beetroot is a vegetable which is used greatly in food making and an important ingredient in recipe...

7/28/2019 Beetroot is a Vegetable Which is Used Greatly in Food Making and an Important Ingredient in Recipe Books

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Beetroot is a vegetable which is used

greatly in food making and an important

ingredient in recipe books. It is usually

recommended that you dont remove the

outer skin of the beetroot and dont 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.


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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 bilayersince 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


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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.

Osmosis is the diffusion of water across a semi-permeable (or

differentially permeable or selectively permeable) membrane. The

cell membrane, along with such things as dialysis tubing and

cellulose acetate sausage casing, is such a membrane. The

presence of a solute decreases the water potential of a substance.

Thus there is more water per unit of volume in a glass of fresh-

water than there is in an equivalent volume of sea-water. In a cell,

which has so many organelles and other large molecules, the water

flow is generally into the cell. Permeability of cell membrane may

be affected in many ways such as addition of alcohol, and

temperature.

When heated, holes in cell membrane become expanded and more

of the betalain can diffuse out through the membrane from the

large vacuole. From this knowledge, the rate of diffusion is

dependant on temperature. As temperature increases, so does the


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rate of diffusion. The permeability of the beetroot is based on the

amount of betalain that has been detected after a certain period of

time. The amount of betalin is measured using a colorimeter.

Temperature also influences movement of the betalain molecules

themselves. Movement of molecules are directly proportional to

temperature i.e. as temperature increases, so does the movement

of betalain molecules as they become more excited. This gives

them energy to be able to move out of the membrane pores.

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If you use a colorimeter what will happen is that the concentration of anthocyanin will increase as temperature increases

so making the water go more opaque. You will eventually find the concentration level off as all the proteins are denatured

and there will be equal amounts of anthocyanin in the water and in the cells - as diffusion will not happen due to there

being no concentration gradient between the inside and outside of the beetroot cells - an equilibrium will be reached - this

will be why your graph of spectral absorbpancy will level off.
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