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GCSE Biology > Topic 1 - Cell Biology > Flashcards

Topic 1 - Cell Biology Flashcards

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1
Q

What are the two types of cells?

A

●Eukaryotic (plant and animal)
●Prokaryotic (bacteria)

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2
Q

What are the differences between
eukaryotic and prokaryotic cells?

A

Prokaryotic cells are much smaller than
eukaryotic cells.

Eukaryotic cells contain membrane
bound-organelles and a nucleus containing
genetic material, while prokaryotes do not.

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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 the 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 the
cytoplasm and separate from the main DNA.
●Carry genes that provide genetic advantages
e.g. antibiotic resistance

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6
Q

What is order of magnitude?

A

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

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7
Q

What is a centimetre (cm)?

A

1 x 10-2 metres

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8
Q

What is a millimetre (mm)?

A

1 × 10-3 metres

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9
Q

What is a micrometre (µm)?

A

1 × 10-6 metres

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10
Q

What is a nanometre (nm)?

A

1 x 10-9 metres

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11
Q

What is the difference in order of magnitude between a human hair (100 µm) and the HIV virus (length = 100 nm)?

A
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12
Q

List the components of both plant and
animal cells (5)

A

●Nucleus
●Cytoplasm
●Cell membrane
●Mitochondria
●Ribosomes

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13
Q

List the additional cell components found
in plant cells (3)

A

●Chloroplasts
●Permanent vacuole
●Cell wall

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14
Q

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

A

Controls cellular activities

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15
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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16
Q

What is the function of the cytoplasm?

A

Site of cellular reactions e.g. first stage
of respiration.

Transport medium.

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17
Q

What is the function of the cell
membrane?

A

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

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18
Q

What is the function of the mitochondria?

A

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

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19
Q

What is the function of the ribosomes?

A

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

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20
Q

What is the plant cell wall made of?

A

Cellulose

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21
Q

What is the function of the plant cell
wall?

A

●Provides strength.
●Prevents the cell bursting when water
enters by osmosis

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22
Q

What does the permanent vacuole
contain?

A

Cell sap (a solution of salts, sugars and
organic acids)

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23
Q

What is the function of the permanent
vacuole?

A

Supports the cell, maintaining its
turgidity.

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24
Q

What is the function of chloroplasts?

A

Site of photosynthesis

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25
Q

Describe how sperm cells in animals are
adapted to their function

A

● Haploid nucleus contains genetic information.
● Tail enables movement.
● Mitochondria provide energy for tail movement.
● Acrosome contains enzymes that digest the egg cell
membrane

26
Q

Describe how nerve cells in animals are
adapted to their function

A

● Long axon allows electrical impulses to be transmitted all over
the body from the central nervous system.
● Dendrites from the cell body connect to and receive impulses
from other nerve cells, muscles and glands.
● Myelin sheath insulates the axon and speeds up the
transmission of impulses along the nerve cell.

27
Q

Describe how muscle cells in animals
are adapted to their function

A

● Arrangement of protein filaments allows them to
slide over each other to produce muscle contraction.
●Mitochondria to provide energy for muscle
contraction.
●Merged cells in skeletal muscle allow muscle fibre
contraction in unison.

28
Q

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

A

●Large surface area to absorb nutrients and
water from surrounding soil.
●Thin walls that do not restrict water
absorption.

29
Q

Describe how xylem cells in plants are
adapted to their function

A

●No upper or lower margins between cells
to provide a continuous route for water to flow.
●Thick, woody side walls strengthen their
structure and prevent collapse.

30
Q

Describe how phloem cells in plants 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.

31
Q

What is cell differentiation?

A

The process by which cells become
specialised

32
Q

Why is cell differentiation important?

A

Allows production of different tissues and organs that perform various vital functions in the human body.

33
Q

At what point in their life cycle do most
animal cells differentiate?

A

Early in their life cycle

34
Q

For how long do plant cells retain the
ability to differentiate?

A

Throughout their entire life cycle

35
Q

What is the purpose of cell division in
mature animals?

A

Repair and replacement of cells

36
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.

37
Q

Define magnification

A

The number of times bigger an image
appears compared to the size of the real
object.

38
Q

Define resolution

A

The smallest distance between two
objects that can be distinguished.

39
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.

40
Q

What are the advantages of light
microscopes? (4)

A

● Inexpensive
●Easy to use
●Portable
●Observe both dead and living specimens

41
Q

What is the disadvantage of light
microscopes?

A

Limited resolution

42
Q

How does an electron microscope work?

A

It uses a beam of electrons which are focused using magnets. The electrons hit a fluorescent screen which emits visible
light, producing an image.

43
Q

Name the two types of electron
microscope

A

Transmission electron microscope (TEM)
Scanning electron microscope (SEM)

44
Q

What is the advantage of electron
microscopes?

A

Greater magnification and resolution.

45
Q

Why do electron microscopes have a
greater magnification and resolution?

A

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

46
Q

How have electron microscopes enabled scientists to develop their understanding of cells?

A

● Allow small sub-cellular structures (e.g. mitochondria,
ribosomes) to be observed in detail.
● Enable scientists to develop more accurate
explanations about how cell structure relates to
function.

47
Q

What are the disadvantages of electron
microscopes? (4)

A

●Expensive
●Large so less portable
●Require training to use
●Only dead specimens can be observed

48
Q

How can magnification be calculated?

A

magnification =
size of image / size of real object

49
Q

What is standard form?

A

A way of expressing numbers - written as
a figure between 1 and 10 multiplied by a
positive or negative power of 10.

50
Q

Write 0.005 in standard form

A
51
Q

Write 10382 in standard form

A
51
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.

52
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 Petri dish and secure it with tape. Label accordingly then turn and store upside down.
  6. Incubate the culture at 25oC in school laboratories.
53
Q

Why must Petri dishes and culture media
be sterilised before use?

A

To kill any bacteria already present.

54
Q

Why must inoculating loops be sterilised by passing them through a Bunsen burner flame?

A

To kill any bacteria present on the
inoculating loop.

55
Q

Why must the Petri dish lid be secured with tape and the whole dish stored upside down?

A

Stops bacteria in the air contaminating the culture.
The 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.

56
Q

Why are cultures incubated at 25oC in
school laboratories?

A

Harmful pathogens are less likely to to
grow at this temperature.

57
Q

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

A

πr>sup>2</sup>
= 3.14
r = radius (diameter/2)

58
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.

59
Q

Calculate the number of bacteria that will be present after 3 hours for a population that divides every 15 mins and has 5 bacterium present now

A

15 minutes = 0.25 hours
3/0.25 hours = 12 divisions
5 x 212 = 20480 or 2.048 x 104

GCSE Biology (3 decks)

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