OCR Module 1 - Human Biology Extensive Notes

These were the revision notes I made for the first module of my AS-level Biology JUST FOR THE HUMAN TOPICS.

It took ages to complete but was well worth it as I found it to be a really useful resource so I hope you do too!

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  • Created by: Emma
  • Created on: 26-04-12 19:06
Preview of OCR Module 1 - Human Biology Extensive Notes

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HUMANBIOLOGY­MRMORGAN
SPECIALSURFACESFOREXCHANGE
WHY ORGANISMS NEED THEM
All LIVING cells need CERTAIN substances to keep ALIVE:
OXYGEN ­ AEROBIC RESPIRATION
GLUCOSE ­ acts an ENERGY SOURCE OGPFWM
PROTEINS ­ needed for GROWTH & REPAIR
FATS ­ for making MEMBRANES + act as an ENERGY STORE
WATER
MINERALS for MAINTAINING WATER POTEN. And for ENZYME ACTION + METABOLISM
Organisms may take these in DIRECTLY FROM ENVIRONMENT
Or into their CYTOPLASM FOR METABOLISM PROCESSES
Also need to REMOVE WASTE PRODUCTS from such activities in cytoplasm:
CARBON DIOXIDE
OXYGEN (in PLANTS FROM PHOTOSYNTHESIS)
Other wastes e.g. UREA AND AMMONIA
SINGLE CELLED/SMALL ORGANISMS ­ can exchange such substances ACROSS THEIR SURFACES
They have LARGE SURFACE AREA-TO-VOLUME RATIO
LARGE, MULTICELLUR ORGANISIMS ­ these need EXCHANGE SURFACES
They have SMALL SURFACE-AREA-TO-VOLUME RATIO and cells need MORE SUPPLY: the
outer surface is NOT LARGE ENOUGH to EFFICIENTLY supply cells with what they need.
Substances also have to TRAVEL FURTHER DISTANCES from the OUTER TO INNER CELLS
As do WASTE PRODUCTS
LARGER organisms need LARGE EXCHANGE SURFACES, + OFTEN A TRANSPORT SYSTEM to move
such substances around the body.
EXCHANGE SURFACE PROPERTIES
GOOD exchange surfaces have:
LARGE SURFACE AREA ­ so there is MORE SPACE for molecules to pass through (often
done by FOLDING MEMBRANES/WALLS)
THIN BARRIER ­ REDUCES diffusion DISTANCE
FRESH SUPPLY of molecules to MAINTAIN CONCENTRATION GRADIENT (a HIGH CONC.)
REMOVAL of REQUIRED molecules on the OTHER SIDE to keep CONCENTRATION LOW
LAST 3 needed for a STEEP DIFFSION GRADIENT
+ SOME exchange surfaces use ACTIVE TRANSPORT MECHANISMS.
EXAMPLES OF SPECIALISED EXCHANGE SURFACES

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Also found at IN ORGANS to REMOVE SUBSTANCES into the transport system
ALVEOLI ­ the WALLS are exchange surfaces to permit GASEOUS EXCHANGE
SMALL INTENSTINE ­ NUTRIENTS are ABSORBED
LIVER ­ LEVELS of SUGAR are adjusted
ROOT HAIRS ­ WATER AND MINERALS absorb
EXCHANGE SURFACE ­ a SPECIALISED AREA that is ADAPTED to make it EASIER FOR MOLECULES
TO CROSS from ONE SIDE of the SURFACE to the OTHER
THE LUNG AS ORGAN OF EXCHANGE
THE LUNGS
A PAIR of INFLATABLE STRUCTURES; in the CHEST…read more

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When BREATHED OUT ­ it EVAPORATES and is lost
Lungs MUST produce substance SURFACTANT to REDUCE COHESIVE FORCES BETWEEN WATER
MOLECULES
WITHOUT, alveolus would COLLAPSE due to cohesive forces of lining water molecules
MAINTAINING DIFFUSION GRADIENT
RAPID diffusion ­ a STEEP DIFFUSION GRADIENT is needed
Meaning HIGH CONC. Of MOLECULES on SUPPLY SIDE/a LOW SUPPLY on DEMAND SIDE
To MAINTAIN ­ a FRESH SUPPLY of molecules ONE SIDE needed to keep CONC.…read more

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Chest cavity VOLUME ­ INCREASES
AIR ­ INTO the lungs
EXHALING = EXPIRATION
DIAPHRAGM ­ RELAXES and PUSHED UP by displaced organs
EXTERNAL INTERCOSTAL MUSCLES ­ these RELAX/RIBS FALL
Chest cavity VOLUME ­ DECREASES
AIR ­ OUT of the lungs
TISSUES IN THE LUNGS
THE LUNGS
There is the TRACHEA, BRONCHI AND BRONCHIOLES which ALLOW AIR INTO and OUT LUNGS
ADAPTED for EFFECTIVE passage of air through these airways:-
LARGER airways = large ENOUGH to allow SUFFICIENT AIR FLOW with NO OBSTRUCTIONS
Must DIVIDE SMALLER…read more

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C-SHAPED RINGS which keep AIRWAY OPEN when PRESSURE LOW in the lungs
(INHALATION)
NOT COMPLETE RINGS = FLEXIBILITY (neck can be MOVED WITHOUT CONSTRICTING
airway) + allows OESOPHAGUS to EXPAND during swallowing
SMOOTH MUSCLE
Type of INVOLUNTARY MUSCLE; allows for INVOLUNTARY MOVEMENTS e.g. BREATHING and
usually found in SOME INTERNAL ORGANS.…read more

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Means MORE OXYGENATED AIR INTO lungs/CARBON DIOXIDE ­RICH AIR
OUT
ELEMENTS OF LUNG VOLUME
TIDAL VOLUME:-
The vol. of air MOVED IN & OUT of the lungs with EACH BREATH AT REST
(approx. 0.5dm3)
VITAL CAPACITY:-
LARGEST (max.) vol. of air MOVED IN & OUT of the lungs in ONE BREATH
(approx. 5.0dm3 but VARIES BETWEEN MEN/WOMEN/AGE/SIZE + regular exercise)
RESIDUAL VOLUME:-
Vol. of air that ALWAYS REMAINS IN LUNGS, even AFTER BIGGEST POSSIBLE EXHALATION
(approx. 1.…read more

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Person BREATHES IN from a DISPOSABLE MOUTHPIECE ATTACHED (FOR
SAFETY) TO A TUBE CONNECTED TO OXYGEN CHAMBER
OXYGEN used in MEDICAL GRADE (FOR SAFETY)
BREATHING IN oxygen from chamber, causes CHAMBER TO SINK DOWN
BREATHING OUT (into the chamber), causes CHAMBER TO FLOAT UP
MOVEMENT OF CHAMBER is RECORDED using a DATALOGGER
This produces a SPIROMETER TRACE
Person breathing can be asked to do so at REST, AFTER EXERCISE or to take DEEP BREATHS
So DIFFERENT BREATHING PATTERNS can be recorded.…read more

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Must also REMOVE WASTES to AVOID TOXIC BUILD UP
SMALL animals DON'T need a SEPARATE TRANSPORT SYSTEM as ALL their
cells are NEAR/SURROUNDED by the EXTERNAL ENVIRONMENT
SMALL ANIMALS = DIFFUSION alone, ENOUGH for their supply of oxygen/nutrients
Animals with 2+ LAYERS OF CELLS, diffusion ALONE = TOO SLOW
3 (THREE) factors AFFECT NEED FOR TRANSPORT SYSTEM:
SIZE
SURFACE- AREA-TO-VOLUME RATIO
LEVEL OF ACTIVITY
SIZE
Animals with SEVERAL LAYERS OF CELLS = OUTER CELLS will USE UP diffusing nutrients/oxygen
So WILL NOT REACH INNER MOST…read more

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SECOND CIRCUIT: carries the OXYGEN & NUTRIENTS AROUND THE BODY ­ the SYSTEMIC
CIRCULATION
MAMMALIAN HEART adapted to have TWO (2) PUMPS ­ one for EACH CIRCULATION
BLOOD goes through HEART TWICE FOR EACH COMPLETE CIRCULATION of the body
HEART ­ BODY ­ HEART ­ LUNGS ­ HEART
PULMONARY CIRCULATION ­ pumps DEOXYGENATED BLOOD to the LUNGS to pick up oxygen
SYSTEMATIC CIRCULATION ­ carries NEWLY OXYGENATED BLOOD to the BODY (TISSUES)
RIGHT SIDE of the heart pumps blood to LUNGS (picks up oxygen -…read more

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BOTH sides apply PRESSURE to the BLOOD by SQUEEZING, forcing the blood INTO the
ARTERIES
EXTERNAL FEATURES OF HEART
It sits SLIGHTLY OFF CENTRE to LEFT of the chest cavity with MAIN PART of the heart being FIRM,
RED MUSCLE
2 main PUMPING CHAMBERS are the VENTRICLES
ABOVE ventricles, are the ATRIA chambers
These have THIN WALLS
CORONARY ARTERIES lie OVER HEART SURFACE
Carry OXYGENATED BLOOD to the HEART ITSELF
As the heart is a MUSCLE so needs to RESPIRE also to gain energy
If…read more

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