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Biology > topic 1- cell biology > Flashcards

topic 1- cell biology Flashcards

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1
Q

State the equation for the total magnification of a microscope

A

eyepiece lens x objective lens

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2
Q

State the equation that links magnification, image size and actual size

A

Image size = Actual size x Magnification

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3
Q

Define “resolution”

A

the ability to distinguish between two separate points that are very close together

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4
Q

Describe how to view an image of a cell using a microscope

A
  • The object is placed on a rectangular glass slide
  • The slide is clipped onto the stage
  • The lowest powered objective lens is selected
  • The coarse adjustment knob should be used to move the stage up to just below the objective lens
  • Look down the eyepiece and use the coarse adjustment knob to move the stage down until the image is roughly in focus
  • Adjust the focus with the fine adjustment knob until you get a clear image
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5
Q

What is the function of a nucleus?

A

Contains genetic material that controls activites of the cell

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6
Q

what is the function of a cytoplasm?

A

a gel-like substance where most of the chemical reactions take place. It contains enzymes that control these chemical reactions

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7
Q

what is the function of a cell membrane?

A

the cell membrane holds the cell together and controls what goes in and out of the cell

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8
Q

what is the function of the mitochondria?

A

it is the site of respiration

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9
Q

what is the function of ribosomes?

A

These are where proteins are made in the cell

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10
Q

what is a cell wall?

A

A cell wall is a rigid structure made of cellulose. It supports and strengthens the cell

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11
Q

What is a permanent vacuole?

A

The permanent vacuole contains cell sap, a weak solution of sugar and salts, to help keep the cell turgid

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12
Q

What is a chloroplast?

A
  • These are where photosynthesis occurs, which makes food for the plant.
  • They contain a green substance called chlorophyll, which absorbs the light energy needed for photosynthesis
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13
Q

What is a specialised cell?

A

A specialised cell is one that peforms a specific function

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14
Q

What is the function of an egg cell?

A

The main functions of an egg cell are to carry the female DNA and to nourish the developing embryo in the early stages, so the egg cell contains huge food reserves to feed the embryo

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15
Q

What is the function of a sperm cell?

A
  • The function of the sperm is to get the male DNA to the female DNA.
  • It has a long tail and a streamlined head to help it swim to the egg.
    -There are also lots of mitochondria in the cell to provide the energy it needs for swimming
  • sperm cells contain enzymes which allow them to digest their way through the outer layers of the ovum
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16
Q

How are red blood cells (animals) adapted for their function?

A
  • Red blood cells are required to carry oxygen to every cell in the body -> they have a biconcave shape which give them a big surface area for absorbing oxygen. This shape also helps them pass smoothly along capillaries to each the body cells
  • Red blood cells are packed with haemogoblin - the pigment that absorbs the oxygen
  • Red blood cells have no nucleus
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17
Q

how are palisade cells (plants) adapted for their function?

A
  • Palisade leaf cells are adapted for photosynthesis. They are grouped together at the top of a leaf where most photosynthesis occurs.
  • They’re packed with chloroplasts, which absorb the light energy needed for photosynthesis.
  • They’re tall with long sides, which means there’s more surface area exposed for absorbing carbon dioxide from the air in the leaf.
  • They’re also thin, which means you can pack loads of them in at the top of a leaf
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18
Q

What is diffusion?

A

Diffusion is the spreading out of particles from an area of high concentration to an area of low concentration

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19
Q

What are the functions of a nerve cell? How is it adapted for its function?

A
  • the job of a nerve cell is to send electrical impulses around the body
  • the axon carries the electrical impulses from one part of the body to another
  • myelin insulates the axon and speeds up the transmission of nerve impulses
  • the end of the axon has synapses - synapses are junctions which allow the impulse to pass from one nerve cell to another
    -Dendrites increase the surface area so that other nerve cells can connect more easily
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20
Q

How are muscle cells adapted for their function?

A
  • when a muscle cell contracts, protein fibres shorten, decreasing the length of the cell
  • Muscle cells are packed full of mitochondria to provide energy for muscle contraction
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21
Q

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

A
  • the hairs increase the surface area of the root, so it can absorb nutrients and water from the surrounding soil more effectively
  • they have thin walls that do not restrict water absorption
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22
Q

Describe how xylem cells in plants are adapted to their function

A
  • xylem is found in the plant stem. They form long tubes - they carry water and dissolved minerals from the roots to the leaves
  • the thick walls contain lignin which strengthen their structure and prevents collapse
  • xylem cells have no nucleus, cytoplasm, or chloroplasts -> this makes it easier for water and minerals to flow
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23
Q

Describe how phloem cells in plants are adapted to their function

A

phloem tubes carry dissolved sugars up and down the plant
- the sieve plates allow dissolved amino acids and sugars to be transported up and down the stem
- the companion cells provide energy needed for active transport of substances along the phloem

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24
Q

what is cell differentiation?

A

the process by which cells become specialised

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25
Q

why is cell differentiation important?

A
  • differentiation allows the production of different tissues and organs that perform various vital functions in the human body
26
Q

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

A
  • allows small sub-cellular structures (e.g. mitochondria, ribosomes) to be observed in detail
  • enables scientists to develop more accurate explanations about how cell structure relates to function
27
Q

what are the disadvantages of electron microscopes? (4)

A
  • expensive
    -large so less portable
  • requires training to use
  • only dead specimens can be observed
28
Q

what are the advantages of light microscopes? (4)

A
  • inexpensive
  • easy to use
  • portable
  • observe both dead and living specimens
29
Q

What is binary fission?

A
  • bacteria multiplying by simple cell division
  • bacteria can carry out binary fission once every 20 minutes as long as they have enough nutrients and the temperature is suitable
30
Q

State two ways in which bacteria can be grown.

A
  • nutrient broth solution
  • colonies on an agar gel plate
31
Q

What nutrients make up a nutrient broth solution?

A
  • nitrogen for protein synthesis, carbohydrates for energy and other minerals
32
Q

What are uncontaminated cultures of microorganisms needed for?

A

Investigating disinfectant and antibiotic action

33
Q

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

A

To kill any bacteria already present

34
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

35
Q

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

A
  • stops bacteria in the air from 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
36
Q

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

A

Harmful pathogens are less likely to grow at this temperature

37
Q

How do you calculate the number of bacteria in a population after a certain time

A

Number of bacteria = 2^number of rounds of division

38
Q

What are chromosomes made up of?

A

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

39
Q

What is a gene?

A

A section of DNA which codes for a protein

40
Q

How are chromosomes arranged in the nucleus of a body cell?

A

Arranged in pairs - 46 chromosomes form 23 pairs

41
Q

What factors affect the rate of diffusion?

A
  • the difference in concentration
  • the temperature
  • the surface area
42
Q

What are the three main stages of the cell cycle?

A
  • Before the cell divides, it needs to grow and increase the number of sub-cellular structures such as ribosomes and mitochondria. The DNA replicates to form two copies of each chromosome (interphase)
  • In mitosis, one set of chromosomes is pulled to each end of the cell and the nucleus divides (mitosis)
  • finally, the cytoplasm and the cell membranes divide to form two identical daughter cells (cytokinesis)
43
Q

What are the functions of mitosis?

A
  • Produces identical cells that all have the same genetic information
  • Produces additional cells for growth and repair
44
Q

What is a stem cell?

A

An unspecialised cell of an organism which is capable of differentiating into other cell types and of self renewal

45
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.
46
Q

What is the function of stem cells in plant meristems?

A
  • meristem stem 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
47
Q

What is therapeutic cloning?

A

A cloning method where an embryo is produced with the same genes as the patient

48
Q

What the advantages of therapeutic cloning?

A
  • this technique could be useful for a range of medical conditions such as diabetes or paralysis
49
Q

What are the issues with therapeutic cloning?

A
  • some people may have ethical or religious objections
  • adult stem cells infected with viruses could transfer infections to patients
50
Q

Give examples of substances transported by diffusion in the lungs and the kidney

A

Lungs:
-> oxygen diffuses into the blood from the lungs and carbon dioxide diffuses into the lungs from the blood, both down their concentration gradient
Kidney:
-> Urea diffuses from cells into blood plasma so it can be excreted in urine

51
Q

How are single-celled organism adapted for diffusion?

A
  • They have a large surface area to volume ratio - this maximises the rate of diffusion of molecules to meet the organism’s needs
52
Q

What four factors increase the effectiveness of a gas exchange surface?

A
  • large surface area
  • thin membrane
  • efficient blood supply
  • ventilation
53
Q

What is osmosis?

A

the movement of water molecules from a dilute solution to a concentrated solution across a partially permeable membrane

54
Q

What is meant when a solution is hypertonic to a cell?

A

The concentration of the external solution is higher than that of the internal solution

55
Q

What is meant when a solution is hypotonic to a cell?

A

The concentration of the external solution is lower than that of internal solution

56
Q

What could occur when an animal cell is placed in a very hypotonic solution?

A

Water moves into the cell, causing it to burst

57
Q

What happens when an animal cell is placed in a very hypertonic solution?

A

Water moves out of the cell, causing it to shrivel up

58
Q

What is active transport?

A
  • the movement of molecules from a low concentration to a high concentration against a concentration gradient, using energy from respiration
59
Q

How do plant root hair cells use active transport?

A
  • they use active transport to take up mineral ions from a more dilute solution in soils. Ions such as magnesium and nitrates are required for healthy growth
60
Q

How is active transport used to absorb the products of digestion?

A
  • Active transport is used to transport glucose from a lower concentration in the gut to a higher concentration in the blood,
  • Glucose is then transported to the tissues where it can be used in respiration

Biology (7 decks)

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