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GCSE AQA biology > Topic 1- Cell biology > Flashcards

Topic 1- Cell biology Flashcards

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1
Q

Eukaryote:

A

Animal and plant cells
* Cell membrane
* Cytoplasm
* Nucleus cotaining DNA

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2
Q

Prokaryote:

A

Bacterial cells
* Cell wall
* Cell memrane
* Cytoplasm
* Single circular strand of DNA
* Pasmid (small loops od DNA)

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3
Q

Permanent vacuole:

A
  • Contains cell sap
  • Foound within cytoplasm
  • Improves cell’s rigidity
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4
Q

Cell membrane:

A
  • Controls what enters and leaves the cell
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5
Q

Cell wall:

A
  • Prevents cell from bursting when water enters by osmosis
  • Provides strength to the cell
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6
Q

Sperm cell:

A

Specialised to carry the male’s DNA to the egg for reproduction.
* Streamlined head and long tail- to aid swimming
* Many mitrochondria (where respiration happens)- supplies the energy to allow the cell to move

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7
Q

Nerve cells:

A

Specialised to transmit electrical signals quickly from one place in the bioy to another
* The axon is long- enables impulses to be carried along long distances
* Many dendrites- branched connections can form with other nerve cells
* Nerve endings have many mitochondria- supplies the energy to make special transmitter chemicals called neurotrnasmitters. These allow the impulse to be passed from one cell to another.

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8
Q

Muscle cells:
💪

A

Specialised to contract quickly to move bones or simply to squeeze, therefore causing moveement.
* Special proteins side over ecahother, causing the muscle to contract
* Lots of mitochondria- provide energy from respiration for contraction
* Stores glycogen- used in respiration by mitochondria

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9
Q

Root hair cells:

A

Specialised to take up water by osmosis and mineral ions by active transport fro t he soil as they are found in thee tips of the roots.
* Have a large surface area due to root hair cells- more water can move in
* Large permaneent vacuole- affects speed of movement of water from soil to cell
* Mitochhondria- provide energy from respiration for the active transport of mineral ions into the root hair cell

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10
Q

Xylem cells:

A

Specialised to transport water and mineral ions up the plant from the roots to the shoots.
* Lignin is deposited- causing the cells to die
* They become hollow and are joined end to end- forms a continuous tube so water and mineral ions can move through

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11
Q

Phloem cells:

A

Specialised o carry the products of photosynthesis to all parts of the plant.
* Cell walls of each cell- form structures called sieve plates when they break down, allowing the movement of substances from cell to cell

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12
Q

Cell differentaiation:

A

To become specialised, stem cells must undergo differentiation to form specialised cells. This invloves them accquiring different sub-cellular structures to enale it to carry out a certain function.
* In animals- most cells differentiate at an early stage, then lose this ability
* In plant cells- many cells retain the zability to differentiate hrough their life.

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13
Q

Microscopy:
🔬

A
  • The first microscpe was the light miscroscpe
  • Light microscpes are used to view tissues, cells and large sub-cellular structures
  • The electron microscope was then developed- allowing siienists to view deep inside sub-cellular structures, such as mitochondria, robosomes, chloroplasts and plamsids.
  • Electron microscopes have a higher magnification than light
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14
Q

Culturing microrganisms:
🧫

A

There are two ways to grow microoganisms in the lab:
1. In nutrient broth solution
2. On an agar plate
Making the plate:
* Hot sterilised agar jelly is poured into a sterile petri dish, which is left to cool and set
* Wire loops containing inoculating loops are dipped into a solution of the microorganism and are spread aver the agar evenly
* A lid is tapped on and the plate iss incubated for a few days so the microorganisms can grow.

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15
Q

Culturing microorganisms- reasons for key steps:

A
  • Petri dishes sterilised using a UV light- so it is not contaminated with other microorganisms (they will compete with desired bacteria for food and space)
  • Inoculating loops must be sterilised by passing them through a flame- kills unwanted organisms
  • The lid of the petri dish should be sealed with tape- stops airborne microorganisms from contaminating the culture
  • Culture dish incubated at 25 degrees- this is the optimum temperature. At a higher temperature, the bacteria could be harmful to humans and any lower, colonies of bacteria would not be able to grow.
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16
Q

How is genetic information stored in a prokaryotic cell?

A
  • Chromosomal DNA
  • Plasmid DNA
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17
Q

What are plasmids?

A
  • Small, circular loops of DNA that are found free in the cytoplasm and seperate from the main DNA.
  • Carry genes that provide genetic advantages e.g. antibiotic reistance.
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18
Q

What is a micrometre?

A

1 x10^-6

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19
Q

What is a nanometre?

A

1x 10^-9

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20
Q

What is the function of the nucleus?

A
  • Controls the cell
  • Stores genetic information
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21
Q

What is the plant cell wall made out of?

A

Cellulose

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22
Q

What is cell differentiation?

A

The process of which cells become specialised.

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23
Q

Why is cell differentiation important?

A
  • Allows for the production of different tissues and organs that perform various vital functions in the human body.
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24
Q

At what point in the life cycle do animal cells differentiate?

A

Early in the life cycle.

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25
Q

How long plant cells retain the ability to differentiate?

A

Throughout their whole life cycle.

26
Q

What is the purpose of cell division in mature animals?

A

Repair and replacement of cells

27
Q

What changes does a cell go through as it differentiates?

A

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

28
Q

Define magnification.

A

The number of times an mage appears bigger compared to the object’s actual size.

29
Q

Define resolution.

A

The smallest distinguishable distance between two objects.

30
Q

What are the advantages of light microscopes?

A
  • Not expensive
  • Portable
  • Able to obseve both dead and living specimens
31
Q

What are the disadvantages of light microscopes?

A

Limited resolution

32
Q

What are the advantages of electron microscopes?

A
  • Greater magnification
  • Greater reoluion
33
Q

How have elctron microscopes allowed scientists to develop a deeper understaning of cells?

A
  • Sub-cellular structures to be observed in detail.
  • Scientists have developed more accurate explanations of how cell structure relates to function.
34
Q

What are disadvantages of electron microscopes.

A
  • Expensive
  • Large, so less portabls
  • Require training to use
  • Only dead specimens can be observed
35
Q

Equation for calculating magnification.

A

Magnification = Image/real

36
Q

How do bacteria multiply?

A

Binary fission.

37
Q

How often do bacteria multiply?

A

Once every 20 minutes if nuterients are available and the temperature is suitable

38
Q

State 2 ways in which bacteria can be grown.

A
  • Nuterient broth solution
  • Colonies on agar gel plate
39
Q

What nutrients make up a nutrient broth solution?

A

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

40
Q

What are uncontaminated cultures of microorganisms needed for?

A

Investigating disinfectant and antibiotic action.

41
Q

Describe the preperation of an uncontaminated culture using aseptic technique.

A

1) Usse pre-sterilised plastic Petri dishes or sterilise glass petri dishes and agar gel before using with an autoclave.
2) Pour the sterilised agar gel into the petri dish and give time for it 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 for 48 hours at 25°C in school labratories

42
Q

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

A

To kill any bacteria already present.

43
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.

44
Q

Why must the petri dish be secured with tape and the whole dish stored uppside down?

A
  • To stop bacteria in the air contaminating the culture
  • But 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.
45
Q

Why are cultures incubated at 25°C in school labratories?

A

Harmful pathogens are less likely to grow at this temperature.

46
Q

What is the equation to calculate the number of bacteria.

A

Number of bacteria at end of time period = number of bacteria at beginning x 2^number of divisions in time period

47
Q

What are chromosomes made up of?

A

Chromrosmes consist of DNA molecules combined with proteins. They contain genes which provide the instructions for protein synthesis.

48
Q

What is a gene?

A

A section of DNA which codes for a specific protein.

49
Q

How many chromosomes are found in the nucleus of a human body cell?

A

46

50
Q

How many chromosomes are found in the nucleus of gametes?

A

23

51
Q

How are chromosomes arranged in the nucleus of a human body cell.

A

In pairs- there are 23 pairs

52
Q

What are the three main stages of the cell cycle?

A

1) DNA replication and number of sub-cellular structures increase
2) Mitosis
3) Division of cell

53
Q

Why is mitosis important?

A
  • Produces identicall cells which all have the same genetic information.
  • Produces additional cells for growth and repair.
54
Q

Describe the first stage of the cell cycle.

A

THE LONGEST STAGE:
* Cells grow
* DNA replicate
* Number of sub-cellular structures increase e.g. mitochondria nad ribosomes

55
Q

Describe the second stage of the cell cycle.

A

Each pair of chromsomes is pulled to each end of the cell, the the nucleus divides.

56
Q

Describe the third stage of the cell cycle.

A
  • The cytoplasm and cell membrane divide
  • Two identical daughter cells are produced
57
Q

What is a stem cell?

A

An unspecialised cell which is capable of differentiating into other cell types and of self-renewal.

58
Q

What is the function of stem cells in embryos?

A
  • Embryonic stem cells can replicate themselves and differentiate into many other types of cells.
  • Embryonic stem cells may be able to treat conditions such as paralysis and diabetes by dividing to replace damaged cells.
59
Q

What is the function of stem cells in adult bone marrow?

A
  • Adult stem cells can differentiate into several cell types to replace dead or damaged tissues.
  • For example, bone marrow stem cells can form many different types of blood cell.
60
Q

What is the function of stem cell in plant meristems?

A
  • Meristem cells retain the ability to differentiate into any type of plant cell throughout their lifespan
  • They can differentiate into any cell which is required by the plant.
61
Q
A

GCSE AQA biology (5 decks)

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