EXCHANGE

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Can you identify how this vilus is adapted for diffusion of food molecules across the intestine?

Vilus

Lymph system

Efficient blood supply

1 cell thick

Large surface area

EXCHANGE SYSTEMS IN PLANTS

• CO2 enters via diffusion (stomata)

• H2O & mineral ions absorbed by roots

• Roots: • Large surface area (root hairs)

• Leaves:• Large surface area (flattened shape & internal air spaces)

• Stomata:• Site of gaseous exchange & water loss• Lots of water loss (evaporation) on hot, dry & windy conditions• Wilting = water lost fast than it can be replaced by the roots• Stomata size controlled by guard cells

• Closed stomata = prevents excess water loss & wilting.

TRANSP

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PLA

NTS &

ANIMALS

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TRANSPORT IN PLANTS• Two different systems

1. Xylem H2O & mineral ions

From roots to stem & leaves Transpiration stream: the movement/flow of H2O from the roots through the xylem & out of the

leaves Crucial for the movement of water especially in very tall plants H2O molecules are ‘sticky’.

When 1 molecule is evaporated others are pulled up through the xylem

2. Phloem Dissolved sugars From leaves to rest of plant such as growing regions & storage areas

EXAM QUESTIONS

Specimen paper Q 2.

January 2013 Q4

Complete on sheet

Mark scheme on next slide

MARK SCHEME

TRANSPORT IN ANIMALS

• What the theory in this section should enable you to do in exam:• Evaluate data on the production & use of artificial blood products• Evaluate use of artificial hearts & heart valves• Evaluate the use of stents

THE CIRCULATORY SYSTEM• The heart, arteries & veins

• The heart:• 4 main chambers (2 atria & 2 ventricles)

• Blood enters atria

• Atria contract forcing blood into ventricles

• Ventricles contract & force blood out of heart

• Valves ensure blood flows in the correct direction

• http://www.usccardiology.org/patienteducation-generalcardiology-bloodflowthroughheart.html

THE CIRCULATORY SYSTEM• 2 separate circulation systems

within the heart• 1 for the lungs and 1 for the rest

of the body

• Right side: • Deoxygenated blood from

body enters right atrium through the Vena Cava.

• Forced to right ventricle• Leaves through pulmonary

artery to the lungs.

• Left side:• Oxygenated blood carried

from lungs to left atrium by pulmonary vein

• Enters left ventricle• Leaves through the aorta

and it carried to the body

MAIN BLOOD VESSELS

• Pulmonary artery: from heart to lungs (CO2 rich blood)

• Pulmonary vein: from lungs to heart (O2 rich blood)

• Vena Cava: from body to heart (CO2 rich blood)

• Aorta: from heart to body (O2 rich blood)

• Usual rule: AA. Arteries away (except for pulmonary artery)

ARTERIES & VEINS

• What differences can you see?• Arteries have thicker walls (muscle & elastic)

– due to very fast blood flow• Veins have thinner walls• Veins have valves – prevents back flow of

blood• Valves needed as flow of blood in veins is

much slower (coming back to heart)

• Arteries & veins linked by Capillaries• Capillaries are very narrow, 1 cell thick

vessels• It’s in the capillaries that diffusion

happens into & out of the cells

STENTS

• Used when arteries begin to narrow or are constricted with fat deposits.

• Restricts blood flow• Can lead to death or organ damage

due to lack of O2.• Stents keep them open• Metal mesh with a balloon• Balloon inflates – pushes metal

mesh – extends the artery• No general anaesthetic required.

ARTIFICIAL VALVES

• Valves prevent back flow of blood

• Under a lot of pressure

• Weak valves can leak

• Not safe in the heart!

• Surgeons can insert artificial valves to replace faulty ones

• Biological or artificial

• Biological:• From other animals• Work well• No other medication needed• Need replacing after 15yrs

• Artificial:• Titanium & polymers• Very long lasting• Anti-clotting medication

must be taken

EXAM QUESTION

MARK SCHEME

THE BLOOD

• Blood is a tissue consisting of liquid & cells

• Fluid = plasma

• Cells:

1. Red blood cells Transport O2 No nucleus Contain haemoglobin Oxyhaemoglobin formed

2. White blood cells Have a nucleus Defense system

3. Platelets Small fragments of cells Help blood to clot