biology 3 ocr gateway

ANIMAL CELLS

• NUCLEUS - CONTAINS DNA IN THE FORM OF CHROMOSOMES
• CELL MEMBRANE - HOLDS CELL TOGETHER AND CONTROLS WHAT GOES IN AND OUT
• RIBOSOME - WHERE PROTEINS ARE SYNTHESISED
• CYTOPLASM - GELL LIKE SUBSTANCE WHERE MOST OF CELLS CHEMICAL REACTIONS HAPPEN
• MITOCHONDRIA - MOST REACTIONS INVOLVED IN RESPIRATION TAKE PLACE (PROVIDES ENERGY FOR CELL PROCESSES) E.G. LIVER CELLS CARRY OUT ENERGY DEMANDING METABOLIC REACTIONS, MUSCLE CELLS NEED ENERGY TO CONTRACT

PLANT CELLS

CHLOROPLASTS - WHERE PHOTOSYTHESIS HAPPENS

CELL WALL - MADE OF CELLULOSE - SUPPORTS CELL

VACUOLE - RELATIVELY LARGE STRUCTURE - CONTAINS CELL SAP (WEAK SOLUTION OF SUGGAR AND SALTS

BACTERIA CELLS

NO CHLOROPLASTS OR MITOCHONDRIA

NO TRUE NUCLEUS - SINGLE CIRCULAR STRAND OF DNA - FLOATS FREELY IN CYTOPLASM

CHROMOSOMES - LONG MOLECULES OF COILED UP DNA

• GENES - SHORT SECTIONS OF DIVIDED DNA
• DNA - DOUBLE HELIX - TWO STRANDS MADE UP OF LOTS OF SMALL GROUPS CALLED NUCLEOTIDES
• NUCLEOTIDE - CONTAINS SMALL MOLECULE CALLED A BASE - DNA HAS FOUR DIFFERENT BASES - A, C, G, T
• COMPLEMENTARY BASE PAIRINGS - A AND T, C AND G - EACH BASE CROSS LINKS AND BINDS TO A BASE ON OTHER STRAND TO KEEP CHROMOSOME TIGHTLY TOGETHER - A AND T

WATSON AND CRICK

• FIRST SCIENTISTS TO COME UP WITH STRUCTURE OF DNA - 1959
• USED DATA FROM OTHER SCIENTISTS TO HELP THEM UNDERSTAND STRUCTURE - X RAY DATA SHOWING DOUBLE HELIX WITH TWO STRANDS WOUND TOGETHER AND DATA SHOWING THAT BASES OCCURED IN PAIRS
• PUT INFORMATION TOGETHER - BUILT MODEL OF DNA - NOT WIDELY ACCEPTED STRAIGHT AWAY - OTHER SCIENTISTS NEED TO REPEAT WORK TO MAKE SURE RESULTS ARE RELIABLE

PROTIENS

• DNA CONTROLS PRODUCTION OF PROTIENS (PROTIEN SYNTHESIS) IN A CELL
• GENE - SECTION OF DNA THAT CODES FOR A PARTICULAR PROTEIN
• MADE UP OF CHAINS OF MOLECULES CALLED AMINO ACIDS - EACH DIFFERENT PROTEIN HAS ITS OWN PARTICULAR NUMBER AND ORDER OF AMINO ACIDS
• GIVES EACH PROTEIN A DIFFERENT SHAPE - EACH A DIFFERENT FUNCTION
• ORDER OF BASES IN GENE DECIDES ORDER OF AMINO ACIDS IN PROTEIN
• EACH AMINO ACID CODED FOR BY SEQUENCE OF THREE BASES IN A GENE
• AMINO ACID ARE JOINED TOGETHER TO MAKE A PROTEIN, FOLLOWING ORDER OF BASES IN GENE
• EACH GENE CONTAINS DIFFERENT SEQUENCE OF BASES - ALLOWS IT TO CODE FOR UNIQUE PROTEIN

mRNA - CARRIES CODE TO RIBOSOMES

• PROTEINS MADE IN CELL CYTOPLASM BY TINY STRUCTURES CALLED RIBOSOMES
• RIBOSOMES USE CODE IN DNA TO MAKE PROTEINS
• DNA FOUND IN CELL NUCLEUS - CAN'T MOVE OUT OF IT - CELL NEEDS TO GET CODE FROM DNA TO RIBOSOMES
• DONE USING mRNA - MADE BY COPYING CODE FROM DNA
• mRNA - ACTS AS MESSENGER BETWEEN DNA AND RIBOSOME - CARRIES CODE BETWEEN THEM

CONTROL OF CELL 

• PROTEINS IN CELL AFFECT HOW IT FUNCTIONS - SOME DETERMINE CELL STRUCTURE - OTHERS E.G. ENZYMES CONTROL CELL REACTIONS
• ONLY MAKE CERTAIN PROTEINS - ONLY SOME OF THE FULL SET OF GENES IS USED IN ANY ONE CELL - REST ARE 'SWITCHED OFF' - PROTEINS THEY CODE FOR AREN'T PRODUCED IN THAT CELL
• GENES THAT ARE SWITCHED ON DETERMINE FUNCTION OF CELL

PROTEINS - FOUR EXAMPLES

• ENZYMES
• CARRIER MOLECULES  - USED TO TRANSPORT SMALLER MOLECULES - HEAMOGLOBIN - BINDS TO OXYGEN MOLECULES AND TRANSPORTS THEM AROUND BODY
• HORMONES - CARRY MESSAGES AROUND BODY - INSULIN - HOURMONE RELEASED INTO BLOOD BY PANCREAS TO REGULATE BLOOD SUGAR LEVEL
• STRUCTURAL PROTEINS - PHYSICALLY STRONG - COLLAGEN - STRUCTURED PROTEIN THAT STRENGTHENS CONNECTIVE TISSUES          --- next line ---- ENZYMES - BIOLOGICAL CATALYSTS

• CELLS HAVE THOUSANDS OF REACTIONS E.G. RESPIRATION, PROTEIN SYNTHESIS GOING ON INSIDE THEM - NEEDS TO BE CAREFULLY CONTROLLED - GET RIGHT AMOUNTS OF SUBSTANCES TO KEEP EACH ORGANISM WORKING PROPERLY
• RAISING TEMP SPEEDS REACTIONS - CELLS START GETTING DAMAGED AT CERTAIN TEMP
• ENZYMES WORK TO SPEED UP CELL REACTIONS - BIOLOGICAL CATALYSTS - REDUCE NEED FOR HIGH TEMP
• EVERY BIOLOGICAL REACTION HAS OWN ENZYME, EACH CODED BY SPECIFIC GENE - UNIQUE SHAPE

SPECIFICITY OF ENZYMES

SUBSTRATE - MOLECULE CHANGED IN CELL REACTION

• ACTIVE SIGHT - PART THAT JOINS ONTO SUBSTRATE TO CATALYSE REACTION
• ENZYMES HAVE A HIGH SPECIFICITY FOR THEIR SUBSTRATE - ACTIVE SIGHT OF AN ENZYME ONLY FITS TO ONE PARTICULAR SUBSTRATE
• FOR ENZYME TO WORK, SUBSTRATE HAS TO FIT ACTIVE SIGHT - REACTION WON'T BE CATALYSED IF SUBSTRATE SHAPE DOESN'T MATCH ACTIVE SIGHT SHAPE - 'LOCK AND KEY' MECHANISM

ENZYMES - pH

• TOO HIGH OR TOO LOW - INTERFERES WITH BONDS HOLDING ENZYME TOGETHER - CHANGES SHAPE OF ACTIVE SITE - DENATURES ENZYME
• ENZYMES HAVE OPTIMUM pH THEY WORK BEST AT - OFTEN NEUTREL (pH 7)

CONDITIONS - TEMPERATURE

• HIGHER TEMPERATURE = FASTER REACTION UP TO CERTAIN POINT
• MORE HEAT MEANS MORE KINETIC ENERGY - PARTICLES MOVE MORE - MORE COLLISIONS
• WHEN TEMPERATURE REACHES CERTAIN POINT, ENZYME IS DENATURED - LOSES SHAPE AND DOESN'T FIT SUBSTRATE ANYMORE - REACTION CAN'T BE CATALYSED
• EACH ENZYME HAS OWN OPTIMUM TEMP - MOST HUMAN ENZYMES IT'S ABOUT 37 DEGREES CELSIUS

Q10 = RATE AT HIGHER TEMPERATURE / RATE AT LOWER TEMPERATURE

• Q10 VALUE FOR REACTION - SHOWS HOW MUCH RATE CHANGES WHEN TEMP IS RAISED BY 10 DEGREES
• Q10 VALUE OF 2 MEANS THAT RATE DOUBLES WHEN THE TEMPERATURE IS RAISED BY 10 DEGREES

Q10 VALUE OF 3 MEANS RATE TREBLES

GENE MUTATIONS - CHANGE IN DNA BASE SEQUENCE 

• IF MUTATION OCCURS WITHIN GENE, COULD STOP PRODUCTION OF THE PROTEIN THE GENE NORMALLY CODES FOR - MAY MEAN A DIFFERENT PROTEIN IS PRODUCED INSTEAD

HARMFUL MUTATIONS

• PRODUCING WRONG PROTEIN OR NO PROTEIN - DISASTER IF IMPORTANT ENZYME
• MUTATION OCCURS IN REPRODUCTIVE CELLS - OFFSPRING MAY DEVELOP ABNORMALLY OR DIE IN EARLY STAGE OF DEVELOPMENT
• MUTATION IN BODY CELLS - MUTANT CELLS START TO MULTIPLY IN UNCONTROLLED WAY - CANCER

BENEFICIAL OR HARMLESS MUTATIONS

• PROTEIN PRODUCED AFTER MUTATION COULD BE IMPROVEMENT TO PROTEIN IT'S SUPPOSED TO BE
• GIVES ORGANISM SURVIVAL ADVANTAGE - PASSES ON QUALITY TO OFFSPRING - BECOMES COMMON
• THIS IS NATURAL SELECTION - EVOLUTION E.G. RESISTANT STRAIN BACTERIA
• SOME MUTATIONS DON'T CHANGE PROTEIN BEING CODED FOR - NO EFFECT ON ORGANISM

CAUSES OF MUTATIONS

• IONISING RADIATION - E.G. X-RAYS, ULTRAVIOLET LIGHT, RADIATION FROM RADIOACTIVE SUBSTANCES - GREATER DOSE OF RADIATION - GREATER CHANCE OF MUTATION
• MUTAGENS - CERTAIN CHEMICALS KNOWN TO CAUSE MUTATIONS - IF MUTATIONS PRODUCE CANCER, CHEMICALS ARE OFTEN CALLED CARCINOGENS - CIGARETTE SMOKE CONTIANS CHEMICAL MUTAGENS

RESPIRATION 

• GOES ON IN EVERY CELL IN BODY - PROCESS OF RELEASING ENERGY FROM GLUCOSE
• ENERGY FROM RESPIRATION CAN'T BE USED DIRECTLY BY CELLS - USED TO MAKE SUBSTANCE CALLED ATP
• ATP ACTS AS ENERGY SOURCE FOR MANY CELL PROCESSES AND TRANSPORTS ENERGY TO WHERE IT'S NEEDED IN CELL
• RESPIRATION CONTROLLED BY ENZYMES - EFFECTED BY TEMP AND pH

AEROBIC RESPIRATION 

• GLUCOSE + OXYGEN ---> CARBON DIOXIDE + WATER (+ ENERGY)
• C6H12O6  +      O2      --->           CO2              +    H2O   (+ ENERGY)
• HAPPENS WHEN THERES PLENTY OF OXYGEN AVAILABLE - MOST EFFICIENT RELEASE OF ENERGY FROM GLUCOSE
• TYPE OF RESPIRATION USED MOST OF THE TIME
• WHEN RESPIRATION INCREASES, OXYGEN CONSUMPTION AND CARBON DIOXIDE PRODUCTION INCREASE
• RATE OF OXYGEN CONSUMPTION USED TO ESTIMATE METABOLIC RATE (AMOUNT OF ENERGY BEING USED)

ANAEROBIC RESPIRATION

• GLUCOSE ---> LACTIC ACID (+ENERGY)
• WHEN ONE DOES VIGOROUS EXERCISE, THEIR BODY CAN'T SUPPLY ENOUGH OXYGEN TO THEIR MUSCLES EVEN THOUGH HEARTRATE AND BREATHING RATE INCREASE AS MUCH AS THEY CAN
• MUSCLES HAVE TO START RESPIRING ANAEROBICALLY ASWELL
• NOT THE BEST WAY TO CONVERT GLUCOSE TO ENERGY - RELEASES MUCH LESS ENERGY PER GLUCOSE MOLECULE THAN AEROBIC RESPIRATION
• GLUCOSE ONLY PARTIALLY BROKEN DOWN - LACTIC ACID PRODUCED
• LACTIC ACID BUILDS UP IN MUSCLES - LEADS TO PAIN AND MUSCLE FATIGUE
• ADVANTAGE - ALLOWS YOU TO KEEP USING MUSCLES WHEN OXYGEN IS USED UP
• AFTER RESORTING TO ANAEROBIC RESPIRATION, WHEN YOU STOP EXERCISING YOU'LL HAVE AN OXYGEN DEBT - NEED EXTRA OXYGEN TO BREAK DOWN LACTIC ACID BUILT UP IN MUSCLES TO ALLOW AEROBIC RESPERATION TO BEGIN AGAIN - NEED TO KEEP BREATHING HARD AFTER EXERCISE - REPAY DEBT
• LACTIC ACID - CARRIED TO LIVER TO BE BROKEN DOWN - HEART RATE HAS TO STAY HIGH FOR THIS.  RESPIRATORY QUOTENT = AMOUNT OF CO2 PRODUCED / AMOUNT OF O2 USED - TELLS WHETHER SOMEONE IS RESPIRING ANAEROBICALLY (>1) OR AEROBICALLY (0.7 - 1)