B3: Organisation & The Digestive System

Tissue and Organs

• Organism - a group systems working together to make 1 independent living thing

• Organ System - organs working together

• Tissues - groups of the same / similar cells linked together with a specific / particular / certain function

• Organs - groups of tissues working together to preform a function

• Cells - the smallest unit of life - they are the basic building blocks of all living organisms

• Cells —> Tissue —> Organs —> Organ System —> Organism

• Muscular Tissue — contracts and relax - Moving the Stomach, Mixed Food with Acid and Enzymes e.g. Mechanical digestion

• Glandular Tissue — secretes substances - Enzymes, Hydrochloric Acid (HCl), Mucus

• Epithelial Tissue — lines surfaces - Protection, Secretion, Cover

Digestive System

• Digestion - the breaking down of food, from large molecules into small/ insoluble into soluble

Mouth

• chews food into smaller pieces - teeth (mechanical digestion)

• tongue helps to manipulate food to be swallowed

Salivary Glands

• produces saliva

• glandular tissue

• produces enzymes - amylase, breaks down starch (chemical digestion)

Oesophagus

• food passes through and transports it to the stomach

• the movement is by ‘Peri Stalsis’

• muscular tissue

Stomach

• mixes enzymes - breaks down food into small molecules

• all 3 tissues - muscular, epithelial, and glandular

• contains acid

• enzymes made here - chemical digestion

Pancreas

• glandular tissue

• makes enzymes e.g. carbohydrase, protease, lipase

• no digestion actually occurs - contributes to chemical digestion

Liver

• makes bile - not an enzyme (a substance to aid fat digestion)

Gall Bladder

• stores bile

Small Intestine

• absorbs nutrients into blood stream

• absorbs soluble food

• makes enzymes - chemical digestion

Enzymes

Metabolism - the sum of all the reaction in a cell or in the body. Different enzymes catalyse different metabolic reaction

• Complimentary - fits perfectly together

• An enzymes job is a biological catalyst - speeds up a reaction, whilst remaining unchanged (lowers the amount of activation energy)

• In the same way a key fits a lock, the substrate is thought to fit into an enzyme’s active site. The enzyme is the lock and the reactant is the key.

• e.g. A molecule of hydrogen peroxide fits into the active site of a catalase molecule —> hydrogen peroxide breaks down into water and oxygen —> molecules of water and oxygen leave the active site of the enzyme ————————————————>

Food tests

• Carbohydrate — iodine test for starch - yellow-red iodine solution turns blue-black if starch is present

• Sugar — Benedict’s test for sugars - blue Benedict’s solution turns brick red on heating if a sugar, such as glucose, is present

• Protein — Biuret test - blue Biuret reagent turns purple if protein is present (Biuret is very corrosive)

• Lipids — ethanol test - ethanol added to a solution gives a cloudy white layer if a lipid is present. Ethanol is highly flammable and harmful.

Factors that affecting enzymes

• Enzymes are not alive - they cannot die!

Colder

• lower temp = less kinetic energy

• enzymes and substrates move slower

• less successful collisions between substrate and active site

• less enzyme substrate complex

• less products, therefore rate of reaction is very slow

• In cold temp - enzymes doesn’t denature

Warmer

• higher temp = more higher kinetic, and thermal energy

• enzymes and substrates move faster

• more successful collisions between substrate and active site

• more enzyme substrate complex

• more products, therefore rate of reaction is faster

• In warm temp - enzymes doesn’t denature

Too Hot

• very high temp = much more kinetic, thermal energy

• enzymes and substrates move even faster

• even less successful collisions between substrate and active site (active site changes shape)

• even less enzyme substrate complex

• even less products, therefore enzyme is denatured

• In too hot temp - enzymes does denature

Small intestine

• Located in your lower abdomen, just below the stomach, the small intestine is a coiled tube-like organ that is the longest part of the digestive system.

• absorbs nutrients by enzymes from the pancreas and the liver

• they break down the food into small molecules that can pass through the wall of the small intestine

• the small intestine also extracts water and helps the food move along to the large intestine

• villi along the walls increase surface area and speeds up digestion

• microvilli further enhances the absorption capacity

• thickness of the villi is only one cell thick

• a network of blood capillaries can transport glucose and amino acids away form the small intestine

• the small intestine is split up into 3 parts: duodenum, jejunum and ileum

Enzymes Required Practical

• Independent variable — pH

• Dependent variable — colour change (presence of starch)

• Control variable(s) — time (10 seconds), temperature (25^o), volume of starch and amylase

Method

• Place several different starch solutions of a known volume and concentration in a water bath at 25^o

• Adding a buffer solution at a different pH to each solution

• Setting up spotting tiles for each test solution with a drop of iodine in each well

• Mixing the same volume and concentration of amylase into each tube

• Starting a stop-watch as soon as the enzyme is added

• Taking samples every 10 seconds using a glass rod and adding each sample to an iodine filled well

• Observing and recording results that can be displayed graphically to compare the effect of pH on the rate of an amylase-catalysed reaction

How digestion works

What are carbohydrates?

• Starch is a complex carbohydrates

• Starch is made of small sugar molecules e.g. glucose

• The small molecules from carbohydrates are used by the body to release energy and make the body work

• Carbohydrates are made of - C,H,O (carbon, hydrogen, oxygen)

What are proteins?

• Proteins are made of long chains of small molecules

• These small molecules are called amino acids

• Proteins are used by the body for growth and repair - enzymes, antibodies and hormones

• Proteins are made of - O,C,H,N,(S) (oxygen, carbon, hydrogen, nitrogen, (sulphur))

What are lipids (fats)?

• Fats are made up of fat molecules which contain fatty acids and glycerol

• 

• 1 glycerol for every 3 fatty acid

• Fat molecules must be broken down by the body so that they can be used for energy storage

• Fats are also used by the body to keep heat in and make cell membranes

• Lipids are made of - C,H,O (carbon, hydrogen, oxygen)

table showing all

Speeding up Digestion

Stomach

• HCl speeds up digestion —> the enzymes break down food —> better (optimum)

  in acidic conditions

Liver

Bile is NOT an enzyme

Bile has 2 role:

1. Neutralisation —> bile neutralises the acidic food form stomach —> food needs to be alkaline to be digested by enzymes

2. Emulsification —> only on lipids / fats —> increases surface area so lipids can digest them faster and more substrate surface to act on