Food production — Edexcel Modular - OL Revision Notes & Topical Questions

Food production Edexcel O Level Modular Biology: what to do next

These Food production Edexcel O Level Modular Biology notes covered the key ideas, worked examples and exam technique for this topic. Check your Food production Edexcel O Level Modular Biology understanding with the practice questions below, then reread any Food production Edexcel O Level Modular Biology point you were unsure about before moving on.

Microorganisms can be used by humans to produce foods and other useful substances.

Yeast can respire anaerobically (without oxygen), breaking down glucose to produce ethanol and carbon dioxide. Anaerobic respiration in yeast cells is called fermentation. Equation: glucose → ethanol + carbon dioxide.

As respiration is an enzyme-controlled reaction, as enzyme activity increases with temperature the rate of carbon dioxide production increases.

As well as fungi, bacteria are also used in the production of certain foods.

Fermenters are containers used to grow microorganisms such as bacteria and fungi.

In brewing the carbon dioxide escapes while ethanol builds up until the concentration is high enough to kill the yeast. Wine and beer production uses the same reaction, with yeast fermenting sugars from grapes or malted barley. Industrial fermenters are sterilised before use, because contaminating microbes would compete with the culture and could spoil the product.

If a plant is given unlimited light, carbon dioxide and water at a warm temperature, the only thing limiting the rate of photosynthesis is its own ability to absorb these materials and make them react. Glasshouses and polythene tunnels let growers control these limiting factors to raise yield.

The specification requires only that magnesium ions are needed for chlorophyll and nitrate ions for amino acids, so learn those two functions. Fertilisers supply them.

Another key way modern technology has increased food supply is the use of pesticides, which kill insects, weeds and fungi that reduce yield. Pesticides can harm other organisms and build up in food chains.

Biological control uses a natural predator or parasite to control a pest. This can happen naturally, for example ladybirds eat aphids. It leaves no chemical residues and is long lasting, but control is slower and the introduced species may become a pest itself.

Fish stocks in the wild are falling because of overfishing, so many fish are now farmed in ponds, cages or tanks.

Genetic modification (genetic engineering) is transferring a gene, or a piece of DNA, into another organism so that it gains a new characteristic. A student can remember the enzymes with a simple memory aid: a restriction enzyme is scissors (it cuts DNA at a specific sequence) and ligase is glue (it joins the cut pieces into one molecule).

A transgenic organism contains DNA from a different species, so every transgenic organism is a GMO, but a GMO may have DNA from the same species.

Microorganisms such as yeast and bacteria can be used by humans to produce foods and other useful substances. In a yeast fermentation practical, carefully adding a layer of oil on top of the solution excludes oxygen, so the yeast respires anaerobically and no further aerobic respiration takes place.

When an exam says "compare", each point must refer to both items; when it says "explain", each marking point is usually a cause followed by a consequence, and unlinked facts often score nothing.