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Biology - Cell biology Flashcards

1
Q

How many micrometers in a centimetre

A

10,000

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2
Q

How to prepare a slide for a microscope

A
  • Add a drop of water to the middle of a clean slide
  • Cut up an onion and separate it out into layers. Use tweezers to peel off some epidermal tissue from the bottom of one of the layers
  • Using the tweezers, place the epidermal tissue into the water on the slide
  • Add a drop of iodine solution
  • Place a cover slip on top
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3
Q

Why is iodine solution used to prepare a slide for a microscope

A

Iodine solution is a stain. Stains are used to highlight objects in a cell by adding colour to them

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4
Q

Why do you not want any air bubbles under the cover

A

It will obstruct the view of the specimen

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5
Q

How to look at a slide using a microscope

A
  • Clip the slide you’ve prepared onto the stage
  • Select the lowest-powered objective lens
  • Use the coarse adjustment knob to move the stage up to just below the objective lens
  • Look down the eye piece and use the coarse adjustment knob to move the stage downwards until the image is roughly in focus
  • Adjust the focus with the fine adjustment knob until you get a clear image of what’s on the slide
  • If you need to see the slide with a greater magnification, swap to a higher-powered objective lens and refocus
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6
Q

Why do cells differentiate

A

To become specialised

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7
Q

Cell differentiation

A

The process by which a cell changes to become specialise for its job

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8
Q

When does most differentiation occur

A

As an organism develops

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9
Q

What are the cells that differentiate in mature cells usually used for

A

Repairing and replacing cells such as skin or body cells

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10
Q

What are undifferentiated cells called

A

Stem cells

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11
Q

What are sperm cells specialised for and how

A

Sperm cells are specialised for reproduction - has a long tail and a streamlined head to help it swim to the egg. There are a lot of mitochondria in the cell to provide the energy needed.
Carries enzymes in its head to digest through the egg cell membrane.

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12
Q

What are nerve cells specialised for and how

A

Nerve cells are specialised for rapid signalling - These cells are long to cover more distance and have branched connections at their ends to connect to other nerve cells and form a network throughout the the body

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13
Q

What are muscle cells specialised for and how

A

Muscle cells are specialised for contraction - Long so they have space to contract, and contain lots of mitochondria to generate the energy needed for contraction

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14
Q

What are root hair cells specialised for and how

A

Root hair cells are specialised for absorbing water and minerals - cells on the surface of the plant grow long “hairs” that stick it into the soil. This gives the plant a big surface area for absorbing water and mineral ions from the soil

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15
Q

How is phloem and xylem cells specialised for and how

A

The cells are long and joined end yo end. Xylem cells are hollow in the centre and phloem cells have very few sub-cellular structures, so that stuff can flow through them.

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16
Q

What are chromosomes

A

Coiled up lengths of DNA molecules

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17
Q

What does mitosis do

A

Used to grow or replace cells that have been damaged

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18
Q

Cell cycle

A

GROWTH AND DNA REPLICATION
- Before the cell divides the DNA is all spread out in long strings
- The cell has to grow and increase the amount off sub-cellular structures such as mitochondria and ribosomes
- It then duplicates its DNA so theres one copy for each new cell. The DNA is copied and forms X-shaped chromosomes. Each ‘arm’ of the chromosome is an exact duplicate of the other
MITOSIS
- The chromosomes line up at the centre of the cell and cell fibres pull them apart. The two arms of each chromosome go to opposite ends of the cell.
Membranes form around each of the sets of chromosomes, these become the nuclei of the two new cells
Lastly the cytoplasm and membrane divide
The cell has now produced 2 new daughter cells. The daughter cells contain exactly the same DNA

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19
Q

How do prokaryotic cells replicate

A

Through binary fission

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20
Q

How does binary fission work

A

The circular DNA and plasmid(s) replicate
The cell gets bigger and the circular DNA strands move to opposite poles of the cell
The cytoplasm begins to divide and new cell walls begin to form
The cytoplasm divides and two daughter cells are produced. Each daughter cell has one copy of the circular DNA, but can have a variable number of copies of plasmids

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21
Q

Conditions for bacteria to divide very quickly

A
  • warm environment, lots of nutrients
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22
Q

Practical to grow bacteria in the lab

A

Place paper discs soaked in different types of antibiotics on an agar plate that has an even covering of bacteria. Leave some space between discs
The antibiotic should diffuse into the agar jelly - non resistant bacteria will die and a clear area will be left where the bacteria have died which is called a zone of inhibition
-Use a control in order to compare results, eg a paper disc that has not been soaked in an antibiotic and instead soaked in sterile water
- the more effective the antibiotic is the larger the zone of inhibition

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23
Q

What is a culture medium

A

Used to grow bacteria and contains the carbohydrates, minerals proteins and vitamins they need to grow
Can be a nutrient broth or a solid agar jelly

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24
Q

How will you know where the bacteria has grown on an agar plate

A

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

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25
Q

How to make an agar plate

A

Hot agar jelly is poured into a petri dis, when the jelly cools and sets

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26
Q

How is bacteria transferred to the culture medium

A

Inoculating loops can be used to transfer microorganisms to the culture medium or a sterile dropping pipette and spreader can be used to get an even covering of bacteria

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27
Q

What temperature are cultures of microorganisms kept at in labs at school and why

A

Not kept above 25 degrees because harmful pathogens are more likely to grow above this temperature

28
Q

Industrial conditions of cultures of microorganisms

A

Cultures are incubated at higher temperatures so they can grow a lot faster

29
Q

How to ensure uncontaminated cultures

A
  • Petri dish and culture medium must be sterilised before use by heating to kill any unwanted microorganisms
  • Inoculating loop should be sterilised before use by passing it through a hot flame
  • The lid of the petri dish should be lightly tapped on to stop microorganisms from the air entering
  • The petri dish should be stored upside down - to stop drops of condensation falling onto the agar surface
30
Q

How to compare the effectiveness of different antibiotics on bacteria

A

Look at the relative sizes of the inhibition zone, the larger the inhibition zone, the more effective the antibiotic is against the bacteria

31
Q

What are stem cells and what do they do

A

Undifferentiated cells that can divide to produce3 lots more undifferentiated cells. They can differentiate into different type of cells depending on what instructions is given.

32
Q

Where are stem cells found

A

Embryonic stem cells are found in early human embryos
Adult stem cells are found in the bone marrow

33
Q

Difference between embryonic stem cells and adult stem cells

A

Unlike embryonic stem cells, adult ones can’t turn into any cell type at all, only certain ones such as blood cells

34
Q

Where are stem cells grown to produce clones

A

In the lab

35
Q

How are stem cells used to cure disease

A

Stem cells can be transferred from the bone marrow of a healthy person to replace faulty blood cells in the patient who receives them

36
Q

What are embryonic stem cells used for

A

Ton replace faulty cells in sick people by using insulin producing cells for people with diabetes, nerve cells for people paralysed by spinal injuries

37
Q

What happens in therapeutic cloning

A

An embryo could be made to have the same genetic information as the patient. This means that the stem cells produced from it would also contain the same genes and so wouldn’t rejected by the patient’s body if used to replace faulty cells

38
Q

Risks involved in stem cells in medicine

A

Stem cells grown in the lab may become contaminated with a virus which could be passed on to the patient and so make them sicker

39
Q

Ethical reasons as to why some people are against stem cell research

A
  • They feel that many embryos shouldn’t be used for experiments since each one is a potential human life
  • People feel that scientists should focus on finding other sources of stem cells so people can be helped without the use of embryos
40
Q

Argument for stem cells

A
  • Embryos used in the research are often unwanted ones from fertility clinics which if they weren’t used for research would probably just be destroyed
41
Q

Where are stem cells found in plants

A

Meristem

42
Q

What are stem cells in plants used for

A
  • To produce clones of whole plants quickly and cheaply
  • Can be used to grow more plants of rare species
  • Stem cells can also be used to grow crops of identical plants that have desired features for farmers
43
Q

What can move in and out of the cell by diffusion

A

Dissolved substances

44
Q

Substances that can diffuse through the cell membrane

A

Oxygen, glucose, amino acids and water

45
Q

Substances that cannot diffuse through the cell membrane

A

Big molecules like starch and proteins

46
Q

What is a partially permeable membrane

A

One with very small holes in it

47
Q

Why do water molecules pass both ways through the membrane during osmosis

A

Because water molecules move about randomly all the time

48
Q

Why is there a steady net flow in osmosis

A

Because there are more water molecules on one side then the other

49
Q

Potato practical

A
  • Cut up a potato into identical cylinders
  • Get some beakers with different sugar solutions in them - one should be pure water, and another should be a very concentrated solution and few others with concentrations in between
  • Measure the mass of the cylinders then leave one cylinder in each beaker for twenty four hours
  • Take them out and dry with a paper towel and measure masses again
  • calculate the percentage mass and then plot on a graph
50
Q

Control variables in potato practical

A
  • Volume of solution
  • Temperature
  • Time
  • Type of sugar used
51
Q

Dependant variable in potato practical

A

Chip mass

52
Q

Potential errors of potato practical and how to reduce them

A

If some potatoes were not fully dried the excess water would give a higher mass
If the water evaporate d from the beaker the concentrations of sugar solutions would change
To reduce the effect of these errors repeat the investigation and calculate a mean percentage change at each concentration

53
Q

How do root hair cells take in minerals and water

A

The cells n plant roots grow into “hairs” which stick out into the soil
Each branch of the root will be covered in millions of microscopic hairs giving it a large surface area to volume ratio
Plants need these minerals for healthy growth
The concentration of minerals is usually higher in the root hair cells than in the soil around them so they move by active transport

54
Q

Where does active transport take place in the body

A

Taking glucose from the gut and from kidney tubules

55
Q

How is active transport used in the gut

A

When there is a lower concentration of nutrients in the gut than in the blood active transport is used which allowed nutrients to be taken into the blood despite the concentration gradient being the wrong way

56
Q

How do organisms exchange substances with environment

A

Cells can use diffusion to take in substances they need and get rid of waste products eg. oxygen and co2 are transferred between cells and the environment during gas exchange

57
Q

Simplify the surface area to volume ratio 64:32

A

Divide both by the volume so 2:1

58
Q

How do single celled organisms exchange surfaces

A

Gases and dissolved substances can diffuse directly into the cell across the cell membrane because they have a large surface area to volume ratio, so enough substances can be exchanged across the membrane to supply the volume of the cell

59
Q

How are surface areas adapted to maximise effectiveness

A
  • Have a thin membrane so substances only have a short diffusion distance
  • Large surface area so lots of substances can diffuse at once
  • In animals they have lots of blood vessels to get stuff in and out of the blood quickly
  • Often ventilated so air moves in and out
60
Q

How are alveoli specialised to have the maximise diffusion of CO2 and O2

A
  • enormous surface area
  • moist lining for dissolving gasses
  • thin walls
  • good blood supply
61
Q

How is the small intestine adapted for exchange

A
  • Inside of small intestine is covered in millions and millions of tiny projections called villi
  • Villi increase surface area in a big way so that digested food is absorbed much more quickly
  • Have single layer of surface cells
  • very good blood supply to assist quick absorption
62
Q

Where does carbon dioxide fiddles in cells

A

Diffuses into the air spaces within the leaf, then it diffuses into the cells where photosynthesis takes place

63
Q

How is the leaf’s structure adapted for diffusion of c02

A
  • The underneath of the leaf is an exchange surface covered in stomata
  • Guard cells close stomata if the plant is losing water faster than its being replaced by the roots
  • The flattened shape of the leaf increases the surface area
  • The walls of the cells inside the leaf form another exchange surface so there’s more chance for carbon dioxide to get into cells
64
Q

What are the gas exchange surface in fish

A

The gills

65
Q

How do fish breath

A

Water enters the fish through its mouth and passes out through the gills, as this happens oxygen diffuses from the water into the blood in the gills and carbon dioxide diffuses from the blood into the water

66
Q

How are gills adapted for gas exchange

A

Each gill is made up of lots of gill filaments which give a big surface area
The gill filaments are covered in lots of lamellae which increases the surface area further
Lamellae have lots of blood capillaries to speed up diffusion and have a thin layer of cells to minimise the distance that gases have to travel through
Blood flows through the lamellae in one direction and water flows over in the opposite direction which maintains a large concentration gradient between the water and the blood

67
Q
A

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