Sockeye salmon (Oncorhynchus nerka) spend the first years of their lives in the freshwater lakes of Alaska before migrating to marine waters. Their first months in marine waters are spent foraging and growing near the shore line. They then move to offshore regions of the North Pacific Ocean for 2 to 3 years.

The graph shows fork length frequency of juvenile O. nerka caught during their first months in marine waters in autumn 2008 and ocean age one O. nerka caught 15 months later during winter 2009 in the North Pacific Ocean.

Low protein diets are a widespread problem in the developing world. A low protein diet in a pregnant mother could affect a developing fetus. Other mammals are used as a biomedical model for energy metabolism and malnutrition in humans.

In an experiment to study the effect of protein levels in the diet, pregnant mammals were fed diets with different ratios of protein to carbohydrate:
- low protein : high carbohydrate (LP),
- adequate protein: adequate carbohydrate (AP),
- high protein : low carbohydrate (HP).

The table shows the average birth mass of the offspring and the body mass gain of the mother during the pregnancy. The concentration of several substances in the plasma of the mothers was also recorded. LDL (low density lipoprotein) is considered "bad cholesterol" and HDL (high density lipoprotein) is considered "good cholesterol".

Edible insects have been a part of traditional human diets in many countries. For example, crickets are insects commonly eaten in Asia and Africa. Many studies have looked at the prospects of raising insects on a commercial scale for direct human consumption as food or indirectly by feeding insects to farm animals.

One factor to consider is which organisms are most efficient at converting the feed they eat into animal protein that can be consumed. A study compared the percentage of mass that was edible in two common farm animals and in crickets.

A1. Iron, folic acid and vitamin B12 (cyanocobalamin) are important components of a healthy diet. These nutrients are necessary for the production of the red blood cells in the body that transport oxygen to the tissues. Deficiency of any of these nutrients can lead to anemia, a condition that causes weakness, tiredness and shortness of breath.

In a study of the Piaroa, a population living in a remote area of Venezuela, investigators discovered very high levels of anemia, especially amongst young children and females of childbearing age. The table below shows the incidence of anemia and deficiencies of iron, folic acid and vitamin B12 in this population, as a percentage.

Which is an effect of protein denaturation?

How are amino acids joined together to form a dipeptide?

The table shows some essential and non-essential amino acids.

What is a valid conclusion for an amino acid in the table?

What must vegans ensure when they plan their diet?

Diagrams of three different proteins, X, Y and Z , are shown.

Which row describes the structure of each protein shown?

Myoglobin is a globular protein in which nearly all the non-polar R-groups point towards the inside of the molecule. The outside surface contains all the polar R-groups. What can be deduced from this?