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Biology > Cell Biology 3 > Flashcards

Cell Biology 3 Flashcards

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1
Q

How do prokaryotic cells reproduce?

A

By simple cell division (binary fission).

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2
Q

What is Asexual reproduction?

A

Reproduction that only requires one parent. It results in the production of genetically identical offspring.

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3
Q

Up to how often can bacteria multiply?

A

As often as 20 minutes if they have enough nutrients and a suitable temperature.

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4
Q

How can bacteria be grown/cultured?

A

In a nutrient broth solution or as colonies on an agar gel plate.

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5
Q

What is required for investigating the action of disinfectants and antibodies?

A

Uncontaminated culture(s) of microorganisms.

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6
Q

What are the conditions affecting speed of bacterial division?

A

-Temperature
-Nutrient availability
-Moisture
-Oxygen

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7
Q

How do we calculate cross-sectional
areas of colonies or clear
areas around colonies?

A

using the formula πr²

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8
Q

How is the number of bacteria in a colony calculated?

A

2 to the power of the number of divisions

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9
Q

How do we work out the number of divisions of a bacterial colony?

A

Total time bacteria are producing cells ÷ mean division time.

(use the same unit of time!!)

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10
Q

What does nutrient broth or agar (‘media’) provide for bacteria in order to grow?

A

Carbohydrates

Nitrogen compounds

Vitamins and minerals

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11
Q

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

A

To kill any bacteria in the agar or petri dish and avoid growing other bacteria.

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12
Q

Why must the inoculating loops used to transfer microorganisms to an agar plate be sterilised/flamed?

A

The inoculating loop must be sterilised/flamed to kill any bacteria on the loop.

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13
Q

Why should the lid of the Petri dish be secured with adhesive tape?

A

To stop microorganisms from the air getting in.

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14
Q

Why should you only tape 3-4 points of a petri dish, not all the way around?

A

To allow oxygen in and prevent the growth of anaerobic bacteria.

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15
Q

In school laboratories, why should bacterial cultures should generally be incubated at 25°C?

A

To prevent the growth of harmful pathogens.

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16
Q

How do we write things in standard form?

A

e.g. 1.23 x 10³

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17
Q

What is the point of using a filter paper disc with distilled water on?

A

As an experimental control - it proves the paper does not affect bacterial growth and that any effect is due only to the disinfectants/antibiotics being tested.

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18
Q

What is an inoculating loop used for?

A

To transfer bacteria from a solution to agar.

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19
Q

What does the nucleus of a cell contain?

A

Chromosomes made of coiled up lengths of DNA molecules

20
Q

How are chromosomes usually found in the body?

A

In pairs.

21
Q

How many pairs of chromosomes do human cells have?

A

23 (46 altogether)

22
Q

How do eukaryotic cells divide?

A

In a series of stages called the cell cycle.

23
Q

What do genes control?

A

The development of different characteristics e.g. hair colour.

24
Q

What are new cells needed for?

A

-Growth
-Development
-Repair

25
Q

Growth and DNA replication step 1:

A

-The cell gets larger and produces more sub-cellular structures such as mitochondria and ribosomes

26
Q

Mitosis:

A

-Chromosomes line up along the centre of the cell
-Cell fibres pull the two arms of each chromosome to opposite poles of the cell

27
Q

Cytokinesis:

A

-Membranes form around each set of chromosomes. These become the nuclei of the two new cells (the nucleus has divided).

-The cytoplasm and cell membrane divide

-The cell has now produced two genetically identical ‘daughter cells’.

-The DNA is also identical to the parent cell.

28
Q

What are the stages of the cell cycle?

A

-Growth and DNA replication
-Mitosis
-Cytokinesis

29
Q

Briefly explain what happens during the Cell cycle.

A

A cell’s genetic material is doubled and then divided into two identical cells.

30
Q

Where does asexual reproduction occur?

A

Predominantly in plants.

31
Q

What are the first 2 steps in binary fission?

A

1- The bacterial cell grows and replicates its genetic material (a circular strand of DNA and plasmids).

2- The two circular strands of DNA move to opposite poles of the cell.

32
Q

What are the third and fourth steps in binary fission?

A

3- The cytoplasm begins to divide and a new cell wall forms down the centre of the cell

4- The cytoplasm divides and two ‘daughter cells’ are produced.

33
Q

What is the final step in binary fission? (hint - daughter cells)

A

5- Each daughter cell has one copy of the circular DNA, but a variable number of plasmid(s).

34
Q

What do we need to make sure is correct in calculations?

A

Units!

35
Q

Why do bacteria need carbohydrates?

A

For respiration, which releases the energy that the cell needs to grow and divide.

36
Q

Why do bacteria need nitrogen compounds?

A

For protein synthesis

37
Q

How do we sterilise inoculating loops?

A

By passing them through a flame (flaming them).

38
Q

Growth and DNA replication step 2:

A

-The cell duplicates its DNA so there’s one copy for each new cell.

-The DNA then condenses to form X-shaped chromosomes.

-Each ‘arm’ of the chromosome is an exact duplicate of the other.

39
Q

What indicates the most effective antibiotic/antiseptic tested? (rp)

A

The largest zone of inhibition and therefore the most bacteria killed.

40
Q

Potential sources of contamination

A

-Skin
-Air
-Soil
-Water

41
Q

For investigations into antibiotics to be useful, the cultures must be what?

A

pure

42
Q

How are solutions and agar sterilised?

A

They must be boiled

43
Q

Why should the dish should be stored upside down? (rp)

A

To prevent condensation forming on the lid and then dripping onto the agar, contaminating the solution.

44
Q

Where are chromosomes found?

A

Chromosomes are found in cell nuclei.

45
Q

What do chromosomes contain? (in the dna molecules)

A

Many different genes that encode (produce) many different proteins.

46
Q

Mitosis ensures that both daughter cells have the same chromosomes as each other and the parent cell. When is this important?

A

For processes that require identical cells to be produced e.g. the growth and repair of tissues and asexual reproduction.

47
Q

Why must we only lift the lid of the petri dish a little?

A

Fewer bacteria will enter.

Biology (18 decks)

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