2.2 Animal Tissues, Organs & Organ Systems

Why does food need to be digested?

• Large and insoluble

• Broken down — can be absorbed by cells

What organs are the digestive system made up of?

• Glands — salivary glands and pancreas

• Stomach

• Small intestine

• Liver

• Large intestine

Explain the function of the glands (salivary glands and pancreas) in the digestive system.

• Produces digestive juices — contains enzymes

  • breaks down food

Explain the function of the stomach in the digestive system.

• Produces HCl

  • kills bacteria

  • optimum pH for protease enzyme

Explain the function of the small intestine in the digestive system.

Soluble molecules are absorbed into blood

Explain the function of the liver in the digestive system.

• Produces bile → stored in gall bladder

  • Helps digest lipids

Explain the function of the large intestine in the digestive system.

• Absorbs water from undigested food → produces faeces

  • passes out of body through rectum and anus

Enzymes __________ specific reactions in living organisms due to the shape of their _________ _____.

• catalyse

• active site

What do digestive enzymes do?

• Converts food → small soluble molecules

  • Can be absorbed into bloodstream

Label this diagram of the human digestive system.

• A — mouth (teeth, tongue, and salivary glands)

• B — oesophagus

• C — stomach

• D — pancreas

• E — large intestine

• F — rectum

• G — anus

• H — appendix

• I — small intestine

• J — bile duct

• K — duodenum

• L — gall bladder

• M — liver

• N — diaphragm

What are enzymes?

• Biological catalysts

• Increase rate of reactions in living organisms

Why is the shape of an enzyme vital to its function?

Each enzyme has uniquely shaped active site — substrate binds to

Explain the ‘lock and key’ theory.

• Shape of substrate complementary to shape of active site

  • They bind → forms enzyme-substrate complex

• Reaction takes place — products released from surface of enzyme

Why do enzymes require an optimum pH and temperature?

They are proteins

What is the optimum temperature for digestive enzymes?

37 °C

Explain the effect of temperature on enzyme action.

• Increased temperature = increased rate of reaction (up to optimum)

• Above optimum — rate rapidly decreases and reaction stops

• Temperature = too hot → bonds in structure break

  • Shape of active site changes → substrate doesn’t fit

  • Enzyme is denatured and doesn’t work

What is the optimum pH for most enzymes?

7 — some in stomach have lower

Explain the effect of pH on enzyme action.

• pH = too high/low → active site changes shape — substrate doesn’t fit

• Enzyme is denatured and doesn’t work

What do carbohydrases do (give an example)?

• Carbohydrates → simple sugars

• Amylase — starch

Where is amylase produced? (3)

• Salivary glands

• Pancreas

• Small intestine

What do proteases do (give an example)?

• Proteins → amino acids

• Pepsin

Where is pepsin produced?

Stomach

What do lipases do?

Lipids (fats) → glycerol and fatty acids

Where are lipases produced? (2)

• Pancreas

• Small intestine

What are the products of digestion used to do?

• Build new carbohydrates, lipids, and proteins

• Glucose → respiration

Explain the role of bile in the digestive system.

• Alkaline — neutralises HCl made in stomach

• Emulsifies fats → forms small droplets → increases SA

  • Alkaline conditions and large SA → increases rate of fat breakdown by lipase

What is used to test for sugars?

Benedict’s solution

What is used to test for starch?

Iodine

What is used to test for lipids?

Ethanol

What is used to test for proteins?

Biuret reagent

Describe how you test for sugars.

• Put food sample in test tube

• Add a few drops of Benedict’s solution

• Place test tube in water bath for 5 mins

• Results: blue → green → yellow → orange → red

  • green = less glucose

  • red = more glucose

Describe how you test for starch.

• Put food sample in test tube

• Add a few drops of iodine

• Results: blue-black if starch is present

Describe how you test for lipids.

• Put food sample in test tube

• Add a few drops of distilled water

• Add a few drops of ethanol

• Shake solution gently

• Results: goes cloudy if lipid is present

Describe the test for proteins.

• Put food sample in test tube

• Add 1 cm³ of biuret solution A and biuret solution B

• Shake solution gently

• Results: turns purple if protein is present

Required Practical 5 — Enzymes:
Describe a method to investigate the effect of pH on the rate of reaction of amylase enzyme.

• Place one drop of iodine solution into each well of spotting tile

• Get three test tubes:

  • 2 cm³ — starch solution

  • 2 cm³ — amylase solution

  • 2 cm³ — buffer solution (pH 5)

• Place test tubes in water bath (30°C) — leave for 10 mins → solutions reach correct temp

• Combine solutions into one test tube — mix with stirring rod

  • Put in water bath — start stopwatch

• After 30s — transfer one drop of solution to well in spotting tile

  • Iodine turns blue-black → starch is present

• Take sample every 30s until iodine remains orange

  • Starch is no longer present — reaction is complete

• Repeat whole experiment using different pH buffer solutions

What are the problems wit RP 5 — Enzymes?

• Taking samples every 30s → only have approx. time for complete reaction

  • take samples every 10s

• Observation of colour change is subjective

What is the heart?

Organ that pumps blood around the body — double circulatory system

Where does the right ventricle pump blood?

Lungs → gas exchange

Where does the left ventricle pump blood?

Around the rest of body

What are the three types of blood vessel in the body?

• Arteries

• Veins

• Capillaries

What is the natural resting heart rate controlled by?

Group of cells in right atrium — pacemaker

What are artificial pacemakers?

Electrical devices — correct irregularities in heart rate

Explain a double circulatory system.

• Deoxygenated blood → right atrium → right ventricle → lungs for gas exchange

• Oxygenated blood → left atrium → left ventricle → O₂ blood around body

What do arteries do?

Carry blood (usually oxygenated) from heart → organs of body

Explain how the structure of arteries relates to their function.

• Thick walls — muscle and elastic fibres

  • Stretch as blood is pumped into them under pressure from heart

  • Returns to original shape

  • Felt as a pulse

What happens if an artery is damaged?

• Blood pumps out rapidly every time heart beats

  • It is under pressure

What do veins do?

Carry blood (low in O₂) from organs → heart

Why do veins have thinner walls than arteries?

Blood is not under pressure — no pulse

Why do veins have valves and what do they do?

• Open as blood flows through them → heart

• Closes if blood flows back → prevents backflow

• Blood squeezed back → heart — skeletal muscles

Explain the function of capillaries.

Allows blood to flow close to cells — enables substances to move between them

How does the structure of capillaries relate to their function?

• One cell thick wall — short diffusion pathway

• Permeable walls — substances can move across them

Label this diagram of the heart.

• A — Right side

• B — Left side

• C — Pulmonary artery

• D — Aorta

• E — Pulmonary vein

• F — Left atrium

• G — Heart valve

• H — Left ventricle

• I — Right ventricle

• J — Tendons — attached to valve and heart wall

• K — Heart valve

• L — Right atrium

• M — Vena cava

Explain how the structure of the heart relates to its function.

• Muscular walls — provides strong heartbeat

• Muscular wall of left ventricle thicker — blood is pumped around body not just to lung

• 4 chambers — separates oxygenated and deoxygenated blood

• Valves — prevents backflow of blood

• Coronary arteries — gives heart oxygenated blood

Explain the process of blood circulation in the heart.

• Blood flows to:

  • right atrium — through vena cava

  • left atrium — through pulmonary vein

• Atria contract → forces blood into ventricles

• Ventricles contract pushes blood in:

  • right ventricle → pulmonary artery → lungs

  • left ventricle → aorta → body

• Valves close — prevents backflow of blood

Label this diagram of the human gaseous exchange system.

• A — Deoxygenated

• B — Air out

• C — Air in

• D — Oxygenated

• E — Aveoli

• F — CO₂

• G — O₂

• H — Red blood cells in capillary

Explain the process of ventilation.

• Ribcage moves up and out → diaphragm moves down — volume of chest increases

  • increased volume = lower pressure

• Air drawn into chest as air moves from high pressure (environment) → low pressure (lungs)

• Opposite when exhaling

Explain the process of gas exchange.

• Inhalation → aveoli fill with O₂

• Deoxygenated blood in capillaries surrounding aveoli — came from pulmonary artery

  • has lots of CO₂ — product of respiration

• O₂ diffuses down concentration gradient → capillary bloodstream — has low O₂ concentration

• CO₂ diffuses down concentration gradient from blood → aveoli

How are aveoli adapted for gas exchange?

• Small and arranged in clusters — large surface area for diffusion

• Capillaries provide large blood supply — maintains concentration gradient

• Thin walls — short diffusion pathway

What is blood?

• Tissue consisting of plasma and:

  • RBC — red blood cells

  • WBC — white blood cells

  • Platelets

What is plasma and what is its function?

Liquid that carries components in blood — e.g. RBC, WBC, platelets, amino acids, urea etc.

What are red blood cells and what is their function?

• Carry O₂ molecules from lungs → cells in body

• Biconcave disc — large surface area

• No nucleus — more space for O₂

• Contains haemoglobin — binds to oxygen

What are white blood cells and what is their function?

• Part of immune system

  • body’s defence against pathogens

• Have a nucleus

• Different types:

  • produce antibodies

  • engulf and digest pathogens

  • produce antitoxins

    • neutralise toxins produced by microorganisms

What are platelets and what is their function?

• Small fragments of cells + no nucleus

• Clot blood at site of wound

  • clot dries and hardens → forms a scab → new skin grows

    • prevents microorganisms entering

• No platelets = excessive cuts and bruising from cuts

Coronary heart disease is a non-communicable disease.

What is a non-communicable disease?

Cannot be spread between individuals

Explain what coronary heart disease is.

• Fatty material builds up inside coronary arteries

• Reduces blood flow

• Lack of oxygen for heart muscle

What are stents and how do they help with coronary heart disease?

Metal tubes — keeps arteries open → blood can flow

What are the advantages and disadvantages of stents?

• Lowers risk of heart attack

• Quick recovery time

• Risk of heart attack during procedure

• Risk of infection

• Blood can clot around stent

What are statins and how do they help with coronary heart disease?

Drugs — decrease LDL cholesterol levels (cause coronary heart disease)

What are the advantages and disadvantages of statins?

• Reduce risk of:

  • strokes

  • heart attacks

  • coronary heart disease

• Increase levels of HDL cholesterol

• Needs to be taken continuously

• Side effects

• May not have immediate effect

What are faulty valves and what problems can they cause?

• Becomes stiff → cannot open

• Damaged → leaks

  • Blood backflows → heart doesn’t work efficiently

What are the advantages and disadvantages of biological valves (e.g. pigs)?

• No anti-clotting drugs

• Readily available

• Ethical/religious objections — use of animal tissue

• Higher chance of rejection

• Tissue can harden over time → less effective

• Doesn’t last very long (12-15 years)

What are the advantages and disadvantages of mechanical valves?

• Long lasting

• Anti-clotting medication needed

• Medication → excessive bleeding

What are the disadvantages of a heart transplant?

• Requires donor — recently died

  • Not always available

• Can be rejected by immune system

What are the advantages and disadvantages of artificial hearts?

• Less likely to be rejected by immune system

• Risk of infection

• Mechanical parts could wear out

• Blood clots → strokes

  • Medication to prevent this → thins blood → affects bleeding

What is the definition of health?

State of physical and mental well-being

• Diseases, both ________________ and ________________, are major causes of ill health.

• Other factors including ______, ______, and _______ situations may have a profound effect on both ___________ and ________ health.

• communicable

• non-communicable

• diet

• stress

• life

• physical

• mental

How can different types of diseases interact (examples)?

• Defects in immune system → more likely to suffer from infectious diseases

• Viruses in cells → trigger cancers

• Immune reactions caused by pathogen → trigger allergies, skin rashes, asthma

• Severe physical ill health → depression

What can risk factors be?

• Aspects of a person’s lifestyle

• Substance in person’s body or environment

What are the causal mechanisms for certain risk factors? (6)

• Diet, smoking, exercise → cardiovascular disease

• Obesity → type 2 diabetes

• Alcohol → liver and brain function

• Smoking → lung disease and lung cancer

• Smoking and alcohol → unborn babies

• Carcinogens — e.g. ionising radiation → cancer

Explain the causal mechanisms for cardiovascular disease.

• Diet — lots of LDL cholesterol = blocked arteries → increases blood pressure

• Smoking — damages artery walls

• Exercise — lowers blood pressure → reduces strain on heart

Explain the causal mechanisms for type 2 diabetes.

Obesity — affects metabolism → fat molecules released into blood → can affect cells uptake of sugar

Explain the causal mechanisms for liver and brain function.

• Alcohol — fatty liver → liver failure

• Alcohol — damage nerve cells in brain

Explain the causal mechanisms for lung disease and lung cancer.

Smoking — damages cells in lining of lungs

Many diseases are caused by the ___________ of a number of factors.

interaction

What is cancer the result of?

Mutations in cells → uncontrolled growth and division

What are benign tumours?

• Growths of abnormal cells — contained in one area

• Don’t invade other parts of body

What are malignant tumours?

• Cancers

• Invade neighbouring tissues — spread to different parts of the body in blood

  • Forms secondary tumours

• Scientists have identified ___________ risk factors for various types of cancer.

• There are also ___________ risk factors for some cancers.

• lifestyle

• genetic

What are some lifestyle risk factors for cancer?

• Smoking

• Obesity

• UV light

• Viral infection

• Figure 6 shows the internal structure of the human heart.

• One of the heart valves is labelled.

• Sometimes a valve in the heart can start to leak.

Explain why a person with a leaking heart valve has difficulty exercising. [4 marks]

• Backflow of blood

• Less blood pumped around body

• Less oxygen supplied to muscles

• Less aerobic respiration → less energy released

• Anaerobic respiration → lactic acid build up → muscle fatigue

• A patient with a leaking heart valve may have the valve replaced.

• A study compared two different types of replacement heart valve:

  • mechanical valves

  • biological valves from pigs

• The data used in the study was collected from female patients aged 50–69.

• Table 4 shows the data.

Metric	Mechanical Valve	Biological Valve
Number of patients given the valve	2852	1754
Number of patients who died from heart-related problems after valve replacement	180	178
Percentage of patients alive after 5 years	91	89
Percentage of patients needing a second valve replacement within 6 years	2.2	5.2
Percentage of patients who had a blood clot on the brain after surgery	5.8	0.1

Evaluate the use of mechanical replacement heart valves and biological replacement heart valves. [6 marks]

Use information from Table 4 and your own knowledge.

• Mechanical valves — longer lasting

• Mechanical valves — blood clots more likely (5.8% > 0.1%)6

  • patient has to take anti-clotting medication

• Medication for mechanical valves → excessive bleeding

• Mechanical valves — lower percentage of deaths due to heart-related problems (6.3% < 10.1%)

• Biological valves — more likely to be rejected

  • patient has to take immuno-suppressant medication

• Both valves are readily available

• Biological valves are better — low risk of blood clots and no anti-clotting medication needed → improves patent’s quality of life

Define the term double circulatory system. [1 mark]

Blood enters the heart twice for every one circuit around the body

Explain why having only one ventricle makes the circulatory system less efficient than having two ventricles. [2 marks]

• Oxygenated and deoxygenated blood mixes

• Less oxygen reaches the tissues

• Pancreatic cancer develops when a malignant tumour grows inside the pancreas.

• The pancreas produces digestive enzymes.

• One symptom of pancreatic cancer is weight loss.

Explain how pancreatic cancer may cause a person to lose weight. [4 marks]

Do not refer to hormones in your answer.

• No enzyme production

• Food is not digested fully

• Less glucose absorbed → less glucose available for respiration

  • More fat used in respiration