unit 1: structure and function of cells and tissues Flashcards

Question

describe the structure and function of the tonoplast membrane

Answer 1

structure- semi-permeable cytoplasmic membrane that surrounds the vacuole function- involved in controlling movement of molecules into and out of the cell

Answer 2

structure- non-pigmented organelles that occur in the cytoplasm of plant cells function- they produce and store starch withing internal membrane compartments

Answer 3

structure- the outermost layer of the cell wall that is made of pectin function- cements together the primary cell walls of adjacent plant cells

Answer 4

structure- channels of cytoplasm that pass between the adjacent cell walls of plant cells function- allows fast communication and exchange of substances between cell

Answer 5

- sections of the cell wall which adjacent plant cells can exchange fluid or communicate through

Answer 6

- this is a prokaryote made of a single cell with no membrane-bound organelles

Answer 7

- plasmids - capsule - ribosome - nucleoid - cell wall

Answer 8

- irregularly shaped region of cytoplasm where loops of bacterial DNA is located

Answer 9

- these are double stranded DNA in a circular structure, often containing additional genes that help the bacterium's survival - they can also be exchanged between bacterial cells via conjugation

Answer 10

- the wall is made of a long chained molecule that is made up of a sugar and amino acids called peptidoglycan which provides mechanical strength

Answer 11

- this is a polysaccharide layer outside the cell wall - it protects cells from drying out, being engulfed by, for example, white blood cells and it also helps to stick to surfaces

Answer 12

- they both make proteins but prokaryotic ribosomes are 70S ( S standing for Svedberg which is a measure of size by rate of sedimentation )

Answer 13

- the degree to which the size of an image is larger than the actual specimen

Answer 14

- the degree to which it is possible to distinguish between two objects that are very close together ( the smallest separation distance )

Answer 15

total magnification = magnification of eyepiece lens x magnification of objective lens - the eyepiece lens usually has a magnification of x10 and the objective lens is normally x100 so the greatest total magnification is normally around x1000

Answer 16

actual image = image size / magnification magnification = image size / actual size image size = actual size x magnification

Answer 17

cm to mm = x10 mm to um = x1000 um to nm = x1000

Answer 18

nm to um = / 1000 um to mm = / 1000 mm to cm = / 10

Answer 19

1. chop a small piece of onion on the chopping board / tile using a scalpel 2. gently remove the single cell epidermis layer from the inside of the onion slice using forceps 3. carefully cut a piece of epidermis about 5mm by 5mm using the scalpel and place it gently onto a clean glass of slide 4. add a few drops of iodine to the sample and then place a glass coverslip gently down on top of it 5. put the slide on the stage of the microscope and then focus it on the cells using the 4x lens 6. change to the 10x lens, focus and then estimate the number or cells across the field of view e.g. 4.5 cell lengths and 8.5 cell widths 7. make a labelled drawing of one cell and label the cytoplasm, nucleus, cell membrane and cellulose cell wall

Answer 20

1. gently swab the inside of one of your cheeks using a cotton bud to rub off a few of the lining cells 2. rub the swapped cotton bud over a clean slide and then put the cotton bud in disinfectant 3. add a few drops of methyl blue to the sample and then place a coverslip gently down on top of it 4. put the slide on the stage of the microscope and then focus in on your cheek cells using the 4x lends ( they will just look like tiny blue dots ) 5. change to the 10x lens, focus, and then change to the 40x lens ( they should look like blue fried eggs ) 6. make a labelled drawing of one cell and label the cytoplasm, nucleus and cell membrane

Answer 21

- this is a microscope that uses optical lenses and a light source to view a 3D image, typically of colour - it is used for examining tissues and counting cells either living or dead

Answer 22

magnification = x2000 resolution = 200 nm or 0.2 micrometres

Answer 23

£300 - 10k

Answer 24

1. lenses focus rays of light and magnify the view of a thin slice of specimen 2. different structures absorb different amounts of wavelengths of light 3. reflected light it transmitted to the observer via the objective lens and eyepiece

Answer 25

- so that light or an electron beam can pass through it

Answer 26

- to protect the specimen and also the lens if they touch

Answer 27

- as they help to distinguish different features in the specimen

Answer 28

- iodine - methyl blue

Answer 29

- a microscope that uses beams of electrons instead of light - the electrons have to be in a vacuum as they cannot ordinarily travel a certain distance in air - they produce a 2D image of only dead specimens as it has a significantly higher magnification than a light microscope

Answer 30

- 100nm or 0.1 micrometre

Answer 31

£1 million, and needs a highly trained operator

Answer 32

- this is a transmission electron microscope that shows 2D images of ultrastructure's - uses a wax stain - its maximum magnification is x500,000 - its max resolution is 0.5nm

Answer 33

1. pass a high energy beam of electrons through a thin slice of specimen 2. more dense structures appear darker since they absorb more electrons 3. focus image onto a fluorescent screen or photographic plate using magnetic lenses

Answer 34

- this is a scanning electron microscope that shows 3D images of external surfaces of cells and tissues - uses heavy metals ( gold ) as a stain - it's max magnification is x100,000 - it's max resolution is 0.1nm

Answer 35

1. focus a beam of electrons onto a specimens surface using electromagnetic lenses 2. reflected electrons hit a collecting device and are amplified to produce an image on a photographic plate

Answer 36

- specialised cells are cells that have a special shape or special features to carry out a certain job in an organism

Answer 37

- sperm cell - egg cell - red blood cell - white blood cell - root hair cell - palisade mesophyll cell

Answer 38

1) the sperm head contacts the zona pellucida and the acrosome reaction occurs- enzymes digest the zona pellucida as the acrosome fuses with the cell membrane of the sperm and releases the digestive enzymes 2) the sperm head fuses with the cell membrane of the egg cell, this allowing the sperm nucleus to enter the egg cell 3) the cortical reaction occurs which then hardens the zona pellucida and prevents polyspermy ( more than one sperm entering ) 4) the nuclei fuse and a full set of chromosomes is restores, this forming a diploid zygote

Answer 39

- the main function of sperm cells is to fertilise the female egg cell to form a zygote ( sexual reproduction )

Answer 40

acrosome ( head )- contains digestive enzymes which break down the zona pellucida and allows sperm to penetrate the egg haploid nucleus- allows the restoration of the full set of chromosomes ( 23 ) at fertilisation mid region- contains many mitochondria to provide energy for rotation of the flagellum which enables the cell to move undulipodium ( tail )- allows the sperm to swim to the egg and fertilise it

Answer 41

- the primary function of the egg cell is to combine with the sperm cell during fertilisation forming a zygote, that matures into a new organism

Answer 42

haploid nucleus- contains half the chromosomes of a body cell, so that when the nucleus from the sperm fuses with the egg cell nucleus the full number of chromosomes is restored at fertilisation special vesicles ( cortical granules )- these contain a substance that helps stop more than one sperm fertilising the egg zona pellucida- protective jelly coating that the sperm has to penetrate through in order for fertilisation to occur and prevents polyspermy corona radiata- supplies vital proteins cytoplasm- full of energy-rich material for the growth of the early embryo

Answer 43

- the main function of the WBC is to protect the body against infectious diseases as they circulate continuously in the blood vessels and attack foreign particles

Answer 44

- neutrophils - lymphocytes

Answer 45

- they provide a tailored response against specific antigens - they contain a large nucleus that contains an immunological memory that produces antibodies - some antibodies remain in the blood as memory lymphocytes

Answer 46

- these WBC's engulf pathogens and then destroys them - these types of WBC's contain a multi-lobed nuclei which enables them to squeeze through small gaps when travelling to the site of function - the cytoplasm holds lysosomes that contain enzymes that are used to digest pathogens that are ingested by the neutrophil

Answer 47

- the main function of the RBC is to deliver oxygen to the tissues in your body and transport carbon dioxide to your lungs for exhalation - red blood cells are made in the bone marrow

Answer 48

- mature red blood cells have no nucleus or other organelles, so there is room for more haemoglobin, which is the protein that carries oxygen - no nucleus also suggests that they cannot divide - they are small, round biconcave discs that optimises their surface area to volume ratio, this allows more oxygen and carbon dioxide to diffuse into the haemoglobin - their size also allows them to squeeze through narrow blood vessels

Answer 49

- root hair cells are specialised structures that are responsible for the nutritional uptake of water and minerals within plants - they are found in the epithelium ( surface cells ) near the root tip where there is no thickening

Answer 50

- the hair is a fine protrusion from the cell out into the soil, this provides a large surface area to volume ratio to absorb water and dissolved minerals from the soil - the cell membrane is thin and partially permeable to water which enables easier water absorption there are also channels in the cell membrane and carrier proteins that enable ions to cross the membrane into the cell, the short distance across the cell wall increases the rate of diffusion - they also contain many mitochondria to help supply energy for active transport of minerals from the soil into the cell

Answer 51

- these cells are located in the upper layer of leaves known as the palisade layer - they play a significant role in photosynthesis, the process by which plants convert light energy into chemical energy

Answer 52

- palisade cells are cylindrical shaped, so they are packed tightly in the upper part of the leaf ( arranged at right angles to the upper epidermis ) - they contain many chloroplasts near the edge of the cell so they can capture as much energy from light as possible for photosynthesis - they also move around in the cytoplasm in order to maximise the amount of light absorbed - have a large vacuole which helps to keep the cell and leaf rigid - there are long, narrow gaps between palisade cells to allow air to circulate for gas exchange and have a thin, transparent cellulose cell wall for easy gas diffusion

Answer 53

- stain culture with crystal violet, remove and rinse with water - add iodine solution, remove after 1 minute and add alcohol - counterstain with red safranin for 1 minute - dry and examine sample under microscope

Answer 54

- thick peptidoglycan cell wall that is insoluble in alcohol - absorbs the crystal violet dye during the gram stain process and appears violet or blue under a microscope

Answer 55

- gram negative bacteria are more resistant to antibiotics such a penicillin which works by damaging the bacterial cell wall because they have an outer membrane which protects them from the antibiotic

Answer 56

- the nervous system is split into the central nervous system which is the body's master control unit and the peripheral nervous system which is the body's link to the outside world - the CNS is split into the spinal cord, brain stem and the brain - the peripheral NS is split into the autonomic NS and the somatic NS - the autonomic NS is split into the sympathetic NS and the parasympathetic NS

Answer 57

spinal cord- a column of nerves between the brain and peripheral nervous system brain stem- connects the brain to the spinal cord brain- divided into 3 major parts; - the hindbrain ( lower part ) - the mid brain - the forebrain

Answer 58

- a specialised nerve cell

Answer 59

- a bundle of neurons

Answer 60

- this carries the nerve impulse from the central nervous system to an effector

Answer 61

- specialised cells that detect stimuli

Answer 62

- an autonomic response to a stimulus thar does not involve conscious thought

Answer 63

- changes in the environment

Answer 64

- these carry out the response and are either muscles or glands

Answer 65

- a junction between 2 neurones

Answer 66

- a sensory neurone carries the nerve impulses from the receptor to the central nervous system

Answer 67

- a motor neurone carries the nerve impulse from the central nervous system to an effector

Answer 68

- a relay neurone connects a motor and a sensory neurone in the central nervous system and is involved in a reflex arc - they make up the brain and spinal cord and is found in the CNS

Answer 69

- sensory neuron or afferent neuron - motor neuron or efferent neuron - relay neuron or interneuron

Answer 70

a relay neurone contains: - dendrites - cell body - axon - synaptic endings

Answer 71

a sensory neurone contains: - synaptic endings - axon - cell body - dendrite - node of Ranvier - myelin sheath - receptors in the skin

Answer 72

a motor neurone contains: - dendrites - cell body - axon - Schwann cell nucleus - node of Ranvier - myelin sheath - motor end plates on muscle fibres

Answer 73

a typical neuron contains: - Nissl granule - nucleus - cell body / soma - dendrites - axon - myelin sheath made of Schwann cells wrapped around - Schwann cells - node of Ranvier - axon terminals where you find the synapse

Answer 74

- large granular structures responsible for protein synthesis

Answer 75

- produces genetic information and directs protein synthesis - contains the nucleolus and chromosomes and controls cell activities

Answer 76

- carry nerve impulses towards the cell body

Answer 77

- nucleus and large amounts of RER that is associated with the production of proteins and neurotransmitters

Answer 78

- forms covering an axon and is made of membranes of Schwann cells - the are rich in lipids ( myelin ) and can be myelinated and unmyelinated with the myelinated neurones transmitting nervous impulses faster

Answer 79

- they surround the axon by wrapping around many times protecting and providing electrical insulation - they help with phagocytosis and nerve regeneration - they contain a: lipoprotein membrane forming myelin sheath, a nucleus of Schwann cells, a fold of Schwann cell around the fibre and a nerve fibre

Answer 80

- these are gaps between adjacent Schwann cells where there is no myelin sheath - the gaps are around 2-3 um and occur every 1-3 mm

Answer 81

- single long fibres that carry nerve impulses away from the cell body

Answer 82

- these are the ends of axons which transmit messages to other cells via use of neurotransmitters at synapses

Answer 83

myelinated- action potentials only occur where the axon is exposed at the nodes of Ranvier, as they are the only regions that can depolarise axon is covered by protective myelin sheath and the conduction of nerve impulse is faster - avoids the loss of impulse during conduction and the nerve impulse jumps from node to node ( saltatory conduction ) unmyelinated- axon is not covered by myelin sheath and the conduction of nerve impulse in the neurone is slower as there is more chance of loss of impulse during conduction - nerve impulse is a continuous wave along the axon

Answer 84

- this happens in a myelinated neuron where the current jumps from node to node, in a process known as saltatory conduction, which increases the speed of nerve impulse transmission

Answer 85

- a synapse is the junction between two neurones - the presynaptic membrane ( before the gap ) allows the release of chemicals ( neurotransmitters ) when impulses are arriving to stimulate impulses in the cell after the gap ( postsynaptic cell )

Answer 86

- an electrical signal that travels along an axon when a nerve impulse is transmitted

Answer 87

- in it's resting state ( -70mV ), the inside of the neuron is negatively charged compared to the outside, which is maintained by sodium-potassium pumps and leak channels depolarisation- when a stimulus reaches a resting neuron, the Na+ gates in the cell membrane open and Na+ diffuse into the neuron, generating a positive charge inside the cell, Na+ gates close - if the potential ( voltage ) change reaches a certain level known as the threshold, a full action potential will be initiated, below this level, no action potential will occur repolarisation- K+ channels open and K+ diffuse out of the neuron, returning the cell to it's original negative charge, K+ gates close recovery- after an impulse has passed, a neuron cannot immediately fire another impulse due to a refractory period where the cell is slightly more negative than at rest ( hyperpolarised ) - the negative charge attracts K+ which move back into the cell through non-voltage gated channels - this resets the neuron, preparing it for the next impulse as resting potential equilibrium is restored

Answer 88

1) an action potential arrives 2) the membrane depolarises and the calcium channel opens allowing them to enter the neuron 3) calcium ions cause synaptic vesicles containing neurotransmitters to fuse with presynaptic cleft 4) neurotransmitter binds with receptors on the postsynaptic membrane, allowing sodium channels to open and sodium ions to flow through the channel 5) the membrane depolarises and initiates an action potential 6) when released, the neurotransmitter will be taken up across the presynaptic membrane ( whole or after being broken down ), or it can diffuse away and be broken down

Answer 89

inhibitory- decreases the likelihood of an action potential excitatory- increases the likelihood of an action potential

Answer 90

- this is an organic compound that functions in the brain and body as a neurotransmitter and was first discovered - it has many functions including the stimulation of muscles and is largely made in brain

Answer 91

- chemical messengers that transmit signals from neurons to muscles, or between neurons and the transmission occurs in the synaptic cleft

Answer 92

- neurotransmitters are released when calcium ions enter the neurone and allow the synaptic vesicles to fuse with the presynaptic membrane - the neurotransmitters bind with receptors on the postsynaptic membrane, allowing sodium ions to flow, and when released, the neurotransmitters will be taken up across the presynaptic membrane or broken down

Answer 93

- Parkinson's disease is associated with the death of a group of dopamine-secreting neurones in the brain, resulting in the reduction of dopamine levels - dopamine is a neurotransmitter that is active in neurons in the frontal cortex, brain stem and spinal cord and is associated with the control of movement and emotional responses

Answer 94

- the symptoms of Parkinson's disease are tremors, poor balance, difficulties with speech etc - these symptoms can be treated via a molecule named L-dopa which can be turned into dopamine, which raises the levels of dopamine, reducing muscle tremor and other motor problems

Answer 95

antagonist- blocks action of transmitter on it's receptor ( e.g. atropine or curare ) agonist- mimics action potential on it's receptors ( e.g. nicotine or muscarine )

Answer 96

- serotonin is a neurotransmitter linked to feelings of reward and pleasure, and a lack of it links to clinical depression

Answer 97

- the symptoms of depression are prolonged feelings of sadness, hopelessness, loss of interest, anxiety etc - Ecstasy ( MDMA ) works by preventing the reuptake of serotonin, causing the maintenance of high concentration of serotonin in the synapse, which brings about the positive mood changes in the users of the drug

Answer 98

1) can affect the synthesis or storage of the neurotransmitter 2) may be excitatory which increases the likelihood of an action potential by binding to the receptors and opening the sodium ion channels 3) may be inhibitory, blocking the receptors on the postsynaptic membrane and preventing the neurotransmitters binding 4) can prevent the reuptake of neurotransmitters back into the postsynaptic membrane 5) may inhibit the enzymes involved in breaking down the neurotransmitters in the synaptic cleft

Answer 99

- serotonin selective reabsorption inhibitor e.g. Prozac which is given to patients to reduce depression a serotonin is not reabsorbed because the SSRI binds to the reuptake proteins - this means there is a high level of serotonin and increased levels in the synapses which continues to bind to receptors in the postsynaptic membranes, increasing the feeling or reward and pleasure

Answer 100

- blood flows into the right atrium through the vena cava, and left atrium through the pulmonary vein - the atria contracts forcing the blood into the ventricles - the ventricles then contract, pushing the blood in the right ventricle into the pulmonary artery to be taken to the lungs, and blood in the left ventricle into the aorta to be taken around the body - as this happens, valves close to make sure the blood does not flow backwards

Answer 101

- it pumps blood a further distance - it must generate a greater force of contraction so blood can be pumped at a higher pressure

Answer 102

- to prevent the backflow of blood

Answer 103

- an electrocardiogram measure the action potentials of the heart

Answer 104

- electrodes are placed on different parts of the body to detect electrical impulses and a machine amplifies the impulses during each heart beat and records them

Answer 105

60 to 100 beats per minute - ECGs can be used in the diagnosis of cardiovascular disease as if a disease disrupts the hearts normal conduction pathways then there will be a disruption if the expected ECG pattern

Answer 106

- one cardiac cycle ( PQRST ) = one heartbeat - P wave = atrial systole ( atria contract and push blood into ventricles ) due to atrial depolarisation as a result of an action potential created by the SAN ( sinoatrial node ) / pacemaker - QRS complex - ventricular systole ( ventricles push blood out through aorta and pulmonary artery ) due to ventricular depolarisation - T wave = ventricular repolarisation during diastole ( chambers are relaxed and filling with blood )

Answer 107

- epithelia are the linings of internal and external surfaces and body cavities, including ducts ( tubes and channels ) carrying secretions from glands - they may be composed of several layers of cells, called compound epithelia, or just a single layer known as simple epithelia - there are 2 types of epithelial tissue: squamous epithelium and columnar epithelium

Answer 108

function- allows gases to be exchanged quickly in and out of blood via osmosis and diffusion e.g. in the alveoli in the lungs, oxygen from the air diffuses into the blood in the capillaries which are located in the alveoli and carbon dioxide, a waste product, diffuses from the blood into the alveoli and is breathed out structure- very flat and thin with egg-shaped nuclei, that line the airways and blood vessels - they are often one cell thick and are very good surfaces for diffusion in the lungs

Answer 109

- lung alveoli - blood capillaries

Answer 110

- flow of red blood cells is slow through alveolar capillaries, maintaining high concentration difference - distance travelled is small due to thin epithelial cells and close proximity of red blood cells - walls of red blood cells are also thin - alveoli and capillary network give very high surface area - lungs are constantly ventilated by muscular movement, maintaining concentration gradient

Answer 111

function- contain goblet cells that secrete mucus to help trap any unwanted particles that are present in the air - they also contain cilia that moves away from the lungs, preventing any inhaled particles causing infection structure- cells are long and column shaped with lots of cilia at the top - they are a single layer of cells that line the trachea

Answer 112

- they line the upper airways e.g. trachea and bronchi

Answer 113

- they are tiny hairs on the outer surface of the epithelial cells that produce rapid wave like motions to waft mucus out of the lungs

Answer 114

elastic fibres- provide stretch and recoil smooth muscle- non-straited and involuntary

Answer 115

- COPD includes several conditions and is more common in smokers than non-smokers, as substance damage the lungs - there are 2 main types of COPD: emphysema and chronic bronchitis

Answer 116

-this is where there is inflammation of the airways in the lungs and the squamous epithelium thickens - the disease causes excessive secretion of mucus ( cough ), resulting in blocked airways and difficulty breathing

Answer 117

- usually developed because of long-term damage to the lungs from smoking - the membranes of the alveoli break apart and create abnormally large air spaces in the lungs, resulting in decrease surface area for gas exchanges to take place, so less oxygen is able to enter the body and less carbon dioxide is able to leave the body - there is also destruction of the elastin of the alveoli cell membranes, resulting in difficulty exhaling

Answer 118

- air is drawn in through the nose where it is warmed, mucus moistens and cleans the air

Answer 119

- the air is drawn down past the pharynx and larynx ( the throat ) - the epiglottis is used to cover the trachea ( wind pipe ) when we swallow food - and so the air carries on towards the two branches which go to the left and right lung

Answer 120

structure- made up of cartilage and is lined with ciliated epithelium to trap dust and mucus function- cartilage stops trachea collapsing

Answer 121

- it is split into 2 bronchi - they are similar to the trachea but have a smaller lumen - contain same tissues but less cartilage

Answer 122

breathing in: - ribcage moves up and out - external contracts - so volume of chest increases and air pressure decreases - diaphragm contracts and flattens, this increased the volume of the chest and decreases pressure so air rushes in breathing out: - ribs go down and in - internal contracts - chest volume decreases, so pressure increases - diaphragm relaxes and moves up - air is forced out

Answer 123

1) concentration gradient- maintained by blood flow ( oxygen out, carbon dioxide in ) - also maintained by ventilation ( breathing ) 2) short diffusion pathway 3) moist- oxygen dissolves in water allowing it to pass through cell membranes 4) large surface area

Answer 124

structure- no cartilage, goblet cells or ciliated epithelium but contains squamous epithelium, smooth muscle and elastic fibres function- site of gaseous exchange

Answer 125

function- site of gaseous exchange ( oxygen into the blood and carbon dioxide out ) structure- are one cell thick with a rich supply of blood and are located at the end of each bronchiole - they contain squamous epithelium which are flat and thin and help with gas exchange and elastic fibres which allows recoil to maintain shape

Answer 126

function- these line the inside of blood vessels and provides a smooth surface so that blood can easily flow over them and maintains the vessel wall permeability ( e.g. for waster and carbon dioxide to move from tissues to blood ) structure- they are made up of single layers of flat, long cells, which are orientated lengthways in the direction of the blood flow - single layers of squamous endothelium cells line the inner surfaces of arteries, capillaries and veins

Answer 127

- they are made up of the same tissues but in different proportions - they both have an outer layer of connective and elastic tissues but this is thicker in the veins to prevent the collapse of the blood vessel - they also have a middle layer composed of smooth muscle which is thicker in the arteries to maintain blood pressure - the inner layer is made up of endothelial tissues

Answer 128

- endothelium reduces friction and allows for smooth flow of blood - damaged endothelium cells release substances that cause blood vessels to constrict - regulates blood flow and pressure

Answer 129

- capillaries only have a single layer of endothelium to allow for easy exchange of nutrients and oxygen into the tissues and the removal of waster products

Answer 130

- this is the disease process that leads to coronary disease and stokes ( cardiovascular disease ) - fatty deposits ( atheroma ) can either block an artery directly or increase it's chance of being blocked by a blood clot - fatty deposits produce plaques ( atheroma ) in the artery walls which reduce the lumen diameter and eventually block the artery completely or increase it's chance of being blocked by a blood clot ( thrombus ) - when plaques form this has the potential to cause a rupture of the protective membrane over the plaque which can then lead to major problems such as a heart attack or stroke

Answer 131

- cigarette smoke contains many toxic chemicals which can lead to atherosclerosis - the thickness of the blood increases causing fatty deposits to build up on the walls of arteries and increases the risk of clotting - smoking also increases blood pressure and heart rate, which can also cause damage to the endothelium

Answer 132

-attached to bones by tendons -stiated / striped appearance due to the arrangement of contractile proteins ( actin and myosin) inside the fibre -made up of large bundles of muscle fibres which form a fascicle -muscle fibres have lots of long, cylindrical organelles called myofibrils which are made up of repeated units of actin ( thin) and myosin ( thick) filaments called sarcomeres -cell membrane of muscle fibre = sarcolemma -cytoplasm = sarcoplasm -endoplasmic reticulum = sarcoplasmic reticulum which stores and releases the calcium ions needed for contraction -lots of mitochondria to provide the ATP -contain many nuclei ( multinucleate ) which are pushed to the edge of the fibre by the contractile proteins inside

Answer 133

-light / I bands = only thin ( actin) filaments -dark / A bands = the entire length of thick ( myosin) filaments and the overlap with actin -H zone = centre of A band which contains only thick ( myosin) filaments so is slightly lighter -Z line = border of sarcomere, the attachment site for actin filaments -M line = middle of A band, the attachment site for myosin filaments

Answer 134

-consists of the proteins actin, tropomyosin and troponin -two actin molecules twist around each other to form a helical structure -tropomyosin is wrapped around the actin -troponin is attached to the tropomyosin along the actin fibre

Answer 135

-made from many myosin molecules -each myosin molecule is composed of a head and tail domain -the head domain binds to the actin forming cross-links that change position to contract the sarcomere -the tail domain provides an anchor for the rest of the molecule

Answer 136

-thin actin filaments are pulled along thick myosin filaments -sarcomeres shorten (increased overlap of actin and myosin filaments, Z lines move closer together ) -H zone and I band become narrower

Answer 137

-when a nerve impulse arrives at the neuromuscular junction, Ca^2+ are released from the sarcoplasmic reticulum into the sarcoplasm •Ca^2+ bind to troponin which removes it from the myosin binding site and takes tropomyosin with it -this exposes the myosin binding sites on the actin so myosin heads can form cross bridges with them -the myosin head bends, pulling the actin past the myosin -ATP at the end of the myosin head is hydrolysed into ADP and Pi which are released -the cross-bridge is broken when ATP attaches to the mosin head which returns it to its original position -more ATP is hydrolysed to ADP and Pi and a cross-bridge forms with the thin filament further along -when the nervous stimulation ends, Ca^2+ are released from troponin and pumped out of the sarcoplasm -the troponin and tropomyosin bind to the myosin heads and prevent any further contraction occurring until the next nervous stimulus -T tubules are located in the sarcoplasm which help to conduct nerve impulses from the neuromuscular junction down into the muscle cell so that all cells in the muscle tissue can be stimulated to contract

Answer 138

- slow, sustained contraction for long periods of time - many mitochondria which supply energy from aerobic respiration - lots of capillaries - does not tire easily - large glycogen and glucose levels - high levels of myoglobin providing high levels of oxygen stores - high levels of respiratory enzymes - people who have a higher proportion of slow twitch muscles are better at endurance events e.g. a marathon, as they use aerobic respiration and can work for a longer time without getting tired

Answer 139

- rapid intense contractions in short burst - few mitochondria so energy for contraction from anaerobic respiration - few capillaries - tires easily - little stored oxygen and glucose - people with a higher proportion of fast twitch muscles can move quickly in short bursts e.g. sprinters, this is because the muscles contract rapidly and strongly in and short bursts using energy from anaerobic respiration

unit 1: structure and function of cells and tissues Flashcards

(164 cards)