IGCSE Biology Paper-4: Specimen Questions with Answers 243 - 245 of 279

Passage

The diagram shows a section through a leaf.

Vascular Bundle

Question 243 (5 of 6 Based on Passage)

Edit

Write in Brief

One Liner▾

State two functions of vascular bundles in leaves.

Explanation

Vascular system, in plants is the assemblage of conducting tissues and associated supportive fibers. Xylem tissue transports water and dissolved minerals to the leaves, and phloem tissue conducts food from the leaves to all parts of the plant.

Question 244 (6 of 6 Based on Passage)

Edit

Write in Brief

One Liner▾

The cuticle is made of a waxy material. Suggest an advantage to a plant of this feature.

Explanation

The upper surface of leaf is covered with a waxy, waterproof cuticle, which serves to reduce water loss from the leaf, so lowers down the transpiration rate.

Question 245

Edit

Describe in Detail

Essay▾

Explain the roles of chewing and of enzymes in the process of digestion.

Explanation

The physical process of chewing food in our mouth helps to break down larger particles of food into smaller particles. This helps to reduce stress on the oesophagus and helps the stomach metabolize and breakdown your food. Saliva also contains digestive enzymes, which are released when chewing and assist in digestion. As our mouth releases these enzymes, which then pass into the throat and stomach, further improve the digestive process.

Explain the Roles of Chewing and of Enzymes in the Process of Digestion
GlandEnzymepHSite of actionSubstrateProduct
CarbohydrateFatProteinNucleic acid
Salivary glands (Saliva)Ptyalin (Amylase)6.7Buccal cavity, Oesophagus & part of stomachStarch.

Glycogen

Limit dextrin՚s, Maltoe, Isomaltose
Gastric glands (Gastric juice)(i) Prorennin ⇾ Rennin (Calf)

(ii) Pepsinogen ⇾ Pepsin

(iii) Gastric lipase (Infants)

2.0 – 3.7

2.0 – 3.7

2.0 – 3.7

Stomach

Stomach

Stomach

Milk Fat

Casein

(a) Protein

(b) Calcium

Paracaseinate

Calcium

Paracaseinate

Peptones

Fatty acid & glycerol

Liver (Bile)No digestive enzymesMakes food alkaline, emulsifies fat and helps in its absorption.
Pancreas (Pancreatic juice)(i) Chymotrypsinogen

⇾ Chymotrypsin

(ii) Trypsinogen Trypsin

(iii) Procarboxy peptidases

⇾ Carboxypeptidases

(iv) Pancreatic Lipase

(v) Pancreatic amylase

(vi) DNA-ase

(vii) RNA ase

7.5 – 8.5

7.5 – 8.5

7.5 – 8.5

7.5 – 8.5

7.5 – 8.5

7.5 – 8.5

7.5 – 8.5

Small intestine

Small intestine

Small intestine

Small intestine

Small intestine

Small intestine

Small intestine

Starch, Glycogen, Dextrins

Fat

Casein

(a) Protein

(b) Calcium

Paracaseinate

Larger Peptides

DNA

RNA

Calcium

Paracaseinate

Peptones & Peptides

Smaller peptides

Fatty acids, Monoglycerides, Glycerol

Limit dextrins maltose, Isomaltose, Deoxyribonucleo-tides Ribonucleotides

Small intestine

(Succus entericus)

(i) Aminopeptidases

(ii) Dipeptidases

(iii) Nucleotidases

(iv) Nucleosidases

(v) Intestinal Lipase

(vi) Isomaltase

(vii) Maltase

(viii) Lactase

(ix) Sucrase (Invertase)

7.0 – 7.5

7.0 – 7.5

7.0 – 7.5

7.0 – 7.5

7.0 – 7.5

7.0 – 7.5

7.0 – 7.5

7.0 – 7.5

7.0 – 7.5

Small intestine

Small intestine

Small intestine

Small intestine

Small intestine

Small intestine

Small intestine

Small intestine

Small intestine

Limit dextrins, Isomaltose

Maltose

Lactose

Sucrose

Fat

Peptides

Dipeptides

Nucleotides

Nucleotides

Amino acids and smaller peptides

Amino acids

Nucleosides, Phosphates

Nitrogen bases, Pentose sugars

Fatty acids, glycerol, Monoglycerides

Glucose

Glucose

Glucose, Galactose

Glucose, Furctose

Developed by: