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Applied Science > Biology Unit 1 - Structure and functions of cells and tissues > Flashcards

Biology Unit 1 - Structure and functions of cells and tissues Flashcards

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Biology 101 flashcards
1
Q

what does cell theory state?

A

-all living things are made of cells
-cells are the basic units of life
-all cells come from the division of other cells

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2
Q

what are the parts of a light microscope?

A

-eyepiece lens = contains the ocular lens
-nosepiece = holds the high and low power objective lenses, can be rotated to change magnification
-objective lens = magnification ranges from 4x to 100x
-stage clips = holds the slide in place
-stage = supports the specimen being viewed
-light source = projects light upwards through the diaphragm, the specimen and the lenses
-base = supports the microscope
-diaphragm = regulates the amount of light on the specimen
-fine focus knob = moves the stage slightly to sharpen the image
-coarse focus knob = moves the stage up and down for focus
-arm = used to pick up the microscope when carried

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3
Q

how can a temporary microscope slide of human cheek cells be made?

A
  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 swabbed 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 glass 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 lens ( they will just look like tiny blue dots )
  5. change to the 10x lens, focus and then change to 40x ( they should look like blue fried eggs )
  6. make a labelled drawing of one cell and label the cytoplasm, nucleus and cell membrane
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4
Q

how can a temporary microscope slide of onion epidermis cells be made?

A
  1. chop a small piece of onion on the chopping board / tile using a scalpel
  2. gently remove the single cell epidermal 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 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 in on the cells using the 4x lens
  6. change to the 10x lens, focus and then estimate the number of 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
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5
Q

why does the specimen need to be thin?

A

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

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6
Q

why do samples need to be stained?

A

-stain binds to structures which helps to distinguish different features in the specimen

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7
Q

what is the purpose of a coverslip?

A

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

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8
Q

how do you convert between units: centimetre, millimetre, micrometre, nanometre?

A

-big → small = divide, small → big = multiply
-cm → mm = / 10
-mm → μm = / 1000
-μm → nm = / 1000

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9
Q

what is magnification?

A

-the number of times bigger an image appears compared to the size of the specimen

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10
Q

what is resolution?

A

-the smallest distance between two objects that can be distinguished

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11
Q

how is total magnification calculated?

A

-magnification of eyepiece lens x magnification of objective lens

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12
Q

how is image size ( I ) calculated?

A

-I = A x M
-image size ( I ) in any unit = actual size ( A ) in same unit as image size x magnification ( M )

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13
Q

what is a micrograph?

A

-a photograph or digital image taken through a microscope

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14
Q

compare the light microscope ( LM ) and electron microscope ( EM )

A

-both use a form of radiation to create an image, but LM uses visible light whereas EM uses x-rays
-LM uses a series of lenses and a light source to view an image whereas EM uses a beam of electrons which scatter over the specimen
-LM’s maximum magnification is around x1500 whereas EM’s is over x500,000
-LM’s maximum resolution is 200nm whereas EM’s is 0.1nm as electron beams have a much shorter wavelength than beams of light
-LM uses coloured stains ( e.g. iodine, methyl blue ) whereas EM uses electron-dense chemicals ( heavy metals e.g. lead, gold ) to stain a specimen
-LM costs around £300-10K so is avaliable for use to students whereas EM costs over £1M and requires a highly trained operator
-LM is small and portable whereas EM is large and requires a special room
-LM produces images in colour whereas EM produces images in black and white and requires a dead specimen in a vacuum as electron beams are deflected by air molecules
-LM is used to view living specimens whereas EM is used to view dead specimens in much more detail

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15
Q

how does the optical ( light ) microscope work?

A

-lenses focus rays of light and magnify the view of a thin slice of specimen
-different structures absorb different amounts and wavelengths of light
-reflected light is transmitted to the observer via the objective lens and eyepiece

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16
Q

how does the transmission electron microscope ( TEM ) work?

A

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

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17
Q

how does the scanning electron microscope ( SEM ) work?

A

-focus a beam of electrons onto a specimen’s surface using electromagnetic lenses
-reflected electrons hit a collecting device and are amplified to produce an image on a fluorescent screen or photographic plate

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18
Q

compare the TEM and SEM

A

-both have a maximum magnification of around x500,000
-TEM’s maximum resolution is 0.5nm whereas SEM’s is 3-10nm
-TEM is used to view 2D images of internal structures and detail of cell organelles whereas SEM is used to view 3D images of surfaces

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19
Q

what are eukaryotic cells?

A

-multi-cellular organisms such as animals and plants
-they are complex cells with a nucleus and membrane-bound organelles

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20
Q

what are prokaryotic cells?

A

-single-celled organisms such as bacteria
-they are simple structures and do not have a nucleus or any membrane-bound organelles

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21
Q

what four structures do all cells contain?

A

-DNA
-cytoplasm
-ribosomes
-plasma membrane

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22
Q

what structures do all eukaryotic cells contain?

A

-nucleus
-nucleolus
-cytoplasm
-80S ribosomes
-plasma membrane
-vesicle
-centrioles ( except plant cells )
-lysosome
-Golgi apparatus
-mitochondrion
-smooth endoplasmic reticulum
-rough endoplasmic reticulum

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23
Q

what is the structure and function of the nucleus?

A

-surrounded by a double membrane ( envelope ), with pores that allow molecules to enter and leave
-stores DNA, coordinates cell activities

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24
Q

what is the structure and function of the nucleolus?

A

-region of dense DNA, RNA and protein, found within the nucleus
-produces ribosomes

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25
Q

what is the structure and function of the cytoplasm?

A

-fluid that fills a cell
-many molecules dissolved in solution ( enzymes, sugars, amino acids, fatty acids )
-site of many metabolic processes

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26
Q

what is the structure and function of the ribosomes?

A

-composed of two subunits, may either be membrane-bound or free in the cytoplasm ( i.e. in prokaryotes )
-site of protein synthesis

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27
Q

what is the difference between ribosomes in eukaryotic and prokaryotic cells?

A

-80S ribosomes in eukaryotes are bigger than 70S ribosomes in prokaryotes
-S is a Svedberg, a measure of size by rate of sedimentation

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28
Q

what is the structure and function of the plasma membrane?

A

-protects cell from its surroundings
-regulates movement of substances in and out of cells

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29
Q

what is the structure and function of the vesicle?

A

-small, membrane-bound sac
-transports and stores substances in the cell

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30
Q

what is the structure and function of the centrioles?

A

-hollow cylinders containing microtubules
-makes the spindle in cell division

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31
Q

what is the structure and function of the lysosome?

A

-vesicles filled with digestive enzymes, bound by a membrane
-breakdown any of the cell’s waste e.g. old organelles, destroy disease-causing organisms ( pathogens ) that enter the cell

32
Q

what is the structure and function of the Golgi apparatus?

A

-a series of flat, curved, fluid-filled sacs enclosed by a membrane and surrounded by vesicles
-processes proteins and lipids and packages them in vesicles for transport, produces lysosomes

33
Q

what is the structure and function of the mitochondria?

A

-bound by a double outer membrane ( envelope ), inner membrane folded into finger-like projections called cristae to increase surface area
-central area contains a jelly called the matrix
-site of respiration and therefore ATP production

34
Q

what is the structure and function of the smooth endoplasmic reticulum?

A

-a series of single, tubular, membrane-bound sacs, without ribosomes on the surface
-produces and processes lipids

35
Q

what is the structure and function of the rough endoplasmic reticulum?

A

-a series of single, flattened, membrane-bound sacs, with large numbers of ribosomes on the surface
-site of protein synthesis and folding

36
Q

what is the role of the RER and Golgi apparatus in transporting proteins?

A

-proteins produced on the ribosomes of the RER, and are then folded and processed
-transported in vesicles to the Golgi body
-modified and repackaged to be transported around the cell, or to leave the cell by exocytosis

37
Q

what other structures do plant cells contain?

A

-chloroplasts
-vacuole
-tonoplast
-cellulose cell wall
-amyloplast
-middle lamella
-plasmodesmata
-pits

38
Q

what is the structure and function of the chloroplasts?

A

-contains chlorophyll ( green substance ) which absorbs light energy
-site of photosynthesis to convert solar energy to chemical energy

39
Q

what is the structure and function of the vacuole?

A

-surrounded by a single phospholipid membrane called tonoplast
-stores cell sap, which contains mineral ions, water, enzymes, soluble pigments

40
Q

what is the structure and function of the tonoplast?

A

-cytoplasmic membrane surrounding a vacuole, separating the vacuolar contents from the cell’s cytoplasm
-controls movement of molecules into and out of the vacuole

41
Q

what is the structure and function of the cell wall?

A

-made of cellulose
-provides structure, support and protection for the cell, preventing bursting when water enters by osmosis

42
Q

what is the structure and function of the amyloplast?

A

-plastid found only in plant cells
-produces, breaks down and stores starch

43
Q

what is the structure and function of the middle lamella?

A

-cementing layer between the primary walls of adjacent cells
-sticks cells together

44
Q

what is the structure and function of the plasmodesmata?

A

-tunnel from one cell to the next
-allows communication and the movement of molecules between cells

45
Q

what is the structure and function of the pits?

A

-minute openings in the secondary cell wall of plant cells
-allows the flow of water and nutrients from one cell to another, linking water uptake in roots with transpiration in leaves

46
Q

what structures do prokaryotic cells ( bacteria ) contain?

A

-nucleoid
-plasmids
-70S ribosomes
-capsule
-cell wall
-pili
-flagellum
-mesosomes

47
Q

what is the structure and function of the plasmids?

A

-double-stranded DNA in a circular structure
-often contain additional genes that aid the bacterium’s survival, such as antibiotic resistance or toxin producing genes
-responsible for DNA replication, transferring DNA between bacteria and gene expression

48
Q

what is the structure and function of the capsule?

A

-thick, slimy layer of polysaccharide that covers the cell wall
-prevents cell from drying out, protects cell from being engulfed by e.g. white blood cells, and helps adhesion to surfaces

49
Q

what is the structure and function of the prokaryotic cell wall?

A

-forms a rigid outer covering over the cell, made of peptidoglycan ( long-chained molecule made up of a sugar and amino acids )
-provides strength, support and protection against damage

50
Q

what is the structure and function of the pili?

A

-hair-like extentions on the surface of bacterial cells
-helps cells adhere to various surfaces, primarily each other

51
Q

what is the structure and function of the flagellum?

A

-a long, thin projection attached to the cell wall
-rotates to move the cell

52
Q

what is the structure and function of mesosomes?

A

-infolds of the plasma membrane
-provides a large surface area for the attachment of enzymes involved in respiration

53
Q

what is the process of gram staining?

A

-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

54
Q

what is the structure of gram-positive bacterial cell walls?

A

-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

55
Q

what is the structure of gram-negative bacterial cell walls?

A

-thinner peptidoglycan cell wall surrounded by an outer lipopolysaccharide ( LPS ) membrane that is soluble in alcohol
-doesn’t retain the gram stain ( crystal violet ) when washed with alcohol and appears red under a microscope

56
Q

why do gram-positive and gram-negative bacteria respond differently to certain antibiotics?

A

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

57
Q

what are specialised cells?

A

-cells that have developed unique features and structures which allow them to perform specific roles
-the process by which cells become specialised for a particular function from stem cells is known as differentiation

58
Q

what are the functions of the specialised animal cells?

A

-sperm cells ( male gametes ) and egg cells ( female gametes ) = carry out fertilisation in organisms that reproduce sexually
-white blood cells = help the body fight infection and other diseases
-red blood cells ( erythrocytes ) = carry oxygen from the lungs to the tissues in different parts of the body

59
Q

how are sperm cells adapted to their function?

A

-the haploid nucleus in the head contains half the normal number of chromosomes ( 23 ) so that the full number is restored at fertilisation
-the acrosome in the head contains digestive enzymes that can break down the outer layer of an egg cell so that the haploid nucleus can enter to fuse with the egg’s nucleus
-the mid region is packed with mitochondria to provide the energy from respiration for movement
-the undulipodium ( tail ) rotates to propel the sperm cell forwards so that it can move towards the egg

60
Q

how are egg cells adapted to their function?

A

-the haploid nucleus contains half the chromosomes of a body cell ( 23 ) so that when the sperm’s nucleus fuses with the egg’s nucleus the full number is restored at fertilisation
-the corona radiata surrounds the egg cell and contains follicle cells which supply it with vital proteins
-the zona pellucida ( jelly layer ) surrounds the plasma membrane of the egg cell and helps to protect it
-the cortical granules ( specialised secretory vesicles ) contain a substance that helps to stop more than one sperm fertilising the egg
-the cytoplasm contains nutrients for the growth of the early embryo

61
Q

what are the two types of white blood cell?

A

-neutrophils = phagocytic WBCs that engulf pathogens and then digest them ( non-specific response )
-lymphocytes = B and T cells ( WBCs ) that produce antibodies which respond to specific antigens on the surface of pathogens

62
Q

compare the structures and functions of neutrophils and lymphocytes

A

-both make up the first line of defence within the body against foreign invaders
-both are made in the bone marrow and lymph nodes
-both contain nuclei / mitochondria / RER / ribosomes
-neutrophils provide a faster, non-specific response before lymphocytes provide a specific response
-neutrophils are more common and bigger than lymphocytes
-neutrophils have a lobed nucleus which enables them to squeeze through small gaps when travelling to the site of infection
-neutrophils have a lobed nucleus, and are flexible and mobile so they can squeeze between cells in the capillary wall and migrate to areas of infection
-neutrophils hold lysosomes in their cytoplasm that contain enzymes which help to digest and destroy pathogens that are ingested
-lymphocytes have a large nucleus and contain an immunological memory
-T lymphocytes send signals to B lymphocytes which makes the B cells produce antibodies
-the B cells proliferate ( reproduce rapidly ) so some of them make antibodies and some become memory lymphocytes
-the T cells destroy infected or cancerous cells

63
Q

how are red blood cells adapted to their function?

A

-the cytoplasm contains haemoglobin which is the protein that binds to oxygen
-they have a thin membrane which decreases the diffusion distance for gas exchange
-they have no nucleus or other organelles so there is more space for haemoglobin, maximising the cell’s oxygen-carrying capacity so more oxygen can be transported around the body
-they are biconcave in shape which increases the surface area over which oxygen can be absorbed
-they are small and flexible so they can squeeze through narrow blood vessels

64
Q

what are the functions of the specialised plant cells?

A

-palisade mesophyll cells = maximise light absorption for photosynthesis to produce glucose and oxygen
-root hair cells = absorb water ( by osmosis ) and mineral ions ( by active transport ) from the soil for photosynthesis and protein synthesis

65
Q

how are palisade mesophyll cells adapted to their function?

A

-they are cylindrical shaped which enables them to pack tightly in the upper part of the leaf ( palisade layer ), increasing the surface area exposed to light which maximises light absorption
-they contain a large number of chloroplasts ( containing chlorophyll which absorbs light ) near to the edge of the cell so they can capture as much energy from light as possible
-the cytoskeleton can move the chloroplasts around in the cytoplasm to maximise the amount of light absorbed
-the cellulose cell wall is thin and transparent which decreases the diffusion distance for gas exchange and allows sunlight to penetrate through to the chloroplasts
-they contain a large vacuole which helps to keep the cell and leaf structure rigid

66
Q

how are root hair cells adapted to their function?

A

-the root hair is a fine protrusion from the cell out into the soil which increases the surface area in contact with the soil, increasing the rate of absorption of water and minerals
-the plasma membrane is thin and partially permeable to water which enables easier water absorption
-the cell membrane contains channels and carrier proteins which enable ions to cross the membrane into the cell
-the short diffusion distance across the thin cell wall increases the rate of diffusion
-they contain a large number of mitochondria which help supply energy for active transport of minerals from the soil into the cell, against the concentration gradient
-the permanent vacuole contains cell sap which is more concentrated than soil water, maintaining a water concentration gradient

67
Q

what are the divisions of the nervous system?

A

-central NS = brain + spinal cord
-peripheral NS = somatic NS + autonomic NS
-ANS = sympathetic NS ( fight or flight ) + parasympathetic NS ( rest and digest )

68
Q

what is the difference between nerves and neurons?

A

-nerves = bundles of neurons
-neurons = specialised nerve cells that make up nerves and carry messages in the form of electrical signals ( known as action potentials ) along axons from one part of the body to another

69
Q

what are the three types of neurons?

A

-sensory ( afferent ) = carry messages from sensory receptors in PNS to CNS, myelinated, long dendrites and short axons
-relay = connect sensory neurons to motor neurons or other relay neurons, non-myelinated, short dendrites and short axons
-motor ( efferent ) = carry messages from CNS to effectors in PNS such as muscles and glands, myelinated, short dendrites and long axons

70
Q

what structures do neurons contain?

A

-nissl granule = responsible for protein synthesis
-cell body ( or soma ) = includes the nucleus which controls the cell’s activities and lots of RER which is associated with the production of proteins and neurotransmitters
-dendrites = carry nerve impulses from neighbouring neurons towards the cell body
-axon = single long fibre that carries nerve impulses away from the cell body down the length of the neuron
-myelin sheath = fatty covering that protects and insulates the axon, and speeds up electrical transmission
-Schwann cell = produces myelin sheath and surrounds the axon by wrapping around it many times
-nodes of Ranvier = gaps between adjacent Schwann cells where there is no myelin sheath which speed up the transmission of the impulse by allowing it to jump along the axon
-axon terminals = transmit messages to other cells ( neurons or effectors ) via neurotransmitters at synapses

71
Q

compare myelinated and non-myelinated neurons

A

-myelinated neurons have myelin sheath and nodes of Ranvier ( saltatory conduction ), whereas non-myelinated neurons have neither ( continuous wave along axon )
-myelinated neurons are white in colour, whereas non-myelinated neurons are grey
-myelinated neurons transmit impulses very fast, whereas non-myelinated neurons transmit impulses slower
-myelinated neurons avoid loss of impulse during conduction, whereas non-myelinated neurons have a higher chance of loss of impulse due to having no insulating layer

72
Q

how is an electrical impulse generated by a neuron?

A

-changes in the concentration of ions inside and outside the cell causes a potential difference ( PD ), called an action potential, which transmits an electrical signal between nerve cells

73
Q

how is an action potential conducted along an axon?

A

-at rest, the inside of a neuron is negatively charged compared to the outside
-depolarisation = when a stimulus reaches a resting neuron, the Na+ gates in the cell membrane open and sodium ions diffuse into the neuron, generating a positive charge inside the cell and triggering an action potential if the PD ( voltage change ) reaches the threshold, and then the Na+ gates close
-repolarisation = the K+ gates open and potassium ions diffuse out of the neuron, returning the cell to its original negative charge, and then the K+ gates close
-hyperpolarisation = after an impulse has passed, a neuron cannot immediately fire another action potential ( to ensure that the impulse travels in one direction ) due to a refractory / recovery period where the cell is slightly more negative than at rest, which attracts potassium ions to move back into the cell through non-voltage gated channels, restoring the resting potential equilibrium ( -60 to -70 mV )

74
Q

how does membrane permeability to sodium and potassium ions change during the conduction of an action potential?

A

-at rest = more permeable to potassium ions because more non-gated K+ channels are open than Na+ channels
-depolarisation = short-lived increase in Na+ permeability
-repolarisation = slower increase in K+ permeability

75
Q

what is saltatory ( jumping ) conduction?

A

-in myelinated neurons, action potentials only occur where the axon is exposed at the nodes of Ranvier as those regions can depolarise
-therefore, the impulse jumps from node to node ( saltatory conduction ), which means that it can travel faster and a much longer distance

Applied Science (3 decks)

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