biology paper 1

• 4 STEP MITOSIS

  -nucleus dissolves and genetic material is duplicated

  -the two sets of chromosomes move to opposite sides

  -mitochondria, ribosomes and other organelles are duplicated

  -the cell divides producing two genetically identical diploid cells(new nuclei are formed)
• THE BRAIN

  CEREBRAL CORTEX(higher functions)

  -memory, speech, problem-solving (front)

  CEREBELLUM(motor skills)

  -movement, balance, coordination

  MEDULLA(unconscious actions)

  -heart&breathing rate

  -signals to adrenal glands to release adrenaline
• CIRCULATORY SYSTEM

  ARTERY(away, oxygen rich)- carries blood away from heart, thick walls and thin lumen to withstand high pressure

  CAPILLARY- one cell think walls to allow fast diffusion between blood and cells

  VEIN(visit+valves, deoxygenated)- carries blood back to the heart, thin walls and wide lumen, valves to prevent backflow
• RESPIRATION & METABOLISM

  ANAEROBIC RESPIRATION (without oxygen)= glucose-> lactic acid

  occurs during intense exercise: oxygen debt, lactic acid is broken back down into glucose by the LIVER using oxygen

  ANAEROBIC RESPIRATION in PLANTS=glucose-> ethanol + CO2 (fermentation)

  METABOLISM

  the sum of all chemical reactions in a cell/organism

  -glucose-> starch, glycogen & cellulose

  -fatty acids-> lipids (fats)

  -respiration

  -breakdown of excess proteins-> urea
• THE HEART

  DOUBLE CIRCULATORY SYSTEM= blood enters heart twice every time its pumped round body

  ORDER= VENA CAVA(from body) RIGHT ATRIUM->(valve) RIGHT VENTRICLE->PULMONARY ARTERY(to lungs)-> PULMONARY VEIN(from lungs) LEFT ATRIUM-> LEFT VENTRICLE(wall thicker to pump blood to body)-> AORTA(to body)

  -a group of cells near the right atrium creates electrical pulse, causing heart to contract- alternately pacemaker used
• THERMOREGULATION

  the brain detects blood temperature then sends nervous & hormonal signal to effectors.

  HOT

  -sweat glands produce water which evaporates , taking away heat. -blood vessels dilate: vasodilation

  COLD

  -hairs stand on end to trap air- layer of insulation

  -shivering- muscles produce more heat

  blood vessels contract- vasoconstriction
• PLANT STRUCTURE PT.1

  LEAF

  -photosynthesis, gas exchange

  -water evaporates out

  FLOWER

  -productive organs

  MERISTEM

  -stem cell production

  PHLOEM

  -tubes of cells that carry sugars(e.g. sucrose) and other nutrients to where needed: TRANSLOCATION- bidirectional
• CONTROLLING BLOOD SUGAR

  high blood glucose levels=

  -pancreas->insulin

  -glucose moves from bloodstream into cells 4 respiration

  -excess glucose=glycogen=energy store
• CONTROLLING BLOOD SUGAR

  TYPE 1 DIABETES

  -pancreas cannot produce(enough)insulin

  injections needed

  TYPE 2 DIABETES

  -cells don't absorb glucose as normal

  -obesity increases risk of developing
• CONTROLLING BLOOD SUGAR

  LOW BLOOD GLUCOSE

  -pancreas->glucagon(remember as hormone)

  -liver+muscles convert glycogen->glucose

  this is negative feedback example!
• CONTROLLING WATER AND NITROGEN LEVELS

  -water lost through: exhalation, sweating, urinating

  -excess water removed in blood by kidneys to bladder

  -water mixed with urea=urine

  -urea=ammonia obtained from excess proteins broken down in liver

  -kidney filters out glucose+useful minerals and ions for body
• CONTROLLING WATER AND NITROGEN LEVELS


  CELLS- TOO MUCH WATER

  -water moves IN by osmosis

  -cell becomes turgid could burst

  CELLS- TOO LITTLE WATER

  -moves OUT by osmosis

  -cell becomes flaccid
• PLANT HORMONES- GIBBERELLINS

  -induce germination

  -promote flowering

  -increase fruit in size
• PLANT HORMONES - ETHENE

  -causes ripening (example bananas-why stored separately)
• PLANT HORMONES-AUXINS

  PHOTOTROPISM

  -destroyed by sunlight, darker(shaded) side of shoot grow quicker

  -shoot bends towards sun

  GEOTROPISM

  -bottom side of roots- inhibits growth

  -grow downward
• PLANT HORMONES- AUXIN(USES)

  -weedkillers

  -rooting powders

  -promoting growth in tissue cultures
• PLANT HORMONES- PRACTICAL

  -place seeds on damp cotton wool

  -in Petri dish stood on edge

  -turn 90degrees after few days

  -observe geotropism in roots
• LEAF STRUCTURE (pt.1)

  WAXY CUTITCLE

  -waterproof=stop water lost from top of leaf

  UPPER EPIDERMIS

  -transparent- let light through

  PALISADE MESOPHYLL

  -photosynthesis

  VASCULAR BUNDLE

  -xylem+phloem
• LEAF STRUCTURE (PT.2)

  SPONGEY MESOPHYLL

  -gaps=facilitate gas exchange(large SA)

  STOMATA

  -holes=allow water/gases out/in

  LOWER EPIDERMIS

  -bottom

  GUARD CELLS

  -change size=control rate of gases entering/exiting
• THE EYE ACCOMODATION

  FAR AWAY

  =CM relax, SL tighten, thin lens

  CLOSE OBJECT

  =CM contracts, SL slackens, thick lens
• THE EYE

  -rods detect light intensity

  -cones sensitive to red, blue and green wavelengths

  -signals travel to brain via optic nerve
• FOOD TESTS

  BENEDICTS

  =sugar

  IODINE

  =starch

  BIURET

  =protein

  ETHANOL

  =lipids
• IODINE TEST FOR STARCH

  1.food sample in test tube

  2.add few drops iodine to sample- using pipette

  3.if starch present=solution from brown-(blue-black)

  4. note any colour change in table of results
• THE BENEDICTS TEST FOR REDUCING SUGARS

  1.add equal volume Benedict's solution to the food sample in test tube

  2.place in hot water bath for few minutes

  3.reducing sugar present=brick red precipitate formed

  4.reducing sugar absent=blue

  5.note colour change in table of results
• TEST FOR LIPIDS

  1.add few cm^3 of ethanol to food sample

  2.pour mixture into test tube of equal volumes of distilled water

  3.lipids present=white emulsion formed on surface of mixture

  4. emulsion test.
• TEST FOR PROTEIN

  1.few drops of biuret's reagent to food sample in test tube

  2. shake solution to mix and wait few minutes

  3.protein present= solution from blue to purple
• OESTROGEN


  -thickening of uterus prepare for implantation of egg

  -level peak on day 10
• FSH

  -causes egg to mature

  -decrease in oestrogen causes increase in FSH
• LH

  -stimulates release of egg

  -decrease in oestrogen= increase in LH
• PROGESTERONE

  -maintains uterus thick lining

  -inhibits LH and FSH

  -mature egg day 14, progesterone peaks 3 days later

  -not fertilised, progesterone levels fall

  -lining breaks down in five days (period)