AQA BIOLOGY UNIT 3 KEY POINTS ON EVERY TOPIC UPDATED with every topic

ACTIVE TRANSPORT

SUBSTANCES ARE SOMETIMES ABSORBED AGAINST A CONCENTRATION GRADIENT BY ACTIVE TRANSPORT.

ACTIVE TRANSPORT USES ENERGY FROM RESPIRATION.

CELLS CAN ABSORB IONS FROM VERY DILUTE SOLUTIONS AND MOVE MOLECULES THROUGH CELL MEMBRANES USING ACTIVE TRANSPORT.

EXCHANGE OF GASES IN THE LUNGS

YOUR BREATHING SYSTEM TAKES AIR INTO AND OUT OF YOUR BODY

OXYGEN FROM THE AIR DIFFUSES INTO YOUR BLOOD STREAM AND CO2 DIFFUSES OUT.

• THE ALVEOLI OF THE LUNGS PROVIDE:
• A VERY LARGE, MOIST SURFACE AREA
• RICH BLOOD SUPPLY
• THIN WALLS

TO MAKE DIFFUSION AS EFFECTIVE AS POSSIBLE.

EXCHANGE IN THE GUT

THE VILLI IN THE SMALL INTESTINEPROVIDES

• A LARGE SURFACE AREA WITH EXTENSIVE NETWORK OF CAPILLARIES

THIS MAKES THEM WELL ADAPTED TO ABSORB THE PRODUCTS OF DIGESTION BY DIFFUSION AND ACTIVE TRANSPORT.

IN MATERIAL EXCHANGES A BIG SURFACE AREA IS VITAL FOR SUCCESSFUL DIFFUSION SO THERE IS PLENTY OF OPPORTUNITY FOR THE SUBSTANCES TO DISSOLVE.

EXCHANGE OF MATERIALS IN OTHER ORGANISMS

FISH

• CANNOT GET OXYGEN DIRECTLY FROM THE WATER AS THEY ARE COVERED IN PROTECTIVE SCALES
• THEIR GILLS ARE MADE UP OF MANY THIN LAYERS OF TISSUE WITH RICH BLOOD SUPPLY
• THE GILLS ARE THIN SO THERE IS A SMALL DISTANCE FOR THE GASES TO DIFFUSE.
• THE SURFACES ARE ALWAYS MOIST AS THEY WORK IN WATER
•  HAVE A CONSTANT SUPPLY OF WATER OTHER WISE THEIR GILL STACKS WILL COLLAPSE THEN EVENTUALLY THE FISH WILL DIE AS THEY ARE NOT GETTING ENOUGH OXYGEN

EXCHANGE OF MATERIALS IN OTHER ORGANISMS

TADPOLES

FROGS ARE AMPHIBIANS AND THEIR EGGS HATCH INTO TADPOLES WHICH SPEND ALL OF THEIR TIME IN WATER.

TADPOLES HAVE FRILLY EXTERNAL GILLS WITH A LARGE SURFACE AREA AND A RICH BLOOD SUPPLY.

THE TADPOLES GET ALL THEIR OXYGEN THROUGH DIFFUSION FROM WATER THROUGH THEIR GILLS. ALSO CARBON DIOXIDE DIFFUSES OUT ALONG A CONCENTRATION GRADIENT INTO THE WATER.

EXCHANGE OF MATERIALS IN OTHER ORGANISMS

FROGS

• WHEN TADPOLES TURN INTO FROGS THEY SPEND MOST OF THEIR TIME ON LAND BUT THEY CAN STILL BREATH IN WATER!
• FROGS HAVE NO EXTERNAL GILLS
•  HAVE VERY MOIST SKIN
• HAVE A RICH BLOOD SUPPLY
• UNDER NORMAL CONDITIONS GAS EXCHANGE TAKES PLACE MOSTLY THROUGH THE SKIN.
•  HAVE MOUTH WHICH ARE VERY LARGE AND THIN SKINNED AS IT IS IMPORTANT FOR GAS EXCHANGE
• IF THE FROG GETS HOT OR IS VERY ACTIVE IT HAS GOT A PAIR OF SIMPLE LUNGS JUST LIKE HUMANS. THIS CAN BE USED TO INCREASE THE SURFACE AREA AVAILABLE FOR GAS EXCHANGE TO TAKE PLACE.
• WHEN THE FROG IS IN WATER ALL THE GAS EXCHANGE TAKES PLACE THROUGH THE SKIN OF THE FROG.

INSECTS:EXCHANGE OF MATERIALS IN OTHER ORGANISMS

INSECTS

• ARE VERY ACTIVE SO THEIR MUSCLES NEED  A LOT OF OXYGEN, BUT NO GAS EXCHANGE CAN TAKE PLACE THROUGH THE OUTER COVERING OF THE INSECTS.
• HAVE AN INTERNAL RESPIRATORY SYSTEM WHICH SUPPLIES OXYGEN DIRECTLY TO THEIR CELLS AND REMOVES CARBON DIOXIDE.
• ON THE SIDE OF THE INSECTS THEY HAVE SPIRACLES. THESE OPEN WHEN THE INSECT NEEDS OXYGEN AND CLOSE WHEN THEY DON'T. THIS PREVENTS WATER LOSS KIND OF LIKE THE GUARD CELLS OF PLANTS.
• SPIRACLES LEAD INTO A SYSTEM OF TUBES WHICH GO RIGHT INTO THE TISSUES THEMSELVES.
• 

 MOST OF THE GAS EXCHANGE TAKES PLACE IN THE TRACHEOLES. THESE ARE FREELY PERMEABLE TO GASES. THESE ARE VERY MOIST AND AIR IS PUMPED IN AND OUT OF THEM BY THE INSECT TO MAINTAIN THE CONCENTRATION GRADIENT.

KEY POINTS

WHATEVER THE ORGANISM, GAS AND SOLUTE EXCHANGE DEPENDS:

• LARGE SURFACE AREA
• MOIST SURFACES
• SHORT DIFFUSION DISTANCES
• LARGE CONCENTRATION GRADIENT

EXCHANGE IN PLANTS

• PLANTS HAVE A STOMATA WHICH ALLOW THEM TO OBTAIN CARBON DIOXIDE FROM THE ATMOSPHERE.
• CARBON DIOXIDE ENTERS THE LEAF BY DIFFUSION.

LEAVES HAVE:

• FLAT THIN SHAPE
• INTERNAL AIR SPACES

TO INCREASE THE SURFACE AREA AVAILABLE FOR DIFFUSION

WATER AND MINERAL IONS NEEDED BY A PLANT ARE ABSORBED BY THE ROOT HAIR CELLS WHICH INCREASE THE SURFACE AREA OF THE ROOTS.

TRANSPIRATION

• IS THE LOSS OF WATER VAPOUR FROM THE SURFACE OF THE PLANT LEAVES
• WATER IS LOST THROUGH THE STOMATA WHICH ARE OPENED AND CLOSED BY GUARD CELLS TO LET IN CARBON DIOXIDE FOR PHOTOSYNTHESIS
• WATER IS PULLED UP THROUHG THE XYLEM FROM THE ROOTS TO REPLACE THE WATER LOST FROM THE LEAVES BY TRANSPIRATION

TRANSPIRATION IS MORE RAPID IN:

• HOT CONDITIONS
• DRY CONDITIONS
• WINDY CONDITIONS
• LIGHT CONDITIONS

THE CIRCULATORY SYSTEM

• THE BODY TRANSPORT SYSTEM CONSISTS OF THE BLOOD VESSELS, THE HEART AND THE BLOOD
• HUMAN BEINGS HAVE A DOUBLE CIRCULATION
• THE HEART WORKS AS A PUMP MOVING BLOOD AROUND THE BODY

THE 3 MAIN TYPES OF BLOOD VESSELS ARE THE:

• CAPILLARIES- USE DIFFUSION TO DELIVER FOOD AND OXYGEN DIRECTLY TO THE BODY TISSUES AND TAKE CARBON DIOXIDE AND OTHER WASTE MATERIALS AWAY. THEIR WALLS ARE 1 CELL THICK TO MAKE DIFFUSION HAPPEN EASIER. YOU CAN'T SEE THEM WITHOUT A MICROSCOPE.
• ARTERIES- CARRY BLOOD AWAY FROM THE HEART TO THE ORGANS AT HIGH PRESSURE. THE COLOUR OF  THE BLOOD IS BRIGHT RED AS IT IS OXYGENATED. THEY HAVE A PULSE.
• VEINS- CARRY BLOOD TOWARDS YOUR HEART AT LOW PRESSURE TO BE PUMPED AROUOND AGAIN. IT IS USUALLY LOW IN OXYGEN SO IT IS A PURPLY-RED COLOUR. THEY DO NOT HAVE A PULSE

TRANSPORT IN THE BLOOD

THE BLOOD IS OUR MAIN TRANSPORT MEDIUM OF OUR BODY

BLOOD PLASMA TRANSPORTS:

• DISSOLVED FOOD MOLECULES
• CARBON DIOXIDE
• UREA

THE RED BLOOD CELLS ARE ADAPTED TO TRANSPORT OXYGEN FROM THE LUNGS TO THE ORGANS IN YOUR BODY.

THE RED BLOOD CELLS ARE BICONCAVE DISCS. THEY HAVE NO NUCLEUS AND ARE PACKED WITH THE RED PIGMENT CALLED HAEMOGLOBIN.

OXYGEN IS CARRIED BY HAEMOGLOBIN WHICH BECOMES OXHAEMOGLOBIN IN A REVERSIBLE REACTION.

THE EFFECT OF EXERCISE ON THE BODY

THE ENERGY THAT IS RELEASED DURING RESPIRATION (CARBON DIOXIDE + WATER) IS USED TO ENABLE MUSCLES TO CONTRACT.

WHEN YOUY USE YOUR MUSCLES YOU NEED GLUCOSE AND OXYGEN TO BE SUPPLIED AT A FASTER RATE. THE RATE AT WHICH CARBON DIOXIDE REMOVED FROM MUSCLE TISSUES NEEDS TO INCREASE TOO.

BODY RESPONSES TO EXERCISE INCLUDE AN INCREASE IN HEART RATE, AND INCREASE IN BREATHING RATE AND DEPTH OF BREATHING. THE ARTERIES SUPPLYING BLOOD TO THE MUSCLES DILATE AND THE GLYCOGEN STORES IN THE MUSCLE ARE CONVERTED TO GLUCOSE TO USE AS FUEL FOR RESPIRATION

REGULAR EXERCISE BENEFITS THE MUSCLES, HEART AND LUNGS

ANAEROBIC RESPIRATION

• IF MUSCLES WORK HARD THEY DON'T CONTRACT PROPERLY. IF THEY DON'T GET ENOUGH OXYGEN THEY WILL RESPIRE ANAEROBICALLY.
• ANAEROBIC RESPIRATION IS RESPIRATION IS RESPIRATION WITHOUT OXYGEN. GLUCOSE IS BROKEN DOWN TO FORM LACTIC ACID, WATER AND A SMALL AMOUNT OF ENERGY
• AFTER EXERCISE, OXYGEN IS STILL NEEDED TO BREAK DOWN THE LACTIC ACID WHICH HAS BUILT UP.
• THE AMOUNT OF OXYGEN NEEDED IS KNOWN AS THE OXYGEN DEBT.

THE HUMAN KIDNEY

A HEALTHY KIDNEY PRODUCES URINE BY FILTERING THE BLOOD.

IT THEN REABSORS ALL OF THE SUGAR, MINERAL IONS AND WATER NEEDED BY YOUR BODY.

EXCESS MINERAL IONS AND WATER ALONG WITH UREA ARE REMOVED IN THE URINE.

SUGAR AND DISSOLVED IONS CAN BE ACTIVELY REABSORBED AGAINST A CONCENTRATION GRADIENT.

DIALYSIS

PEOPLE SUFFERING FROM KIDNEY FAILURE MAY BE TREATED BY REGULAR SESSIONS ON A KIDNEY DIALYSIS MACHINE OR BY HAVING A KIDNEY TRANSPLANT

IN A DIALYSIS MACHINE, THE CONCENTRATION OF DISSOLVED SUBSTANCES IN THE BLOOD IS RESTORED TO NORMAL LEVELS.

THE LEVELS OF USEFUL SUBSTANCES IN THE BLOOD ARE MAINTAINED, WHILE UREA AND EXCESS SALT PASS OUT FROM THE BLOOD INTO THE DIALYSIS FLUID.

KIDNEY TRANSPLANTS

IN A KIDNEY TRANSPLANT, DISEASED OR DAMAGED KIDNEYS ARE REPLACED WITH A HEALTHY KIDNEY FROM A DONOR.

THE DONOR KIDNEY MAY BE REJECTED BY THE RECIPIENT'S IMMUNE SYSTEM.

TO TRY AND PREVENT REJECTION THE TISSUE TYPES OF THE DONOR AND THE RECIPIENT ARE MATCHED AS CLOSELY AS POSSIBLE AND IMMUNOSUPPRESSANT DRUGS ARE USED.

GROWING MICROBES

MICROORGANISMS CAN BE GROWN IN AN AGAR CULTURE MEDIUM WITH A CARBOHYDRATE ENERGY SOURCE AND VARIOUS:

• VITAMINS
• MINERALS
• PROTEINS

YOU NEED TO TAKE CAREFUL SAFETY MEASURES AND USE STERILISED EQUIPMENT TO GROW UNCONTAMINATED CULTURES OF MICROORGANISMS AND TO AVOID THE GROWTH OF HARMFUL PATHOGENS

YEAST:

• IS A SINGLE CELLED ORGANISM
• IT CAN RESPIRE AEROBICALLY PRODUCING CARBON DIOXIDE AND WATER
• THIS REACTION IS USED IN BREADMAKING TO MAKE THE DOUGH RISE
• CAN ALSO RESPIRE ANAEROBICALLY PRODUCING ETHANOL AND CARBON DIOXIDE IN A PROCESS KNOWN AS FERMENTATION

THE FERMENTATION REACTION OF YEAST IS USED TO PRODUCE ETHANOL TO PRODUCE BEER AND WINE.

FOOD PRODUCTION USING BACTERIA

BACTERIA IS USED TO MAKE YOGHURT AND CHEESE.

WHEN MAKING YOGHURT A STARTER CULTURE OF BACTERIA ACTS ON THE WARM MILK

LACTOSE IS CONVERTED TO LACTIC ACID IN A LACTIC FERMENTATION REACTION. THIS CHANGES THE TEXTURE AND THE TASTE OF THE MILK TO MAKE YOGHURT.

TO MAKE CHEESE A DIFFERENT STARTER CULTURE IS ADDED TO WARM MILK PRODUCING A LACTIC FERMENTATION WHICH RESULTS IN SOLID CURDS AND LIQUID WHEY

THE CURDS ARE OFTEN MIXED WITH OTHER BACTERIA OR MOULDS BEFORE THEY ARE LEFT TO RIPEN INTO CHEESE

LARGE SCALE MICROBE PRODUCTION

MICROORGANISMS CAN BE GROWN ON A LARGER SCALE IN VESSELS KNOWN AS FERMENTERS TO MAKE USEFUL PRODUCTS SUCH AS ANTIBIOTICS AND MYCOPROTEIN.

INDUSTRIAL FERMENTERS HAVE A RANGE OF FEATURES TO MAKE SURE THE FERMENTATION TAKES PLACE IN THE BEST POSSIBLE CONDITIONS FOR A MAXIMUM YIELD OF THE PRODUCT.

THE FUNGUS "FUSARIUM" IS GROWN ON SUGAR SYRUP IN AEROBIC CONDITIONS TO PRODUCE MYCOPROTEIN FOODS.

MYCOPROTEINS CAN BE MADE TO LOOK LIKE MEAT, CHICKEN OR FISH

THE PROTEIN CONTENT OF MYCOPROTEIN IS SIMILAR TO THAT OF PRIME BEEF!!

ANTIBIOTIC PRODUCTION

THE ANTIBIOTIC PENICILLIN WAS DISCOVERED BY ALEXANDER FLEMING. THE METHOD OF MASS PRODUCTION WAS DONE BY HOWARD FLOREY AND ERNST CHAIN

PENICILLIN IS MADE BY GROWING THE MOULD PENICILLIUM IN A FERMENTER

THE MEDIUM CONTAINS SUGARS AND OTHER NUTRIENTS  AND HAS A GOOD SUPPLY OF OXYGEN

THE MOULD ONLY STARTS MAKING PENICILLIN AFTER MOST OF THE NUTRIENTS ARE USED UP.

BIOGAS-

• MAINLY METHANE
• CAN BE PRODUCED BY ANAEROBIC FERMENTATION OF A WIDE RANGE OF PLANT PRODUCTS AND WASTE MATERIALS THAT CONTAIN CARBOHYDRATES.

MANY DIFFERENT ORGANISMS ARE INVOLVED IN THE BREAKDOWN OF MATERIAL IN BIOGAS PRODUCTION