Biology paper 2

How can cardiac output stay the same even when the resting heart rate has decreased?

• cardiac output = stroke volume x heart rate

• Stroke volume has increased, meaning the volume of ventricles has increased

Which blood vessels are linked to the kidneys?

Renal

Which blood vessels are linked to the liver?

Hepatic

Adaptations of aorta:

• aorta has more elastic tissue

• Recoil to maintain a smooth blood flow

• Because aorta is directly connected to the heart

Adaptation of capillaries:

• greater number of capillaries

• Greater cross sectional area of capillaries compared to arterioles

How is tissue fluid formed?

• greater outward pressure at arteriole ends than lymohs

• Forces small molecules of of caipillaries

What do you call an organism with transferred DNA?

• transgenic organism

• GMO (genetically modified organism)

What are the three different ways to produce fragments of DNA?

• conversion of mRNA to complementary DNA (cDNA) using reverse transcriptase

• Using restriction enzymes to cut a fragment containing desired gene from DNA

• Creating a gene in a ‘gene machine‘

How is reverse transcriptase used for producing DNA fragments?

• cells that produce a large amount of mRNA that codes for desired protein is isolated

• mRNA acts as a template strand on which single stranded complementary copy of DNA (cDNA) is formed using reverse transcriptase

• The sscDNA is isolated by hydrolysis of the mRNA with an enzyme

• Double stranded DNA formed on the template of the cDNA using DNA polymerase

• Forms a copy of the human insulin gene

How to use restriction endonucleases to produce DNA fragments?

• restriction endonucleases cuts the DNA double strand at specific sequence of bases called the recognition site

• The recognition sites are palindromic, and the top and bottom strand are the same when read backwards

How does the gene machine work?

• desired sequence of nucleotides is determined from desired protein

• Sequence is fed into a computer

• Sequence is checked for biosafety and security

• Short single strands of nucleotides (oligonucleotides) are produced which can be assembled into desired gene

• Gene doesn’t contain non-coding DNA or introns. This gene is then replicated by PCR

Define allopatric speciation:

• speciation resulting from a physical barrier

• Environments occupied by the two groups are different

• Random mutation occurs in both groups

• Different alleles are favoured

• Favoured alleles passed down to future generations

• Different gene pools

• Unable to interbreed, leading to two different species

Define sympatric speciation:

• speciation resulting from non-physical barriers

• For example mutation that no longer allows two organisms to produce fertile offsprings

• Change in behaviour, anatomy

• Different gene pools → unable to interbreed

Define genetic drift:

• change in population’s allele frequency that occurs due to chance NOT selective pressures

• By random during reproduction

Why does genetic drift affect small populations more than large ones?

• gene pool is smaller

• Less alleles available and any change is more pronounced

Define community:

• all the different species that live in one area and interact with each other

Define ecyosystem:

• all living organisms found in one area, combined with non-living aspects of their environment

Phosphorous cycle

Function of mycorrhizae:

• fungi that acts as extensions of the plants root system

• Increases total surface area for absorption of water and minerals

• Mutualistic relationship with plants

• Plants receive improved water and inorganic ion uptake

• Mycorrhizae receives organic compounds (sugars, amino acids)

Definition of biomass

Dry mass of tissue per given area

What is NPP and how do you calculate it?

• NPP - net primary production

• Chemical energy store in plant biomass after respiratory losses to environment has been taken into account

• NPP = GPP - R

• Gross primary production

• R = respiratory losses to environment

How to calculate net production of consumers?

N = I - (F+R)

I = chemical energy store in ingested food

F = chemical energy lost in faeces and urine

R = respiratory losses

Units of primary and secondary productibity

Biomass in a given area in a given time

E.g. kj ha^-1 year^-1

How does a heart beat?

• impulse arrives at SAN

• Wave of excitation spreads out from the sinoatrial node across both atria causing it to contract

• Layer of non-conductive tissue prevents wave crossing the ventricles

• Wave of excitation reaches AVN

• After a short delay the AVN conveys wave of excitation between ventricles along the Purkyne tissue (collectively called the bundle of His)

• Bundle of His conducts wave through atrioventricular septum to base of ventricle

• Wave of excitation released from Purkyne tissue

Where is change in heart rate controlled

Medulla oblongata

What is saltatory conduction

Action potential jumps from one node of Ranvier to another

Draw structure of a sarcomere

• myosin length: A band

• Between A bands: I band

• myosin only: H zone

During contraction, the zones:

• I band become narrower

• Sarcomere shorterns

• H-zone becomes narrow

• A bands stay the same length

How is a muscle stimulated?

• action potential reaches many neuromuscular junctions at once

• Ca2+ channels open and Ca2+ diffuse into synaptic knob

• Ca2+ causes synaptic vessels to fuse with presynaptic membrane and release acetylcholine into synaptic cleft

• Acetylcholine diffuses across cleft and binds with receptors on the muscle cell-surface membrane causing it to depolarise

How does a muscle contract?

• action potential travels deep into fibre through system of tubules

• Tubules are in contact with the sarcoplasmic reticulum which has actively transported Ca2+ from cytoplasm of muscle so very low Ca2+ in cytoplasm

• Action potential opens Ca2+ channels on the sarcoplasmic reticulum and Ca2+ diffuse into muscle cytoplasm

• Ca2+ move the tropomyosin molecules that were blocking the binding sites on the actin filaments

• ADP molecules attached to myosin head and so they binds to actin filaments to form cross bridge

• Myosin head changes angle and pulls filament along, which releases the ADP molecule

• ATP attaches to myosin head, causing it to detach

• Enzyme ATPase hydrolyses ATP to ADP, provides energy for head to return to original position

How is blood glucose level controlled when it is too high

• insulin produced from beta cells in the pancrease

• Insulin opens glucose transporter protein channels within cells

• Increase number of glucose carrier proteins

• Activates enzymes which convert glucose to glycogen

How is blood glucose levels controlled when it falls

• detected by alpha cells on the pancreas

• Alpha cells secrete glucagon

• Causes liver cells to convert glycogen to glucose

Mechanism of adrenaline:

• adrenaline binds to transmembrane protein receptor within cell-surface membrane of a liver cells

• Binding of adrenaline changes shape of protein inside membrane

• Leads to activation of enzyme called adenyl cyclase

• Converts ATP to cAMP

• cAMP acts as second messenger that binds to protein kinase enzyme, changing the shape to activate it

• Active protein kinase enzyme catalyses conversion of glycogen to glucose

Difference in diabetes 1 and 2

1: don’t produce/ produces non-functioning insulin

2: produces functional insulin but cells are no longer sensitive to it

Describe ultrafiltration in the kidney

• High hydrostatic pressure in the renal artery as the afferent arteriole splits into many capillaries

• Water, glucose, ions, urea forced out small gaps/ fenestrations in the capillary

• Thorough the capillary basement membrane

• Blood leaves through efferent arteriole

Describe selective reabsorption:

• concentration of Na+ in PCT is decreased as Na+ actively transported out of PCT into blood stream

• Due to concentration gradient, Na+ diffuse down gradient from lumen of the PCT into cells lining the PCT

• As Na+ move into cells, takes a glucose molecule with it

• Glucose can then diffuse from PCT epithelial cells into blood stream

Osmoregulation in nephron

• mitochondria in walls of cells provide energy for active transport of Na+ out of ascending limb into loop of Henle

• Accumulation of Na+ outside nephron in medulla lowers water potential in the interstitial space

• Water in the descending limb diffuses out by osmosis into the interstitial space and then into the blood capillaries

• Some Na+ diffuse into the interstitial space at the bottom of the loop

• due to all the Na+ transported out of the loop of Henle, the filtrate reaching the DCT is very dilute

• Water moves into collecting duct

• Interstitial area between collecting duct and ascending limb has low water potential due to high Na+ concentration

• Water diffuses out by osmosis

Adaptation of PCT:

• microvilli provides large SA

• Lots of mitochondria to provide energy for active transport

Where are osmoreceptors found

Hypothalamus

Where is ADH secreted from

Posterior pituitary

Describe steps of PCR:

• increase temperature to 95C to denature hydrogen bonds between complementary bases

• Decrease temperature to 55C as optimum temperature for primers to bind to DNA

• Increase temperature to 72C for DNA polymerase to join nucleotides together via condensation reaction forming phosphodiester bonds

in vitro application:

• Cut DNA fragmentation

• Add promoter regions and terminator regions to the fragment

• Insert into a vector (host bacteria cell)

• Restriction endonuclease cuts plasmid

• DNA ligase joins the sticky ends together

What are DNA probes and what do they do?

Short, single stranded DNA with a label attached

Binds to complementary DNA sequence

Identify specific alleles of genes

DNA hybridisation

• DNA sample heated to denature

• Probe mixed with the single stranded DNA

• Probe binds to complementary base sequence

This is called DNA hybridisation

• x-ray or uv light

What is VNTR

• variable number tandem repeats

• Non coding regions of DNA

• short sequence that repeats

DNA fingerprinting:

• DNA separated from cell

• Amplify DNA using PCR

• VNTR isolated using restriction endonuclease

• VNTR Loaded into walls in agar gel

• Electrical voltage applied

• VNTR travels based on length

Describe how succession occurs:

• named species is the pioneering species

• Changes the abiotic factors of the area

• Makes it less hostile for named species

• Climax community when final species introduces

How is an impulse sent across neurones

• acetylcholine diffuses across synaptic cleft

• Binds to receptors on the membrane of the post synaptic neurone

• Cacuses Na+ channels to open and influx of Na+ generates an action potential/ causes depolarisation

How has farming cattle as a source of milk led to an increase in LP?

• LP due to mutation of genes

• Milk provides galactose

• Individuals with LP more likely to survive and reproduce

• Directional selection

• Frequency of allele in gene pool increases

Why are muscles antagonistic?

• works in pairs an oppose one another

What is dihybrid inheritance?

Two characters determined by two different genes located on different chromosomes

What is codominance?

When both alleles are dominant and both expressed in the phenotype

What is autosomal linkage?

• Two or more genes are carried on the same chromosome

• 22 chromosomes that are not sex chromosomes = autosomes

What is epistasis?

• when the allele of one gene affects or masks expression of another in the phenoytpe

Definition of ecosystem:

Dynamic system made up of a community and all non-living factors in the environment

Definition of population

Total number of individuals of one species that occupy the same habitat at the same time and are able to interbreed

What is a carrying capacity

Certain size of a population of a species the ecosystem can carry

What is a community

Populations of different species living in the same area at the same time

Intraspecific vs interspecific competition

• intraspecific: individuals of the same species compete with one another for food, water, breeding sites

• Interspecific: individuals of different species compete fr resources such as food, light, water

Mark release recapture equation

Estimated population size = (total no. Of individuals in first sample x total number of individuals in the second sample) / number of marked individuals recaptured

What are the different stats tests and what do they test for?

• spearmans rank: test for correlation between two named variables

• T test: determine if there is significant different between the means of two named variables

• Chi squared: test the difference between observed frequency and expected frequency

How is myelinated axons adapted for faster impulse transmission?

• provides electrical insulation

• In saltatory conduction

• Non-myelinated depolarisation occurs along whole length of axon

How is a resting potential maintained in an axon?

• higher concentration of K+ inside and higher concentration of Na+ outside neurone

• Membrane more permeable to K+

• Na+ actively transported out and K+ in

What is taxis?

• response to stimuli in organisms

• Move whole body towards a favourable stimulus or away from unfavourable stimulus

What is kineses?

• organism changes the rate at which it changed direction

• In favourable environment, the rate of change decreases

What is the order of a reflex arc?

• stimulus detected at receptor

• Signal sent down sensory neurone, entering CNS

• Carried by coordinator (relay neurone)

• Motor neurone

• Effector

Importance of reflex arcs:

• doesn’t require decision making from the brain, so it is not overloaded with situations needing responses all at once

• Protect body from harm

• Rapid action

Rod cells:

• cannot distinguish between wavelengths

• Multiple cells are connected to a bipolar cell

• Greater chance the threshold value is exceeded, so generates generator potential at lower light intensities

• results in lower visual acuity

Cone cells:

• cone cells of three different wavelengths

• Each cone cell connected to their own bipolar cell

• No summation

• High visual acuity

• If two cells stimulated, two different impulses sent to brain, so brain can distinguish between two different light sources

How does the heart beat:

• impulse arrives at SAN

• Wave of electrical excitation spreads out across both atria, causing them to contract

• Layer of non-conductive tissue prevents wave crossing to the ventricles

• Wave of excitation enters AVN

• After a short delay, wave is conveyed along the Purkyne tissue

• Bundle of His conducts wave through atrioventricular septum to the base of the ventricles

• Ventricles contract from the bottom up