2. Biological molecules
A section of Biology, 9700
Listing 10 of 748 questions
Hummingbirds are the smallest of birds and are found in the Americas. Some species migrate hundreds of kilometres between warmer overwintering areas and summer breeding grounds. Like mammals, birds maintain a constant body temperature. Hummingbirds have a high requirement for sugars because they have a very high metabolic rate. shows a hummingbird feeding on nectar, one of their main food sources. Nectar is a sugary liquid containing mainly sucrose, fructose and glucose. Sucrose has the molecular formula C12H22O11. Fructose and glucose each have the molecular formula C6H12O6. State two differences between sucrose and fructose, other than the number of carbon, hydrogen and oxygen atoms present. In preparation for migration, sugars need to be converted to triglycerides to function as energy reserves. Hummingbirds can double their body mass during this time. shows the structural formula of one type of storage triglyceride. The triglyceride has two types of fatty acid residue, palmitate and oleate. H H C O O C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H H C H palmitate oleate H C O O C H H C H H C H H C H H C H H C H H C H H C H C H C H H C H H C H H C H H C H H C H H C C H H H H C H C H H H H C H H C O O C H H C H H H C H H C H H C H H C H H C H H C H C H C H H C H H C H H C H H C H H C H H C Outline the features of the molecular structure of the triglyceride shown in . In hummingbirds, glycogen is the long-term carbohydrate energy store. Suggest one reason why hummingbirds build up a greater energy store in the form of triglyceride, rather than a greater energy store of glycogen, in preparation for migration. In birds such as hummingbirds: • blood is kept within vessels • for each complete circuit of the body, blood passes through the heart twice. State the term used to describe this type of circulatory system. The heart of birds has the same structure as the heart of mammals. Compared with the heart of mammals, the heart of birds is larger in proportion to their body size. Suggest why the heart of birds is larger in proportion to their body size. Complete Table 3.1 to show the names and functions of the main blood vessels associated with the heart of mammals. Table 3.1 function of blood vessel name of blood vessel carries blood from the heart to the lungs carries blood to the heart from the lungs carries blood from the heart to the rest of the body carries blood to the heart from the rest of the body
9700_s22_qp_22
THEORY
2022
Paper 2, Variant 2
View
Starch molecules are the main storage molecules in many types of cereal grain, such as the grain of the barley plant. When the seed inside a barley grain germinates, genes coding for digestive enzymes are switched on. The enzymes that are synthesised catalyse the hydrolysis of storage molecules such as proteins and starch. Explain what is meant by a gene. The hydrolysis of proteins in the barley seed produces amino acids that can be used in the synthesis of the proteins required for formation of the seedling (young plant). is an incomplete diagram of the molecular structure of the smallest amino acid, glycine. Each molecule of glycine has two carbon atoms. H C C H Complete to show the molecular structure of glycine. Starch is a mixture of two different molecules. Name these two molecules. Two of the enzymes synthesised by the barley seed are α-amylase and maltase. These are involved in the hydrolysis of the stored starch during seedling formation. In the food industry, the starch extracted from barley seeds (barley starch) is used in the production of sugar syrups. summarises the reactions catalysed by α-amylase in the production of maltose syrup and by maltase in the production of glucose syrup. barley starch maltose maltose glucose α-amylase maltase Some of the substances shown in are listed in Table 2.1. Complete Table 2.1 to identify which of the terms polysaccharide, monosaccharide and macromolecule apply to each of the substances listed. Use a tick (3) if the term applies and a cross (7) if the term does not apply. Put a tick (3) or a cross (7) in every box. Table 2.1 substance polysaccharide monosaccharide macromolecule glucose maltase maltose starch When producing sugar syrups, there are advantages in using enzymes extracted from microorganisms. For example, some enzymes extracted from microorganisms are heat stable. Heat-stable enzymes are used to increase productivity because the reactions can be carried out at higher temperatures. Suggest one other advantage of using enzymes obtained from microorganisms, rather than enzymes extracted from barley seeds, in the production of sugar syrups. is a graph showing how the activity of a-amylase extracted from barley seeds changes as the temperature increases from 10 °C to 66 °C. temperature / °C percentage enzyme activity Explain the effect of temperature on the activity of α-amylase extracted from barley seeds, as shown in . Sketch on the curve that would be obtained using α-amylase enzyme that is heat stable.
9700_m21_qp_22
THEORY
2021
Paper 2, Variant 2
View
Questions Discovered
748