Module 5 – Communication, Homeostasis & Energy Flashcards
C13) what is the definition of homoeostasis
The function of organs must be coordinated in order to maintain a relatively constant internal environment
C13) what is cell signalling
Communication at a cellular level where one cell releases a chemical which has an affect on another cell called a target cell
C13) What is the structure of a neurone
Cell body- contains the nucleus surrounded by cytoplasm. The cytoplasm contains large amounts of endoplasmic reticulum and mitochondria involved in the production of neurotransmitters, the chemicals used to pass signals from one Neurone onto the next
Dendrons- are short extensions which come from the cell body. Extensions divide into smaller and smaller branches known as dendrites responsible for transmitting electrical impulses towards cell body
Axons- singular, elongated nerve fibres that transmit impulses away from the cell body. These fibres can be very long, cylindrical in shape consisting of very narrow regions of cytoplasm
C13) What is an myelinated neurones
The axons of some neurons are covered in a myelin sheath, made of many layers of plasma membrane.
Special cells called schwann cells produce the layers of membrane by Growing around the axon.
each time they grow around of the axon a double layer of phospholipid bilayer is laid down
When the cells stop growing there may be more than 20 layers of membrane
Between myelin sheath there is a gap called the node of ranvier
C13) What is the importance of myelin sheath
Act as an insulating layer and allows these neurons to conduct the electrical impulses at a much faster speed
As the myelin sheath is an insulator the electrical impulse jumps from one node of ranvier to the next as it travels along the neuron allowing for faster transmission of current
In non-myelinated Neurons the impulse does not jump but transmits continuously along the neuron fibre so is much slower
C13)What are the features of a sensory receptor
Specific to a single type of stimulus
They act as a transducer – convert a stimulus into a neuron impulse
C13) How does a sensory receptor become a transducer
They detect a range of different stimulus. The receptor converts the stimulus into a nervous impulse called a generator potential
C13) what is the purpose of cell signalling
Transfer signals locally. For example between neurons and synapses using neurotransmitters
Transfer signals across long distances using hormones. For example the pictureIt tree gland secretes ADH to act on the kidneys to maintain water balance
C13) how does the pacinian corpuscle work
A specific sensory receptors that detect mechanical pressure located in your skin, fingers and the soles of your feet
The end of the sensory neuron is found within the centre of the corpuscle founded by connective tissue each layer of tissue is separated by layers of gel
The membrane of the neuron has sodium ion channels responsible for transporting sodium ions across the membrane but this sodium ion channel is special because it is stretch mediated
C13) how does a pacinian corpuscle convert mechanical pressure into a nerve impulse
In its normal state the stretch mediated sodium ion channels in the sensory neurones membrane are too narrow to allow sodium ions to pass. It has a resting potential
When pressure is applied to the corpuscle it changes shape causing the membrane surrounding it’s neutrons to stretch
When the membrane stretches the sodium ion channels present widen allowing sodium ions to diffuse into the neuron
The influx of positive sodium ions changes the potential of the membrane it becomes depolarised resulting in a generator potential
The generator potential creates an action potential that passes along the sensory neuron. Action potential will be transmitted along neurons to the central nervous system
C13) what is resting potential
When in your own is not transmitting and impose the potential difference across the membrane is known as a resting potential.
The outside of the membrane is more positively charged than the inside of the axon.
The membrane is said to be polarised as there is a potential difference across it
Normally about -70 mV
C13) how is the resting potential created
Sodium ions (Na+) are actively transported out of the axon but the potassium ions (K+) are actively transported into the axon by a the sodium-potassium pump
For every 3 sodium ions pumped out, 2 potassium ions are pumped in therefore there are more sodium ions outside the membrane than inside the axon cytoplasm and also more potassium ions in the cytoplasm than outside the axon
So sodium ions diffused back into the axon down its electrochemical gradient whereas potassium ions diffused out of the axon but the gated sodium ion channels are closed preventing the movement of sodium ions but the potassium ion channels are open allowing potassium ions to defuse out of the axon as a result more positively charged ions are outside the axon than inside.
The inside is negative relative to the outside
C13) What is depolarisation of the axon membrane
The energy of the stimulus temporarily reverses the charge on the axon membrane
The potential difference across the membrane rapidly changes and becomes positively charged at approximately 40mV.
A change in potential difference from negative to positive
C13) What is the repolarisation of the axon membrane
After depolarisation, the membrane repolarisation occurs
A change in potential difference from positive back to negative returning to arresting potential
C13) What is the sequence of events that takes place during an action potential
1) The nerve has a resting potential-not transmitting an impulse. Potassium ion channels are open but sodium voltage gated ion channels are closed
2) The stimulus triggers some sodium voltage gated ion channels to open making the membrane more permeable to sodium ions, diffusing into the axon down the electrochemical gradient making the inside of the neuron less negative
3) The change in charge causes more sodium ion channels to open allowing more sodium ions to diffuse into the axon-positive feedback
4) When the potential difference reaches 40mV the voltage gated sodium ion channels close and voltage gated potassium ion channels open. Sodium ions no longer into the axon but the membrane is now permeable to potassium ions
5) Potassium ions diffused out of the Exon down there electro chemical gradient reducing the charge resulting in the inside of the axon becoming more negative than the outside
6) Initially loads of potassium ions diffused out of the axon resulting in the inside of the axon becoming more negative than its normal resting potential- hyper polarisation. Voltage gated potassium channels close. The sodium potassium pump causes sodium ions to move out of the cell and potassium ions to move in the axon returns to its resting potential and is polarised
C13) How is an action potential propagated along the axon to the end of a myelinated nerve
Initial stimulus causes an action potential in the sensory receptor.
So the first region of the axon membrane is depolarised acting as a stimulus for the depolarisation of the next region of the membrane through the use of localised electrical circuit
Process continues along the length of the axon forming a wave of depolarisation
Once sodium ions are inside the axon they are attracted by the negative change ahead and the concentration gradient to defuse further along inside the axon triggers the depolarisation of the next section
The region of the membrane which has been depolarised as the action potential passes along undergo Repolarisation to return to its resting potential
C13) How does a propagation of action potential occur in a non-myelinated nerve
A stimulus causes a sudden influx of sodium ion and reverses the charge on the axon membrane causing an action potential and the membrane to depolarised
The localised Electrical circuit established by the influx of sodium ions cause the opening of sodium voltage gated channels a little further along the axon causing depolarisation. Behind the new region of depolarisation the sodium voltage gated channels close and potassium ones open. Potassium ions leave the axon along the electrochemical gradient
Continues along the length of the axon, Repolarisation occurs behind action potential
The axon as a result of repolarisation returns to normality
C13) What is the refectory period of a neuron
After an Action potential there is a short time when the axon cannot be excited again
During this time The voltage gated sodium ion channels remain closed and prevent the movement of sodium ions into the axon
C13) what is the importance of refractory period of a neuron
Because it prevents the propagation of an action potential backwards along the axon as well as forwards
Make sure action potentials are unidirectional
Insures that action potentials do not overlap and occur as a discrete impulse
C13) how does saltatory conduction work
Myelinated axons transfer impulses faster than non-myelinated axons because depolarisation of the axon membrane can only happen at the node of Ranvier
this is the only place sodium ions can pass through the protein channels into the membrane
Larger localised circuits arise between adjacent roads allowing action potential then to jump from one load to another this called saltatory conduction
C13) How does saltatory conduction increase the speed of an electrical impulse
Every time channels open and ions move it takes time so reducing the number of cases this happens speeds up the process
Long term it is more energy-efficient Repolarisation uses ATP in the sodium pump so reducing the amount of repolarisation needed makes the conduction of impulses more efficient
C13) What factors affect the speed at which an action potential travels
Axon diameter – the bigger the axon diameter the faster the impulse transmits because there is less resistance to the flow of ions in the cytoplasm
Temperature-the higher the temperature the faster the nerve impulse because Ions always diffuse faster at high temperatures because up to about 40°C
C13) what is the all or nothing principal of the transmission of an electrical impulse in a neuron
A certain level of stimulus (threshold value) always triggers a response.
If this threshold is reached an action potential is created no matter how large the stimulus is the same sized action potential is triggered. If the threshold is not reached there is no action potential
The size of the stimulus affects the number of action potential is generated in a given time. Large the stimulus the more frequent the action potentials are.
C13) What are the structural components of a synapse
Synaptic cleft- the gap which separates the axon of one neuron from the dendrite of the next neurone
Presynaptic Neurone- Neurone along which the impulse has arrived
Postsynaptic Neurone- Neuron that receives the neurotransmitter
Synaptic knob- The end of the presynaptic Neuron containing mitochondria and endoplasmic reticulum to manufacture neurotransmitters
Synaptic vesicles- vehicles containing neurotransmitters. They fuse with the presynaptic membrane and release their contents into the synaptic cleft
Neurotransmitter receptors- receptor molecules which the neurotransmitter binds to in the postsynaptic membrane
C13) What are the different types of neurotransmitters
Excitatory- neurotransmitters result in the depolarisation Of the postsynaptic nerve by triggering a action potential (acetylcholine)
Inhibitory- neurotransmitters results in the hyperpolarisation of the postsynaptic membrane preventing an action potential to be triggered
C13) How does a impulse transmit across the synapse
Action potential reaches the end of the presynaptic nerve
Depolarisation of the presynaptic membrane causes calcium ion channels to open
Calcium ions diffused into the presynaptic knob
Causes synaptic vesiclesContaining neurotransmitters to fuse with the presynaptic membrane. Neurotransmitters are released into the synaptic class by exocytosis
Neurotransmitters diffuse across the synaptic cleft and binds with the specific receptor molecules on the postsynaptic membrane
Causing sodium ion channels to open allowing sodium ions to defuse into the postsynaptic neurone
Triggering an action potential and the impulse is propagated along the postsynaptic neurone
Neurotransmitters are removed by the stimulus not being maintained. So that other stimulus can arrive and affect the synapse
Neurotransmitters left in the synaptic cleft is removed.
C13) What happens to the neurotransmitter after an action potential is triggered in the postsynaptic neurone
Neurotransmitters are removed by the stimulus not being maintained. So that other stimulus can arrive and affect the synapse
Neurotransmitters left in the synaptic cleft is removed.
acetylcholine is broken down by enzymes, they also release them from the receptors of the postsynaptic membrane
They are take back into the presynaptic knob
The removal of neurotransmitters prevent the response from happening again and allows the neurotransmitters to be recycled
C13) What is the cholinergic synapses and where can it be found
They use the neurotransmitter acetylcholine
Common in the central nervous system of vertebra and at neuromuscular junction where a motoneuron and a muscle cell meet
C13) what is the process of transmission across the cholinergic synapses
1) The arrival of the action potential at the end of the presynaptic nerve causes calcium ion channels to open and calcium ion enters the synaptic knob
2) The increase in calcium ions in the presynaptic neurone causes synaptic vehicles to fuse with the presynaptic membrane therefore releasing acetylcholine into the synaptic cleft
3) acetylcholine Molecules fuse with the receptor sites on the sodium ion channels in the membrane of the postsynaptic Neurone causing the sodium ion channels to open allowing sodium Ions to diffuse in along a concentration gradient
4) The sodium ions generate a new action potential in the postsynaptic nerve
5) acetylcholinesterase hydrolyse acetylcholine into choline and acetyl, They diffuse back into the presynaptic Neurone for recycling and to prevent generating a new action potential in the postsynaptic Neurone
6) ATP is used to re-combine choline and acetyl into acetylcholineStored in vesicles for future use. Sodium ion channels close because of the absence of acetylcholine
C13) What is the role of the signups in the nervous system
Ensure impulses are unidirectional as neurotransmitter receptors are only present on the postsynaptic membrane impulses can only travel from the presynaptic nerve to the postsynaptic nerve
Allow an impulse from one Neurone to be transmitted to a number of Neurons at multiple synapses resulting in a single stimulus creating in number of simultaneous responses
A number of neurons may feed into the same synapse with a single postsynaptic Neurone resulting in a give stimuli from different receptors interacting to produce a single result
C13) what is summation and control of a synapse
Stimulus from a presynaptic Neuron causes the release of some neurotransmitters Into the synapse.
Some synapses however, the amount of neurotransmitters from a single impulse is not enough to trigger an action potential in the postsynaptic neurone because the threshold level isn’t reached
Summation: If the amount of neurotransmitters build up significantly to reach the threshold then it will trigger an action potential
C13) What is spatial summation of a synapse
Occurs when a number of presynaptic neurons connect to one postsynaptic neuron. Each releases neurotransmitters which build up to a high level to trigger an action potential
C13) what is temporal summation of a synapse
Occurs when a single presynaptic nerve releases neurotransmitters as a result of an action potential several times in a short period. The buildup in the synapse reaches the threshold value and triggers the action potential in the postsynaptic neurone
C13) what are the structural organisations of the nervous system of a mammal
Central nervous system- consists of the brain and the spinal cord
peripheralNervous system- consists of all the Neurons that connects to the central nervous system to the rest of the body (sensory neurons, Motor neurons
C13) What are the functional organisations of the nervous system in a mammal
Somatic nervous system- system is under conscious control. Used when you voluntarily decide to do something. (Contraction of muscles to move the arm)
Autonomic nervous system- works constantly. Under subconscious control and is used when the body does something automatically without you deciding – involuntary (causes the heartbeat by carrying nerve impulses to the Cardiac muscle)
C13) how is the Autonomic nervous system further organised functionally
Sympathetic nervous system- is if the outcome increases activity (increase heart rate)
Parasympathetic nervous system- if the outcome decreases activity (a decrease in heart or breathing rate after exercise)
C13) what is the gross structure of the Brain
Surrounded by a protective membrane called the meninges
Cerebrum- controls voluntary activities such as learning, memory, personality and conscious thought
Cerebellum- controls unconscious functions such as posture, balance and non-voluntary movement
Medulla oblongata -used in autonomic control for example it controls heart rate and breathing rate
Hypothalamus-regulatory control for temperature and water balance
Pituitary gland-stores and releases hormones that regulate many body functions
C13) what is the important information about the cerebrum
Receives sensory information and then sends impulses along motoneurons to affecters to produce a response
Responsible for coordinating the body voluntary response
Highly convoluted which increases its surface area considerably therefore increasing its capacity for complex activities
The left and right halves are known as the cerebral hemisphere. Each hemisphere has specific functions devoted to specific areas
The outer layer of the cerebral hemisphere is known as the cerebral cortex.
C13) what is the importance of the frontal and pro frontal lobe of the cerebral cortex
Sophisticated processes such as reasoning and decision-making occur in the frontal and profrontal lobe of the cerebral cortex
C13) what is the importance of sensory areas within the cerebral hemisphere
Sensory areas within cerebral hemispheres receive information from receptor cells in sensory organs. The size of the sensory area is proportional to the number of receptor cells present in that part of the body
Then is passed onto the part of the brain known as the associated area to be analysed and acted upon
Impulses then come to the motor area where motoneurons send out impulses
The size of the motor area is proportional to the relative number of motor endings in it
The main region that controls movement is the primary motor cortex located at the back of the frontal lobe
C13) What happens at the base of the brain
Impulses from each side of the brain cross.
The left hemisphere receives impulses from the right hand side of the body and the right hemisphere receives impulses from the left hand side of the body
Impulses from the eye pass to the visual area in the occupational lobe. Impulses from the right side of the field of view in each eye are sent to the visual cortex in the left hemisphere and vice versa
C13) what is the important information about the Cerebellum
Concerned with the control of muscular movement, body posture and balance – does not initiate movement but coordinates it
If this part of the brain is damaged a person suffers from Jackie and uncoordinated movement
Receives information from organs of balance in the ears and information about the tone of muscle and tendons
Relate this information to the cerebral cortex, to the area of motor control
C13) what is the important information about the Medela oblongata
Contains many important regulatory centres of the autonomic nervous system
Controls reflex actions such as ventilation and heart rate
Controls activities such as swallowing and coughing
C13) what is the important information about the hypothalamus
Main controlling region for the autonomic nervous system
Two controls- one for the parasympathetic and one for the sympathetic nervous system
Functions include:
Controlling complex patterns of behaviour such as feeding, sleeping and aggression
Monitoring the composition of blood plasma such as the concentration of blood and blood glucose
Producing hormones –it is an endocrine gland so it produces hormones such as antidiuretic hormone
C13) what is the important information about the pituitary gland
Found at the base of the hypothalamus
Control most of the glands in the body
Divided into two sections:
Anterior pituitary –produces six hormones including follicle-stimulating hormone which is involved in the reproduction and growth hormones
Posterior pituitary- Stores and releases hormones produced by the hypothalamus, such as antidiuretic hormone
C13) How does a knee-jerk reflects occur
A spinal reflex meaning that the natural circuit only goes up to the spinal-cord
The latest tap just below the kneecap
Stretches the patellar tendon and acts as a stimulus.
Stimulus initiates a reflex arc that causes the extensor muscle on top of the thigh to contract
At the same time a relay neurone inhibits the motor neuron of the flexor muscle causing it to relax
The contraction coordinated with the relaxation of the antagonistic flexor hamstring
Causing the leg to kick
The absence of the reflex may indicate nervous problems and Multiple Sclerosis of the legs
C13) why does a blinking reflects occur
Because of the cornea is stimulated to prevent it from being damaged due to foreign bodies this type of response is known as a corneal reflex
Blink reflex also occurs when sounds great than 40 to 60 dB are heard or as a result of very bright light to protect the lens and retinal is known as an optical reflex
A blinking reflex is a cranial reflex, occurs in the brain
C13) how does a blinking reflex occur
When the cornea is irritated by foreign bodies, The stimulus triggers an impulse along a sensory Neuron
The impulse then passes through a relay neuron in the lower brainstem
Impulses are then sent along branches of the motor neuron to initiate a motor response to close the eyelids
The reflex initiates a consensual response- means that both eyes are closed in response to the stimulus
Doctors test for blinking reflexes when examining unconscious patients. If the reflexes present it indicates the lower brainstem is functioning.
Used to determine whether patient is brain-dead
C13) why are reflexes considered important for survival
Reflexes avoid the body from being harmed or reduce the severity of any damages. For example the iris constricts the pupil to prevent light from damaging the retina
Bringing involuntary responses- the decision-making region of the brain is not involved therefore the brain is able to deal with more complex responses preventing the brain being overloaded
Not have to Learned- they are present at birth and therefore provide immediate protection
Extremely fast- the reflex arc is very short normally involves one or two synapses
Many reflexes are considered to be everyday actions such as the control of digestion
C13) What are the types of muscle
Skeletal muscle - makes up the bulk of body muscle tissue. The cells responsible for movement for example the biceps and triceps
Cardiac muscle - are found only in the heart. Are myogenic meaning they contract without the need for a nervous stimulus causing the heart to beat in a regular rhythm
Involuntary muscle (smooth-muscle)- found in many parts of the body for example the walls of hollow organs such as the stomach and bladder
C13) what are the differences between skeletal, cardiac and involuntary muscle
The appearance of fibre in skeletal muscle is striated while cardiac muscle have specialised striated tissue and within involuntary muscle it is non-striated
Control of skeletal muscle is conscious and voluntary while cardiac muscle and involuntary muscles are in voluntarily controlled
Arrangement of fibres in skeletal muscle is regular so that muscles can contract in One Direction. They arrangement of the fibres in the cardiac muscle is branched and interconnected resulting in simultaneous contraction. In voluntary muscles have no regular arrangement different cells can contract in different directions
The structure of skeletal muscle is striated and fibre are tubular and multinucleated. The cardiac muscle does have striations but are more fainter than skeletal muscle and Fibres are branched and uninuclated. In voluntary muscles have no cross-section striations and fibres are spindle shaped and uninuclated
C13) what is the structure of a muscle fibre
Skeletal muscle is made up of bundles of muscle fibres
Muscle fibres are enclosed within a plasma membrane known as the sarcolemma
Muscle fibres contain nuclei which are longer than normal cells formed because of individual embryonic muscle cells fusing together allowing the muscle to be stronger as the junctions between adjacent cells are a point of weakness
The shared cytoplasm within a muscle fibre is called sarcoplasm
Parts of the sarcolemmal are folded inwards known as transverse to help spread electrical impulses throughout the sarcoplasm Allows the whole fibre to receive the impulse to contract at the same time
Muscle fibre have loads of mitochondria to provide the ATP needed for muscle contraction they have a modified version of endoplasmic reticulum known as the sarcoplasmic reticulum. Contains calcium ions require for muscle contraction and is throughout the whole muscle fibre
C13) what is the structure of myofibrils
Every muscle fibre contains many myofibrils
They are long cylindrical organelles made of proteins and specialised for contraction.
On the phone they provide almost no force but collectively they are very powerful.
Myofibrils all lined up in parallel to provide maximum force when they contract together
C13) what type of proteins make up myofibrils
Actin- the thinner filament. Consists of two strands twisted around each other
Myosin- the thicker filament. Consist of long rod shaped fibres with bulbous heads that project to one side
C13) what is the light band of a myofibril
Area appears light as they are the region where the acting and myosin filaments do not overlap
Known as isotopic bands or I bands
C13) what is the dark bands band of a myofibril
Area appear darker because of the presence of thick myosin filaments
Edges are particularly dark as the myosin is overlapped with acting
Anisotropic Band or A band
C13) what is the z-line of a myofibril
Line found at the centre of each light band
The distance between adjacent deadlines is called a sarcomere
The sarcoma is the functional unit of myofibril. When a muscle contracts the sarcomere shortens
C13) what is the H-zone of a myofibril
Lighter coloured regions found in the centre of each dark band
Only myosin filaments are present at this point
When the muscle contracts the H-Zone decreases
C13) what is the sliding filament model
The acting and myosin filaments within the myofibril has to slide past each other
Therefore muscle contraction is usually described as this
C13) what is the result of the myosin filament pulling the actin filament inwards towards the centre of the sarcomere cause
The light band becomes narrow
The sideline moves closer together shortening the sarcomere
The H zone becomes narrower
The dark band remains the same width as the myosin filaments themselves are not shortened but overlap the actin filament by a greater amount
The simultaneous contraction of loads of sarcomeres mean that the myofibril and muscle fibres contract. Therefore there is enough force to pull on a bone and cause movement
When is sarcomere returned to their original length the muscle relaxers
C13) What is the structure of myosin
Filaments have globular heads that are hinged which allow them to move back and forwards
The head is a binding site for actin and ATP
Tales of several hundred myosin molecules are aligned together to form a myosin filament
C13) What is the structure of actin
Actin filament have a binding site for myosin heads called actin-myosin binding site
The binding sites are often blocked by the presence of other proteins called tropomyosin which are held in place by the protein troponin
C13) What happens to actin and myosin when the muscle is that rest
When muscle is at rest the actin-myosin sites are blocked by tropomyosin.
The myosin heads cannot bind to the actin so the filament cannot slide past each other
C13) what happens to acting and myosin when the muscle is contracted
When the muscle is contracted The myosin heads form bonds with acting filaments known as actin-myosin cross bridges.
The myosin head changes angle in union pulling the actin filament along the myosin filaments.
Myosin and then detaches from the actin and its heads return to its original angle using ATP.
The myosin reattach is further along the actin filament and the process occurs again
C13) how does the neuromuscular junction cause a muscle contraction to occur
Triggered when an action potential arrives at a neuromuscular junction (point where a motor neurone and a skeletal muscle fibre meet)
Many neuromuscular junction is along the length of the muscle to ensure all muscle fibres contract simultaneously.
If a strong force is needed a large number of Motor units are stimulated whereas only a small number are stimulated if a small force is required
When an action potential reaches the neuromuscular junction. It stimulates calcium ion channels to open, calcium ions diffused into the synaptic knob where they cause synaptic vesicles to fuse with the presynaptic membrane
Acetylcholine is released into the synaptic cleft by exocytosis and defuses across the synapse binding to receptors on the sarcolemma.
Opening sodium ion channels and resulting in depolarisation
C13) what happens if only one neuromuscular junction was available
If only one existed the muscle fibre would not contract together therefore the contraction of the muscle would not be powerful.
Also be much slower as a wave of contraction would have to travel along the muscle to stimulate the individual fibres to contract
C13) what is a motor unit
All the muscle fibres supplied by a single neuron are known as motor unit - the fibres act as a single unit
C13) what happens to Acetylcholine after an action potential passes neuromuscular junction
It is broken down by Acetylcholinesterase into choline and ethanolic acid
This prevents the muscle being overstimulated
Choline and ethanolic acid diffuse back into the neuron where they are re-combined into Acetylcholine using energy provided by mitochondria
C13) what happens to the sarcolemma when the electrical current passes the intramuscular junction
depolarisation of the sarcolemma travels deep into the muscle by spreading through the t-tubules which are in contact with the sarcoplasmic reticulum containing stored calcium ions which is actively absorbed by the sarcoplasm
As the action potential gets to the sarcoplasmic reticulum stimulating the calcium ions channels to open. Calcium ion diffuse dawn their concentration gradient into the sarcoplasm
The calcium ions bind to troponin causing it to change shape. This pulls on the tropomyosin moving it away from the actin-myosin binding site on the actin filament. The myosin head binds to the actin filament forming a actin-myosin Crossbridge
C13) what happens after the myosin heads attach to the actin filament
The head flex, pulling the actin filament along. The molecule of ADP bound to the myosin head is released. An ATP molecule can now bind the myosin head causing the head to detach from the actin filament
The calcium ions present in the sarcoplasm activate ATPase activity of the myosin. Hydrolysing the ATP to ADP and phosphate releasing energy which the myosin heads used to return to its original position
The myosin heads can now attach itself to another actin-myosin binding site further along the actin filament and the cycle is repeated while the muscle remains stimulated. During a period of stimulation many acts in myosin bridges form and break pulling the actin filament along, shortening the sacrament and causing the muscle to contract
C13) how and why is energy used during muscle contraction
Provides energy for muscle contraction is by the hydrolysis of ATP into ADP and phosphate
The energy is required for the movement of the myosin heads and to enable the sarcoplasmic reticulum To actively re-absorb calcium ions from the Sarcoplasm
C13) What are the different ways energy is supplied for muscle contraction
Aerobic respiration- most of the ATP used is generated from ATP during oxidative phosphorylation. The reaction happens in the mitochondria which are plentiful in muscles. Only occur in the presence of oxygen. is used for long periods of low intensity exercise
Anaerobic respiration- in very active muscles oxygen is used more quickly than the blood supply can replace it. ATP is therefore generated anaerobically. ATP is made by glycolysis but as no oxygen is present, The pyruvate which is produced is converted into lactic acid which can quickly buildup in the muscles resulting in fatigue. Is used for short periods of high intensity exercise
Creation phosphate- Body can generate ATP by using the chemical creation phosphate which is stored in the muscles. To form ATP, ADP has to be phosphorylated which creation phosphate acts as a reserve supply off. phosphate which is available immediately. This system generates ATP rapidly, but the store of phosphate is used up quickly. This is used for short bursts of vigourous exercise. when the muscle is relaxed the creation phosphate is replenished using phosphate from ATP
C17) What is the importance of ATP production in photosynthesis
It provides the energy needed to build organic molecules like glucose
Energy is used to form chemical bonds in ATP which are then broken to relieve the energy needed to make bonds as glucose is formed
C17) What is the importance of ATP production in respiration
Organic molecules such as glucose or broken down and the energy released is used to synthesise ATP
ATP is then used to supply the energy needed to break Bonds in the metabolic reactions of cells
C17) What is chemiosmosis
Process by which ATP is produced in both photosynthesis and respiration
Involves the diffusion of protons from a region of high concentration to a region of low concentration through a semipermeable membrane
Movement of the protons as they flow down the concentration gradient releases energy that is used in the attachment of an inorganic phosphate to ADP forming ATP
Depends on the creation of a proton concentration gradient.The energy to do this comes from high energy electrons
C17) what are the ways in which electrons are raised to higher energy levels
Electrons present in pigment molecules are excited by absorbing light from the Sun
High energy electrons are released when chemical bonds are broken in respiratory substrate molecules
Excited electrons pass through a electron transfer chain and are used to generate a proton (H+) gradient
C17) What are the stages of chemiosmosis with the use of an electron transport chain
An electron transport chain is made up of a series of electron carriers with progressively lower energy levels. As higher energy electrons move from one Carrier to another, energy is released which is used to pump protons Across a membrane creating a concentration difference and a proton gradient. The proton gradient is maintained because of the permeability of the membrane to hydrogen ions
Protons can move down the concentration gradient through hydrophilic membrane channels linked to the enzyme ATP synthase. The flow of protons through these channels provide the energy used to synthesise ATP from ADP and phosphate ions
C17 what are the structures and functions of chloroplast
The network of membranes present within the chloroplast provides a large surface area to maximise the absorption of light essential for photosynthesis
Membranes form flattened sacs called thylakoids which are stacked to form grana which are joined by membrane channels called lamella
Light is absorbed by complex pigments such as chlorophyll embedded within the thylakoids membrane
The fluid include in the chloroplast is called the stroma and is the site of many chemical reaction resulting in the formation of complex organic molecules
C17) what is the function of chlorophyll in photosynthesis
Pigment molecules Absorb specific wavelengths of light and reflect others. Different pigments absorb and reflect on different wavelengths that is why they have different colours
Primary pigment is chlorophyll in photosynthesis, mainly absorbs red and blue light and reflects Green light. Large quantities of chlorophyll is the reason for the green colour implants
A number of different pigments that absorb light, The primary pigment is chlorophyll A and other pigments like chlorophyll b,xanthophyll absorb different wavelengths of light than those absorbed by chlorophyll A. Combinations of pigments are the reason for different shades and colours of leaves
C17) how is a photosystem constructed
chlorophyll b and xanthophyll are embedded in the thylakoids membrane of the Chloroplast, these and other proteins and pigments form a light harvesting system (Antennae complex) which has the role to absorb or harvest light energy in different wavelength and transfer this energy quickly and efficiently to the reaction centre
Chlorophyll a is located in the reaction centre which is where the reactions involved in photosynthesis take place
The light harvesting system and the reaction centre is collectively known as a focus system
C17) what happens to the protons that are released during photolysis
The protons (H+) is released into the Lumen of the thylakoids increasing the proton concentration across the membrane.
They moved back through the membrane down a electrochemical gradient driving the formation of more ATP.
Once the hydrogen ions are returned to the stroma they are combined with NADP with an electron from photosystem one to form reduced NADP.
Used by the light independent reaction of photosynthesis.
This process removes hydrogen ions from the stroma so it helps to maintain the proton gradient across the thylakoids membranes
C17)What happens during non-cyclic phosphorylation of photosynthesis
2 photosystems are involved with non-cyclic phosphorylation. The reaction centre of photosystem 2 absorbs wavelength of 680nm while photosystem 1 absorbs higher wavelengths of 700nm
The light absorbed excites electrons and the reaction centre of the photo system
The excited electrons are released from the reaction centre of PS2 and are passed to an electron transport chain. ATP is produced by the process of Chemiosmosis.
The electrons lost from the reaction centre of PS2 are replaced from water molecules are broken down using energy from the Sun
Excited electrons are released from the reaction centre of PS1 passing another Electron transport chain, and ATP is produced again by Chemiosmosis. The electrons lost from the reaction centre are replaced by electrons travelling from PS2
The electrons leaving the electron transport chain from PS1 are excepted with hydrogen ions by the coenzyme NADP forming a reduced NADP
C17) what is the importance of reduced NADP
Provides the hydrogen or reducing power in the production of organic molecules such as glucose in the light independent stage
C17) what occurs during photolysis
Oxygen evolving complex which forms part of PS2 is an enzyme that catalyse is the breakdown of water
Water molecules are split into hydrogen ions, electrons and oxygen molecules using energy from the Sun
The electrons replace the electrons lost from the reaction centre of PS2
Oxygen gas is released as a by product
The protons are released into the lumen of the thylakoids increasing the proton concentration across the membrane. As they move back through the membrane down a concentration and electrochemical gradient to drive the formation of more ATP
Once the hydrogen ions are released to the stroma they combine with NADP and an electron to form a reduced NADP
This process removes hydrogen ions from the stromuhr to help maintain the proton gradient across the thylakoids membrane
C17) what is the equation for photolysis
H2O = 2H+ + 2e- + 0.5O2
C17) how does cyclic phosphorylation occur
The electrons leaving the electron transport chain off the PS1 can be returned to PS1 instead of being used to form reduce NADP
PS1 can still lead to the production of ATP without any electrons being supplied from PS2
Reduced NADP is not produced when this happens
C17) what is the light independent stage of photosynthesis
Takes place in the stroma of chloroplasts
Uses carbon dioxide as a raw material
The products of the light dependent stage - ATP and reduced NADPAre required
Organic molecules are produced in reactions within the Calvin cycle
C17) what are the stages of the Calvin cycle
Carbon dioxide enters the intercellular spaces within the spongy Mesophyll of leaves by diffusion from the atmosphere into the stomata. Defuses into the stroma of chloroplasts where it combines with a five carbon molecule called Ribulose bisphosphate. The carbon in carbon dioxide is therefore fixed into an organic molecule
The enzyme Ribulose bisphosphate carboxylase catalyses the reaction and an unstable six carbon intermediate is produced.
The unstable six carbon compound breaks down forming 2 3 carbon glycerate3 phosphate molecules
Each GP molecule is converted to another three carbon molecule, triose phosphate using a hydrogen atom from reduced NADP and energy supplied by ATP From the light Dependent reaction
TP is a carbohydrate, a three carbon sugar
TP molecules are recycled to regenerate Ribulose bisphosphate so the Calvin cycle can continue and is the starting point for complex biological molecules
C17) How important is ruBisCO to photosynthesis
RuBisCO is a key enzyme in photosynthesis, a very ineffective enzyme as it is completely inhibited by oxygen so a lot of it is needed to carry out photosynthesis successfully.
C17) what are the three summarise steps to the Calvin cycle
Fixation - carbon dioxide is fixed in the first step
Reduction - GP is reduced to TP by the addition of hydrogen from reduced NADP using energy supplied by ATP
Regeneration - Ribulose bisphosphate is re-generated from recycled TP
C17) How does the regeneration of Ribulose bisphosphate occur
For one glucose molecule to be produced six carbon dioxide molecules have to enter the Calvin cycle
Resulting in the production of 12 TP molecules, two of which will be removed to make glucose molecules
Meaning that 10 TP molecules are recycled to generate six Ribulose bisphosphate molecules
10 * 3-Carbon TP = 30 carbons/ 5 carbon Ribulose bisphosphate = 6
Energy is supplied by ATP for the reaction involved in regenerating Ribulose bisphosphate
C17) what are the three limiting factors of photosynthesis
Light intensity
Carbon dioxide concentration
Temperature - affects the rate of enzyme controlled reactions.
c17) how does the stomata affect photosynthesis
Will close to avoid water loss by transpiration during dry spells
The closure of the stomata stops the diffusion of carbon dioxide into the plant reducing the rate of the light independent reaction and stopping photosynthesis
C17) why is water not considered to be a limiting factor in photosynthesis
Because for water potential to have become low enough to limit the rate of photosynthesis the plant will have closed it’s stomata and ceased photosynthesis and therefore unlikely to survive
C18) what is cellular respiration
The carbon framework of glucose is broken down and the carbon hydrogen bonds broken
The energy released is then used in the synthesis of ATP by Chemiosmosis
Prokaryotic cells have a similar process but they do not have mitochondria so many of the reactions take place on the cell membrane
C18) What is glycolysis
Occurs in the cytoplasm of the cell
Does not require oxygen – it is an aerobic process
Glucose, six carbon sugar is split into two smaller, three carbon pyruvate molecules
ATP and reduced NAD are also produced
C18) what are the main steps in glycolysis
Phosphorylation - requires two molecules of ATP. Two phosphate released from the two ATP molecules are attached to a glucose molecule forming hexose bisphosphate
Lysis - this destabilises the molecule causing it to split into two triose phosphate molecules
Phosphorylation - another phosphate group is added to each triose phosphate forming to triose bisphosphonate. The phosphate groups come from free inorganic phosphate ions present in the cytoplasm
Dehydrogenation and formation of ATP - the 2 triose bisphosphate molecules are then oxidised by the removal of hydrogen atoms (Dehydrogenation) to form two pyruvate molecules. NAD coenzymes except the removed hydrogens - they are reduced forming reduced NAD molecules. 4 ATP molecules are produced using phosphates from the triose bisphosphonate molecule
C18) what is substrate level phosphorylation
The formation of ATP without the involvement of an electron transport chain.
ATP is formed by the transfer of a phosphate group from a phosphorylated intermediate to ATP
C18) what is the net yield of ATP in glycolysis
Two molecules of ATP from glycolysis
As to ATP molecules are used to prime the process at the beginning and for ATP molecules are produced
C18) how is the mitochondria structured for aerobic respiration
Crusta our projections of the inner membrane which increases the surface area available for oxidative phosphorylation
Inner mitochondrial membrane contains electron transport chain and ATP synthase
Matrix contains enzymes for the Krebs cycle and the link reaction also contains mitochondrial DNA
In a membrane space, proteins are pumped into the space by the electron transport chain. The space is small so the concentration builds up quickly
C18) what is oxidative decarboxylation
First step in aerobic respiration
Sometimes referred to as the link reaction because it is the step that links anaerobic glycolysis occurring in the cytoplasm to the aerobic steps of respiration occurring in the mitochondria
C18) what are the steps of oxidative decarboxylation
In eukaryotes pyruvate enters the mitochondrial matrix by active transport via specific carrier proteins
Pyruvate undergoes oxidative decarboxylation
Carbon dioxide is removed (decarboxylation) along with hydrogen (oxidation)
The hydrogen atom is removed or excepted by NAD. NAD is reduced to form NADH or reduced NAD
Resulting in a 2 carbon acetyl group which is bound by coenzyme a forming acetylcoenzyme A
Acetyl group is known as ethanoyl group
C18) What happens to the products of oxidative decarboxylation
acetylcoenzyme A delivers the acetyl group to the next stage of aerobic respiration known as the Krebs cycle
The reduced NAD is used in oxidative phosphorylation to synthesise ATP
The carbon dioxide produced to either diffuse away and be removed as metabolic waste or in autotrophic organisms may be used as raw material in photosynthesis
C18) What is the krebs cycle
Takes place in the mitochondrial matrix
Each complete cycle breaks down and acetylgroup
Involves decarboxylation, dehydrogenation and substrate level phosphorylation
The hydrogen atoms released of picked up by the coenzyme NAD and FAD
Carbon dioxide is a byproduct of the reaction
ATP produced is available for use by energy requiring processes
Reduced NAD and reduced FAD produced are used in oxidative phosphorylation to produce large quantities of ATP by Chemiosmosis
C18) What are the stages of the Krebs cycle
acetylcoenzyme A delivers an acetyl group to the kerbs cycle. The two carbon acetyl group combines with four carbon oxaloacetate to form six carbon citrate
The citrate molecule undergoes decarboxylation and dehydrogenation producing one reduced NAD and carbon dioxide. A five carbon compound is formed
The five carbon compound undergoes further decarboxylation and dehydrogenation eventually regenerating oxaloacetate and the cycle continues. Producing carbon dioxide, 2 reduced NAD, One reduced FAD and ATP is also produced by substrate level phosphorylation
C18) what is the importance of coenzymes in respiration
Coenzymes are required to transfer protons, electrons and functional groups between many of enzyme catalysed reactions
Redox reactions have an important role in respiration and without coenzymes transferring electrons and protons between these reactions many respiratory enzymes would not function
NAD and FAD are both coenzymes that accept protonsAnd electrons releasing during breakdown of glucose in respiration
C18) what is the difference between NAD and FAD
NAD takes part in all stages of cellular respiration but FAD the only except hydrogens in the Krebs cycle
NAD except one hydrogen and FAD except two hydrogens
Reduced NAD is oxidated at the start of the electron transport chain releasing protons and electrons while reduced FAD is oxidised further along the chain
Reduced NAD results in the synthesis of three ATP molecules but reduced FED results in the synthesis of only two ATP molecules
C19) how does oxidative phosphorylation occur
The hydrogen atoms collected by coenzymes NAD and FAD are delivered to the electron transport chain present in the membrane of the Cristae
Hydrogen atoms dissociate into hydrogen ions and electrons.The high energy electrons are used to synthesise ATP by chemiosmosis
Energy is released during redox reactions as the electrons reduce and oxidised electron carriers as they flow along the electron transport chain. The energy is used to create a proton gradient leading to the diffusion of protons along ATP synthase resulting in ATP synthesis
At the end of the electron transport chain electrons combined with hydrogen ions and oxygen to form water.Oxygen is the final electron exceptor and the electron chain cannot operate without oxygen
C18) what is oxidative phosphorylation
The phosphorylation of ADP to form ATP is dependent on electrons moving along electron transport chain. This requires the presence of oxygen
Oxidative phosphorylation
C18)What is fermentation
Process by which complex organic compounds are broken down into similar inorganic compounds without the use of oxygen or the involvement of an electron transport chain
Organic compounds such as glucose are not fully broken down so fermentation processes less ATP than aerobic respiration
Small quantities of ATP produced is synthesised by substrate level phosphorylation
C18) what is alcohol fermentation
Different type of fermentation for different organisms
Occurs in yeast and some plant root cells
The end products are ethanol and carbon dioxide
C18)What is lactate Fermentation
A different type of fermentation
Lactate fermentation results in the production of lactate and is carried out in animal cells
C18) why does fermentation occur
There is no oxygen to act as a final electron Exceptor at the end of the electron transport chain in oxidative phosphorylation, the flow of electrons stop meaning the synthesis of ATP by Chemiosmosis stops
As the flow ofElectrons has stopped, the reduced NAD and FAD are no longer able to be oxygenated because there is nowhere for the electrons to go
Means FAD and NAD cannot be regenerated and so the decarboxylation and oxidisation of pyruvate and the Krebs cycle comes to a halt as there are no coenzymes available to except the hydrogen being removed
The process of fermentation allows NAD for glycolysis
C14Why is the pituitary gland in close proximity to the hypothalamus
To ensure the nervous and hormonal responses of the body are closely linked and coordinated
C14)What is the importance of the pituitary gland
Produces growth hormones which control growth of bones and muscles
Antidiuretic hormone which controls reabsorption of water in kidneys
Genodotropin Which control development of the ovaries and testes
C14) what is the pineal gland
Produces melatonin which affects reproductive development and daily cycles
C14) what is the importance of the thyroid gland
Produces thyroxine which controls rate of metabolism and rate that glucose is used up in respiration and promotes growth
C14) what is the importance of the thymus gland
Produces thymosin which promotes production and maturation of white blood cells
C14) what is the importance of the adrenal glands
Produces adrenaline which increases heart rate and breathing rate and raises blood sugar levels
C14) what is the importance of the pancreas gland
Produces insulin which converts excess glucose into glycogen in the liver
Glucagon which converts glycogen back into glucose in the liver
C14) what is the importance of the testes
Produces testosterone which controls sperm production and secondary sexual characteristics
C14) what is the importance of the ovaries
Produces oestrogen which controls ovulation and secondary sexual characteristics
And progesterone which prepares the uterus lining to receive an embryo
C14) what is the difference between endocrine glands and exocrine glands
Exocrine glands secrete chemicals through ducts into organs or to the surface of the body
Endocrine glands secrete chemicals directly into the blood
C14) what are hormones
Referred to as chemical messengers because they carry information from one part of the body to another
Can be steroids, proteins, glycoproteins, Polypeptide
Hormones are secreted directly into the blood when a gland is stimulated which can occur because of a change in concentration of a particular substance, as a result of another hormone or a nerve impulse
C14) how does hormone action occur
Once secreted, hormones are transported in the blood plasma.
The hormones diffuse out of the plasma and binds to specific receptors for that hormone, found on the membrane or in the cytoplasm of the cell in the target organ, Known as target cells
Once bound to the receptor the hormones emulate the target cells to produce a response
C14) how does a steroid hormone affect a target cell
Are lipid soluble
Passed through the lipid compound of the cell membrane and bind to steroid hormone receptors to form a hormone receptor complex
The receptors may be present in the cytoplasm or the nucleus depending on the hormone
The hormone receptor complex formed acts as a transcription factor which in turn facilitate or inhibit the transcription of a specific gene
