Cell Biology

• Found in the NUCLEUS of a cell
• COILED UP lengths of DNA MOLECULES
• Each carries a large number of GENES --- control development of different characteristics e.g. hair colour
• In BODY CELLS they're normally found in PAIRS
• 23 PAIRS  IN A HUMAN CELL

GROWTH & DNA REPLICATION

1.  Cell GROWS + INCREASES the amount of MITOCHONDRIA, RIBOSOMES etc.

2. DNA is  COPIED  -   ONE COPY for  EACH new CELL

3. It forms  X-SHAPED CHROMOSOMES                                               

ARMS =  copies of each other

DIVISION

1.  Chromosomes LINE UP at CENTRE of CELL

2.  ARMS are  PULLED APART  to  OPPOSITE SIDES

3.  Which DIVIDES  the  NUCLEUS

4. Each SET of  CHROMOSOMES become the  NUCLEUS of a  NEW CELL

5.   CYTOPLASM +  CELL MEMBRANE   DIVIDE

6. Now produced  TWO NEW CELLS

• Same DNA - IDENTICAL
• IDENTICAL to  ORIGINAL CELL

STEM CELLS (UNDIFFERENTIATED) - NOT become SPECIALISED

EMBRYO develops from a FERTILLISED EGG

EMBRYONIC STEM CELLS (REMOVED from EMBYRO) - DIFFERENTIATE into ANY CELL

ADULT STEM CELLS - CELLS remained in BODIES of ADULTS

          ( Can be FOUND in SEVERAL PARTS of the BODY)

• BRAIN                                 Can DIFFERENTIATE into (RELATED) CELL TYPES ONLY!
• EYES
• BLOOD                          EMBRYONIC STEM CELLS - used to REPLACE FAULTY CELLS
• HEART 
• LIVER                            THERAPEUTIC CLONING -  EMBRYO is made from the
  
• BONE MARROW           (SAME) GENES as a PATIENT
• SKIN 
• MUSCLE 

CELL DIVISION in PLANTS occurs in MERISTEMS

Can DIFFERENTIATE to PRODUCE (ALL TYPES) of PLANT at ANYTIME during PLANTS LIFE

(MAIN) MERISTEMS - close to TIP of SHOOT & ROOT

(GROWING) SHOOT - NEW CELLS PRODUCE (CONTINOUSLY) near the TIP

As CELLS become OLDER (FURTHER AWAY) from TIP , they become DIFFERENTIATED,                 ENLARGE & DEVELOP (VACUOLES)

PRO'S (STEM CELL)                                                

• Provides potential for DISCOVERING TREATMENTS & CURES to DISEASES                                                 
• SCIENTISTS & DOCTORS will be able to TEST                                                                                      (MILLIONS) of potential DRUGS & MEDICINES       

CON'S (STEM CELL)

• Each (ONE) could be a HUMAN LIFE
• CURING PATIENTS (MORE IMPORTANT)

SPREADING OUT of PARTICLES from an AREA of HIGHER CONCENTRATION to an AREA of LOWER CONCENTRATION

HAPPENS in SOLUTIONS & GASES 

CONCENTRATION GRADIENT - The DIFFERENCE in CONCENTRATION 

BIGGER the DIFFERENCE in CONCENTRATION - the FASTER the DIFFUSION RATE                   BECAUSE  (PARTICLES have MORE ENERGY - MOVE around FASTER)

CELL MEMBRANES - Let stuff DIFFUSE (IN & OUT) of the CELL                                                          (Only VERY SMALL MOLECULES can FIT through them)                                                                (OXYGEN, GLUCOSE, WATER , AMINO ACIDS)

BIG MOLECULES (STARCH, PROTEINS) CAN'T 

MOLECULES flow through MEMBRANE from a HIGHER CONCENTRATION ( A LOT OF THEM) TO a LOWER CONCENTRATION (NOT A LOT)

LARGER (SURFACE AREA) - FASTER (DIFFUSION RATE)   BECAUSE...........                   MORE (PARTICLES) can pass through at the SAME TIME

MOVEMENT of WATER MOLECULES across a PARTIALLY PERMEABLE MEMBRANE from a LESS CONCENTRATED (SOLUTION) TO a MORE CONCENTRATED (SOLUTION)

PARTIALLY PERMEABLE MEMBRANE- one with VERY SMALL (HOLES) in it

TINY (MOLECULES) (WATER) CAN PASS THROUGH 

BIGGER (MOLECULES) (SUCROSE) CAN'T

WATER MOLECULES pass BOTH WAYS through MEMBRANE during OSMOSIS 

NORMALLY, move from LESS CONCENTRATED SOLUTION (LOTS of WATER MOLECULES)

TO  

                    MORE CONCENTRATED SOLUTION (LESS WATER MOLECULES)

MORE CONCENTRATED SOLUTION - MORE DILUTE

 1.  CUT UP  a POTATO into CYLINDERS with the SAME (LENGTH & WIDTH)

2.   TWO   BEAKERS - 1 (PURE WATER) 1 (VERY CONCENTRATED SUGAR SOLUTION),       FEW OTHER BEAKERS - (LESS CONCENTRATED)

3. MEASURE the MASS of each POTATO CYLINDER , put 1 in each BEAKER

4. LEAVE the POTATO CYLINDERS - 24 HOURS

5. TAKE them OUT & DRY them with PAPER TOWEL

6. MEASURE their MASSES again

7. MASS INCREASED - WATER has MOVED INTO the POTATO CELLS                                         MASS DECREASED - WATER has MOVED OUT the POTATO CELLS

8. CALCULATE (PERCENTAGE CHANGE IN MASS) for each POTATO CYLINDER ---                         This means you can .... COMPARE the EFFECTS of each SUGAR SOLUTION

INDEPENDENT VARIABLE -  CONCENTRATION of SUGAR SOLUTION                                                                CONTROL VARIABLE -   (VOLUME of SOLUTION , TEMPERATURE , TIME , TYPE OF SUGAR USED)

SUBSTANCES are ABSORBED from a LOWER CONCENTRATION TO a HIGHER CONCENTRATION AGAINST the CONCENTRATION GRADIENT 

PLANT ROOTS - covered in MILLIONS of ROOT HAIR CELLS which STICK OUT into SOIL

HAIRS- give ROOTS a LARGE SURFACE AREA --- USEFUL for ABSORBING (WATER & MINERAL IONS) from the SOIL

PLANTS- NEED (MINERAL IONS) for HEALTHY GROWTH

CONCENTRATION OF (MINERALS) is usually HIGHER in the ROOT HAIR CELLS than in the SOIL around them ------- (ROOT HAIR CELLS) CAN'T use DIFFUSION to (TAKE UP) MINERALS from the SOIL

Use ACTIVE TRANSPORT instead ---- ALLOWS the PLANT to ABSORB (MINERALS) from a VERY (DILUTE SOLUTION) in the SOIL------ moves the minerals AGAINST the CONCENTRATION GRADIENT  

ACTIVE TRANSPORT needs ENERGY from RESPIRATION to make it WORK

BODY - needs to ABSORB NUTRIENTS (GLUCOSE & AMINO ACIDS) from FOOD to SURVIVE

NUTRIENTS move from GUT into BLOOD 

When theres a HIGHER CONCENTRATION of NUTRIENTS in the GUT, they DIFFUSE into BLOOD 

SOMETIMES - there's a LOWER CONCENTRATION of NUTRIENTS in the GUT than there is in the BLOOD

BODY- uses ACTIVE TRANSPORT to move NUTRIENTS (GLUCOSE) from A ....

LOWER CONCENTRATION (GUT)

TO

HIGHER CONCENTRATION (BLOOD)

GLUCOSE can be taken into the BLOOD AGAINST the CONCENTRATION GRADIENT. 

Is then TRANSPORTED to CELLS, where it's USED for RESPIRATION

Cells can use DIFFUSION to TAKE IN (SUBSTANCES) from the ENVIRONMENT (OXYGEN)

Use DIFFUSION to GET RID of WASTE PRODUCTS (CARBON DIOXIDE- From RESPIRATION)   (UREA- From the BREAKDOWN of PROTEINS)                                                                               

UREA- DIFFUSES from CELLS into the BLOOD PLASMA                                                               Then removed from the body by the KIDNEYS 

How EASY it's for an ORGANISM to EXCHANGE (SWAP) SUBSTANCES with it's ENVIRONMENT depends on the ORGANISM'S (SURFACE AREA - VOLUME RATIO)

A RATIO shows HOW BIG (ONE VALUE) is COMPARED to ANOTHER                                          A SURFACE AREA - VOLUME RATIO shows how BIG a shape's SURFACE is compared to it's VOLUME                                                                                                                                              The LARGER the ORGANISM, the SMALLER it's SURFACE AREA is comapred to it's VOLUME       The SMALLER it's SURFACE AREA compared to it's VOLUME, the HARDER it's for an ORGANISM to EXCHANGE SUBSTANCES with it's ENVIRONMENT

SINGLE-CELLED ORGANISMS - have a LARGE SURFACE AREA compared to their VOLUME       SO... They can EXCHANGE ALL THE SUBSTANCES they need across their SURFACE            (CELL MEMBRANE)                                                                                                                               MULTI-CELLULAR ORGANISMS (ANIMALS) - have a SMALLER SURFACE AREA compared to their VOLUME ---- They have SPECIALISED EXCHANGE SURFACES                                               Have TRANSPORT SYSTEMS that CARRY (SUBSTANCES) TO & FROM their EXCHANGE SURFACES        

EXCHANGE SURFACES - ADAPTED to allow DIFFERENT SUBSTANCES to PASS THROUGH

• THIN MEMBRANE (SO SUBSTANCES have a SHORT DISTANCE to DIFFUSE)
• LARGE SURFACE AREA (LOTS can DIFFUSE at ONCE)
• EXCHANGE SURFACES in (ANIMALS) - LOTS of BLOOD VESSELS (STUFF can get in & out QUICKLY)
• GAS EXCHANGE SURFACES in (ANIMALS) (Alveoli) - VENTILATED ( AIR moves IN & OUT)

GAS EXCHANGE - Happens in the LUNGS  

OXYGEN (O2) & CARBON DIOXIDE (CO2) are EXCHANGED in the LUNGS

LUNGS - contain (MILLIONS) of LITTLE AIR SACS called ALVEOLI : where GAS EXCHANGE happens

ALVEOLI - SPECIALISED for the DIFFUSION of OXYGEN & CARBON DIOXIDE                             They HAVE:

• (LARGE) SURFACE AREA
• (VERY THIN) WALLS (so GASES DON'T have FAR to DIFFUSE)
• (GOOD) BLOOD SUPPLY

VILLI - Provide a (REALLY BIG) SURFACE AREA

(INSIDE) SMALL INTESTINE is COVERED in (MILLIONS) of VILLI                                                   INCREASE the SURFACE AREA so... DIGESTED FOOD is ABSORBED MORE QUICKLY into the BLOOD                                                                                                                                                              SINGLE layer of (SURFACE) CELLS                                                                                             (VERY GOOD) BLOOD SUPPLY