Organisation

What are cells?

Cells are the basic building blocks of all living organisms.

What are tissues?

A tissue is a group of cells with a similar structure and function.

What are organs?

A collection of tissues working together to perform a specific function

What is an organ system?

Organs are organised into organ systems, which work together to form organisms

What is the difference between unicellular and multicellular organisms?

Unicellular organisms are made from one cell, whereas multicellular organisms are made up of collections of cells

What are substrates?

Substrates temporarily bind to the active site of an enzyme

Explain the locke and Key model

The shape of the enzyme active site and the substrate are complementary, so they can bind together to form an enzyme-substrate complex.

What are Carbohydrates, proteins and lipids?

Carbohydrates, proteins and lipids are large molecules that are needed by the body for growth, repair and metabolism.

What are enzymes?

Enzymes are biological catalysts made from protein

When do enzymes work fastest?

Enzymes work fastest at their 'optimum temperature' - in the human body, the optimum temperature is around 37⁰C

What is metabolism?

Metabolism is the sum of all the reactions happening in a cell or organism, in which molecules are synthesised or broken down

What happens when enzymes are heated beyond the optimum

Heating to high temperatures break the bonds of an enzyme → enzyme will start to distort and lose its shape → reduces the activity of the enzyme

What is the optimum PH for most enzymes?

The optimum pH for most enzymes is 7. (If the pH is too high or too low this causes denatured enzymes)

What is Carbohydrase

They break down carbohydrates → simple sugars.

What are proteins?

proteins are long chains of chemicals called amino acids

What is starch?

starch is a chain of glucose molecules

What is amylase ?

Amylase is a carbohydrase which breaks down starch → maltose.

Where is amylase made?

Amylase is made in the salivary glands, the pancreas and the small intestine

What are Proteases?

Proteases break down proteins → amino acids in the stomach and small intestine.

Where is protease made?

They are made in the stomach (pepsin), pancreas and small intestine

What are lipases?

Lipases break down lipids → glycerol + fatty acids.

Where is lipase made?

They are produced in the pancreas and small intestine

What is maltase?

Maltase catalyses the breakdown of maltose → glucose in the small intestine

What are the products of digestion used for?

used to build new carbohydrates, lipids and proteins. Some glucose is used in respiration

What is isomerase?

It changes glucose syrup into fructose syrup

What organ produces bile?

The liver

What is bile?

Bile is made in the liver and stored in the gall bladder.

What are the 2 main roles of the bile?

-it neutralises the acid

-it emulsifies fats

How does bile neutralising the acid help the body?

providing the alkaline conditions needed in the small intestine

How does bile emulsifies fats help the body?

providing a larger surface area over which the lipase enzymes can work

Method for Iodine test for starch

1. Put some of the food sample into a test tube.

2. Add a few drops of iodine solution to the food sample using a pipette.

3. If starch is present, the solution turns from brown to blue-black.

Method for Benedict's test for reducing sugars

1. Add an equal volume or excess of Benedict's solution to the food sample in a test tube

2. Place in a hot water bath for a few minutes

3. If reducing sugar is present, it turns from blue to a brick red precipitate formed

Method to Test for protein

1. Add a few drops of Biuret's reagent to the food sample in a test tube

2. Shake the solution to mix and wait for a few minutes

3. If protein is present, the solution turns from blue to purple.

Method to Test for lipids (emulsion test)

1. Add a few cm3 of ethanol to the food sample.

2. Pour this into a test tube of equal volumes of distilled water

3. If lipids are present, a white emulsion is formed on the surface of the mixture.

Enzymes practical

1. On a tile, label each well with the time and add a drop of iodine solution to each well.

2. Add 2 cm3 of buffer solution using a syringe into each labelled test tube.

3. Immerse the solutions and the test tubes of buffer solution in a water bath at 25°C and allow to equilibrate

4. Use a syringe to add 2 cm3 of amylase and starch into the test tube of buffer solution and start timing immediately

7. Use the glass rod to transfer a drop of the mixture to the well labelled '0' on the tile.

8. Repeat step 6 every 30 seconds, rinsing the glass rod in between every test, until the iodine solution remains brown and does not turn blue-black.

9. Calculate the rate of enzyme reaction by using 1/ time taken for iodine solution to remain brown. 10. Repeat steps 2-8 for buffer solutions with different pH values.

What is the heart?

The heart is an organ that pumps blood around the body in a double circulatory system

Why is the double circulatory system important?

It makes the circulatory system more efficient

What is the natural resting heart rate is controlled by?

a group of cells called a pacemaker

Where is the pacemaker located?

In the right atrium

What is the role of a pacemaker?

The role of the pacemaker is to coordinate the contraction of the heart muscle

What is an artificial pacemaker?

An electrical device used to correct irregularities in the heart rate.

What is the difference between the walls of the ventricles compared to those of the atria?

The walls of the ventricles are much thicker than those of the atria

Why are the walls of the ventricle thicker?

they are responsible for pumping blood out of the heart and so they need to generate a higher pressure

What is the difference between the walls of the left ventricles compared the right ventricle?

The wall of the left ventricle is much thicker than that of the right ventricle

Why is the wall of the left ventricle thicker than the right?

as it has to pump blood at high pressure around the entire body, whereas the right ventricle is pumping blood at lower pressure to the lungs

What is the difference in oxygen when a person is at rest compared to when they are excersing?

-When a person is at rest, the oxygen demand of their cells is low and so a lower heart rate is maintained.

-When a person is exercising, the oxygen demand of their muscle cells increases, so a higher heart rate is necessary

What is the right ventricle

pumps blood to the lungs where gas exchange takes place.

What is the left ventricle

pumps blood around the rest of the body

What is the aorta (left)?

carries oxygenated blood from the heart to the body

What is the vena cava (right)?

carries deoxygenated blood to the heart from the body

What is the pulmonary artery (right)?

carries deoxygenated blood from the heart to the lungs

What is the pulmonary vein (left)?

carries oxygenated blood to the heart from the lungs

What are the coronary arteries

they supply oxygenated blood to the heart muscle

What is the right atrium

receives deoxygenated blood

What is the left atrium

receives oxygenated blood

How does blood flow? (VAVA)

blood flows into the heart from a vein, goes into an atrium, then a ventricle, and out through an artery.

What are Arteries

transport blood away from the heart (usually at high pressure)

What are Veins

transport blood to the heart (usually at low pressure)

What are Capillaries

found in the lungs + enable transfer of substances between the blood and tissues.

How is the structure of an artery related to its function? (2)

-The wall of the artery is thick with layers of collagen, smooth muscle and elastic fibres.

-The elastic fibres allow the artery wall to expand around blood, they then recoil when the heart relaxes

How is the structure of a vein related to its function? (3)

-The wall of the vein is relatively thin with thinner layers of collagen, smooth muscle and elastic fibres.

-The lumen of the vein is larger than that of an artery.

-Veins contain valves that prevent the backflow of blood, helping return blood to the heart

How is the structure of a capillary related to its function? (2)

-The wall is only one cell thick - short diffusion path for oxygen and carbon dioxide .

-The cells of the wall have pores which allow blood plasma to leak out and form tissue fluid

How would you calculate the rate of blood flow?

Volume of blood / number of minutes

How are lungs adapted for gas exchange (3)

-Large surface area

-Thin walls

-Dense capillary network

Why do the lungs have a Large surface area?

to allow faster diffusion of gases across the surface.

Why do the lungs have a thin walls?

to ensure diffusion distances remain short.

Why do the lungs have a Dense capillary network?

to maintain a high concentration gradient so diffusion occurs faster

What makes up the lungs?

trachea → bronchi → bronchioles → alveoli

What is the alveoli?

Tiny air sacs in the lungs, where gas is exchanged during breathing.

What is the alveoli like? (3)

-Rich blood supply - maintains concentration gradient.

-Small and arranged in clusters - larger surface area.

-They have very thin walls for short diffusion pathway

Describe how gas exchange occurs at the alveoli (2)

-Oxygen diffuses from the alveoli into the capillary

-Carbon dioxide diffuses from the capillary into the alveoli

Why does the aveoli have a lot of moisture

The layer of moisture in the alveoli allows gases to dissolve so that they can diffuse quickly.

What is the circulatory system?

a system of blood vessels with the heart and valves

What is the pulmonary circuit?

the pulmonary circuit is between the heart and lungs.

What is the systemic circuit?

the systemic circuit is between the heart and the other organs.