TOPIC 1 BIO PMT CORRECTIONS (22-24) , (16-21) , (<16)

1.1 MONOMERS AND POLYMERS

1.1 MONOMERS AND POLYMERS

Give 2 differences between structure of GOS and lactose (2)

Lactose contains alpha glucose and GOS does not

Lactose is a dipeptide and GOS is a polysaccharide

Explain why amylsae produced in the human digestive system does not digest GOS (2)

Active site not complimentary to the GOS

Due to tertiary structure

Suggest how GOS can be used as a prebiotic (3)

Provides sugar for Bacteria

Bacteria respire using sugar

Bacteria use sugar for cell division

1.2 CARBOHYDRATES

1.2 CARBOHYDRATES

Explain expected result for reducing sugar test (2)

Solution will go from blue to yellow or orange or red

Because of presence of reducing sugars

Why would air pressure increase in tube containing sugar molasses that is in a beaker of water (3)

Molasses solution has lower water potential

Water moves across partially permeable bladder

Increased volume of molasses solution

Explain the importance of the xylem being kept open as a continuous tube (3)

Allows for unbroken water column

Cohesion occurs due to H bonds between all water molecules

Transpiration creates tension in column as water moves via osmosis

Suggest why the water potential of apples decreases when they are stored (2)

Starch is hydrolised into maltose for food

Maltose is soluble so dissolves and reduces water potential

Compare structure of starch and of cellulose (3)

Comparisons

Both have glycosidic bonds

Both polymers of glucose

Both contain H,O,C

Contrast structure of starch and cellulose (3)

Starch is branched and cellulose is not

Starch molecule coiled and cellulose molecule is straight

Starch made of A glucose and Cellulose made of B glucose

Stach has 1 - 6 glycosidic bonds, cellulose has 1-4

Describe complete hydrolysis of by a mammal (3)

Hydrolysis of glycosidic bonds

Starch hydrolysed to maltose by amylase

Maltose hydrolised to glucose by maltase (membrane bound disaccharidase)

1.3 LIPIDS

1.3 LIPIDS

Explain why phopholipids can form a bilayer but triglycerides cannot (3)

Phospholipids are both hydrophobic and hydrophilic

Tryglycerides are fully hydrophobic

Hydrophilic heads attract water to either side of the bi layer, allowing bilayer to be formed with hydrophobic tails facing inwards

Suggest why rat red blood cell mebrane was more fluid after being fed fish oil diet

Fatty acid B was unsaturated

Fatty acid A was saturated

Increase in fluidity of cell surface membrane caused by increase in fatty acid B

Carbon double bond causes kink which means phopholipids cannot be packed as tightly together

Give 2 functions of bile salts (2)

Emulsify lipids

Form micelles

Describe how natural selection may have led to all mammals in a population producing CEL (triglyceride digesting enzyme) (4)

Mutation results in a new allele

Those with the allele able to digest milk

Individuals with CEL more likely to reproduce and survive

Directional selection causes increase of allele in population

1.4 PROTEINS AND ENZYMES

1.4 PROTEINS AND ENZYMES

The students test was positive for protein, explain why (2)

Enzymes are proteins

Enzymes are not used up in the reaction

A non competitive inhibitor decreases the rate of an enzyme controlled reaction, explain how (3)

Inhibitor binds away from active site (to allosteric site)

Changes teritary strcuture of protein

Enzyme active site changes shape as a result and can no longer form ESCs because it is no longer complimentary to substrate

Why might one variety of apple turn brown faster (3)

It has a higher concentration of enzymes

Forms more ESCs

Faster rate of reaction

Why does changing the temp to the optimum temp cause pigment on apple to appear faster (2)

More kinetic energy so more ESC forming

Faster rate of reaction

Describe the primary strucuture of proteins (2)

The order and sequence of amino acids

Joined by peptide bonds

How does the shape of ATP synthase enzyme allow it to catalyse the synthesis of ATP (2)

Active site is complimentary to ADP + Pi

Forms ESCs

How does the shape of ATP synthase enzyme allow the movement of H+ ions (2)

Channel/pore in the enzyme

Allows facilitated diffusion of H+ ions

How is the teritary structure of a protein formed (1)

Folding of polypeptide chain stabilised by the interaction of R groups (side chains)

Define the quarternary strcture of a protein

Te quarternary structure contains more than one polypeptide chain intertwined together

Describe the strucuture of a chromosome (1)

During mitosis when visible, chromosome consists of two chromatids joined together at a centromere

Describe two other processes other than mutation that can cause genetic variation in a species (4)

Random fertilisation of gametes

Produces new combinations of alleles

Independent segregation of homologous chromsomes

Random crossing over between homologous chromsome pairs

Explain how two enzymes with different amino acid sequences can catalyse the same reaction (2)

Both active sites have similar tertiary structures

They can form ESCs with same substrates

What should the scientists place in the control tube in the enzyme activity experiment (3)

Same volume of buffer pH solution

Same concentration of susbstrates at the start

Same concentration of denatured enzymes

Suggest and explain when it would be an advantage to a human for BPG (which reduces affinity of haemoglobin for oxygen) to bind to haemoglobin (2)

During exercise

To allow for more aerobic respiration and delay anaerobic respiration

1.5 NUCLEIC ACIDS

1.5 NUCLEIC ACIDS

A substitution mutation may stilll produce a functional protein - explain why (3)

Only one base pair is changed

The genetic code is degenerate which means multiple triplets code for the same amino acid

Therefore, the subsitituted base may still code for the same amino acid which means the tertiary strucuture will be unchanged

Give 4 strcutural differences between mRNA and tRNA (3)

mRNA is straight chained and tRNA is clover shaped

mRNA has codons and tRNA has anticodons

mRNA does not have H bonds but tRNA has H bonds

mRNA does not have an amino acid binding site but tRNA does

Outline 3 similarities between chloroplasts and mitochondria (3)

Both have a double membrane

Both contain circular DNA

Both contain ribosomes (70s)

Outline 3 differences between mitochondira and chloroplasts (3)

Chloroplasts have thylakoids and grana whereas mitochondria have cristae

Chloroplasts have stroma whilst mitochondria have a matrix

Chloroplasts have starch grains but mitochondria do not

Give the two molecules that ribosomes are made from (2)

Protein

RNA/mRNA

1.6 ATP

1.6 ATP

Describe and explain how you would use cell fractionation and ultracentrifugation to obtain a sample of nuclei from muscle tissue (6)

Homogenise tissue to break open cells and release organelles

Filter to remove debris

Place in cold, isotonic and buffered solution

Centrifuge at low speed so nuclei pellet forms at the bottom

Discard supernatant

Describe the role of organelles in the production and release of enzymes by animal cells (5)

DNA in nucleus codes for an enzyme

Ribosome produces the enzyme

Rough endoplasmic reticulum transports protein to golgi

Mitichondira produce ATP

Golgi uses ATP to modify proteins and package them into vesicles

Describe the structure of ATP (1)

Ribose, Adenine and 3 phosphates

1.7 WATER

1.7 WATER

How does water having a high specific heat capacity benefit living organisms (1)

Buffers the temperature changes in aquatic environments

How does water having a large latent heat of vaporisation benefit living organisms

Provides a cooling effect via evaporation during sweating

1.8 INORGANIC IONS

1.8 INORGANIC IONS

Give 3 locations where phosphate ions can be found (3)

DNA and RNA

Phospholipids

ATP and ADP

Describe the effect that a build up of carbon dioxide (Which leads to higher conc of hydrogen ions) in blood plasma has on proteins and the blood plasman (3)

Higher conc of hydrogen ions decreases the pH

Causes plasma to become more acidic

This can change the tertiary structure of proteins which could cause active site of enzymes to no longer be able to form ESCs

How do sodium ions move into the cytoplasm and out of the cell (2)

They move into cells via facilitated diffusion down conc gradient

They move out of cells by active transport against a concentration gradient

What property of iron ions allows them to carry out their role in red blood cells (2)

They are charged

So they can bind to oxygen