Describe the structure of starch.

Explain how amino acids in casein could reach the liver, starting from the moment when the person takes a bite of pastry cream pie.

Congenital lactase deficiency is a type of lactose intolerance that occurs in infants. It is inherited in an autosomal recessive pattern. Calculate the chance of congenital lactose intolerance in a child whose parents are both carriers for the disorder, showing fully how you reached your answer.

a. starch is a carbohydrate ✔

b. starch is formed by carbon, hydrogen and oxygen ✔

c. it is a polymer/chain/polysaccharide ✔

d. formed from monosaccharides/simple sugars/glucose ✔

e. linked together by condensation/dehydration ✔

f. consists of amylose and amylopectin ✔

g. amylose is a long chain/unbranched ✔

h. amylopectin is branched ✔

a. food is mechanically/physically digested in the mouth through mastication/chewing ✔

b. mixed with saliva (to form the bolus) in mouth ✔

c. moved through esophagus/peristalsis ✔

d. proteins digested in the stomach (pepsin) ✔

e. pancreas secretes enzymes into lumen of small intestine
OR
(endo)peptidases/trypsin) are secreted by pancreas ✔

f. enzymes digest macromolecules to monomers
OR
endopeptidases digest polypeptides to peptides/amino acids ✔ 

g. villi of small intestine absorb amino acids ✔  Allow pepsin. 

h. amino acids carried to blood capillaries ✔

i. blood (capillaries) carry amino acids to (hepatic portal) vein/blood vessel going to liver ✔

j. amino acids absorbed by active transport/protein pumps in the villi ✔

a. gametes of both parents shown as a capital and small letter (e.g. L and l) ✔

b. possible F1 genotypes ✔

c. 25 % lactose intolerant, 50 % carriers, 25 % lactose tolerant
OR
75 % tolerant and 25 % intolerant
OR
child has 25 %/1:4/$\frac{1}{4}$ chances of inheritance of intolerance ✔

(attempted by about 40 % of the cohort)

The question was put in the context of the composition of pastry cream, rather than just diving in with questions. In part (a), the structure of starch was quite well known. The better answers included descriptions of polymers and monomers, amylose and amylopectin, and glucose. Part (b) was challenging to many, requiring a knowledge of the digestive system, enzyme action and the blood supply to the liver. It was possible to gain all of the marks by omitting the references to the blood stream. This was an example of where a clear 'essay plan' would have helped. Weaker candidates wrote at length about carbohydrate and fat digestion which was not required. Surprisingly the position of the pancreas was often confused, with pancreatic enzymes appearing in the stomach. The fundamental idea of the digestion of large molecules (proteins) to small soluble ones (amino acids) which can be absorbed into the blood stream at the villi was missed by many. Part (c) was a straightforward genetics cross, put into the context of lactose intolerance. In general, it was well answered. Although the question clearly stated that it was an autosomal recessive condition, many weaker students were determined to make it sex linked.

(attempted by about 40 % of the cohort)

The question was put in the context of the composition of pastry cream, rather than just diving in with questions. In part (a), the structure of starch was quite well known. The better answers included descriptions of polymers and monomers, amylose and amylopectin, and glucose. Part (b) was challenging to many, requiring a knowledge of the digestive system, enzyme action and the blood supply to the liver. It was possible to gain all of the marks by omitting the references to the blood stream. This was an example of where a clear 'essay plan' would have helped. Weaker candidates wrote at length about carbohydrate and fat digestion which was not required. Surprisingly the position of the pancreas was often confused, with pancreatic enzymes appearing in the stomach. The fundamental idea of the digestion of large molecules (proteins) to small soluble ones (amino acids) which can be absorbed into the blood stream at the villi was missed by many. Part (c) was a straightforward genetics cross, put into the context of lactose intolerance. In general, it was well answered. Although the question clearly stated that it was an autosomal recessive condition, many weaker students were determined to make it sex linked.

(attempted by about 40 % of the cohort)

The question was put in the context of the composition of pastry cream, rather than just diving in with questions. In part (a), the structure of starch was quite well known. The better answers included descriptions of polymers and monomers, amylose and amylopectin, and glucose. Part (b) was challenging to many, requiring a knowledge of the digestive system, enzyme action and the blood supply to the liver. It was possible to gain all of the marks by omitting the references to the blood stream. This was an example of where a clear 'essay plan' would have helped. Weaker candidates wrote at length about carbohydrate and fat digestion which was not required. Surprisingly the position of the pancreas was often confused, with pancreatic enzymes appearing in the stomach. The fundamental idea of the digestion of large molecules (proteins) to small soluble ones (amino acids) which can be absorbed into the blood stream at the villi was missed by many. Part (c) was a straightforward genetics cross, put into the context of lactose intolerance. In general, it was well answered. Although the question clearly stated that it was an autosomal recessive condition, many weaker students were determined to make it sex linked.