B7 Human nutrition

What is a balanced diet?

A balanced diet includes all essential nutrients in the correct amounts

Why do balanced diets vary between people?

it depends on age, gender and amount of physical activity

What are the 7 most important nutrients?

carbohydrates, fats and oils, proteins, vitamins(C&D), mineral ions(calcium and iron), fibre (roughage), water

Where is carbohydrates found and what is its importance?

Found in pasta, rice and potatoes

Used as a source of energy in respiration in cells.

Where is fats and oils found and what is its importance?

Found in fatty meats, cheese and butter

Used for long-term energy, insulation, waterproofing, structure and protection around delicate organs.

Where is proteins found and what is its importance?

Found in meat, fish and eggs

Used in protein synthesis (new cells for growth and repair0, produces antibodies, enzymes and hormones, carries other proteins

Where is vitamin c found and what is its importance?

Found in citrus fruits and vegetables

Used in the synthesis of proteins which help make up the skin, ligaments and blood, repair of tissues/healing wounds, supports immune system

Where is vitamin d found and what is its importance?

Found in dairy products, eggs and fish oil

Used in the absorption of calcium during digestion, maintaining healthy bones.

Where is calcium found and what is its importance?

Found in dairy products and fish

Used for healthy bones and teeth, helps blood clotting

Where is iron found and what is its importance?

Found in red meats and green vegetables

Used in: Key component in haemoglobin in red blood cells which help transport oxygen around the body

Where is fibre found and what is its importance?

Found in vegetables, fruits and whole grains

Used in: It is not digested and which helps food to move through the stomach and intestines

Where is water found and what is its importance?

Comes from both drinks and food, moves into the body by osmosis during digestion.

Used in: acts as a solvent for chemical reactions, help maintain body temp, removes waste product through urine and sweat

What is the cause of scurvy?

Caused by lack of vitamin C

Leads to bleeding under the skin and gums, premature stopping of bone growth in children leading to stunted growth, and very dry skin and hair

What is the cause of rickets?

Caused by lack of vitamin D (sunshine)

Causes weak and soft bones and stunted growth in children as the bones cannot develop correctly.

Draw the digestive system

Label this diagram

What is the alimentary canal and what is in it?

a long tube which runs from the mouth to the anus

mouth, oesophagus, stomach, small intestine (duodenum and ileum) and large intestine (colon, rectum and anus)

What are the associated organs?

salivary glands, pancreas, liver and gall bladder

What is the pathway food takes?

mouth → oesophagus → stomach → small intestine → large intestine

Mouth and salivary glands function

food is mechanically digested in the mouth by the teeth. the salivary glands release saliva which contains amylase that begins the chemical digestion of starch into simple sugars

Oesophagus function

allows food to pass from the mouth to the stomach by peristalsis

Stomach function

-muscles contract and relax to churn the food into smaller pieces by mechanical digestion. secrets gastric juice which contains;

-protease enzymes break down protein in chemical digestion

-hydrochloric acid

What is the function of hydrochloric acid in gastric juice?

-killing harmful microorganisms in food with its high acidity which causes the denaturation of enzymes

-providing an acidic pH for optimum enzyme activity of proteases in the stomach

Small intestine function

consists of the duodenum and ileum

-duodenum is where the acidity from the stomach is neutralised and the enzymes are secreted into from the pancreases to break down molecules

-ileum is where the products of digestion are absorbed into the blood

Pancreas function

secretes pancreatic juices into the small intestine which contains lipase, protease and amylase enzymes to break down food so that it can be absorbed

Liver function

makes bile that is secreted into the small intestine

What are the two things that bile does?

bile is an alkaline mixture

-neutralises the acidic conditions from the stomach (bile is alkaline) to provide a suitable pH for enzymes to work at

-emulsifies fats, increasing their surface area so enzymes can digest them more quickly for chemical digestion

Gall bladder function

bile made in the liver is stored here before being secreted into the small intestine

Large intestine function

consists of the colon, rectum and anus

-remaining salt and water is absorbed from the undigested food in the colon

-indigestible food, bacteria and dead cells form faeces which are passed out through anus

What is ingestion?

taking in substances (food and drinks) into the body.this occurs in the mouth.

What is digestion?

the breakdown of large molecules into smaller molecules (food into nutrients). There are two types of digestion:

-Physical digestion - occurs in the mouth and stomach

-Chemical Digestion - occurs mainly in the small intestine

What is absorption?

the movement of nutrients from intestines into the blood

-in small intestines, most nutrients in the food are absorbed

-in large intestine, remaining water and salts are absorbed

What is assimilation?

uptake and use of nutrients by cells. This occurs throughout the body but mainly in the small intestines

-nutrients absorbed into the blood and transported to the cells where they are used

What is egestion?

removal of indigestible remnants of food from the body as faeces. This occurs in the anus.

What is the difference between excretion and egestion?

excretion- is the removal of metabolic waste that originate inside cells and cross membranes during transport and elimination

egestion- removes undigested food that has never entered the cells or crossed membranes

What is physical digestion?

the breakdown of food into smaller pieces without chemical change to the food molecules

What is the role of physical digestion?

increases the surface area of food for the action of enzymes in chemical digestion

Role of teeth in physical digestion

incisors and canines at the front of the mouth are used to bite and tear food, before it is passed to the premolars and molars at the back of the mouth which are used for chewing and grinding food into smaller sections

Role of stomach in physical digestion

the walls in the stomach contain muscle which contract to mix and grind the food

Role of bile in physical digestion

used to emulsify fats and oils, increasing their surface area for chemical digestion

What is chemical digestion?

the breakdown of large insoluble molecules into small soluble molecules

What is the purpose of chemical digestion?

producing small soluble molecules that can be absorbed and used in the body

What does amylase do?

breaks down starch to simple reducing sugars

-breaks down starch into maltose then maltase breaks down maltose into glucose

Where is amylase secreted and acts? [2]

secreted by salivary glands in saliva

acts in mouth

secreted by pancreas in pancreatic juice

acts in small intestine (duodenum)

What does protease do?

break down protein to amino acids

What are the two types of proteases?

pepsin and trypsin

Where is pepsin secreted and acts?

secreted by stomach in gastric juice

acts in acidic conditions of stomach

Where is trypsin secreted and acts?

secreted by pancreas in pancreatic juice

acts in alkaline conditions of the small intestines

What does lipase do?

breaks down fats and oils to fatty acids and glycerol

Where is lipase secreted and acts? [2]

secrets by pancreas in pancreatic juice

acts in small intestine (duodenum)

secreted by cells covering the villi

acts in small intestine (ileum)

Fill in the substrate → enzyme → product:

starch →

proteins→

fats →

starch → amylase → maltose

proteins→ protease (pepsin/trypsin) →polypeptides

fats → lipase → fatty acids and glycerol

What 2 things aid chemical digestion?

hydrochloric acid and bile

Role of hydrochloric acid in chemical digestion

-increases the stomach's acidity which will kill any harmful bacteria in the food by denaturing it

-the low pH is the optimum pH for protease so it can effectively break down proteins

Role of bile in chemical digestion

an alkaline mixture that neutralises the acidic mixture of food and gastric juices entering the duodenum from the stomach, to provide a suitable pH for enzyme action in the small intestine