Biology Flashcards
What is a cell’s genome?
The complete set of genes in a cell
What is a cell’s proteome?
The full range of proteins produced by the cell
What are alleles?
Different forms of genes
What are genes?
Sections of DNA that code for polypeptides
What is special about embryonic stem cells?
They can differentiate and give rise to any cell type
What happens to a cell’s ability to form other cells?
It loses this ability as the cell matures
Describe natural selection:
Overproduction of offspring
More are produced that the environment can support
Variation exists / (random) mutations give rise to variation
Some varieties better adapted than others
Best adapted reproduce and pass on characteristics
So the new generation has these characters too
This leads to changes in the population as a whole
Give an example of natural selection
Bacterial resistance
What are the two varieties of variation?
Genetic or environmental
When will a species become extinct?
When they can’t adapt quickly enough to changes
What are enzymes?
Biological catalysts
What is the definition of an enzyme?
Proteins that alter the rate of reaction without being affected themselves
Define respiration
Produces co2, h2o and ATP
What is the word equation for aerobic respiration?
Glucose + oxygen -> carbon dioxide + water
What is the word equation for anaerobic respiration in animals?
Pyruvate + reduced NAD -> lactate + oxidised NAD
Why is anaerobic respiration in animals important?
NAD from glycolysis must be removed - pyruvate gains two hydrogen atoms to form lactate
What are the male chromosomes?
XY
What are the female chromosomes?
XX
What is homeostasis?
Maintaining a constant internal environment
What is negative feedback?
The stimulus causes the corrective measures to be turned off to maintain optimum conditions
How is temperature regulated?
Hypothalamus detects a rise in temperature - this causes vasodilation, sweating and lowering of body hairs
How is blood glucose regulated?
Alpha cells in the islets of Langerhans detect a fall in blood glucose concentration and release glucagon
Beta cells in the islets of Langerhans detect a rise in blood glucose concentration and release insulin
Describe the process of denitrification
Anaerobic bacteria convert soil nitrates into nitrogen gas
Describe the process of nitrogen fixation
Nitrogen gas is converted to ammonia
Describe the process of decay
Saprobionts break down nitrogenous compounds into ammonia compounds
Describe the process of nitrification
Ammonia is oxidised into nitrite
Nitrite is oxidised into nitrate
What are mycorrhizae?
They form a mutualistic relationship with plants
Describe the process of phagocytosis
The phagocyte moves towards the pathogen by following chemical secretions
The phagocyte attaches to the pathogen
Lysosomes in the phagocyte engulf the pathogen
Lysozymes hydrolyse the pathogen
The hydrolysis products are absorbed the phagocyte
How do hormones reach their targets?
In the blood
How is water content regulated?
The hypothalamus of the brain detects a fall in water potential
The anti-diuretic hormone is released and travels to the kidneys, which allows more water to be absorbed
How do white blood cells produce antibodies?
B cells present foreign antigens on their surfaces
Helper T cells activate the B cell
The B cell divides by mitosis
This produces plasma cells, that secrete antibodies, and memory cells
Describe the process of combustion
The material is burnt in excess oxygen to produce water and carbon dioxide
What is the equation for combustion
Material + oxygen -> carbon dioxide + water
How does decay contribute to the carbon cycle?
Microorganisms break down dead or decaying matter and release CO2 through respiration
How does respiration contribute to the carbon cycle?
Acetyl CoA combines with a 4C compound to produce a 6C compound
This 6C compound releases one CO2 molecule and hydrogen atoms to form a 5C compound
These hydrogen atoms are used to form reduced NAD
The 5C compound has another molecule of CO2 removed to form a 4C compound
This time, one molecule of reduced FAD, one molecule of ATP, and two molecules of reduced NAD are produced
The 4C compound combines with the CoA to repeat the cycle again
What are the four processes in the carbon cycle?
Respiration, photosynthesis, decomposition, combustion
What role does photosynthesis play in the carbon cycle?
CO2 diffuses into the leaf through the stomata and then into the stroma
Here, the CO2 combines with RuBP in a reaction catalysed by rubisco. This forms an unstable 6 carbon compound which quickly breaks down into two molecules of GP
The hydrolysis of ATP provides every and reduced NADP provides H+ ions to tun this GP into TP
The NADP goes back to the light-dependent reaction to accept more protons
Some TP is turned into glucose and the rest continues to regenerate RuBP
Where is amylase produced?
The salivary glands and pancreas
What does amylase do?
Breaks down carbohydrates into sugars
Where is lipase produced?
Pancreas and small intestine
What does lipase do?
Breaks down lipids into fatty acids and glycerol
Where is protease produced?
Stomach, pancreas and small intestine
What does protease do?
Breaks down proteins into amino acids
What does the process of genetic modification include?
Taking a copy of a gene from one organism and inserting it into the DNA of another organism
What is monohybrid inheritance?
Inheriting a single gene
What is the central nervous system comprised of?
The brain and the spinal cord
Function of sensory neurons
Transmit an impulse from a receptor to a motor neurone
Structure of the sensory neuron
One long dendron that carries the impulse towards the cell body and one long axon to carry it away
Function of motor neurons
Transmit impulses from a relay neuron to an effector
Structure of the motor neuron
A long axon and many short dendrites
Function of the relay neuron
Transmit impulses between neurons
Description of cell body
Contains all the normal cellular organelles
Function of cell body
Produces neurotransmitters and proteins
Description of dendrons
Extensions which sub divide into dendrites
Function of dendrons
Carry nerve impulses towards the cell body
Description of Schwann cells
Surround the axon and providing electrical insulation
Function of Schwann cells
Carry out phagocytosis
Description of the myelin sheath
Is made of the membranes of Schwann cells and covers the axon
What are myelinated neurones?
Those with a myelin sheath
What are the nodes of Ranvier?
Constrictions between Schwann cells where there is no myelin sheath
Describe the reflex arc
R - receptor S - sensory neuron R - relay neuron M - motor neuron E - effector
Describe the structure of a synapse
The presynaptic neuron releases neurotransmitters from vesicles, which diffuse across the gap to postsynaptic neurones
Function of a synapse
Transmit information between neurones
What effects can drugs have on synapses?
They inhibit the nervous system by creating fewer action potentials in the postsynaptic neurons, either by inhibiting the release of a neurotransmitter or by blocking receptors on the potassium/sodium channels on the postsynaptic nerve
Function of an ECG
Monitors heart rhythm and electrical activity
What do the different blood types mean?
The blood cells have different antigens
What is the SAN?
An area of muscle in the right atrium which results in contraction
What is the AVN?
Picks up the electrical signal and passes it to the bottom of the ventricles
How do the kidneys contribute to homeostasis?
Maintain a constant blood water potential
Function of the fibrous capsule
A protective outer membrane
What is the cortex of the kidney?
An outer region made of Bowman’s capsules
What is the medulla of the kidney?
An inner region made of loops of Henle
Function of ureter
A tube carrying urine to the bladder
Function of renal artery
Supplies the kidney with blood
Function of renal vein
Returns blood to the heart
Description of Bowman’s capsule
Contains the blood capillaries known as the glomerulus
Description of the proximal and distal convoluted tubules
Loops surrounded by capillaries
Description of the loop of henle
A hairpin loop that extends from the cortex to the medulla
What is the genome?
The entire genetic material of an organism
How many strands form DNA?
2
Shape of DNA?
A double helix
What does adenine pair with?
Thymine
What does guanine pair with?
Cytosine
What does each triplet code for?
An amino acid
How is the genetic code read?
In triplets
What is a mutation?
A change in DNA
What impact will most mutations have on the phenotype?
No effect
Function of adult stem cells
Produce the cells of a particular tissue or organ to maintain them throughout the organism’s life
Function of embryonic stem cells
Differentiate into various cell types during development
Benefits of stem cells
Could save many lives and improve those of others
Disadvantages of stem cells
Ethical dilemmas
Could divide too much to form tumours
What do restriction enzymes do?
They cut the DNA base sequence at a specific sequence of bases called a recognition sequence
What is the role of ligases?
They catalyse the formation of a phosphodiester bond between two sticky ends
Impacts of selective breeding on animals
The gene pool is reduced, producing organisms more prone to rare genetic conditions as a result of inbreeding
Benefits of genetic engineering
Gene therapy to treat diseases
Disadvantages of genetic engineering
Reduced diversity, ‘designer babies’
How does speciation occur?
Populations are isolated by a barrier
Conditions on either side of the barrier will be different
Each population shows genetic variation
Different alleles will be successful (different natural selection)
These organisms will be successful and pass on these alleles
Different characteristics will become more common
What is antibacterial resistance an example of?
Evolution through natural selection
How do bacteria become resistant?
They develop a mutation which allows them to survive, breed and pass on the resistant allele, leading to a whole species becoming resistant
What are the four components making up the blood?
WBCs, RBCs, plasma, platelets
What does blood plasma do?
Transports blood components and other dissolved substances
Why is the water cycle so important?
It ensures that there is always water available for living organisms, where otherwise there may not be
What is type 1 diabetes?
The body becomes unable to produce insulin, normally occurs in childhood
How is type 1 diabetes treated?
Insulin injections
What is type 2 diabetes?
Glycoprotein receptors lose their responsiveness to insulin, normally occurs as a result of lifestyle choices
What is important to remember about diseases like cardiovascular disease, cancer and type 2 diabetes?
They are caused by the interaction of many factors
How can cardiovascular disease be managed?
Statins, anti-coagulants, stents, bypass, lifestyle changes
How are new drugs developed?
Drug discovery Preclinical trials First clinical trial Second clinical trial Third clinical trial
When are human volunteers used in drug testing?
During clinical trials
What are communicable diseases caused by?
Pathogens, viruses, protists and fungi
What impact does thyroxine have on the body?
Controls metabolism
How is thyroxine an example of negative feedback?
If the levels of thyroxine begin to fall, it is detected by sensors in the brain and more TSH is released
TSH stimulates the production of thyroxine by the pituitary gland
What impact does adrenaline have on the body?
Increases heart and breathing rate so more oxygen is circulated to cells in preparation for fight or flight
What role does FSH have in the menstrual cycle?
Causes the egg to mature, stimulates the ovary to make oestrogen
What role does LH have in the menstrual cycle?
Ovulation
What role does oestrogen have in the menstrual cycle?
Inhibits FSH, stimulates LH
What role does progesterone have on the body?
Inhibits FSH and LH, maintains womb lining
Which hormones are in the combined pill?
Oestrogen and progesterone- inhibits FSH release so no egg matures
What is peristasis?
The contraction of the muscles in the stomach to bring about movement
What is digestion?
Breaking down large, insoluble pieces of food into smaller, soluble pieces
What is absorption?
Absorbing the soluble products of digestion into the blood stream
What is egestion?
Excreting the waste products
What happens when you look at a bright light?
Circular muscles contract
Radial muscles relax
Pupil constricts
What happens hen there is little light?
Circular muscles relax
Radial muscles contract
Pupil dilates
What happens when you are focussing on a object that is far away?
The lens is less convex
Ciliary muscles relax
Suspensory ligaments contract
What happens when you are looking at a near object?
Ciliary muscles contract
Suspensory ligaments relax
Lens is more convex
Which side of the heart pumps blood to the body?
Left
Characteristics of recessive X-linked conditions
Carried by females
Appears in males
Characteristics of dominant X-linked conditions
Fathers will only pass to daughters
Mothers can pass to either sons or daughters
