B4 Organising animals and plants

Components of blood = plasma, RBC, WBC and platelets. Plasma transports all these.

Plasma transports other substances too -

• waste C02 (produced by cells) carried to lungs
• urea (formed in liver) carried to kidneys where it is removed from blood to form urine
• soluble products of digestion pass into plasma from small intestine and transported to cells.

RBCs - carry oxygen cells.

• Biconcave shape = increased SA for carrying oxygen
• Haemoglobin - binds to oxygen
• No nucleus - more space for haemoglobin

 WBC's - Lymphocytes form antibodies and antitoxins. Phagocytes engulf and digest pathogens.

Platelets - fragments of cell that help blood clot at wound sites. Forms jelly-like clot to stop blood and infection getting in. 

Arteries

• blood away from the heart to body
• Usually oxygenated blood
• Thick walls, elastic fibres
• High pressure

Veins

• blood from the body to the heart 
• Usually deoxygenated blood
• Thin walls and valves to prevent back flow of blood
• Low pressure

Capillaries 

• Link arteries and veins
• Narrow, thin walls to enable substances to like oxygen and glucose to diffuse easily into cells.

Blood flow 

VENA CAVA (vein bringing in deoxygenated blood to heart)

Right atrium

Right ventricle

PULMONARY ARTERY (brings deoxygenated blood to lung) 

LUNGS

PULMONARY VEIN (brings oxygenated blood from lungs to heart)

Left Atrium

Left Ventricle

AORTA (brings oxygenated blood to from heart to body)

Coronary Heart Disease

Coronary arteries supply blood to heart

Can become narrow because of fatty material build up

Supply of oxygen is reduced

Treatment

Stents - metal mesh placed in arteries, that widens it, allowing blood to flow. No need for anaesthetic.

Bypass Surgery - bits of vein placed in artery. Expensive and risky with anasesthesia required.

Statins - drugs that reduce blood cholesterol levels and slows down fatty deposit rate. 

Remember SBS - Stents, Bypass, Statins

Heart valve treatment

• Valve becomes leaky or too stiff - heart less efficient
• Mechanical heart valves - made of titanium, last very long, must take medicine for life
• Biological heart valves - made from pig or human donors, work very well, only last 12-15 years

Artificial Pacemakers

• Resting heartrate controlled by cells in right atrium that form natural pacemaker
• Irregular heartbeat can be a problem
• Artificial pacemaker - electrical device sends out strong signals that stimulate heart to beat properly
• Regular checkups needed

Artificial Hearts

• Keep patients alive while they wait for a heart transplant
• Risk of blood clotting 

Gas exchange system

• Large difference in concentrations of gas needed to maintain a steep concentration gradient - because then diffusion happens faster (steep concentration gradient)
• Oxygen diffusing into blood
• C02 diffusing out of blood

Features

• Lungs found in chest cavity
• Protected by ribcage
• Separated by diaphragm

Breathing in = oxygen rich air coming into lungs 

Lungs contain alveoli that diffuse oxygen into the bloodstream (capillaries)

Breathing out = removal of C02

Capillaries diffuse C02 out of bloodstream back to air in lungs

Breathing in and out

Breathing in = volume increase (lungs), lower pressure in chest. Outside pressure is higher so air moves in. 

Breathing out = volume decreases, higher pressure in chest. Chest pressure is higher so air forced out of lungs.

Adaptations of the alveoli

Alveoli

- provide large surface area for diffusion of oxygen and C02

- rich blood supply of capillaries to maintain a steep concentration gradient - blood into lungs low in oxygen and high in C02 compared to inhaled air

- Steep concentration gradient = fast and effective 

- Thin layer of cells between alveoli and capillaries = short diffusion distance

Plant tissues 

• Epidermal tissue - covers surface of plant and protects. Waxy, waterproof substance.
• Palisade mesophyll tissue - contains lots of chloroplasts which carry out photosynthesis
• Spongy mesophyll - big air spaces and surface area to make diffusion of gases easier
• Xylem - transport tissue that transports water and mineral ions from roots to leaves
• Phloem - transport tissue that transports dissolved food from leaves to rest of plant

Plant organs

• Leaf - photosynthetic cells, gas exchange, phloem, stomata, guard cells
• Stem - phloem, xylem, vascular bundle
• Roots - root hair cells, xylem

Xylem

• Transport tissue that moves water and mineral ions from roots to stem and leaves
• Cells are dead 
• Spirals form long tubes 

Phloem

• Transport tissue that moves sugars (glucose) made from photosythesis from leaves to the meristems (growing points) - stem and roots
• Needed for making new plant cells
• Transported to storage organs for energy store

Water needed for photosynthesis and for support (hypotonic pressure)

Sugars needed for cell respiration 

Mineral ions needed for protein production

Water loss from leaves

Stomata = small holes in the surface of the leaf that open and close to diffuse in C02 from air and diffuse out oxygen produced in photosynthesis

Maintains steep concentration gradient

Guard cells control the opening and closing of stomata

Open stomata = water loss from surface of leaf by evaporation ----> called transpiration

Water evaporates from leaves. Water pulled up through xylem from roots to replenish ---> transpiration stream

Transporation stream driven by rate of evaporation

Stomata close to reduce water loss 

Factors affecting rate of transpiration

• Temperature
• Humidity
• Amount of air movement 
• Light intensity

Rate of photosynthesis increased = rate of transpiration increased. Stomata opens to let in C02, and open stomata means water lost by evaporation. Increase in light intensity increases transpiration rate.

Hot, dry climate = rapid transpiration rate. More water evaporates because concentration gradient is steeper in dry air than humid air.

Windy conditions = steep concentration gradient, increase in rate of evaporation

High temperature = diffusion occuring more rapidly because molecules move faster. Rate of photosynthesis increases, meaning more stomata open for water loss to occur. 

Controlling water loss

• Plants need to photosynthesise as much as possible with less water loss

Leaves = waxy, waterproof substance to control water to prevent water loss

If a plant loses water faster than it can replace it:

• Wilting can occur - protection against further water loss. Leaves collapse reducing surface area available for water loss
• Stomata close - prevents water loss and reduces photosynthesis

Potometer - measures transpiration

The faster the bubble moves, the greater the rate of water uptake - and so the greater the rate of transpiration. You can vary the conditions to investigate the effect of changing temperature, humidity, wind speed (for example, with a hair dryer) or light intensity.