Nanye Osae-Asare
BEETROOT REPORT
PLAN
The aim of the following experiment is to use beetroot to examine the effect of temperature on cell membranes and relate the effects observed membrane structure.
Hypothesis
I predict that upon heating beetroot to a certain temperature colour will leak out and give out a reading on a colorimeter.
Scientific Background
Beetroot is a vegetable which is used greatly in food making and an important ingredient in recipe books. It is usually recommended that you don’t remove the outer skin of the beetroot and don’t cut off all the stalk and root if you want to avoid getting lots of red dye in the cooking water. Beetroot contains red pigments called betalains, located within the cell vacuole. Normally the pigments cannot pass through membranes but they leak out when the beetroot is cooked or put in alcohol. The beetroot is protected by a cell membrane.
The cell membrane functions as a semi-permeable barrier, allowing a very few molecules across it while fencing the majority of organically produced chemicals inside the cell. Electron microscopic examinations of cell membranes have led to the development of the lipid bilayer model (also referred to as the fluid-mosaic model). The most common molecule in the model is the phospholipids, which has a polar (hydrophilic) head and two non-polar (hydrophobic) tails. These phospholipids are aligned tail to tail so the non-polar areas form a hydrophobic region between the hydrophilic heads on the inner and outer surfaces of the membrane. This layering is termed a bilayer since an electron microscopic technique known as freeze-fracturing is able to split the bilayer.
Phospholipids and glycolipids are important structural components of cell membranes. Phospholipids are modified so that a phosphate group (PO4-) replaces one of the three fatty acids normally found on a lipid. The addition of this group makes a polar "head" and two non-polar "tails". Water, carbon dioxide, and oxygen are among the few simple molecules that can cross the cell membrane by diffusion (or a type of diffusion known as osmosis). Diffusion is one principle method of movement of substances within cells, as well as the method for essential small molecules to cross the cell membrane. Gas exchange in gills and lungs operates by this process. Carbon dioxide is produced by all cells as a result of cellular metabolic processes. Since the source is inside the cell, the concentration gradient is constantly being replenished/re-elevated, thus the net flow of CO2 is out of the cell. Metabolic processes in animals and plants usually require oxygen, which is in lower concentration inside the cell, thus the net flow of oxygen is into the cell.
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Teacher Reviews
Here's what a teacher thought of this essay
Overall, this report of an investigation into the effect of temperature on the permeability of biological membranes is well-structured with a fair degree of supporting theory. Most of the key areas are covered in a logical order allowing the reader to follow the scientific process. There are, however, a number of weaknesses that would need to be addressed before submitting this as A'Level coursework. [1] The hypothesis needs to refer to the relationship between IV and DV; [2] The introduction needs to be wholly focused on the area of biology under investigation - membrane structure and effect of heat on permeability; [3] Control variables need to be discussed in full with the aim of increasing the validity of the results; [4] The results themselves need to be discussed in the light of sound biological facts with references to previous work by other biologists on the same hypothesis.
