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1-cell biology Flashcards

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1
Q

what are eukaryotic cells

A

Plant and animal cells (eukaryotic cells) have a cell membrane,
cytoplasm and genetic material enclosed in a nucleus.

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2
Q

what are prokaryotic cells

A

Bacterial cells (prokaryotic cells) are much smaller compared to eukaryotic. They have cytoplasm and a cell membrane surrounded by a cell wall. The genetic material is not enclosed in a nucleus. It is a single DNA loop and there may be one or more small rings of DNA called plasmids.

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3
Q

name the subcellular structures of an animal cells and its functions

A
  • a nucleus
  • cytoplasm
  • a cell membrane
  • mitochondria
  • ribosomes.
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4
Q

nucleus

A

contains genetic material , controls activites of the cell

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5
Q

cytoplasm

A

gel like substance when chemical reactions occur, contains enzymes to help control these reactions

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6
Q

cell membrane

A

holds cell together and controls what goes in and out

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7
Q

mitochondria

A

where most of reactions for aerobic respiration occurs, respiration transfers energy that cell needs to work

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8
Q

ribosomes

A

where proteins are made in the cells

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9
Q

what extra structures do plant cells have

A

rigid cell wall
permanent vacuole
chloroplasts

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10
Q

rigid cell wall

A

made of cellulose , supports cell and strengthens it

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11
Q

permanent vacuole

A

contains cell sap, weak solution of sugars and salts

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12
Q

chloroplasts

A

where photosynthesis occurs, makes food for the plant, contains chlorophyll which absorbs light for photosynthesis

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13
Q

bacteria are prokaryotes, what does a bacterial cell contain

A

cell membrane
cell wall
cytoplasm
singular strand of dna
small rings of dna called plasmids

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14
Q

explain how light microscopes work

A

use light and lenses to form an image of a specimen and magnify it - lets us see individual cells and large subcellular structures like nuclei

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15
Q

explain how electron microscopes work

A

use electrons to form an image, higher magnification, higher resolution- helps us see smaller things like internal structures of mitochondria and chloroplasts, or ribosomes and plasmids

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16
Q

what is resolution

A

the ability to distinguish between 2 points, a higher resolution gives a sharper image

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17
Q

a-how to calculate magnification

b-how do you go from micrometres to millimetres

A

a-image size/ real size

b- divide by 1000

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18
Q

explain the microscopy practical

how do you prepare your slide
part one

A

preparing slide- a slide is a strip of clear glass or plastic that the specimen is mounted on
1- add drop of water to middle of clean slide
2- cut up onion and separate it into layers(use tissue to peel epidermal tissue from bottom of one of these layers)
3-with tweezers place epidermal tissue into water on slide
4- add drop of iodine solution to stain to highlight obejcts in cell by adding colour to it
5- place coverslip on top-stand coverslip upright on the slide next to water droplet, tilt and lower it so it covers speicmen without airbubbles

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19
Q

microscopy practical

part two

how do you use the light microscope

A

1- clip slide youve prepared onto the stage
2- select lowest powered objective lens (lowest magnification)
3- use coarse adjustment knob to move the stage up to just below the objective lens
4- look down the eyepiece, use coarse adjustment knob to move stage down until image is roughly in focus
5- adjuct focus with fine adjustment knob until you get clear image
6-if you need greater magnification, swap to highest powered objective lens and refocus

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20
Q

microscopy practical
part 3
drawing observation out with pencil

A

1- draw what you see uusing a pencil and a sharp point
2- make sure drawing takes up at least half of the space available
-drawn with clear unbroken lines
3- no colouring or shading
4- subcellular structures should be drawn in proportion
5- write title of cell and write down the magnification that you have observed it under
6- label important features e.g. straight uncrossed lines

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21
Q

what is cell differentation

A

process by which cells change to become specialised for its job-occurs as an organism develops

as cells change they develop different subcellular strcutres and turn into dfferent types of cells to carry out specific functions

  • lots of plant cells never lose this ability
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22
Q

explain what differentiation is like in an animal cell

A

ability to differentiate is lost at an early stage for most animal cells -after they become specialised (cells that differentiate in mature animals do it to repair and replace cells like skin or blood cells)

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23
Q

specialised cells- explain sperm cells

A

specialisation for reproduction

function- get male dna to female dna. long tail and streamlined head helps it swim t egg. lots of mitochondria in cell to provide the energy needed. carries enzymes in its head to digest through egg of cell membrane

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24
Q

specialised cells - nerve cells

A

specialised for rapid signalling-

function is to carry electrical signals from one part of body to another , cells are long to cover more distance

has branched connections at its ends to connect to other nerve cells to form network throughout body

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25
Q

specialised cells- musclecells

A

specialised for contraction

function is to contract quickly, cells are long so they have space to contract, contains lots of mitochondria to generate energy for contraction

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26
Q

specialised cells- root hair cells

A

specialised for absorbing water and minerals
long projections, large surface area for absorbing water and mineral ions from the soil
thin walls so that movement of water is not restricted

27
Q

specialised cells- phloem and xylem cells

A

specialised for transporting substances

they form phloem and xylem tubes to transport substances like food and water around plants

to form the tubes the cells are long and joined end to end

xylem cells are hollow in the centre

phloem cells have very few subcellular structures so stuff can flow through them

28
Q

what are chromosomes, what do they contain

A

the nucleus contains your genetic material in the form of chromosomes

chromosomes are coiled up lengths of dna molecules

each chromosomes carries a large number of genes , different genes control different characteristics

we have 23 pairs of chromosomes (humans have 2 copies of 1 type of chromosome)

28
Q

what are chromosomes, what do they contain

A

the nucleus contains your genetic material in the form of chromosomes

chromosomes are coiled up lengths of dna molecules

each chromosomes carries a large number of genes , different genes control different characteristics

we have 23 pairs of chromosomes (humans have 2 copies of 1 type of chromosome)

29
Q

what is the cell cycle

A

when body cells in mutlicellular organisms divide to produce new cells.
when the cell divides it is called mitosis which grows or replaces the cells that have been damaged
at the end 2 new cells identical to the original are formed

30
Q

explain stages of mitosis

A

GROWTH AND DNA REPLICATION -
1- in a cell thats not dividing, dna is spread out in long strings,
2- before dividing, cell grows and increases amount of subcellular structures
3- it duplicates its dna so theres 1 copy for each new cell
4- the dna is copied and froms x shaped chromosomes(each arm is an exact duplicate of the other)

MITOSIS-
5- chromosones line up at the centre of cell and cell fibres pull them apart, 2 arms of each chromosome go to opposite ends of the cell
6- membranes form around each of the sets of chromosomes - becomes nuclei of the 2 new cells - nucleus has divided
7- cytoplasm and cell membrane divides

cell has produced 2 new daughter cells (same dna identical to parent cell)

30
Q

explain stages of mitosis

A

GROWTH AND DNA REPLICATION -
1- in a cell thats not dividing, dna is spread out in long strings,
2- before dividing, cell grows and increases amount of subcellular structures
3- it duplicates its dna so theres 1 copy for each new cell
4- the dna is copied and froms x shaped chromosomes(each arm is an exact duplicate of the other)

MITOSIS-
5- chromosones line up at the centre of cell and cell fibres pull them apart, 2 arms of each chromosome go to opposite ends of the cell
6- membranes form around each of the sets of chromosomes - becomes nuclei of the 2 new cells - nucleus has divided
7- cytoplasm and cell membrane divides

cell has produced 2 new daughter cells (same dna identical to parent cell)

31
Q

prokaryotic cells replicate by binary fission- explain binary fission

A

1- cell splits into 2
2-circular dna and plasmids replicate
3- cell gets bigger and circular dna strands move to opposite poles of the cell
4- cytoplasm begins to divide and new cell walls begin to form
5- cytoplasm divides and 2 daughter cells are produced
6- each daughter cell has 1 copy of the circular dna. but can have a variable number of copies of the plasmids

32
Q

what conditions are required for bacteria to divide quickly - what happens in the wrong conditions

A

warm environment
lots of nuterients

(some bacteria e.g. E colitake as little as 20 mins to replicate in right environment)

if conditions are unfavourable, cells will stop dividng and eventually begin to die

32
Q

what conditions are required for bacteria to divide quickly - what happens in the wrong conditions

A

warm environment
lots of nuterients

(some bacteria e.g. E colitake as little as 20 mins to replicate in right environment)

if conditions are unfavourable, cells will stop dividng and eventually begin to die

33
Q

how to find number of bateria in a population using mean division time

A

the mean divison time is the avergae amount of time it takes for 1 bacterial cell to divide into 2

1- make sure both times are in the same unit
2- divide the total time the bacteria are producing cells by the mean divison time = this gives you the number of divisions
3-mutliply 2 by itself for the number of divisons to find the number of cells

34
Q

how can you grow bacteria in a lab - PRACTICAL

A

-bacteria is grown in a culture medium (carbohydrates, minerals,proteins,vitamins)- that can be nutrient broth solution or solid agar jelly

  • the bacteria grown on agar plates will form visible colonies on surface of jelly, or will spread out to give an even covering of bacteria

(to make an agar plate- hot agar jelly poured into round plastic petri dish, when jelly has cooled and set, inoculating loop used to transfer microorganism to culture medium / or sterile pipette and spreader to get even covering of bacteria ) microorganisms then multiply

in lab - cultures aare not kept above 25 degrees bc harmful pathogens are more likely to grow above this temp.

cultures are incubated at higher temps so they grow faster (industrial conditions)

35
Q

how to investigate effect of antibiotics on bacterial growth (practical)

A

1- place paper disks soaked in different types/concentrations of antibiotics on agar plate that has even covering of bacteria- leave space between disks

2- antibiotic should difuse into agar jelly, antibiotic resistant bacteria is not affected so it will continue to grow on agar - non resistant strains will die - clear area will be left where the bacteria has died - INHIBITION ZONE

3- use a control, this is a paper disk that has not been soaked in an antibiotic - instead soak in sterile water - then it shows that difference between growth of bacteria around control disc and antibiotic disk due to affect of antibiotic

leave plate for 48 hrs at 25 degres

the more effective the antibiotic againt bacteria, the bigger the zone of inhibition.

36
Q

how to avoid contamination by unwanted particles

A

1- petri dish and culture medium must be sterilised before (by heating to a high temp) to kill unwanted microorganisms
2- inoculating loop used to transfer bacteria to culture medium , should be sterilised first over hot flame
3- after transferring bacteria, lid should be tightly taped on to stop microorganisms in air from getting in
4- petri dish should be stored upside down to stop condensation from going on agar surface

37
Q

how to calculate size of inhibition zones to compare results (u can also use this to find the area of a bacterial colony)

A

the larger the inhibition zone around disc = more effective the antibiotic
= do π·r²

37
Q

how to calculate size of inhibition zones to compare results (u can also use this to find the area of a bacterial colony)

A

the larger the inhibition zone around disc = more effective the antibiotic
= do π·r²

38
Q

what are stem cells and what are its advantages

A

-undifferentiated cells that can divide to produce lots more undifferentiated cells
- found in early human embryos
-found in the bone marrow of adults
-have potential to turn into any kind of cell
(embryonic stem cells cant turn into any cell type only certain ones like blood cells)
- stem cells from embryos can bone marrow can be grown in lab to produce clones (genetically identical) and made to differentiate into specialised cells

39
Q

how would stem cells be able to cure disease?

A

-stem cells transferred from the bone marrow of a healthy person can replace faulty blood cells in the patient who receives them
- embryonic stem cels can be used to replace faulty cells in sick people-you could produce insulin producing cells for ppl with diabetes, nerve cells for people with spinal injury
-therapeutic cloning- an embryo could be made t have same genetic info as patient, stem cells produced would have same genes and wouldnt be rejected by patients body to replace the faulty cells

40
Q

what are cons of stem cells(arguments against)

A

cons-risks as stem cells grown in lab might be contaminated with a virus that could be passed on to patient and make them sicker
-ethical- some feel that human embryos shouldnot be used for experiments bc each one is a potential human life
-campaigners believe scientists should concentrate more other sources of stem cells so ppl dont have to use embryos

arguments against-
- they say curing exisiting patients is more important than the rights of embryos
-embryos used in this research are usually unwanted ones from fertility clinics- if they werent used theyd probably be destroyed
- allowed in the uk as long as it follows strict guidelines

41
Q

how do stem cells produce identical plants

A

in plants , stem cells are found in meristems( part of plant where growth occurs)
through plants life, cells in meristem tissues differentiate into any type of plant cell
- stem cells can be used to make clones of whole plants cheap and quick
- used to grow more plants of rare species to stop them from being wiped out,
stem cells can be used to grow crops of identical plants that have desirec feautres for farmers e.g. disease resistance

42
Q

explain diffusion

A

the movement of particles from an area of higher concentration to an area of lower concentration. - happens in both solutions and gases, as particles are free

simplet type is when different gases diffuse through each other e.g. perfume

the bigger the concentration gradient= the faster the diffusion rate

a higher temp = faster diffusion rate , particles have more energy so move faster

43
Q

function of cell membranes during diffusion

A

allows dissolved substances to move in and out of cells by diffusion
- only small molecules can dissolve through cell membranes (like oxygen, glucose,amino acids, water)
- big molecules like starch and protein cant
-particles flow from where theres a higher concentration to a lower
-theres a net movement if all particles are on one side
-the larger the surface area of the membrane , faster the diffusion rate, more particles can pass through

44
Q

what is osmosis

A

(type of diffusion )the passive movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration.

water moleucles pass both ways bc they are moving randomly
more water molecules on one side than the other - so there is steady net flow of water into region with fewer water molecules(into a stronger sugar solution) making the stronger sugar solution more dilute

45
Q

what is a partially permeable membrane

A

a membrane with very smal holes in it- only tiny molecules like water can pass but big molecules like sucrose cannot

46
Q

how can you observe the effect of sugar solutions on plant tissue

A

1- cut up potato into identical cylinders, get beakers with different sugar solutions in them
2- one should be pure water , another should be a very concentrated sugar solution, (have other concentrations in between)
3- measure mass of cylinders- leave one cylinder in each beaker for a day
4- take them out , dry them , measure mass again
5-if cylinders have drawn in water by osmosis, theyll have increased in mass
6- if water has been drawn out, they will have decreased in mass
(calculate percentage change in mass to compare effect of sugar conc on cylinders that didnt have same initial mass)- use to plot graph

47
Q

how to observe effect of sugar solution on plant tissue- part two- practical
what are the variables

A

dependent- chip mass
independent- concentration of the sugar solution
control- vol of solution, temp, time, type of sugar used

48
Q

how to observe effect of sugar solution on plant tissue- part three
how can errors occur

how do u reduce effect of errors

A
  • if some potato cylinders were not fully dried, the excesss water would have given a higher mass
  • if water evaporated from beaker , the concentrations of the sugar solution would change

reduce the effect by repeating experiment and calculate a mean percentage change at each concentration

49
Q

what do root hair cells have and how does this help take in minerals and water

A

roots grow into hairs which stick out into the soil, each branch of a root will be covered in millions of these microscopic hairs
- gives plant a large surface area for absorbing water and mineral ions from soil
- mineral ions needed for healthy growth
- concentration of minerals is usually higher in root hair cells that in the soil around them
(root hair cells csnt use diffusion to take up minerals from soil)

50
Q

how do root hairs take in minerals using active transport

A

active transport allows plant to absorb minerals from a very dilute solution against a concentration gradient, essential for growth (forthis to work it needs energy from respiration)

can also happen in humans e.g. taking glucose from the gut and from kidney tubes

51
Q

how does active transport help stop us from starving

A

it is used in the gut when there is a lower concentration of nutrients in the gut , higher concentration of nutrients in the blood

when theres a higher concentration of glucose and amino acids in the gut they diffuse naturally into blood

sometimes theres a lower concentration of nutrients in the gut than there is in the blood
(this is when the concentration gradient is the wrong way) but it still allows nutrients to be taken into blood

glucose is then taken into bloodstream when its concentration is already higher than in the gut- it can then be transported to the cells where its used for respiration

52
Q

how do organisms exchange substances with their environment

A

cells use diffusion to take in substances they need and get rid of waste products
- oxygen and co2 transferred between cells and environment during gas exchange
- humans- urea (waste product from breakdown of proteins) diffuses from cells into blood plasma for removal from body by kidneys

how easy it is for an organism to exchange substance with its environment depends on organism surface area to volume ratio

53
Q

how to compare surface area to volume ratio

A

(length x width x height) : (length x width)

simplify is needed

54
Q

in single celled organisms why can gases and dissolved substances diffuse directly into and out of the cell across the membrane

A

because theyhave a large surface area compared to their volume so enough substances can be exchanged across membrane to supply the volume of the cell

55
Q

how does multi cellular organisms having a smaller surface area compare to volume affect their diffusion rate

A

not enough substances can diffuse from their outside surface to supply their entire volume - so they need some sort of exchange surface for efficient diffusion(e.g. villi) -these structures allow enough of the necessary substances to pass through

56
Q

in what ways are exchange surfaces adapted to maximise effectiveness

A
  • thin membrane so substances only have a short distance to diffuse
  • large surface area so lots of substances can diffuse at once
  • exchange surfaces in animals have lots of blood vessels to get stuff into and out of the blood quickly
  • gas exchange surfaces in animals like alveoli are often ventilated too so air can move in and out
57
Q

function of lungs ?

where does gas exchange in the lungs and how are they adapted for this

A

job of lungs is to transfer oxygen to the blood and remove waste co2 from it
- gas exchange takes place in tiny air sacs called alveoli

-alveoli is specialised to maximise diffusion bc of
- enormous surface area (around 75m^2 in humans)
-moist lining for dissolving gases
- thin walls
-good blood supply

58
Q

function of the villi in the small intestine

A

small intestine is covered with villi-
provides a large surface area so that digested food is absorbed more quickly into the blood
- single layer of surface cells(thin)
- good supply to assist quick absorption

59
Q

how does the structure of leaves let gases diffuse in and out of the cells

A

-co2 diffuses into the air spaces within leaf - then diffuses into cells where photosynthesis occurs- leafs structure adapted so it can easily occur

  • STOMATA- underneath of leaf is exchange surface, covered in little holes which C02 diffuses through

-oxygen produced by photosynthesis & water vapour diffuse out through stomata, (water vapour lost from all over leaf surface-most lost through stomata)

-size of stomata controlled by guard cells. closes stomata if plant is losing water faster than it’s being replaced by roots- without guard cells-plant would wilt

  • flattened shape of leaf increases area of exchange surface so more effective
    -walls of cells inside leaf form another exchange surface, air spaces in leaf increase area of surface-more chance of co2 getting in

-water vapour evaporates from cells inside leaf - escapes by diffusion as theres lots of it inside leaf , less of it in the air outside

60
Q

how are gills adapted in fish for gas exchange

A

-water (with o2) enters mouth , passes through gills, - oxygen diffuses from water into blood in the gills and co2 diffuses from blood into water
-each gill is made of lots of THIN PLATES called gill filaments- gives BIG SURFACE AREA for gas exchange
-gill filaments covered in small structures called LAMELLAE which increase surface area and has lots of blood capillaries to speed up diffusion
-THIN SURFACE LAYER to minimise distance that gases have to diffuse
-blood flows through lamellae in one direction and water flows over in opposite direction - maintains large concentration gradient

  • concentration of oxygen in water is always higher than in blood so as much oxygen as possible diffuses from water into blood

biology (8 decks)

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