biology Flashcards
1
Q
what are the only organelles visible under light microscopes?
A
nucleus, nucleolus and plasma membrane
2
Q
what is the function of plasma membrane?
A
- controls what goes in and out of the cell
- protects the cell
3
Q
what is rER and its functions?
A
- its a a series of flattened sacs enclosed by a membrane
- it has ribosomes on its surface
- proteins are synthesised here
4
Q
what is sER and its functions?
A
- it is a series of single tubular sacs made of membrane
- involved in synthesis and transport of lipids
5
Q
what are the different organelles in the mitochondria
A
- DNA
- inter membrane space
- ribosome (70s)
- outer membrane
- enzyme
- matrix
- inner membrane
- cristae
6
Q
what is the function of mitochondria?
A
- it is the site of respiration
produces ATP
7
Q
what is the function of cytoplasm?
A
- site of metabolic processes
- contains lots of dissolved molecules
8
Q
what is the function of lysosome? (3)
A
- releases hydrolytic enzymes which digest material
- digests and engulfs non functioning organelles
- releases enzymes outside the cell
9
Q
what are lysosomes?
A
- sacs containing hydrolytic enzymes surrounded by a single membrane
- kept away from rest if cell to prevent digestion
- formed by golgi apparatus
10
Q
what are ribosomes?
A
- small organelle made up of proteins and rRNA
- used for protein synthesis by joining amino acids together
11
Q
what is a golgi apparatus?
A
- flattened membrane sacs
- adds carbohydrates to proteins from rER to make glycoprotein
- packages proteins into golgi vesicles for secretions
- produces lysosomes
12
Q
what are centrioles?
A
- two hollow cylinders
- makes the spindle in cell division
13
Q
what is the nucleolus and its function?
A
- it has a high density of DNA and proteins
- produces ribosomes
14
Q
what is a vesicle and its function?
A
- small membrane bound sac
- transports and stores substances in the cell
15
Q
what is the function of the nucleus?
A
- contains RNA and linear DNA
controls protein synthesis = development and function of a cell
16
Q
what is the structure of a cell membrane?
A
- made of a phospholipid bilayer and protein
- its a fluid-mosaic model
17
Q
in a dividing cell, what form is DNA and protein found as?
A
as a chromosome
18
Q
what are the organelles found in prokaryotes?
A
- cell wall
- cell surface membrane
- circular DNA
- ribosomes
- cytoplasm
somtimes: - capsule
- plasmid
- flagella
19
Q
what is gram staining?
A
it allows bacteria to be classified as gram positive and gram negative which is then used to treat the bacteria
20
Q
what does it mean if a bacteria is gram negative? and how do we test it?
A
- test produces pink colour
- it has thin cell wall and only contains 5% murein
- this means they are more resistant to antibiotics
this is because the cell wall protects them from the antibiotics
21
Q
what does it mean if a bacteria is gram positive and how do we test for it?
A
- gram stain produces a purple colour
- it has 40-90% murein in their cell wall
- doesn’t have an outer membrane so antibiotics can penetrate through it
22
Q
what is tonoplast?
A
the membrane surrounding a large vacuole
23
Q
what are the organelles only found in plant cells as well as what is NOT found in plant cells?
A
-NO centrioles
-cell wall
- chloroplast
-large vacuole
-amyloplasts
-plasmodesmata
24
Q
what are the organelles found in chloroplast?
A
- lipid droplets
- stroma
- thylakoid
-granum
-inner membrane
-ribosomes (free+membrane bound)
-starch grains
-outer membrane
25
what is the structure of chloroplasts?
flattened biconcave discs surrounded by an envelope with two membranes
26
what are thylakoids?
a membrane system consisting of many flattened sacs
27
what is grana?
stack of thylakoids
28
what is the function of thylakoids
provide a large surface area for chlorophyll
29
what is the stroma?
- what surrounds the memebrane system
-consists of enzymes,sugars and starch granules
30
what is amyloplast?
- non pigmented organelles
-synthesise and store starch granuels
- convert starch into sugar when plant needs energy
31
what is plasmodesmata?
microscopic channels which transverse the cell walls of plant cells so they can communicate between each other
32
what are pits?
-depressions on the cell wall of plant cells
-act as a channel for transport of water and minerals between plant cells
33
how does electron microscopes have a higher resolution?
they use electrons that have a short wavelength than light
34
how do SEM (scanning) and TEM (transmission) differ?
-TEM produces 2D images while SEM produces 3D images
-TEM produces a higher resolution imagine (can view small organelles)
- TEM must be done under a vacuum
-SEM can be used for thick specimens
35
how is an electron microscope focused?
using magnets
36
what are palisade mesophyll cells and how are they specialised?
- they are found in leaves
-they contain a lot of chloroplast =absorb lots of light for photosynthesis
- the chloroplast can move = can move towards sun light
- columnar shape = closely packed together
-cellulose cell wall = protect and keep rigid
- large vacuole = maintain turgor pressure
37
what are the specialisation of root hair cells?
- partially permeable membrane= to let water and ions through
-provide large surface area = can absorb water and dissolved minerals
- thin cell wall = easier water transport
- lots of mitochondria = help supply ATP for active transport
38
what are the specialisations of a sperm cell?
- tail (undulipodium) = swim to egg
- many mitochondria = energy for movement
-acrosome = enzyme in head to break egg
-haploid nucleus = one set of chromosomes so it can be a full set when fertilised
39
what are the specialisation of an egg cell?
-zona pellucida = protective membrane which hardens when sperm enters
-corona radiata = supplies with proteins that a fertilised egg requires
-haploid = can be a full chromosome once fertilised
40
what are the specialisations of a red blood cell?
-contains lots of haemoglobin
-no nucleus = more space to carry haemoglobin
-biconcave flexible discs = can squeeze through capillaries and increases S.A.
-short diffusion pathway for oxygen =increases rate of diffusion
41
how many oxygen molecules can a haemoglobin bind to?
4
42
what are the specialisations of a white blood cell?
-multi lobed nuclei = can spilt to squeeze through small gaps and reach site of infection
-cytoplasm has lysosomes =digests pathogens during phagocytosis
-lymphocytes = produces antibodies which destroy pathogens
43
what are the 4 main types of tissue in animals?
-epithelial
-muscle
-connective
-nervous
44
what are epithelial tissues?
-lines organs and surfaces
45
what are the three types of epithelial tissues?
-squamous epithelial
-columnar epithelial
-endothelium
46
what is squamous epithelial tissue?
-lining tissue that is one cell thick
-made from flattened squamous epithelial cells
-forms thin and smooth layer which is ideal for gas exchange
-found in the alveoli
47
what is empysema and what is it’s cause?
-caused by smoking
-damages the alveoli lining in lungs
-forms large air spaces which decreases surface area for gas exchange
-destroys the elasticity of alveoli so it cant recoil
-causes respiratory problems
48
what is columnar epithelial cells and goblet cells?
-lining on the trachea
- goblet cells secrete mucus
- cilia covers the surface of the cell which makes a wave like motion
-this motion allows mucus to more up and out of the respiratory system
49
what is chronic bronchitis?
- it is the inflammation of airways in lungs
- epithelium cells thicken
- mucus is secreted excessive = cough
- blocked airways = difficulty breathing
50
what is squamous endothelium?
-it lines the inside of arteries, veins and capillaries
51
what is the purpose of squamous endothelium cells?
veins and arteries:
- reduces friction and allows for smooth flow of blood
-regulates blood flow ad pressure
-when damaged it causes blood constriction by releasing a substance
capillaries:
- single layer which makes it easy to exchange oxygen and nutrients as well as removing waste products
52
what is atherosclerosis?
-fatty deposits that block an artery
-increases risk of strokes and coronary disease
- caused by smoking, high saturated fats in diets and high blood pressure
53
what are the other names for skeletal muscles?
striped muscles and striated muscles
54
what are the characteristics of a muscle fibre:
-cylindrical in shape
-enclosed by cell surface membrane or sarcolemma
-have lot of nuclei
-contain lots of protein strands/ myofibrils
-arranged in parallel to give striped appearance
55
what is myosin?
a type of protein and forms thick filaments
56
what is actin?
a thin filament
57
where are thick filaments present?
a band and dark band
58
why are the outer regions of a bands darker?
because they have overlapping myosin and actin filaments
59
what is the h zone?
what is found at the centre of the A band and only contains myosin filaments
60
what is the M line?
what connects myosin filaments in the A band
61
what is the I band (light band) ?
only contains actin filaments
62
what is the Z line?
what connects actin filaments and boundary of sacromere
63
what is another name for the mechanism of muscle contraction?
the sliding filament mechanism
64
describe the sliding filament mechanism
-the process is triggered by calcium ions
-the ions then bind to troponin molecules which changes the shape of troponin which makes them move away from the actin myosin binding site
- this means the actin myosin binding site is now exposed
-this allows myosin head groups to bind to the actin myosin binding sites which forms actin myosin cross bridge
- myosin head relaxes and pulls the actin filament along
-at the same time the myosin head releases the ADP molecule and then ATP attaches to the myosin head
-this causes the myosin head to detach from the actin myosin binding site
-myosin head acts as a ATPase and hydrolyses it into ADP and phosphate
- the energy released is used to get the myosin head back into its original shape
-process repeated while there is a high concentration of calcium ions
-this pulls actin filament along
65
what the the features of an actin filament?
-has two strands that wrap together into a helical structure
-it has a binding site for myosin called actin myosin binding sites
- a thread like structure called tropomyosin covers the actin myosin binding site when muscle is relaxed.
66
what are the features of a myosin filament?
-consists of two parts
-first part has a long tail structure and they're clustered together which forms the filament
-the second part has a head group that points outwards
-each head has a binding site for actin as well as binding site for ATP
67
what hold the tropomyosin in place?
a protein called troponin
68
what releases calcium ions?
sarcoplasmic reticulum
69
what activates ATP activity?
high concentration of calcium ions in the sarcoplasm
70
what direction do myosin heads face and why/
-opposite sides on each side of the filament
-this allows actin to be pulled closer on either side of the sarcomere
71
what is the overall affect on sarcomere during muscle contraction?
they shorten
72
what happens during muscle relaxation?
-calcium ions are transported from sarcoplasm into sarcoplasmic reticulum (active transport)
- energy used for this is from ATP hydrolysis
troponin and tropomyosin return to their prior positions
-muscle fibres return to their relaxed positions
73
what is the neuromuscular junction?
-specialised form of synapse between motor neurone and surface membrane (sarcomere) of skeletal muscle fibre.
-it is the end of a motor neurone
74
what is the process for the transmission across a neuromuscular junction?
-action potentials at synaptic knob causes depolarisation of presynaptic membrane
-this stimulates calcium channels to open in the pre synaptic membrane allowing calcium ions to diffuse into synaptic knob
-the calcium ions causes synaptic vesicles to fuse with presynaptic membrane and break open
-acetylcholine is released and diffuses across the synaptic cleft
-acetylcholine attaches to specific protein receptor sites on sarcolemma
-this stimulates the entry of sodium ions which causes depolarisation
-an action potential is created along the sarcolemma and into the muscle fibre which stimulates the release of calcium ions
-acetylcholine is broken down by enzyme cholinesterase to turn into acetyl and choline
-they are taken up by active transport into the synaptic knob and acetylcholine is resynthesized using ATP
75
what are the two components that make up a skeletal muscle?
slow and fast muscle fibres
76
what are the differences between fast and slow muscle fibres? (8)
-fast contracts quickly while slow contracts slowly
-fast has a few of mitochondria per fibre while slow has many mitochondria per fibre
-fast releases energy slowly while fast releases energy quickly
-fast has low resistance to fatigue while slow has a high resistance
-fast is good for short bursts of speed and power while slow is good for endurance based activity
-fast is whitish in colour while slow is red
-fast has a high concentration of phosphocreatine while slow has a low concentration of phosphocreatine
77
why are fast muscle fibres white while slow muscle fibres are red?
fast has little to no myoglobin while slow has a high presence of myoglobin which is a pigment that stores oxygen
78
what is a cell body?
contains the nucleus and most other cell organelles
79
what is an axon?
it conducts nerve impulses
80
what is myelin sheath?
-consists of lipid and surrounds the axon.
-formed from Schwann cells and provides electrical insulation
81
what is nodes of ranvier/
gaps in the myelin sheath along the axon
82
what are synaptic knobs?
they allow communication with other neurones or effectors
83
what is the resting potential?
-this is when neurones are polarised since inside the axon is -ve compared to the outside
-the potential difference across the membrane of the axon when an impulse is not being transmitted is called the resting potential
-in a polarised neurone there are more sodium ions outside the axon but there more more potassium ions inside the axon
84
how is the resting potential maintained?
the membrane is more permeable to the loss of potassium than to intake sodium ions because more potassium channels are open than sodium channels which means there is a NET loss in +ve charged ion from the axon
-the sodium/potassium pump actively transports the ions against concentration gradient which requires ATP
-this maintains the concentration gradient for movement of ions through the membrane
85
when can the sodium potassium pump not function and what is the aftermath?
-when neurones are treated with respiratory inhibitor which prevents the production of ATP
-this leads to the concentration to reach equilibrium and the potential difference becomes 0
86
what is depolarisation?
-when a receptor stimulated above its threshold generates an action potential and transmits a nerve impulse
-action potential involves a change in potential across the axon membrane from -ve inside to +ve value.
87
what causes depolarisation/
-an increase in permeability of the axon membrane to sodium ions since sodium channels are open.
the sodium ions diffuse in down a concentration gradient.
-this results in more sodium channels to open which further increases permeability of the membrane to sodium ions so more diffuse in
-the negative resting potential is initially cancelled out and the more sodium enter
-a positive charge develops inside the neurone
88
what happens once the membrane has fully depolarised?
-sodium channels close and the potassium channels open
-more potassium ions begin to diffuse out of the axon
-this causes repolarisation
89
what is repolarisation?
-the inside of axon becoming less positive since potassium begins to diffuse out of the axon
90
how and what restores resting potential?
-restored via sodium potassium pump
-this is done by actively removing sodium ions that enter the axon and return potassium back into the axon
91
what is the resting potential?
-70v
92
what is the action potential?
+40v
93
how is action potential transmitted?
-increasing permeability of the membrane to sodium ions in one area
-this stimulates an increase in permeability of the next area of the axon and so on along the neurone
94
what is the transmission speed of nerve impulses?
-the speed of a nerve impulse in humans is 1 to 3 m/s
- in unmyelinated neurones its 3 to 120m/s
95
what are the factors that affect the speed of conductance along neurones?
-temperature
-axon diameter
-number of synapses involved
-myelination
96
how does temperature affect speed of conductance along neurones?
-increase in temperature =increase in speed of transmission
- this is because of an increase in diffusion of ions and in enzyme activity
97
how does axon diameter affect speed of conductance along neurones?
the greater the diameter the faster the speed of conductance
98
how does myelination affect speed of conductance along neurones?
-increases speed of transmission as the action potential jumps from one gap to the next for myelinated neurones
-opposite affect for non myelinated neurones as depolarisation slows down transmission
99
how does number of synapses involved affect speed of conductance along neurones?
-the fewer the synapses to cross the faster the impulse
100
what is the synapse?
the functional connection between neurones
101
what does the synaptic knob consist of?
-synaptic vesicles which contain neurotransmitter chemical
-mitochondria which provide ATP for synthesis of neurotransmitter
-thickened membrane called presynaptic membrane
102
what is the function of the synaptic gap?
separates the presynaptic membrane from the postsynaptic membrane to dendrite on following neurone
103
what are cholinergic neurones?
neurones that contain the neurotransmitter acetylcholine
104
what is the mechanism for synaptic transmission?
-arrival of action potentials at synaptic knob which causes depolarisation of presynaptic membrane
-this stimulates influx of calcium ions into synaptic knob
-this causes synaptic vesicles to fuse with presynaptic membrane and break open
-neurotransmitter is released and diffuses across the synaptic cleft
-acetylcholine attaches to specific protein receptor sites on the postsynaptic membrane
-this attachment stimulates the entry of sodium ions, the more the acetylcholine molecules attach more sodium ions enter which eventually leads to depolarisation of the postsynaptic neurone and transmission of an impulse
-the acetylcholine is broken down in the postsynaptic membrane by enzyme acetyl cholinesterase forming acetyl and choline
-acetyl and choline are taken up into synaptic knob by active transport and acetylcholine is re synthesised
105
what is electroencephalograph(EEG)?
-this is a test that looks at the activity of brain cells
-as nerve impulses are passed from neurone to another they produce electrical signals that can be picked up by detectors
-these are recorded to produce a graphical trace which can be used to determine if there is abnormal activity that would suggest an epileptic seizure has occurred
106
what is parkinson's disease?
a genetic disease that effects the nervous system
-they cannot produce dopamine that helps smooth and normal movements
107
what are the symptoms of parkinson's disease?
-slow movements
-tremors when moving
-speech problems
-poor balance
108
what is used to replace dopamine?
the drug L-dopa
109
how does L-dopa function
-increases amount of dopamine stored in the vesicle and then released by presynaptic neuron
-therefore a normal level of dopamine stimulate the postsynaptic neuron
110
what is serotonin?
-neurotransmitter found in the brain
111
what are the impacts of low levels of serotonin?
-depression
-this is because fewer receptors in the brain can be stimulated so less neurotransmitter is released across synapse which leads to fewer impulses in the brain
112
what are the impacts of high levels of serotonin?
=more receptors in the brain can be stimulated so more impulses in the brain which leads to feeling happy
