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aqa gcse biology free > T1 cell structure > Flashcards

T1 cell structure Flashcards

1
Q

two types of cells

A

eukaryotic (plant and animal)

prokaryotic (bacteria)

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2
Q

differences between eukaryotic and prokaryotic cells?

A

P - smaller

E - contain membrane bound-organelles and nucleus containing genetic material

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3
Q

what is the prokaryotic cell wall composed of?

A

peptidoglycan

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4
Q

how is genetic information stored in a prokaryotic cell?

A

found free within cytoplasm as:
chromosomal DNA (single large loop of circular DNA)
plasmid DNA

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5
Q

what are plasmids?

A

small, circular loops of DNA found free in cytoplasm and separate from the main DNA

carry genes that provide genetic advantages

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6
Q

order of magnitude?

A

power to the base 10 used to quantify and compare size.

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7
Q

list the components of both plant and animal cells

A 
nucleus
cytoplasm
cell membrane
mitochondria
ribosomes
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8
Q

list additional cell components found in plant cells

A

chloroplasts
permanent vacuole
cell wall

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9
Q

other than storing genetic information, what is the function of the nucleus?

A

controls cellular activities

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10
Q

describe the structure of the cytoplasm

A

fluid component of the cell

contains organelles, enzymes and dissolved ions and nutrients.

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11
Q

function of the cytoplasm

A

site of cellular reactions

transport medium

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12
Q

function of the cell membrane

A

controls the entry and exit of materials into and out of the cell

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13
Q

function of the mitochondria

A

site of later stages of aerobic respiration in which ATP is produced

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14
Q

function of the ribosomes

A

joins amino acids in a specific order during translation for the synthesis of proteins.

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15
Q

what is the plant cell wall made of

A

cellulose

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16
Q

function of the plant cell wall

A

provides strength

prevents the cell bursting when water enters by osmosis

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17
Q

what does the permanent vacuole contain?

A

cell sap (solution of salts, sugars and organic acids)

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18
Q

function of the permanent vacuole

A

supports the cell, maintaining its turgidity.

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19
Q

function of the chloroplasts

A

site of photosynthesis

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20
Q

describe how sperm cells in animals are adapted to their function

A

haploid nucleus - contains genetic information

tail - enables movement

mitochondria - provides energy for tail movement

acrosome - contains enzymes that digest the egg cell membrane

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21
Q

describe how nerve cells in are adapted to their function

A

long axon - allows electrical impulses to be transmitted all over the body from CNS

dendrites - from the cell body connect to and receive impulses from other nerve cells, muscles and glands

myelin sheath - insulates axon and speeds up the transmission of impulses along the nerve cell

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22
Q

describe how muscle cells are adapted to their function

A

arrangement of protein filaments - allows them to slide over each other to produce muscle contraction

mitochondria - provides energy for muscle contraction

merged cells in skeletal muscle - allow muscle fibre contraction in unison.

23
Q

describe how root hair cells in plants are adapted to their function

A

large surface area - absorbs nutrients and water from surrounding soil

thin walls - don’t restrict water absorption.

24
Q

describe how xylem are adapted to their function

A

no upper or lower margins between cells - provide a continuous route for water to flow

thick, woody side walls - strengthen their structure and prevent collapse

25
Q

describe how phloem cells are adapted to their function

A

sieve plates - let dissolved amino acids and sugars be transported up and down the stem

companion cells - provide energy needed for active transport of substances along the phloem

26
Q

what is cell differentation

A

process by which cells become specialised

27
Q

why is cell differentiation important

A

allows production of different tissues and organs that perform various vital function in the human body

28
Q

At what point in their life cycle do most animal cells

differentiate?

A

early in their life cycle

29
Q

how long do plant cells retain the ability to differentiate?

A

throughout their entire life cycle

30
Q

purpose of cell division in mature animals

A

repair and replacement of cells

31
Q

what changes does a cell go through as it differentiates

A

becomes specialised through acquisition of different sub-cellular structures to enable a specific function to be performed by the cell.

32
Q

how does a light microscope work

A

passes a beam of light through a specimen which travels through the eyepiece lens, allowing the specimen to be observed

33
Q

advantages of light microscopes (4)

A

inexpensive
easy to use
portable
observe both dead and living specimens

34
Q

disadvantage of light microscopes

A

limited resolution

35
Q

how does an electron microscope work

A

uses a beam of electrons which are focused using magnets.

electrons hit a fluorescent screen which emits visible light, producing an image

36
Q

name the two types of electron microscope

A

transmission electron microscope (TEM)

scanning electron microscope (SEM)

37
Q

advantages of electron microscopes

A

greater magnification and resolution

38
Q

why do electron microscopes have a greater magnification and resolution?

A

use a beam of electrons which has a shorter wavelength than photons of light.

39
Q

how have electron microscopes enable scientists to develop their understanding of cells?

A

allow small sub-cellular structures to be observed in detail

enable them to develop more accurate explanations about how cell structure relates to function

40
Q

disadvantages of electron microscopes (4)

A

expensive
large so less portable
require training to use
only dead specimens can be observed

41
Q

magnification equation

A

mag=
size of image/
size of real image

42
Q

how do bacteria multiply

A

binary fission (simple cell division)

43
Q

how often do bacteria multiply

A

once every 20 mins if enough nutrients are available and the temperature is suitable

44
Q

2 ways in which bacteria can be grown

A

nutrient broth solution

colonies on an agar gel plate

45
Q

what nutrients make up a nutrient broth solution

A

all nutrients required for bacteria to grow including nitrogen for protein synthesis, carbohydrates for energy and other minerals.

46
Q

what are uncontaminated cultures of microorganisms needed for?

A

investigating disinfectant and antibiotic action

47
Q

describe the preparation of an uncontaminated culture using aseptic technique

A
  1. use pre-sterilised plastic petri dishes or sterilise glass petri dishes and agar gel before using with an autoclave
  2. pour the sterile agar gel into the petri dish and allow time to set
  3. sterilise the inoculating loop by passing it through a Bunsen burner flame
  4. dip the inoculating loop into the solution of microorganisms and make streaks with the loop on the surface of the agar
  5. put the lid on the dish and secure with tape, label and store upside down
  6. incubate at 25C in school labs
48
Q

why must petri dishes and culture media be sterilised before use

A

kill any bacteria already present

49
Q

why must inoculating loops be sterilised by passing them through Bunsen burner flame

A

kill any bacteria present already

50
Q

why must a Petri dish be secured with tape and stored upside down

A

stops bacteria in the air contaminating the culture

lid is not fully sealed to prevent the growth of anaerobic bacteria in a lack of oxygen

upside down to prevent condensation from forming and dripping down onto the colonies

51
Q

why are cultures incubated at 25C in school laboratories

A

harmful pathogens are less likely to grow at this temperature

52
Q

what is the formula used to calculate cross-sectional area of a bacteria colony or clear area around a bacterial colony

A

πr2
= 3.14
r = radius (diameter/2)

53
Q

how is the number of bacteria in a population after a certain time calculated from the mean division time

A
  1. Calculate the number of times the bacteria will divide in the given time period
    from the mean division time.
  2. Use the following equation to calculate the number of bacteria:
    Number of bacteria in population at end of time period = number of bacteria at
    the beginning of the time period x 2number of divisions in the time period

Express the answer in standard form if possible.

aqa gcse biology free (25 decks)

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