Essays Flashcards
How does the body respond to a fall in blood water potential? (essay)
- Osmoreceptors in hypothalamus detect fall in blood water potential, lose water by osmosis and shrink
- Hypothalamus produces more ADH, which is secreted into capillaries by posterior pituitary gland
- ADH binds to receptors on distal convoluted tubule and collecting duct
- Activates phosphorylase enzyme within the cell
- Causes vesicles containing aquaporins to fuse with the cell-surface membrane, increasing permeability to water
- Increased permeability of collecting duct to urea, which passes out, lowering water potential of fluid around the duct
- Combined effect causes more water to leave collecting duct by osmosis
- More water reabsorbed into blood, less lost in urine, more concentrated urine produced
- As reabsorbed water came from blood originally, it won’t increase water potential of blood, just stops it decreasing further
- Osmoreceptors detect rise in water potential and send fewer impulses to pituitary gland
- Pituitary gland reduces release of ADH and permeability of collecting ducts to water and urea reverts to original state
How does the body respond to a rise in water potential? (essay)
- Osmoreceptors in hypothalamus detect rise in water potential and increase frequency of nerve impulses to pituitary gland to reduce its release of ADH
- Less ADH in the blood = decrease in permeability of collecting ducts to water and urea
- Less water reabsorbed into blood from collecting duct
- More dilute urine produced and water potential of blood falls
- When water potential has returned from normal, osmoreceptors in hypothalamus cause pituitary gland to raise its ADH release back to normal
Describe ultrafiltration in the nephron (essay)
Blood enters kidney through renal artery, which branches into many afferent arterioles, each entering a renal capsule of a nephron. Afferent arteriole divides into the glomerulus - glomerular capillaries merge to form the efferent arteriole, which divides into capillaries around the nephron tubules, which feed into the renal vein.
The glomerular capillary walls are made from endothelial cells with pores between them. Diameter of the afferent arteriole is greater than the efferent arteriole, so hydrostatic pressure builds up in the glomerulus, so water, glucose and mineral ions are squeezed out the capillary, forming the glomerular filtrate. Blood cells and large proteins are too large to pass into the renal capsule.
Movement of filtrate out the glomerulus is resisted by capillary endothelial cells, connective tissue (basement membrane), podocytes (epithelial cells of renal capsule), hydrostatic pressure of fluid in renal capsule space, low water potential of blood in the glomerulus.
To help filtrate move out glomerulus, podocytes have spaces between them so filtrate can pass through, endothelium of glomerular capillaries has spaces between cells.
Describe reabsorption in the nephron (essay)
- 3Na+ actively transported out proximal convoluted tubule epithelial cells into interstitial fluid, then into blood
- Lowers Na+ conc inside cell compared to glomerular filtrate in lumen of proximal convoluted tubule
- Na+ diffuse through co-transport proteins into epithelial cells
- Each type of co-transport protein brings glucose, amino acids, Cl-, vitamins with the Na+
- Diffusion of soluble substances into epithelial cells lowers water potential so water moves into epithelial cell, interstitial fluid then capillary by osmosis
- Lipid-soluble substances move across epithelial cell-surface membranes by diffusion
- Glucose, amino acids, Cl-, vitamins diffuse from epithelial cells into capillaries by facilitated diffusion
- Loop of Henle acts as a counter-current multiplier. Fluid in 2 limbs move in opposite directions.
- Na+ actively transported out ascending limb loop of Henle
- Creates low water potential in interstitial region between 2 limbs - thick walls of ascending limb impermeable to water so very little escapes
- Walls of descending limb very permeable to water so passes out filtrate into interstitial space then capillaries
- Filtrate progressively loses water as it moves down descending limb, lowering water potential until lowest at tip of hairpin
- At base of ascending limb, Na+ diffuses out, up the limb Na+ is actively transported out, so filtrate has progressively higher water potential
- In interstitial space between ascending limb + collecting duct, there is a water potential gradient, highest in cortex and lower into medulla
- Collecting duct is permeable to water so as the filtrate moves down it, water passes out into the space + blood vessels
- As water passes out filtrate its water potential decreases, but also decreases in interstitial space, so water continues to move out by osmosis down whole length of collecting duct
Describe the process of muscle contraction (essay)
- ACh released from neurone binds to receptors on sarcolemma = depolarisation
- Action potential travels deep into fibre through T-tubules (extensions of sarcolemma)
- Tubules are in contact with sarcoplasmic a reticulum, which has a store of actively transported Ca2+
- Action potential opens Ca2+ channels on reticulum and Ca2+ diffuses into sarcoplasm
- Ca2+ cause tropomyosin to change shape, exposing binding sites on actin filament
- ADP molecules on myosin heads let them bind to actin + form cross-bridges
- Once attached to actin, myosin heads change angle, pulling actin filament + releasing ADP
- ATP molecule attaches to each myosin head, detaching it from actin filament
- Ca2+ activate ATP hydrolase, ATP => ADP, myosin returns to its original position using the energy released
- Myosin head has an ADP molecule again = reattaches further along the actin filament
- Cycle repeated as long as Ca2+ conc in myofibril remains high
- As myosin molecules are joined in opposite facing sets, myosin heads and actin filaments move in opposite directions towards each other, contracting muscle.
- When nervous stimulation ceases, Ca2+ actively transported into sarcoplasmic reticulum using energy from ATP hydrolysis
- Allows tropomyosin to block actin filament again = myosin heads can’t bind and contraction ceases
- Force from antagonistic muscles can pull actin filaments out from between myosin, so muscle relaxes.
Describe the importance of protein structure to their function
- Primary / tertiary / secondary structure
- Enzymes - active site
- Hormones and receptors
- Translation
- Epigenetics
- Transcriptional factors
Describe the importance of nitrogen-containing substances in organisms
- DNA
- Proteins - enzyme function e.g Calvin cycle
- Proteins - channel proteins e.g synaptic transmission
- ATP - transport e.g co-transport
- Proteins - receptors e.g immune response
- Haemoglobin - oxygen dissociation
- Proteins - hormones e.g blood glucose
Describe the importance of diffusion in organisms
- Respiration - oxidative phosphorylation
- Synaptic transmission
- Resting potential
- Absorption in the ileum - co-transport
- Gas exchange - oxygen dissociation
- Gas exchange in fish / insects
- Mass transport in plants
- Plant responses to stimuli
- Muscle contraction
- Control of blood glucose
- Control of blood water potential
Describe the importance of the control of movement in cells and organisms
- Transport across membranes
- Respiration - oxidative phosphorylation
- Absorption in ileum - co-transport
- Mass transport in plants
- Control of heart rate (so blood flow)
- Gas exchange in fish / insects
- Synaptic transmission
- Muscle contraction
- Control of blood water potential
- Control of blood glucose
- Transcriptional factors
Describe the importance of interactions between cells and organisms
- Synaptic transmission
- Control of heart rate
- Control of blood glucose
- Immune response
- Control of blood water potential
- Speciation
- Succession
- Sexual reproduction
- Cardiac cycle
- Nutrient cycles
Describe the importance of DNA as an information carrying molecule and its use in gene technology
- Genetic fingerprinting
- Meiosis
- Semi-conservative replication
- Recombinant DNA technology
- Protein synthesis
- Speciation
- Types of mutation
- Transcriptional factors
- Gene expression and cancer
Describe the importance of bonds and bonding in organisms
- Protein structure
- DNA replication
- Carbohydrates - starch, cellulose, glycogen
- Enzyme structure - pH, temperature
- Lipids
- Water - cohesion
- Mass transport - haemoglobin
- Mass transport in plants
- Synaptic transmission
- Control of blood glucose concentration
- Control of blood water potential
- Transcriptional factors
- Recombinant DNA
- Epigenetics
Describe the functions of enzymes and their importance in organisms
- Enzyme structure
- Respiration - oxidative phosphorylation
- Synaptic transmission
- Photosynthesis
- DNA replication
- Control of blood glucose concentration
- Immune system - lysozymes
- Protein synthesis
- Nutrient cycles
- Recombinant DNA
- Genetic fingerprinting
Describe the causes and importance of variation and diversity in organisms
- Speciation
- Types of mutation
- Sexual reproduction, meiosis
- Succession
- Transcriptional factors
- Epigenetics
- Genetic fingerprinting
- Recombinant DNA
Describe the importance of complementary shapes of molecules in organisms
- Immune system
- Synaptic transmission
- Transcriptional factors
- Control of blood glucose concentration
- DNA replication
- Transport across cell membranes
- Absorption of products of digestion
- Protein synthesis
- Control of blood water potential
Describe the importance of ions in metabolic processes
- Synaptic transmission
- Resting potential
- Respiration
- pH - enzymes
- Muscle contraction
- Haemoglobin
- Co-transport
- Mass transport in plants
- Nutrient cycles
- Control of blood water potential
- Genetic fingerprinting
Describe the uses and importance of ATP in organisms
- Muscle contraction
- Protein synthesis
- Absorption of products of digestion
- DNA replication
- Mitosis
- Mass transport in plants
- Meiosis
- Photosynthesis
- Respiration
- Nutrient cycles
- Resting potential
- Synaptic transmission
- Control of blood glucose concentration
- Control of blood water potential
Describe the importance of cycles in biology
- Synaptic transmission
- Cardiac cycle / control of heart rate
- Control of blood glucose
- Cell cycle
- Meiosis
- Nutrient cycles
- Krebs cycle
- Calvin cycle
- PCR
- DNA replication
- Nerve impulses
- Muscle contraction
- Control of blood water potential
Describe the importance of interactions between organisms and their environment
- Speciation
- Sexual reproduction
- Succession
- Nutrient cycles
- Plant growth responses
- Taxis / kinesis
- Nerve impulses
- Immune system
- Gas exchange in fish / insects
- Mass transport in animals
- Mass transport in plants
- Photosynthesis
- Control of heart rate
- Synaptic transmission - effects of drugs
- Control of blood glucose concentration
- Control of blood water potential
- Mutations - mutagenic agents
- Epigenetics
- Gene expression and cancer
Describe the importance of membranes in the functioning of cells
- Transport across membranes
- Respiration
- Absorption of products of digestion
- Mass transport in plants
- Synaptic transmission
- Muscle contraction
- Photosynthesis
- Nerve impulses
- Immune response
- Mitosis
- Control of blood glucose concentration
- Control of blood water potential
- Transcriptional factors
Describe the importance of receptors in living organisms
- Immune response
- Synaptic transmission
- Transcriptional factors
- Control of blood glucose concentration
- Control of blood water potential
- Receptors and responses
- Control of heart rate
- Nerve impulses
- Skeletal muscles
Describe the importance of responses to changes in the internal and external environment of organisms
- Control of blood glucose concentration
- Control of blood water potential
- Control of heart rate
- Receptors and responses
- Taxis and kinesis
- Plant growth responses
- Mass transport in plants
- Epigenetics
- Haemoglobin
- Speciation
- Succession
Describe the importance of humans in the growth, reproduction and development of organisms, including themselves
- Recombinant DNA
- Sexual reproduction
- Managing succession
- Immune response and vaccination
- Fertilisers - eutrophication
- Gene therapy
- Induced pluripotent stem cells
Describe the importance of proteins in the control of processes and responses in organisms
- Synaptic transmission
- Respiration
- Photosynthesis
- Immune response
- Control of blood glucose concentration
- Control of blood water potential
- DNA replication
- Protein synthesis
- Haemoglobin
- Nutrient cycles
- Nerve impulses
- Tissue fluid
- Absorption of products of digestion
- Transport across membranes
- Pacinian corpuscles
- Transcriptional factors
Describe the causes and importance of variation and diversity in organisms
- Sexual reproduction - meiosis
- Types of mutation
- Transcriptional factors
- Epigenetics
- Speciation
- Succession
- Genetic fingerprinting
Cells and organisms carry out exchanges with their external environment to maintain their internal environment
- Control of blood glucose concentration
- Control of blood water potential
- Gas exchange in fish and insects
- Absorption of products of digestion
- Mass transport in plants
- Nutrient cycles
- Response to stimuli
- Tissue fluid
- Epigenetics
Describe how energy is transferred within and between organisms
- ATP and its importance
- Enzymes, kinetic energy, reaction rates
- Respiration
- Absorption of products of digestion
- Nerve impulses
- Synaptic transmission
- Muscle contraction
- Photosynthesis
- Mass transport in plants
The membranes of different cells are involved in many different functions
- Respiration
- Photosynthesis
- Control of blood glucose concentration
- Control of blood water potential
- Transport across membranes
- Absorption of products of digestion
- Immune response
- Nerve impulses
- Synaptic transmission
- Transcriptional factors
- Muscle contraction
There are many different types of relationships and interactions between organisms
- Speciation
- Sexual reproduction - diversity
- Succession
- Nutrient cycles
- Pathogens
- Gene technology / selective breeding
How can bacteria affect the lives of humans and other organisms?
- Immune system
- Recombinant DNA
- Nitrogen cycle
- Eutrophication
- PCR
How is DNA used in science and technology?
- Genetic fingerprinting
- Recombinant DNA
- PCR
- Genetic screening
- Medical diagnosis
Carbon dioxide may affect organisms directly or indirectly. Describe and explain these effects
- Oxygen dissociation
- Control of heart rate
- pH - enzymes
- Gas exchange in fish and insects
- Photosynthesis - light-independent reaction
Causes of disease in humans
- Pathogens e.g HIV
- Gene expression and cancer
- Genetic disorders - genetic screening
- Types of gene mutation
The movement of substances within living organisms
- Mass transport in plants
- Transpiration
- Mass transport in animals
- Transport across membranes
- Absorption of products of digestion
- Synaptic transmission
- Nerve impulses
- Gas exchange in fish and insects
- Mitosis and meiosis
- Tissue fluid
- Photosynthesis
- Respiration
- Muscle contraction
- Kidneys
