Lesson 2 : Organisation

Different levels of organisation

1. Organelles/Sub-cellular structures

2. Cells

3. Tissues

4. Organs

5. Organ systems

6. Organism

Tissue

A group of similar cells that work together to carry out the same function

Examples of tissues (which make up the stomach)

1. Muscular tissue

2. Glandular tissue

3. Epithelial tissue

Organs

A group of different tissues that work together to perform a particular function

Organ system

A group of organs that work together to perform a particular function

Metabolism

The sum of all the chemical reactions taking place in an organism

Enzyme

Biological catalyst that speed up metabolic reactions without being used up themselves

Factors that affect enzyme activity

1. Temperature

2. pH

What happens when an enzyme exceeds its optimum temperature?

The enzyme is denatured (Some of the bonds holding the enzyme together break, and the enzyme's active site changes shape, resulting in the substrate not being able to fit in the active site, and therefore the reaction cannot take place)

Types of digestive enzymes

1. Carbohydrases

2. Proteases

3. Lipases

Carbohydrases convert...

Carbohydrates ~ simple sugars

Amylase converts...

Starch ~ maltose

Where is Amylase produced?

1. Salivary glands

2. Pancreas

3. Small intestine

Proteases convert...

Proteins ~ amino acids

Where are proteases produced?

1. Stomach (Pepsin)

2. Pancreas

3. Small intestine

Lipases convert

Lipids ~ glycerol and fatty acids

Where are lipases produced?

1. Pancreas

2. Small intestine

Where is bile produced?

The liver

Where is bile stored?

The gallbladder

What is the function of bile?

Bile neutralises stomach acid and emulsifies fats

What is emulsification?

Breaking down of fat globules into tiny droplets. They have a higher SA to volume ratio which makes their digestion faster

Why does the stomach produce hydrochloric acid?

1. To kill bacteria

2. To give the optimum pH for pepsin to work in

Adaptations of lungs to increase rate of gas exchange

1. Millions alveoli increase SA

2. Alveoli have thin walls and there diffusion pathway is short

3. Alveoli have very good blood supply (ensures concentration gradient is as steep as possible)

4. Breathing (takes away carbon dioxide and brings fresh oxygen to alveoli)

What are the adaptations of the alveoli?

large surface area (folds on surface and microvilli), thin walls, good blood supply

What type of circulatory system do humans have?

Double circulatory system

What is a double circulatory system?

Blood passes through the heart twice for each complete circuit of the body

What are the two circuits of the circulatory system?

1. Pulmonary circuit - (The right ventricle pumps deoxygenated blood to the lungs where gas exchange takes place)

2. Systemic circuit - (The left ventricle pumps oxygenated blood to the rest of the body)

4 chambers of the heart

1. Left atrium

2. Right atrium

3. Left ventricle

4. Right ventricle

What is the function of atrioventricular valves?

Ensuring that blood flows in only one direction

Why does the left ventricle have a thicker wall than the right ventricle?

It has to pump blood all around the body

4 blood vessels that enter and leave the heart (right to left)

1. Vena Cava (d)

2. Pulmonary artery (d)

3. Aorta (o)

4. Pulmonary vein (o)

What supply's oxygenated blood to the heart muscle?

Coronary artery (branch off from aorta)

Arteries

carry blood away from the heart

Veins

carry blood back to the heart

Capillaries

Exchanges oxygen and nutrients with tissues

How are arteries adapted to their function?

1. Thick layer of elastic tissue (to withstand the high pressure blood is pumped out of the heart at)

2. Thick layer of muscle tissue

3. Small lumen

How are capillaries adapted to their function?

1. Walls are only one cell thick (increases rate of diffusion)

2. Permeable walls (so substances can diffuse in and out)

How are veins adapted for their function?

1. Large lumen (to held blood flow despite low pressure)

2. Small layers of elastic fibres and smooth muscle (low pressure so do not ned thick walls)

3. Have valves (to prevent back flow of blood)

Parts of the blood

1. Red blood vessels

2. White blood vessels

3. Plasma

4. Platelets

What pigment carries oxygen?

Haemoglobin

What is haemoglobin called when it binds with oxygen

Oxyhaemoglobin

Adaptations of red blood cells

1. No nucleus - increased space for Haemoglobin and oxygen

2. Biconcave disk shape - large surface area for absorbing oxygen

Two types of white blood cells

1. Phagocytes

2. Lymphocytes

Function of lymphocytes

1. Produce antitoxins that neutralise pathogen toxins

2. Produce antibodies that bind to foreign antigens

Function of phagocytes

1. Phagocytosis (engulf and destroy pathogens)

Platelets

Small fragments of cells

Function of platelets

1. Blood clotting

What does blood plasma carry

1. Red blood cells

2. White blood cells

3. Platelets

4. Glucose and amino acids (nutrients)

5. CO2 and urea (waste products)

6. Hormones

7. Proteins

8. Antibodies

9. Antitoxins

What is the resting heart rate controlled by?

A group of cells in the right atrium wall that act as a pacemaker

Artificial pacemaker

An electrical device that is used to correct irregularities in the heart rate

Coronary heart disease

The coronary arteries that supply oxygen to the heart/cardiac muscle get blocked by a build up of fatty material

Stents

Tubes inserted into arteries to keep them open

Statins

Drugs that lower cholesterol levels in the blood

What are the possible consequences of faulty heart valves

1. Damage may valve tissue to stiffen (valves won't open properly), or become leaky (allow blood to flow in both directions)

2. This means that blood may not circulate as effectively as normal

How can faulty heart valves be replaced?

1. Biological valves (from humans or other animals)

2. Mechanical valves

Health

An individuals state of physical and mental well-being

Factors that affect health

1. Disease

2. Diet

3. Stress

4. Life situations

Communicable disease

A disease that can be transmitted from one person to another

Non-communicable disease

Disease that cannot be transmitted from one person to another

Cancer

The result of changes in cells that lead to uncontrolled cell division and growth

Benign tumours

Growths of abnormal cells that are contained in one area, usually within a membrane. They do not invade other parts of the body

Malignant tumours

Tumours that can spread around the body invading neighbouring tissues and spreading to different parts of the body via blood where they form secondary tumours

Risk factors for cancer associated with lifestyle

1. Smoking

2. Obesity

3. UV exposure (skin cancer)

4. Viral infection

Risk factors for Diabetes

1. Obesity

2. Poor diet

Risk factors for Heart Disease/CVD/CHD

1. Diet

2. Smoking

3. Lack of exersice

Risk factors for liver disease

1. Alcohol

Risk factors for lung disease/ cancer

1. Smoking

What is a carcinogen?

Any substance that increases the risk of developing cancer

Function of epidermal tissues

Protects surface of the leaf

Why is the upper epidermis transparent?

To allow light to pass through to the photosynthetic cells below

What is the function of the waxy cuticle?

1. Reducing evaporation of water form surface of the leaf and prevents leaf from drying out

2. Protects leaf when raining as heavy droplets will slide down it

What is the role of stomata and guard cells?

Control gas exchange and water loss

Function of palisade mesophyll cells

1. Site if photosynthesis

Why are palisade cells packed tightly together?

In order to minimise the amount of light lost

Function of spongy mesophyll

Air spaces between the cells allow gases to diffuse through the leaf

Function of xylem

transports water and minerals

Adaptations of xylem tissue for function

1. Dead cells : no cytoplasm or other sub-cellular structures to disrupt water flow

2. Cells joined end to end to form a long continuous tube

3. No end walls : allows water to flow freely

4. Walls contain lignin : makes walls strong and waterproof and prevents them from collapsing

5. Pits in the walls : allows movement of water and mineral ions sideways between xylem vessels and sorrow dung cells

Where does xylem transport

Roots to leaves

Function of phloem

transport dissolved sugars

Adaptations of phloem tissue for function

1. Sieve cells joined end to end : form long tubes for transportation

2. Sieve plates between cells have pores : allows dissolved sugars to flow from one cell to the other

3. Sieve cells have very little cytoplasm : more space for substances to flow

4. Companion cells contain many mitochondria : provide energy for active transport/ loading of sugars into and out of sieve tubes

5. Companion cells connected to sieve tubes : help control and maintain the sieve tubes

Where does phloem transport

Both directions

What is translocation?

The movement of sugars and other molecules through phloem tissue

Where is meristem tissue found?

Growing tips of shoots and roots

What is the function of meristem tissue?

Contains stem cells that can differentiate into different types of plant tissue

Function of root hair cells

Absorption of water and mineral ions from soil

How are root hair cells adapted for their function?

1. Long hair like extension : increases surface area, increasing rate of absorption

2. Thin cell wall : short diffusion distance

3. Many mitochondria : provide energy for active transport

Transpiration

Evaporation of water from the leaves of a plant

Function of transpiration

1. Bringing water to the leaf (water required for photosynthesis)

2. Transpiration stream transports dissolved mineral ions

3. Evaporation of water from leaf cools leaf down

What factors affect transpiration

1. Light intensity

2. Wind speed

3. Temperature

4. Humidity

How does tempreture affect transpiration?

Higher temperature result in faster evaporation

How does humidity affect transpiration?

Drier the conditions, the faster evaporation takes place

How does wind speed affect the rate of transpiration?

Higher wind speed removes any water vapour faster, allowing more water to evaporate

How does light intensity affect the rate of transpiration?

Higher light intensity means greater rate of transpiration due to increased rate of photosynthesis