Feb Mocks Flashcards
2.7 identify elements present in carbohydrates and what it breaks down as
CHO - carbon hydrogen oxygen
- polymers that break down into simple sugars
2.7 identify elements present in proteins and what it breaks down as
CHOSPN - carbon, hydrogen, oxygen, sulphur, phosphate, nitrogen
- polymers that can be broken down into its monomer: amino acids
2.7 identify elements present in lipids and what it breaks down as
CHO - carbon, hydrogen, oxygen
- large polymers that can be broken down into 3x fatty acid molecules and glycerol molecule
Carbohydrates smaller basic units
Starch and glycogen
Proteins smaller basic units
Amino acids
Lipids smaller basic units
Fatty acids and glycerol
Investigate food samples for presence of glucose
- add sample solution in test tube
- add drops of Benedict solution in test tube
- heat in water bath at 60-70 for 5 mins
- glucose - brick red
- no glucose - remains blue
Investigate food samples for presence of starch
- pipette the sample solution into a tile
- add drops of iodine solution and leave for 1 minute
• If starch is present, the solution will turn blue-black
• If starch is not present, the solution will remain brown
Investigate food samples for presence of protein
- add the sample solution into a test tube
- add drops of Biuret solution into the test tube
- leave for 1 minute and then record the colour
• If protein is present, the solution will turn purple
• If protein is not present, that the solution will remain blue
Investigate food samples for presence of lipids
- add 2cm” of ethanol to the test solution
- add 2cm’ of distilled water
- leave for 3 minutes and then record the colour
• If fat is present, a milky white emulsion will form
• If fat is not present, that the solution will remain colourless
Role of enzymes
Biological catalysts in metabolic reactions that speed up rate of reaction without being used up itself
How does temperature effect enzymes
- optimum is 37 degrees
- rate of reaction increases with an increase in temperature up to the optimum
- but after optimum temp it rapidly decreases and eventually stops reaction
- bonds in structure breaks
- changes shape of AS so substrate can no longer fit
- enzyme denatures and doesn’t work
Practical: investigate how enzyme activity can be affected by changes in temp
1) Starch solution is heated to set temperature
2) Amylase is added
3) lodine is added to each tile after a minute
4) Measure the time it takes until the iodine stops turning blue-black
(this means that starch is not present as amylase has broken the starch down into glucose)
5) Repeat the test with different temperature
Starch —-amylase—-> glucose
How does ph effect enzymes
- optimum is usually 7, stomach is lower
- if ph is too high/low, the forces that hold the amino acid chains will be affected
- changes shape of AS so substrate can no longer fit in
- enzyme denatures and no longer works
Practical: investigate how enzyme activity can be affected by changes in pH
- enzyme amylase used - which breaks down carbohydrates such as starch into simple sugars such as maltose
- add 2cm of amalyse solution and starch solution
- iodine (dark orange colour) to check for the presence of starch in the solution at any time. When starch is present, the iodine solution will turn to a blue-black colour.
Diffusion
Random net movement of particles from an area of higher concentration to an area of lower concentration over a partially permeable membrane
Why do single celled organisms use diffusion to transport molecules in thier body
- large SA:Vol
- diffusion is sufficient and enough to meet demand
Why do multicellular organisms not use diffusion
- SA:Vol is small so they can’t rely on diffusion alone
- number of adaptations that allow molecules transported in and out cells
How does conc gradient affect rate of moment
The greater the difference in concentration, the faster the rate of diffusion. This is because more particles are randomly moving down the gradient than are moving against it.
How does temperature gradient affect rate of moment
The greater the temperature, the greater the movement of particles, resulting in more collisions and therefore a faster rate of diffusion.
How does SA:VOL gradient affect rate of moment
The greater the surface area, the more space for particles to move through, resulting in a faster rate of diffusion.
How does distance gradient affect rate of moment
The longer the distance, the slower it takes for molecules to pass through, resulting in a slower rate of diffusion
Osmosis
Movement of water from a high water potential to a low water potential through a partially permeable membrane
Isotonic
Conc of sugar in outside solution is same as internal
- no movement
Hypertonic
Concentration of sugar in outside solution is higher than internal
- water moves out
Hypotonic
Conc of sugar in outside solution is lower than internal
- water moves in
Osmosis in animals
- out has higher water potential so it moves into cell, bursts
- out has lower water potential so it moves out, shrivelled
More concentrated
Lower water potential
Turgid osmosis and plants
- outside solution high water potential
- water moves inside
- more pressure and is turgid
Plasmolysis
- outside is lower water potential
- water moves out
- cell membrane moves and detaches from cell wall
Active transport
Movement of particles from an area of lower to and area of higher concentration
Active transport in root hair cells
- take up water and mineral ions from soil
- active transport used and requires energy from respiration
Practical: diffusion in non-living systems
1) Cut a 1cm3 cube of agar made of sodium hydroxide and phenolphthalein indicator
2) Place cube in solution of HCL
3) Cut the cube in half and measure the distance that the acid has caused the agar to become colourless from outside inwards
4) Repeat the experiment calculate the mean
5) Repeat with different concentrations of hydrochloric acid
Practical: investigating osmosis in potatoes
1) Place different sucrose solutions including 0% for a control, in different boiling tubes
2) Dry potato strips on a paper towel and measure the masses
3) Place each potato strip into each sucrose solution for 20 minutes and record how the mass changed
4) Repeat tests at each solution several times with potato strips of similar masses
Photosynthesis word equation
Carbon dioxide + water ——sunlight——> glucose + oxygen
Photosynthesis chemical equation
6C02 + 6H20 —> C6H1606 + 6O2
Factors affecting photosynthesis: temperature
• With an increase in temperature, the rate of photosynthesis increases.
• However, as the reaction is controlled by enzymes, this trend only continues up to a certain temperature until the enzymes begin to denature and the rate of reaction decreases.
Factors affecting photosynthesis: light intensity
• For most plants, the higher the light intensity, the higher the rate of photosynthesis
• As the distance between the light source and the plant increases, the light intensity decreases
Factors affecting photosynthesis: carbon dioxide concentration
• Carbon dioxide is also needed to make glucose
• As the concentration of carbon dioxide increases, the rate of reaction increases
Investigating effect of light intensity on photosynthesis
1) Place pondweed in water and set up a desk lamp next to a ruler so that you can measure the distance between the light and the beaker
2) Move the lamp away by 10cm
3) Leave for 5 minutes to allow for the pondweed to adapt
4) Count the number of bubbles given off in 1 minute and record
5) Repeat steps 2-4
Investigating effect of carbon dioxide on photosynthesis
1) Place pondweed in water and use different concentrations of sodium hydrogen carbonate solution
3) Leave for 5 minutes to allow for the pondweed to adapt
4) Count the number of bubbles given off in 1 minute and record
5) Repeat steps 2-4
Investigating starch production
1) Cover half of a small leaf with foil
2) Place the plant on a windowsill for 48 hours so that light can reach it
3) Put the leaf into boiling water to kill and preserve it.
4) Put the leaf in a boiling tube containing hot ethanol for 10 minutes (this removes the chlorophyll pigment).
5) Dip the leaf in boiling water to soften it.
6) Put the leaf in a Petri dish and cover with iodine solution.
6) The covered half of the leaf will remain orange-brown, whereas the exposed half will change to blue-black (as iodine solution changes colour in the presence of starch, as photosynthesis turned the glucose into starch for storage)
Variegated leafs
Variegated plants are white and green and only contain chlorophyll in the green parts.
Therefore, only the green areas of the plant will test positive for starch (i.e. turn blue-black) as a result of photosynthesis occuring.
The white areas that do not contain chlorophyll remain orange-brown.
Waxy cuticle
Helps reduce water loss by evaporation and is a protective layer at top of leaf
Upper epidermis
Very thin and transparent in order to let light into palisade mesophyll
Palisade mesophyll
Contains lots of chloroplasts so that photosynthesis can happen rapidly
Spongy mesophyll
Has lots of air spaces to allow gases to diffuse in and out of cells faster
- increases SA:VOL
Lower epidermis
Contains guard cells and stomata
(Gaps)
Guard cell
Kidney shaped cells that open and close stomata by absorbing or losing water
Lots of water available -> cells fill and open stomata
Stomata
Where gas exchange and loss of water by evaporation takes place
- opens during day
-closes at night
Mineral ions: magnesium
- required for chlorophyll production
Decifiency: causes leaves to be yellow
Mineral ions: nitrate
- required to produce amino acids
Deficiency causes stunted growth and turns leaves yellow
Balanced diet
Carbohydrates, protein, lipid, vitamins, minerals, water, fibre
Source and function of carbohydrates
Source - bread/cereal/pasta/rice
Function - high energy source
Source and function of proteins
Source - meat/eggs/fish
Function - growth and repair
Source and function of lipids
Source - butter/oil/nuts
Function - high energy source and insulation
Source and function of fibre
Source - vegetables/bran
Function - prevents constipation as it helps food move through gut
Source and function of vitamin a
Source - carrots/greens vegetables
Functions - needed for vision in dark and growth
Source and function of vitamin c
Source - citrus fruits
Functions - bone and teeth strength and prevents scurvy
Source and function of vitamin d
Source - margarine/oily fish
Function - helps absorbing of calcium
Source and function of calcium
Source - milk
Function - bone and teeth strength, prevents rickets
Source and function of iron
Source - red meat
Function - needed for haemogoblin, prevents anaemia
Source and function of water
Function - needed for cell metabolic reactions to take place
How does age affect energy requirements
Energy requirements increases
- energy of adults go down as they age
How does activity levels affect energy requirements
More active - more energy for movement
How does pregnancy affect energy requirements
Energy requirements increase to support growth of foetus
- extra mass of baby needs more energy
Alimentary canal order
Mouth - oesophagus - stomach - small intestine duodenum and ileum - large intestine colon and rectum - pancreas
Bile
Produced in liver and stored in gall bladder
Practical: investigate energy content in food sample
Calorimetry
- cold water in boiling tube
- record start temp with thermometer
- record mass of food sample on scale
- heat food on Bunsen burner until it catches fire
- put sample underneath test tube base to heat water
- record final temp when food stops burning
Energy transferred (J) =
Temperature increase x mass of water x 4.2
Lungs excrete
Carbon dioxide
Kidneys secrete
Urea, excess water and salts
Skin secretes
Excess water and salts through sweat
Roles of kidney
Filtration, selective reabsorption, osmoregulation, excretion
Filtration
Filters out waste products (water ions urea) at high pressures to form urine
Selective reabsorption
Useful substances like glucose, ions and water are reabsorbed in PCT
Osmoregulation
Controlling water content in body
Excretion
Removal of waste products
Inner part of kidney
Medulla
Outer part of kidney
Cortex
Ureter
Carries urine from kidney to bladder to be excreted out of body
Renal artery
Supplies kidney with oxygenated blood
Renal vein
Takes deoxygenated blood away
Nephron: renal artery
Transports oxygenated blood to Bowman’s capsule under HIGH pressure
Nephron: glomerulus
Pressure increases even further as capillaries exiting to renal vein is narrower than capillary entering
Nephron: ultrafiltration
Pressure leads to ultrafiltration as water/salts/glucose/urea pass out capillary and into Bowman’s capsule
Capillaries get narrower as they go further into glomerulus which increases pressure
What stays in the blood
Proteins and blood cells since they are too big
Layers of cell and membrane separate capillaries of glomerulus from bowman’s capsule like a sieve
PCT - proximal convoluted tubule
Selective reabsorption - all glucose reabsorbed at PCT by active transport whilst rest of filtrate continues
Mitochondria - provides energy for active transport
Loop of henle
Salts reabsorbed
Collecting duct
Water is reabsorbed into blood at collecting ducts depending on levels of water in body
- depends on secretion of ADH
What happens to remaining filtrate in collecting duct
Remaining filtrate (water/salts/urea) forms urine which is transported through ureters
- stored in bladder and through urethra to leave body
ADH - anti-diuretic hormone released by
Pituitary gland
ADH
Hormone involved in control of loss of water
- travels in bloodstream to kidney tubules
Negative feedback loop: water levels
- drank water
- increase H20
- detected by osmoreceptors found in hypothalamus
- hypothalamus signals to pituitary gland
- less ADH released/secreted
- less water reabsorbed by collecting duct -> less permeable
- urine is less concentrated as volume increases
Urine contains
Water/urea/ions
Renal pelvis
Tube that links kidney to ureter
Nephron in order
Bowman’s capsule - surrounds glomerulus
PCT
Loop of Henle
DCT
Collecting duct
Presence of protein or blood in urine
Sign of damage to glomerulus or bowman’s capsule
- kidney disease of high blood pressure
Glucose in urine
Diabetes
- not all glucose filtered out can be reabsorbed
Selective reabsorption
Glucose in PCT by active transport whilst
Reabsorption of water
Necessary salts are reabsorbed back into blood by diffusion and active transport in Loop of Henle
Water also reabsorbed via osmosis and also in collecting duct
Negative loop: controlling blood glucose
- increase in blood glucose
- change detected by cells in pancreas
- pancreas releases insulin
- liver cells store more glucose from blood as glycogen (stored in liver)
- decrease in blood glucose
Body temp increases
Sweat/vasodilation response
Body temp decreases
Body temp decreases
Ice bath
Vasoconstriction
Hairs stand
Shivering
Sweat
Evaporates from skin surface resulting in increased energy transfer away from body
- produced from sweat glands
Vasodilation
More blood flows closer to surface of skin
Arterioles vasodilate
- more heat loss via radiation
Hairs standing
Insulation and traps air
Air is poor conductor of heat
Shivering
- exothermic
- more muscle contracting
- more glucose released for respiration
Why’s glucose in plasma and filtrate but not urine
Glucose molecules small enough to fit into filtrate
- selectively reabsorbed in PCT by active transport so it goes back into plasma
Composition of urine in warm environment
Decrease in water levels due to sweating causes urine to be concentrated but there’s less volume of urine
Hormones are
Proteins
Why’s insulin injected rather than taken by mouth
Mouth -> insulin is protein and is broken down and digested by pepsin in stomach to amino acids
ADH source
Pituitary gland
ADH role
Regulates water content in body
ADH effect
Increases permeability of collecting ducts in kidneys to reabsorb more water into blood
FSH source
Pituitary gland
FSH role
Causes ovary to develop and mature egg
FSH effect
Stimulates development of egg and release of oestrogen
LH source
Pituitary gland
LH role
Causes ovaries to release matured eggs
LH effect
Stimulates release of egg cells and release of progesterone
Gamete
Entire DNA of an organism
Gene
Section of molecule of DNA that codes for a specific protein
DNA molecule
Two strands coiled to form double helix
- strands linked by series of paired bases
Adenine with
Thymine
Cytosine with
Guanine
RNA
Single stranded molecule that contains Uracil instead of thymine
RNA compared to DNA
RNA:
- uracil
- single stranded
- ribose
DNA:
- thymine
- double stranded
- deoxyribose
Nucleotide
Pentose sugar - deoxyribose
Phosphate
Nitrogenous bases
Allele
Alternative form of a gene
Dominant
Allele always expressed in phenotype
Recessive
Only shows up in phenotype when there’s no dominant allele
Homozygous
Same allele - bb
Heterozygous
Different allele - Bb
Phenotype
Appearance
Genotype
Alleles
Codominance
Many genes (two or more) working together
E.g. skin colour
Phenotypic features
Result of polygenic inheritance rather than single genes
XX
Female
XY
Male
Mutation
Rare random change in genetic material that can be inherited
Variation
Difference between different individuals of the same species
Phenotypic variation
Variability in phenotype that exists in a population
Causes of variation
- controlled entirely by genes (genetic variation)
- controlled entirely by environment
21 pairs of chromosomes
Autosome
Template strand
Only one strand of DNA molecules codes for proteins of cell c
Protein synthesis proteins made
- enzymes
- structural proteins -> keratin,myosin, collagen
- haemogoblin
- hormones
DNA RNA similarities
Both have C/G/A
Both made of nucleotides
Both have phosphate
Genetic code is
Degenerate
DNA code is a
Triplet
DNA code is universal
Same in all organisms
Protein synthesis
Transcription then translation
DNA replication
- DNA helices unravels double helix which separates hydrogen bonds
- bases are exposed so free DNA nucleotides in nucleus align with complementary base paring
- DNA polymerase forms sugar phosphate backbone
- two identical DNA molecules formed
Transcription
- DNA helicase seperates the strands so bases are exposed on template strand
- free RNA nucleotides in nucleus align to bases on strand due to complimentary base parings
- RNA polymerase forms sugar phosphate backbone between RNA molecules
- RNA polymerase reaches STOP codon
- synthesis mRNA strand detaches from template strand DNA -> released in nucleus
- nucleus -> cytoplasm -> ribosome
- recoils back into double helix
Translation
- mRNA exits nucleus into cytoplasm and binds to ribosome
- mRNA joins with mRMA at start codon
- tRNA are in cytoplasm
-1st tRNA molecule enters ribosome and binds with colon - 2nd tRMA enters ribosome and binds with next complementary codon to thier anticodon
- peptide bond formed between AA on tRNA molecules
- ribosome moves along to next codon
- tRMA with complementary anticodon enters ribosome
- tRMA leaves and ribsome moves along until STOP codon reached
- 1st tRNA molecule leaves ribsome
- forms polypeptide chain of proteins
Protein synthesis easier
1) DNA helix is unwound and unzipped
2) mRNA nucleotides match to their complementary base on the strand.
3) The mRNA nucleotides are then joined together, creating a new strand called a template strand of the original DNA. This process is called transcription.
4) The strand of mRNA then moves out of the nucleus to the cytoplasm and onto structures called ribosomes.
5) At the ribosomes, the bases on the mRNA are read in threes to code for an amino acid (the first three bases code for one amino acid, the second three bases code for another etc). This is called translation.
6) The corresponding amino acids are brought to the ribosomes by carrier molecules.
7) These amino acids connect together to form a protein. It is therefore the triplet code of bases that determines which protein is produced and therefore expressed.
8) When the chain is complete the protein folds to form a unique 3D structure.
Change in DNA can affect phenotype by
Altering sequence of amino acids in a protein
Most genetic mutations have
No effect on phenotype
Some have small effect and rarely is significant
Incidence of mutations can be increased by
- exposure to ionising radiation (gamma/x-rays/UV)
- some chemical mutagens (chemical in tobacco) -> carcinogens
Darwins theory of evolution by natural selection
- change in inherited characteristics of population over time through natural selection which may result in formation of new species
- mutation has survival advantage and more likely to survive -> mutation passed on to offspring
- mutation frequency increase within population
Advantage of mutation
- mutation causes species to be better adapted to environment
- Likely to survive
- without mutation dies
- servicing ones reproduce and pass on alleles to offspring
Antibiotics
Made to treat bacterial infections so it doesn’t replicate
- targets cell wall as it wont harm animal cell
What can ONLY be treated by antibiotics
Bacteria
Antibiotic resistance
- mutation occurs in bacteria
- conveys resistance to antibiotic fir specific bacterium
- when antibiotics area added, bacteria with resistance will survive and those without resistance dies
- surviving bacteria reproduces rapidly by mitosis and gene for antibiotic resistance is passed on to offspring bacteria
E.g. MRSA
Producers
Organisms that make their own food by photosynthesis
E.g. plant or algae
Primary consumers
Herbivores than only eats producers/plants
Secondary consumers
Carnivores that each primary consumers
Tertiary consumers
Carnivores that eat secondary consumers
- no predators and are apex predators
Decomposers
Bacteria and fungi that break down dead animals bodies and waste for energy using enzymes
Food chain shows
Feeding relationships between organisms
Pyramids of biomass
Shows relative biomass at each tropic level
- shows relative dry mass of material
How much incident energy do producers transfer from producers to light
1%
How much biomass of each tropic level is transferred to next
10%
Why is only 10 percent of biomass
- not all biomass eaten -> carnivores eat bone
- not all biomass eaten is converted into biomass
—> glucose in respiration, waste product carbon dioxide
—> urea is waste substance released in urine
—-> faeces
Efficiency of biomass transfers =
Biomass transferred to next level / biomass available at previous level x100
Yeast uses anaerobic respiration to make bread rise
Glucose —> ethanol + carbon dioxide
Role of bacteria lactobacillus in production of yoghurt
Milk contains lactose sugar which lactobacillus can break down to form lactic acid
- acid lowers pH of milk and denatures proteins to give yoghurt texture
Process of making yoghurt
1) All equipment is sterilised to kill unwanted microorganisms
2) Milk is heated to 72°C for 15 seconds to kill any microorganisms in the milk - this is called pasteurisation
3) The milk is cooled and lactobacillus is added
4) The mixture is incubated at around 40°C in a fermenter - here the bacteria breaks down lactose to lactic acid
5) The thickened yoghurt is produced and any flavouring, colorants or fruit are added before packaging
Industrial fermenter
Containers that grow bacteria and fungi in large amounts
Industrial fermenter conditions
Aseptic, nutrients, optimum temp and ph, agitation
Aseptic
So no other microorganism grows and contaminates containers
Nutrients
Needed for microorganism to use in respiration
Optimum temp and pH
Needed so enzymes work efficiently at high rate and don’t denature
Agitation
Stirring paddles required to ensure everything is distributed evenly
