell wall is dissolved making it a protoplast. The Beetroots pigments are unstable at high
temperatures and will turn brown at around 80℃ as this vegetable contains phenolics and
other reactive substances which will make the pigments react (Using Beetroot in the Lab).
The cell membrane is semipermeable which is due to the internal hydrophobic
environment, created by the fatty acid tails, this gives the membrane fluidity and prevents
free diffusion, keeping internal and external environment separate (The Cell. 3. Cell
Membrane. Permeability, Fluidity. Atlas of Plant and Animal Histology). This is illustrated in
diagram 1. Membrane permeability can be affected by temperature change as the membrane's
fluidity will be altered. When the fluidity of the membrane is changed from its original state
to an increased or decreased state the membrane either becomes stiff or more fluid. A stiff
membrane will occur due to low temperatures, the fatty acid tail of the phospholipids will
become inflexible which will decrease permeability and can restrict the entry of molecules
that are vital for growth. At high temperatures, the membrane will become more fluid which
is due to the fatty acid tails of the phospholipids becoming more flexible and will allow for
more molecules to come in and out of the cell. High temperatures can damage integral and
peripheral proteins and will cause them to break down (Chandler, 2019). The concentration
of the pigment Betalain in the surrounding solution, will indicate the permeability of the
membrane as an increase in fluidity due to a change in temperature will result in more
pigment moving from the vacuole to the external environment.
, The independent variable is temperature (°C) as Beetroot has medical benefits when
consumed. The Beetroot causes an increase in muscle strength, as it contains natural nitrates
and minerals which regulate blood flow and muscle contraction. This was supported by a
study conducted in 2015 were nine patients suffering from heart failure were given
concentrated beetroot juice. There was a 13% increase in cardiovascular muscle strength.
Differences between cooked and raw beetroot were found, vitamin levels in the raw vegetable
were higher than the cooked. High temperature causes a loss in vital minerals and vitamins
due to the breaking of the semi-permeable membrane and increasing fluidity. The raw
beetroot had 8 milligrams of Vitamin C while the cooked one had 3.6 milligrams, similarly in
a raw state it had 26.2 milligrams of Calcium and 16 milligrams when cooked. Therefore in a
raw state Beetroot has more valuable vitamins which can improve muscle contraction and
prevent cancer from accumulating (Kerr). This shows the relevance of this investigation as
there are medical benefits from the targeted use of beetroot.
Hypothesis
As the temperature (°C) of the solution increases membrane permeability which will
increase the concentration of the pigments evident in the solution. An increase in temperature
(°C) will cause the fatty acid tails of the phospholipids to be more fluid, letting more
molecules come in and out of the cell membrane, causing more pigments to leave the cell
membrane. Causing the solutions pigment concentration to increase and let less light pass
through it.
Null Hypothesis
An increase in the temperature of the solution will have no effect on the concentration
of the beetroots pigment
Variables
Independent The temperature (℃) of the distilled water. It will be controlled using
a water bath (±0.1 °C) at different temperatures (30, 40, 50, 60, 70,
80, 90 °C)
Dependent Through observation, the color of the solutions will be used as
Qualitative data. The concentration of the color in the solution will be
measured using a colorimeter (%) (± 0.05 %) indicating the
percentage of light that can pass through the solution in comparison to
a pure solution. The smaller the reading the more pigment is evident
in the solution.
3
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