Assignment Brief Title of Access to HE Diploma: Unit title(s): Diet and Nutrition Unit code(s): NH2/2/LN/014 NH2/3/LN/014 Learner: Tutor/Assessor: Chad Gunasinghe Title of Assignment: Assignment...

1) Digestive process:
Digestion is a process by which complex macromolecules are broken down into small
particles and chemically acted upon to provide fuel for body functions. The digestive process
starts with ingestion of foods and ends with removal of undigested food from body. Digestion
process basically divided into two parts: Mechanical digestion and Chemical digestion
(Anthea & Hopkins, 1993). Below discussed are the components of digestive tract and
process of digestion.
a) Oral cavity: Digestion starts with ingestion of foods by mouth where these are chewed
by teeth. Teeth churn the food materials and make them into small particles. Three
different glands secrete large amounts of saliva into mouth. This saliva gets mixed
with churned food particles. Saliva moistens the food and contains digestive enzymes.
It contains salivary amylase which breakdown polysaccharides like starch into
disaccharides like maltose. It contains mucus, a glycoprotein which softens the food
and help forming bolus. Another enzyme lingual lipase hydrolyses long chain fatty
acids to fattyacids.
b) Pharynx: It is present between oral cavity and oesophagus. Pharynx is a passage for
both food and air. While food is passing air passage stops in order to prevent choking.
Pharynx serves as the gateway for food and food passes through pharynx to reach
oesophagus.
c) Oesophagus: Oesophagus is a tube like structure starting from pharynx and ends at
stomach. The chewed food is pushed down to stomach through esophagus by
peristaltic movement. This peristaltic movement helps in passage of food along with
more mechanical churning of food (Farrell. 2010). It also contains mucus which
mixes with food and softens it.
d) Stomach: It is a small sac like organ which stores and break down foods. Stomach
wall is made up of many types of cells which secrete different type of chemicals
which help in the process of digestion. It secretes pepsin, gastric acid, digestive
enzymes, intrinsic factors. Pepsin helps in digestion of proteins. Glycoprotein like
intrinsic factor helps in absorption of Vitamin B-12. It also secretes mucus and gastric
juice which softens and lubricates food.
e) Small intestine: After processing in stomach food passes to small intestine where it is
acted upon by many hormones and chemicals. Among these are bile, pancreatic juice
and intestinal juice. Bile secreted from liver helps in emulsification of fats and its
absorption. Pancreatic juice contains pancreatic amylase, lipase and trypsinogen
which help in digestion of carbohydrate, lipids and proteins (Kong & Singh, 2008).
Intestinal juice contains enzymes such as enteropeptidase, erepsin, trypsin,
chymotrypsin, maltase, lactase and sucrase (all three of which process only sugars).
f) Large intestine: In large intestine no more food digestion occurs. Here food is
fermented and small particles are absorbed. The undigested food excretes out of body.
Absorption of food particles: The different of components of digestive tract have lined by
specialized cells. These cells are epithelial in nature and contain cilia and villi. These cilia
and villi increase surface area of these cells and help in absorption of different food
http://en.wikipedia.org/wiki/Enteropeptidase
http://en.wikipedia.org/wiki/Erepsin
http://en.wikipedia.org/wiki/Trypsin
http://en.wikipedia.org/wiki/Chymotrypsin
http://en.wikipedia.org/wiki/Maltase
http://en.wikipedia.org/wiki/Lactase
http://en.wikipedia.org/wiki/Sucrase
http://en.wikipedia.org/wiki/Sugar
components. The most food absorption takes place in stomach and intestines. Carbohydrate,
lipids, proteins, amino acids, vitamins are all absorbed at these places. Absorption of food
may or may not require energy expenditure (Rockville, 2005). This absorption can be passive
process or active process. Nutrients are absorbed by the intestinal wall, reach blood
circulation and distributed to different organs.
2) Different roles of carbohydrates, proteins and lipids are described below
Carbohydrate:These are complex molecules composed of Carbon, Hydrogen and Oxygen.
These are polyhydroxy aldehydes and ketones. There are two different kinds of carbohydrate
are found: Simple like malt, sugar, glucose etc. and Complex like cereals and grains. The
major sources of carbohydrates are plant products. The primary function of carbohydrate is
supply of energy. These upon oxidation produce large amount of energy and stored in
chemical form like ATP, FADH2 and NADH. Carbohydrates are very essential for brain
functioning as only these can pass blood-brain barrier. Mostly hexose sugars are burnt down
to produce energy, while other types of carbohydrates are stored in body. Human body stores
carbohydrate in form of glycogen (Westman, 2002). One of the other functions of
carbohydrate is presence in cell membranes and cell surfaces as receptors. Taking an
example, one molecule of glucose during cellular respiration produces at about 38 ATPs. So
this energy drives many cellular processes and carries on body function.
Proteins:Proteins are large macromolecular polymers of composed of 20 different types of
amino acids joined by peptide linkage. Virtually proteins are involved in all basic cellular
function starting from growth, multiplication, energy production, nutrient absorption etc.
Some basic functions of proteins are discussed below (Nelson & Cox, 2005).
Antibodies: Specialized proteins involved in protection of body from foreign invaders
(pathogens/antigens).
Contractile proteins: Proteins like actin and myosin are responsible for muscle contraction
and movement.
Transport proteins: These are carrier proteins and help in moving molecules from one point...