All-In-One: Organisation (P1)

Cell

The basic building block of a living organism.

Tissue

A group of cells with a similar structure and function working together.

E.g. muscular tissue contracts to bring about movement

Organ

A collection of tissues working together to perform a specific function.

E.g. The stomach contains different types of tissues.

Organ System

A group of organs working together to perform specific functions.

E.g. The digestive system contains organs like stomach, small and large intenstine.

Main function of the digestive system

To digest food and absorb the nutrients obtained from digestion.

Stages of digestion

1. Food chewed in mouth. Enzymes in saliva begin to digest the starch into smaller sugar molecules.

2. Food passes down oesophagus into stomach.

3. Stomach contains hydrochloric acid and enzymes like protease begin the digestion of proteins.

   Causes a churning effect with stomach muscles to increase surface area for enzymes.

4. Passed to the small intestine where enzymes from liver and pancreas are released.

   Continuing digestion of proteins and starch, whilst starting digestion of lipids. Liver releases bile which speeds up digestion of lipids, whilst neutralising acid released from stomach.

5. In the small intestine, small food molecules produced by digestion are absorbed into the bloodstream by diffusion or active transport.

6. Passed into large intestine where water is absorbed into the bloodstream and faeces are produced.

7. Faeces are released from the body.

Role of the pancreas and salivary gland

Glands which produce digestive juices containing enzymes.

Role of the stomach

Produces hydrochloric acid - which kills any bacteria present and provides the optimum acidic pH for the protease enzyme to function.

Role of the small intestine

Site where soluble food molecules are absorbed into the bloodstream.

Small intestine adaptations

• large surface area - increased absorption of products of digestion

• contains villi - increases surface area further, has very rich blood supply which increases concentration gradient, thin membrane which ensures a short diffusion pathway

Role of the liver

Produces bile which emulsifies lipids (fats) and allows the lipase enzyme to work more efficiently.

Role of the large intestine

Absorbs water from undigested food, producing faeces.

Enzymes

protein molecules that act as biological catalysts → speed up the rate of biological reactions (the breakdown of food) without being used up.

Shape of an enzyme and its function

Have a specific active site which is complementary to their substrate.

Metabolism

The sum of all the reactions in a cell or an organism.

Why is the digestive system needed?

Breaking down larger molecules into smaller molecules, as bigger ones cannot be absorbed into the bloodstream.

eg. proteins broken down by proteases into amino acids

Lock and key hypothesis of enzyme function

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

Effect of temperature on enzyme action

• Increasing temperature increases enzyme action, as molecules have a higher kinetic energy and there are more successful collisions between enzyme and substrates.

• Above optimum temperature: the shape of the active site is altered → enzyme becomes denatured → substrate doesn’t fit → so it no longer works

Effect of pH on enzyme function

The optimum pH for most enzymes is 7 (apart from proteases in the stomach).

• If the pH is too high or too low, the shape of the active site may be altered → enzyme denatured and no longer works.

Production sites of carbohydrases, proteases and lipases

Carbohydrases - Salivary gland, stomach and small intestine.

Proteases - Stomach, pancreas and small intestine.

Lipases - Pancreas and small intestine.

Role of carbohydrases in the digestive system

Carbohydrases break down carbohydrates into glucose.

Amylase breaks down starch into glucose.

Proteases

Proteases break down proteins into amino acids.

Lipases

Lipases break down lipids into fatty acids and glycerol.

Where is bile made and stored?

made: liver

stored: gallbladder.

Role of bile in the digestive system

alkaline substance that neutralises the hydrochloric acid secreted by the stomach + emulsifies lipids (fat)

Food test for sugars and positive test colours

Food tester: Benedicts (blue)

Positive for sugar:

• Small amount: Blue → Green

• Bigger amount: Blue → Yellow

• Large amount: Blue → Brick-red

Food test for starch and positive test colours

Food tester: Iodine

Positive for starch:

• Yellow → Blue / Black

Food test for proteins and positive test colour

Food tester: Biuret (blue)

Positive for protein:

• Blue → Purple/Lilac

Food test or lipids (fats) and positive test colour

Food tester: Ethanol (clear)

Positive test for lipids:

• Clear → Cloudy emulsion

Heart

An organ that pumps blood around the body.

Purpose of the circulatory system

Carries oxygen and other useful substances to bodily tissues, and removes waste substances.

Double circulatory system

One pathway: deoxygenated blood flows into right atrium and ventricle → to lungs for gaseous exchange

Other pathway: oxygenated blood flows into left atrium and ventricle → to body

Importance of the double circulatory system

makes the circulatory system more efficient

Chambers of the heart

4 - right atrium, right ventricle, left atrium, left ventricle.

Heart circulation steps

1. Vena cava brings deoxygenated blood from the body to the heart.

2. Passes from heart → lungs in the pulmonary artery.

3. In the lungs, blood collects oxygen.

4. Oxygenated blood passed from lungs → heart in the pulmonary vein.

5. This blood is pumped from the heart → body in the aorta.

6. Oxygen is transported around the body + repeat

Pumping of blood in heart steps

1. Blood enters left atrium and right atrium.

2. Atria contract and blood is forced into the ventricles.

3. Ventricles contract and force blood out of the heart.

   Valves prevent back flow of blood when ventricles contract.

Specific role of the left ventricle?

Pump blood at a higher pressure around the whole body.

What is the function of the aorta?

Carries oxygenated blood from the heart to the body.

What does the pulmonary vein do?

Carries oxygenated blood from the lungs to the heart.

What is the role of the vena cava?

Carries deoxygenated blood from the body to the heart.

What does the pulmonary artery carry?

Carries deoxygenated blood from the heart to the lungs.

Purpose of valves in the heart

Prevent the backflow of blood.

Purpose of coronary arteries

Coronary arteries supply the heart muscle with oxygenated blood.

Control of heart rate

Controlled by a group of cells in the right atrium → act as a pacemaker by releasing waves of electrical activity → causes the heart muscle to contract

How is irregular heart rhythms treated?

Using an artificial pacemaker: sends out electrical signals to correct the heart's rhythm.

Types of blood vessels

Arteries, Veins, Capillaries.

Arteries function and adaptation

Function: carry blood away from the heart.

Adaptations:

- Thick muscle layer: adds strength → withstand high pressure.

- Thick elastic layer: allows arteries to stretch and recoil → withstand high pressure.

Veins function and adaptation

Function: carry blood towards the heart.

Adaptations:

- Wide lumen: enables low pressure.

- Valves: prevent backflow of blood.

Capillaries function and adaptation

Function: enable transfer of substances between the blood and tissues

Adaptations:

- Walls are one cell thick: short diffusion path.

- Permeable walls: substances can efficiently diffuse across.

- Narrow lumen: blood moves slowly → more time for diffusion.

Rate of blood flow calculation

Volume of blood / number of minutes.

Gas exchange system components

Trachea, Bronchi, Bronchioles, Alveoli, Diaphragm

Ventilation process

1. The ribcage moves up and out → diaphragm moves down → volume of chest increases

2. Increased volume = lower pressure

3. Air is drawn into the chest: air moves from areas of high pressure (the environment) to low pressure (the lungs)

4. Opposite when exhaling

Gas exchange at the alveoli

1. Alveoli fill with oxygen

2. Oxygen diffuses down its concentration gradient into the capillary bloodstream (from high to low concentration)

3. Carbon dioxide diffuses down its concentration gradient from the blood to the alveoli (from high to low concentration)

Alveoli adaptation for gas exchange

- Larger surface area

- Rich blood supply: maintains concentration gradient.

- Thin walls: short diffusion pathway.

Substances transported by plasma

Red blood cells, White blood cells, Platelets, Carbon dioxide, Urea, Products of digestion.

Definition of plasma

A yellow liquid within blood that transports substances around the body.

Purpose of red blood cells

Transport of oxygen around the body.

Red blood cells adaptation

- Biconcave shape: increased surface area

- No nucleus: more room haemoglobin and therefore oxygen.

- Contain haemoglobin: binds to oxygen.

Purpose of white blood cells

They form part of the immune system → protects the body from invading pathogens.

Nucleus

Contains DNA

Platelets

Small cell fragments which aid the clotting of blood at the site of a wound.

→ clot dries and hardens to form a scab → new skin can grow

Coronary heart disease

When the coronary arteries that supply the heart muscle become blocked with a buildup of fatty material.

→ less blood flows to heart → reducing oxygen supply → heart attack

Stent

A tube that is inserted into a blocked artery to keep it open.

Advantages of stents

• quick recovery time

• lower the risk of a heart attack.

Disadvantages of stents

• Risk of infection

• risk of blood clots at the site of stent.

Statins

Drugs which reduce the level of (bad) cholesterol in the blood.

Advantages of statins

• Reduce risk of strokes, coronary heart disease and heart attacks

• increase level of (good) cholesterol.

Disadvantages of statins

• Have to be taken continuously

• may have side effects

• effect may not be immediate.

Heart bypass surgery

A surgery where blocked coronary arteries are replaced with sections of veins taken from other parts of the body.

Leaky heart valves

Cause blood to flow in the wrong direction, making the heart less efficient.

Mechanical valves

Valves made of metal used to replace leaky valves.

Biological valves

Valves taken from animals (pigs, sometimes humans) used to replace leaky valves.

Advantages of mechanical valves

• Last for a very long time.

Disadvantages of mechanical valves

• Need to take medication to prevent blood clotting around valve.

Advantages of biological valves

• Work very well

Disadvantages of biological valves

• Only lasts 12-15 years.

Artificial heart

Intended to support a patient's heart while they wait for a suitable donor heart.

Advantages of artificial hearts

• Less likely to be rejected by immune system

• allows damaged heart to rest to help recovery.

Disadvantages of artificial hearts

• Risk of infection due to surgery

• risk of blood clots

• have to take blood-thinning drugs.

Health

The state of physical and mental wellbeing.

Diet in health

Eating too much or too little → not enough or wrong type of nutrients → prevents good and balanced diet

• Causing: Type 2 diabetes / obesity

Stress in health

Physical and mental strain on the body.

• Causing: heart disease, cancers, mental illness

Life situations in health

Where you live, financial status, ethnic group, access to medical care, hygiene levels in your area → affecting physical and mental health

• Causing: Communicable diseases (e.g. malaria), non-communicable diseases (e.g. heart disease)

Cancer

Cancer is the development of a tumour as a result of uncontrolled cell division.

factors leading to cancer

Genetics.

Smoking.

Obesity.

Viral infections.

Factors causing cardiovascular disease

• Bad diet containing bad cholesterol → arteries become blocked → increase blood pressure

• Smoking → damages artery walls

Factors causing type 2 diabetes

• Obesity: fat molecules released into blood → affect cells uptake of sugar

Factors causing liver and brain function

• Alcohol → fatty liver causing liver failure → damage nerve cells in brain

Factors causing lung disease and lung cancer

• Smoking → damages cells in lining of lungs

Factors affecting unborn babies in pregnancy

Smoking + Alcohol

Epidermal tissue

Function: reduce water loss by evaporation → prevents water from moving out

Features: covers whole plant and covered with waxy cuticle

Palisade mesophyll tissue

Function: site of photosynthesis

Features: many chloroplasts → photosynthesis can happen rapidly → positioned at the top of the leaf to receive lots of light

Spongy mesophyll tissue

Function: allows diffusion of gases in and out of cells

Features: has lots of air spaces

Xylem function and adaptations

Function: A continuous hollow tube of dead cells that allows the movement of water and mineral ions from the roots to the leaves.

Features:

- Strengthened by lignin: makes the vessel strong and waterproof.

- Has bordered pits: allow minerals to be transported to specific places

Lignin makes it waterproof, water cannot leave except at bordered pits.

Phloem function and adaptation

Function: Transportation of sugars around a plant in both directions

Features:

- Made up of elongated living cells that have sieve plates - holes in cell walls

Meristem tissue

Function: allows plant to grow

Features: undifferentiated stem cells

Leaf organ tissues

Contains epidermis, palisade mesophyll, spongy mesophyll, xylem, phloem, and guard cells.

Guard cells

Control the opening and closing of the stomata according to the water content of the plant.

Stomata function and adaptations

Function: Allow the control of gaseous exchange and water loss from the leaf.

Features:

• More stomata on the base of the leaf - minimises water loss as this side is cooler and shaded.

• Have guard cells which control their opening and closing.

Root hair cells function and adaptations

Function: Allow the uptake of water and mineral ions from the soil.

• Large surface area - maximises rate of absorption.

• Contain lots of mitochondria - release energy for active transport of mineral ions.