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(18) Biology 2 > Key Concepts > Flashcards

Key Concepts Flashcards

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1
Q

What is an electron microscope?

A

Microscopes which use electrons rather than light and have a higher magnification and resolution (1930s)

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2
Q

What is meant by the resolution of a microscope?

A

Resolution means how well a microscope distinguishes between two points that are close together (higher resolution - more detail)

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3
Q

What can be seen through a light microscope?

A

Nuclei and chloroplasts (used to study living cells)

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4
Q

What can be seen through an electron microscope?

A

Internal structure of mitochondria and chloroplasts

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5
Q

Why can some cell structures be seen with an electron microscope but not a light microscope?

A

Electron microscopes have a higher magnification and resolution

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6
Q

What is the equation for total magnification?

A

Total magnification = eyepiece lens magnification x objective lens magnification

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7
Q

What is the equation for calculating sizes using magnification?

A

magnification = image size

real size

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8
Q

How do you convert milli - micro - nano - pico

A

x 1000

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9
Q

What is a millimetre (mm) in standard form?

A

x 10 -3 m

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10
Q

What is a micrometre (um) in standard form?

A

x10 -6 m

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11
Q

What is a nanometre (nm) in standard form?

A

x10 -9 m

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12
Q

What is a picometre (pm) in standard form?

A

x10 -12 m

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13
Q

What does the nucleus do?

A

contains genetic material (arranged into chromosomes) that controls the cell’s activities

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14
Q

What is the cytoplasm?

A

gel-like substance where chemical reactions happen, contains enzymes

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15
Q

What does the cell membrane do?

A

Holds the cell together and controls what enters and leaves

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16
Q

What do mitochondria do?

A

Most reactions for respiration take place, respiration transfers energy that the cell needs to work

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17
Q

What do ribosomes do?

A

Involved in translation of genetic material in the production of proteins

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18
Q

What is a cell wall?

A

Subcellular structure of the plant cell which supports and strengthens the cell (made of cellulose)

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19
Q

What does the large vacuole do?

A

Contains cell sap (sugar and salt solution), maintains the internal pressure to support the cell

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20
Q

What do chloroplasts do?

A

Contain a green pigment called chlorophyll, where photosynthesis occurs

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21
Q

What is a eukaryotic and prokaryotic cell?

A

Eukaryotic cells - include animal and plant cells, more complex
Prokaryotic cells - smaller, simpler, no nucleus (bacteria)

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22
Q

How are sperm and egg cells adapted to work together?

A
  • contain half the number of chromosomes so can combine with the egg cell which also has half so the embryo will have the right amount (haploid)
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23
Q

What does “haploid” mean?

A

The cell contains half the number of chromosomes that’s in a normal body cell

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24
Q

How are egg cells adapted for reproduction? (3)

A
  • Nutrients in cytoplasm to feed embryo
  • Haploid nucleus
  • after fertilisation, membrane changes structure to stop more sperm getting in so offspring have right amount of DNA
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25
Q

How are sperm cells adapted for reproduction? (4)

A
  • long tail so it can swim
  • lots of mitochondria to provide energy (from respiration) needed to swim to the egg
  • has an acrosome in head where enzymes are stored which digests through the egg membrane
  • haploid nucleus
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26
Q

How are ciliated epithelial cells specialised for moving materials?

A
  • have cilia which move substances in one direction

e. g. moving mucus up to the throat so it can be swallowed and doesn’t reach the lungs

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27
Q

What subcellular structures do bacteria have?

A
  • Chromosomal DNA (one long circular chromosome - no nucleus)
  • Ribosomes
  • Cell membrane
  • Plasmid DNA (loops of extra DNA)
  • Flagellum
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28
Q

Which type of cell is smaller and simpler and doesn’t have a nucleus? (eukaryotic or prokaryotic)

A

Prokaryotic

29
Q

What is the function of a flagellum in bacteria cells?

A

Long, hair-like structure that rotates to make the bacterium move away from harmful substances like toxins and towards nutrients and oxygen

30
Q

What is the function of Plasmid DNA?

A

Contain things like drug resistance and can be passed between bacteria

31
Q

Why is bacteria a prokaryotic cell?

A

Doesn’t have a nucleus or organelles

32
Q

What are enzymes?

A

Proteins produced by living things, act as biological catalysts

33
Q

What are the three different enzymes?

A
  • Carbohydrase
  • Protease
  • Lipase
34
Q

What do enzymes do?

A

Speed up (catalyse) chemical reactions in the body

35
Q

What is the substrate?

A

Molecule changed in reaction

36
Q

What is an active site?

A

The part on an enzyme which joins to its substrate to catalyse the reaction

37
Q

How does pH affect enzymes?

A
  • Too high or low can denature enzymes (pH interferes with bonds holding enzyme together, changing shape of active site so it can’t attach to the substrate) all have optimum pH
38
Q

How does substrate concentration affect the rate of reaction?

A
  • The higher the substrate concentration, the faster the reaction (more likely to meet and react)
  • This is only true up to a point when all the active sites are full so no more will make a difference
39
Q

What do carbohydrases do?

A

convert carbohydrates into simple sugars (e.g. amylase - starch to maltose)

40
Q

What do proteases do?

A

convert proteins into amino acids

41
Q

What do lipases do?

A

convert lipids into glycerol and fatty acids (fatty acids lower the pH of the solution they’re in)

42
Q

Which enzyme joins chains of glucose molecules together to make glycogen?

A

Glycogen synthase

43
Q

Why are enzymes important for life processes?

A

Because reactions can happen much faster

44
Q

What does enzyme specificity mean?

A

Enzymes only work with one substrate as they have to fit the specific active site

45
Q

What is the “lock and key” mechanism?

A

The specific substrate fits into the specific enzyme just like a key fits into a lock

46
Q

What is amylase?

A

An enzyme that catalyses the breakdown of starch to maltose

47
Q

How do you calculate the rate of reaction?

A

Rate = 1000

time

48
Q

What is diffusion?

A

The net movement of particles from an area of high concentration to an area of low concentration (ovement is random and passive)

49
Q

What is osmosis?

A

The net movement of water particles across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration - movement is random and passive (water molecules move randomly all the time so they pass both ways during osmosis, but more will travel to the more dilute side)

50
Q

What is active transport?

A

The movement of particles across a membrane against a concentration gradient from an area of lower to an area of higher concentration using energy transferred during respiration

51
Q

How can you investigate osmosis?

A
  • Prepare sucrose solutions of varying concentrations (pure water to very concentrated)
  • Cut a potato into same sized pieces (about 1cm in diameter)
  • Use a mass to measure the mass of each cube and place one in each solution for 40 mins (could use groups of potatoes rather than single ones for more accuracy)
  • Remove potatoes and dry gently (removing excess water), weigh each potato, calculate percentage change in mass and record your results
52
Q

How do light microscopes work?

A

By passing light through the specimen

53
Q

What have electron microscopes allowed for?

A

A greater understanding of how cells work and the role of subcellular structures

54
Q

What is a prokaryote?

A

A single-celled organism

55
Q

What does a plant cell have that an animal cell doesn’t?

A
  • cell wall
  • chloroplasts
  • large vacuole
56
Q

What does chromosomal DNA do in bacteria?

A

One long, circular chromosome that controls the cell’s activities and replication (floating free in the cytoplasm as no nucleus)

57
Q

What is the difference between chromosomal and plasmid DNA?

A

Chromosomal: long, circular, controls replication and activities
Plasmid: small loops with genes for drug resistance, can be passed between bacteria

58
Q

How do you view a specimen using a light microscope? (Core Practical)

A
  1. take clean slide and use pipette to drop water on it (to secure specimen in place)
  2. use tweezers to place thin slice of specimen (so light can travel through) on slide
  3. add stain if specimen is colourless (e.g. methylene blue stains DNA)
  4. place cover slip at one end of the specimen (at angle) with a mounted needle and carefully lower onto slide (press down gently so no air bubbles)
  5. clip slide onto stage
  6. select lowest-powered objective lens
  7. use coarse adjustment knob to move stage up until the slide is underneath the objective lens
  8. move stage downwards until specimen in focus
  9. adjust focus with the fine adjustment knob until clear image
  10. use clear ruler to measure the diameter of the circular area visible (FOV -field of view)
  11. If greater magnification is needed, swap objective lens, refocus and recalculate FOV ??
59
Q

How do you create a scientific drawing of a specimen?

A

(it’s really obvious - also mention labelling important features)

60
Q

What does increasing the temperature do to reactions?

A

speeds them up - enzymes reduce the need for high temperatures (because they speed up reactions too)

61
Q

What is pepsin?

A

An enzyme that breaks down proteins in stomach (works best at pH 2)

62
Q

How does temperature affect enzymes?

A

Higher temp increases the rate at first, but too hot and the bonds holding the enzyme together will break, changing the active site (denature) all have optimum temperature

63
Q

How can you investigate the effect of pH on Enzyme Activity? (core practical)

A
  1. drop iodine solution into every well on a spotting tile
  2. put a bunsen burner on a heat-proof mat, and a tripod and gauze over it
  3. put beaker of water on gauze and heat until 35ºC (try to keep temp the same throughout)
  4. use syringe to add 3cm^3 of amylase solution and 1cm^3 of buffer solution (with pH 5) to a boiling tube and leave in water for 5 mins
  5. add 3cm^3 of starch solution to the boiling tube, mix, and start stop watch
  6. drop samples from boiling tube into the wells of iodine every 10 secs (when iodine remains brown/orange it means no starch is present and the amylase has finished reacting)
  7. repeat this whole thing with different pH values to see how it affects the time taken for the starch to be broken down
  8. control any variables to make a fair test (e.g. volume of amylase)
64
Q

Why are molecules in food broken down?

A

Too big to pass through walls of our digestive systems, so they are broken down so they can easily be absorbed into the blood stream

65
Q

How is energy stored in plants?

A

in the form of starch - when its needed enzymes break it down into smaller molecules (sugars) - these can then be respired to transfer energy to be used by the cells

66
Q

How are enzymes used to join molecules together (synthesis)?

A
  • carbohydrates can be synthesised by joining together simple sugars (glycogen synthase joins chains of glucose molecules together to make glycogen)
  • proteins made by joining amino acids (enzymes catalyse the reactions needed to do this)
  • enzymes are also involved in the synthesis of lipids from fatty acids/glycerol
67
Q

When does diffusion occur?

A

In liquids and gases (random movement) - only very small molecules (e.g. glucose, amino acids, oxygen and water) can diffuse through cell membranes (not big molecules like starch/protein/sucrose)

68
Q

What is an example of active transport in the digestive system?

A
  • sometimes there is a lower concentration of nutrients in the gut than the blood, active transport allows nutrients to still be taken into the blood from the gut (this process stops us from starving)

(18) Biology 2 (5 decks)

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