unit 1/ Flashcards
Define osmosis
Net movement of particles from a higher region of water potential to a lower region of water potential through a partially permeable membrane
Define homeostasis
Organisms that need to maintain their internal environment
Name 3 negative feedback effects
- pH
- temperature
- water potential
Define negative feedback effect
Body’s mechanism for reversing change and retuning it back to optimum conditions
What are the steps for negative feedback including effectors , receptors and coordinators
1 - receptors detect change in optimum conditions and send signals to coordinators
2 - the coordinators decides which receptors are appropriate by sending signals to effectors
3 - the effectors change internal conditions back to optimum conditions
Where are temperature receptors located
Skin
Hypothalamus
What is the positive feedback effect?
Opposite of negative feedback effect
Any changes away from optimum conditions are increased
Name an example of positive feedback and explain
- action potential
- the influx of sodium ions causes depolarisation which results to more sodium channels to open
- therefore membrane potential increases
Where does transcription take place in?
The nucleus
Where does mRNA move to?
The cytoplasm
What are the steps for transcription?
1 - DNA helicase breaks hydrogen bonds between the 2 strands
2 - complimentary RNA nucleotides move into place and form hydrogen bonds with bases on the exposed nucleotides on one of the DNA strands
3 - enzyme RNA polymerase joins RNA nucleotides by forming phosodiester bonds
4 - once mRNA has been synthesised the RNA polymerase detaches from the DNA and the DNA goes back into its normal double helix structure
5 - mRNA moves out of the nucleus from nucleus pores
6 - once in cytoplasm, mRNA can take part in translation
What are the steps for translation
1 - once the mRNA moves from the nucleus to the cytoplasm a small subunit of ribosome binds with the mRNA at the start codon
2 - the tRNA molecules with an anticodon complementary to the start codon attaches and is held by hydrogen bonds between the complementary base pairs on mRNA and tRNA
3 - a 2nd tRNA molecule moves into place
4 - peptide bonds are formed between the 2 amino acids
5 - ribosome moves to the next codon and the first tRNA molecules has ben released
6 - when ribosome reaches to the stop codon the polypeptide chain is released
Where is mRNA created in?
Nucleus
Why does mRNA leave the nucleus?
To carry the Copy of the genetic code of one gene to a ribosome in the cytoplasm
Why is mRNA much shorter than DNA?
It is only the length of 1 gene and therefore can leave the nucleus
Where is tRNA found in?
Cytoplasm
What is the structure of tRNA
Single stranded
Cloverleafed shape that is held by hydrogen bonds
What does rRNA make up?
Bulk of ribosomes by combining with proteins
How are nucleotides formed?
By phosphodiester bonds
What 5 molecules are the fluid mosaic model
- Phosphobilayer
- Glycoprotein
- Glycolipids
- Proteins
- Cholesterol
What are the differences between the phosphobilayer head and tails
- Tail is hydrophilic as it has no charge
- Head is hydrophobic as it is negatively charged
- Head contains glycerol and phosphate group
- Tails contain fatty acid chains
What does cholesterol do in the membrane?
Restrict movement of the molecules
What are 2 types of protiens?
Peripheral
Integral
What are peripheral proteins?
Proteins that do not extend completely across the membrane and are there for mechanical support and to connect lipids or proteins into glycoproteins and glycolipids
What are integral protiens?
Proteins that extent fully to the membrane and are used for protein carriers / channels for transport of molecules across the membrane
What protein structure are enzymes?
Tertiary
What is induced fit?
When the active site slightly changes shape to mould around the substrate
What happens to the bonds in induced fit?
Weakens and activation energy is lowered
What are the 5 factors effecting enzyme action?
- pH
- temperature
- inhibitors
- enzyme concentration
- substrate concentration
How does pH affect enzyme activity?
If pH is too low or too high it can interfere with the charges in the amino acids in the active site.
This can break bonds in the tertiary structure so active site changes
How does enzyme concentration effect enzyme activity?
If there is insufficient enzyme - the enzymes active site will be more saturated with the substrate and will be unable to work faster
How does substrate concentration affect enzyme activity?
If there is insufficient substrate the reaction will be slower and fewer collisions happen between enzymes and substrate
What is and describe a competitive inhibitor?
Has the same shape as substrate and binds to the active site temporarily so it prevents the substrate from binding, this lowers rate of reaction
By adding more substrate this will out compete the inhibitor
Describe non competitive inhibitors
Binds away from the active site
Causes active site to change shape so substrate is no longer complimentary to the active site
What are 3 samples of monosaccharides?
Glucose
Galactose
Fructose
What is a property of monosaccharides?
Soluble in water
What are OH groups called?
Hydroxyl groups
What are isomers?
Same formula but different arrangement of atoms
What does non polar means?
Not easily dissolved in water - hydrophobic
What does substrate mean?
Surface where organisms live on
What is active site?
Enzyme where Substrate binds to undergo a chemical reaction
Why do we need ATP? 2 reasons
For energy
Hydrolysis of one of the 3 phosphate groups of the ATP to provide energy
What are the roles of ATP?
- metabolic processes - build large complex molecules from a smaller molecule
- active transport - changes shape of carrier proteins in membrane and allows molecules and ions to move against a concentration gradient
- muscle contraction / movement
Why is there a leading strand and a lagging stand in DNA replication?
Leading strand - replicate continuously
Lagging strand - replicate forming short fragments discontinuously
What is a gene?
Segment of DNA that codes for a protein
Name 3 examples of a disaccharide
- maltose
- sucrose
- fructose
What are 4 properties of polysaccharides?
- large
- compact
- insoluble
- easily broken down
What are triglycerides made of?
3 fatty acids + glycerol
Explain the test for proteins
Biuret solution - turns from blue to purple if present
Explain the test for lipids
Ethanol and water - cloudy / white if present
How does the body regulate water potential?
- If the water potential is lower than set point it is detected by Osmoreceptors
- This causes ADH to be released from the pituitary gland - ADH is the coordinator in the feedback loop
- ADH travels from blood into the kidneys nephron
- The cell linings in the collecting duct and distal convoluted tubule have ADH receptors on them
- ADH causes vesicles of aquaporins to fuss with the membrane increasing permeability of the collecting duct to water
- Water moves out by osmosis to the medulla and into the blood, concentrating the urine and reducing water loss
What does ADH stand for?
Antidiuretic hormone
