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OCR Gateway A GCSE Biology > B1: Cell level systems > Flashcards

B1: Cell level systems Flashcards

1
Q

define magnification

A

how much larger an image is compared to the actual object

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2
Q

define resolution

A

the ability to distinguish between two points

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3
Q

what’s the formula to calculate magnification

A

I AM formula
Image size = Actual size x Magnification

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4
Q

how do you calculate total magnification

A

Total magnification = Eyepiece magnification x Objective lens magnification

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5
Q

describe how you can use a light microscope to view cells

A
  1. set up microscope with lowest power objective lens
  2. take a thin piece of specimen and put on a clean slide
  3. put a stain on top
  4. carefully cover with cover slip using mounted needle and don’t trap any bubbles
  5. examine the slide under the microscope through the eyepiece lens with the lamp on to let light through and see the specimen clearly
  6. gradually increase magnification
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6
Q

why is a stain used

A
  • to view colourless specimens
  • to highlight different structures/tissues
  • to increase contrast
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7
Q

give 3 main descriptions of a Eukaryote

A
  • plant & animal cells
  • DNA in nucleus
  • membrane bound organelles
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8
Q

give 3 main descriptions of a Prokaryote

A
  • bacterial cells
  • have free DNA (not in nucleus)
  • no membrane bound organelles
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9
Q

state 5 parts of an animal cell

A
  • nucleus
  • cytoplasm
  • mitochondria
  • cell membrane
  • ribosome
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10
Q

state 2 functions of the nucleus

A
  • contains genetic material in form of chromosomes
  • controls cell activities + has instructions on making new cells
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11
Q

state the function of cytoplasm

A

site of chemical reaction

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12
Q

state the function of mitochondria

A

site of aerobic respiration + contains enzymes needed for it

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13
Q

state the function of ribosomes

A

site of protein synthesis

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14
Q

state the functions of cell membrane

A
  • selective barrier controlling what substances can enter/leave
  • has receptor molecules to identify the cell
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15
Q

state 3 organelles only found in plant cells

A
  • cell wall
  • vacuole
  • chloroplasts
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16
Q

what’s the function of the cell wall and what is it made of

A
  • it surrounds and supports the cell
  • it’s made of tough cellulose
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17
Q

what’s the function of a vacuole and what does it contain

A
  • it supports the cell
  • contains cell sap - a watery solution of sugars and salt
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18
Q

what is the function of chloroplasts and what does it contain

A
  • contains chlorophyll (green pigment)
  • site of photosynthesis
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19
Q

what are some of the functions of a prokaryotic cell

A
  • free DNA coiled up
  • flagella - tail like structures allowing cell to move through liquids
  • pili - tiny hair like structures allowing cell to stick to structures and also used to transfer genetic material between bacteria
  • slime capsule - outside cell wall and protects bacterium from dying and poisonous substances, also helps bacteria stick to smooth surfaces
  • plasmid - circular piece of DNA used to store extra genes ie. for antibiotic resistance
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20
Q

how has electron microscopy increased our understanding of sub-cellular structures

A

in transmission electron microscopes the resolution is increased and magnification is better

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21
Q

what 2 types of electron microscopes are there

A
  • transmission electron microscope (TEM) send electrons through specimen producing 2D image
  • scanning electron microscope (SEM) bounce electrons off surface of object and produce 3D image
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22
Q

what is DNA

A
  • it’s all the genetic material found in the nucleus of a cell
  • it coils up into chromosomes
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23
Q

what is a gene

A

a short section of DNA that codes for a particular protein

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24
Q

describe the structure of DNA

A
  • it’s a polymer made of nucleotide monomers
  • it’s made up of 2 strands forming a double helix
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25
Q

describe the structure of a nucleotide

A
  • nucleotides consist of a sugar molecule joined to a phosphate group to form a sugar phosphate backbone
  • one of 4 bases is attached to the sugar
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26
Q

what are the pairs of complementary bases

A
  • A + T - Adeninine + Thymine
  • C + G - Cytosine + Guanine
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27
Q

how are the two sugar phosphate backbones joined to create a double helix

A

with hydrogen bonds

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28
Q

what is protein synthesis

A

the creation of protein in a cell controlled by DNA

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29
Q

describe transcription

A
  1. DNA unzips around the gene
  2. free mRNA (messenger RNA) nucleotides pair up with complementary bases on DNA strand
  3. DNA zips back up
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30
Q

describe translation

A
  1. mRNA travels to the ribosome
  2. tRNA (transfer RNA) carry amino acids in to the ribosome and join to triplet / codon
  3. each triplet codes for a specific amino acid
  4. the amino acids are joined together
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31
Q

how does the structure of DNA affect the proteins made in protein synthesis

A
  • DNA is a triplet code where 3 bases code for one amino acid and the order in which they are put together
  • the order of amino acids determines the protein
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32
Q

what are enzymes

A

biological catalysts that speed up the rate of metabolic reactions (reactions that happen inside an organism are part of processes called metabolism)

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33
Q

describe the structure of enzymes

A

enzymes are proteins containing an active site which fits a specific substrate

34
Q

how can enzymes speed up reactions in the body

A
  • break large molecules to smaller ones
  • build large molecules from smaller ones
35
Q

describe the lock and key hypothesis

A
  • a substrate that fits the specific active site of the enzyme binds together forming an enzyme-substrate complex
  • the enzyme-substrate complex break up into an enzyme and products
  • the products are released from the active site and the enzyme can be used again
36
Q

describe the relationship between an enzyme and substrate

A

they are complementary to each other

37
Q

what factors affect the rate of enzyme controlled reactions

A
  • pH
  • temperature
  • substrate concentration
  • enzyme concentration
38
Q

describe the effect of pH on the rate of an enzyme controlled reaction

A
  • different enzymes work best at different pH’s
  • optimum pH of enzyme depends on its site of action
  • enzymes become inactive (not denatures) as pH varies on either side of optimum
  • only in extreme pH’s are enzymes denatured
39
Q

describe the effect of temperature on the rate of an enzyme controlled reaction

A
  • as temperature increases so does the rate of reaction because enzyme and substrate move around more and collide more, often resulting in successful collisions
  • however as temperature gets too high (beyond an enzyme’s optimum temp) the bonds holding enzyme together break
  • the enzyme becomes denatured as the enzyme’s active site loses it’s shape and substrate no longer fits
  • the enzyme can’t catalyse anymore and the reaction stops
40
Q

describe the effect of substrate concentration on the rate of an enzyme controlled reaction

A
  • the higher the substrate concentration, the faster the rate until (more likely for an enzyme to meet up and react with substrate molecule)
  • once all active sites are locked with a substrate molecule (saturation point) adding more substrate won’t make a difference
41
Q

describe the effect of enzyme concentration on the rate of an enzyme controlled reaction

A
  • the higher the enzyme concentration the faster the rate
  • however the substrate will be limited and so the reaction will stop once all available substrate has reacted
42
Q

what is cellular respiration

A

a universal chemical process continuously occurring in all living cells that supplies ATP

43
Q

what type of reaction is respiration

A

an exothermic reaction

44
Q

what is aerobic respiration and where does it take place

A
  • it’s a chemical reaction that breaks down glucose with oxygen to release energy
  • it takes place in the mitochondria
45
Q

what’s the word and symbol equation for aerobic respiration

A

Glucose + Oxygen —> Carbon dioxide + water + (energy)
C6H12O6 + 6O2 —> 6CO2 + 6H2O + (energy)

46
Q

what is anaerobic reaction

A

a chemical reaction that breaks down glucose into energy without oxygen

47
Q

what does anaerobic respiration produce in animals

A

glucose —> lactic acid + (energy)
C6H12O6 —> C3H6O3 + energy

48
Q

what does anaerobic respiration produce in yeast

A

fermentation:
glucose —> ethanol + carbon dioxide + (energy)

49
Q

which type of respiration produces more ATP

A
  • aerobic respiration produces 36 ATP
  • anaerobic only produces 2 ATP
50
Q

what happens during exercise

A
  • muscles contract to cause movement, requiring energy from respiration
    during strenuous exercise heart and lungs cant deliver oxygen to muscles quickly
  • muscles start to respire anaerobically
  • glucose is partially broken down into lactic acid, releasing only a small amount of energy
51
Q

describe lactic acid and oxygen debt

A
  • lactic acid is toxic so a build up of it in blood and muscles can make them feel tired and ache , causing an oxygen debt
  • therefore muscles can only respire anaerobically for a short period of time
  • after vigorous exercise, the heart pumps fast to transport lactic acid in blood from muscles to liver to be broken down
  • breathing is also fast to supply extra oxygen (oxygen debt) needed to break down lactic acid into CO2 and water, using aerobic respiration
52
Q

how are molecules taken into the body and used

A
  • digest - enzymes break polymers into monomers
  • absorb - monomers can now be absorbed into the blood
  • assimilate - monomers are built back into polymers in the body
53
Q

what is the metabolic rate

A

the speed at which cells transfer energy in metabolism

54
Q

what are carbohydrates

A
  • polymers made of monomers of simple sugars such as glucose
  • elements present = carbon , hydrogen , oxygen
55
Q

what are proteins

A
  • polymers made of monomers of amino acids
  • order of amino acids determines the protein being synthesised
  • elements present = carbon, hydrogen , oxygen , nitrogen
56
Q

what type of enzymes break down carbohydrates

A

carbohydrase (mouth + small intestine)

57
Q

what types of enzymes break down proteins

A

protease (small intestine)

58
Q

what type of enzymes break down lipids and what are they broken into

A
  • lipids are broken down by lipase (small intestine)
  • produces 3 fatty acids and a glycerol molecule
  • elements present = carbon, hydrogen, oxygen
59
Q

what is used to test for carbohydrates and results produced

A

glucose:
- blue benedict —> orange-red
starch:
-brown iodine —> blue-black

60
Q

what is used to test for proteins and results produced

A
  • pale blue biuret —> purple
61
Q

what is used to test for lipids and results produced

A

clear ethanol —> cloudy

62
Q

what are photosynthetic organisms

A
  • they’re the main producers of food
63
Q

what type of reaction is photosynthesis

A

endothermic

64
Q

where does photosynthesis take place

A

chloroplasts

65
Q

why are leaves and stems green

A

because they contain the pigment chlorophyll

66
Q

what’s the word and symbol equation for photosynthesis

A

carbon dioxide + water —> glucose + oxygen
6CO2 + 6H2O —> C6H12O6 + 6O2

67
Q

what do plants take in to make food and how

A
  • carbon dioxide - diffuses from air into plant through the stomata
  • water - enters roots from soil through root hair cells by osmosis
68
Q

how is the oxygen used that’s produced by photosynthesis

A
  • some of it is used in respiration
  • the rest of the oxygen diffuses out of the leaves through the stomata
69
Q

how is the glucose used that’s produced by photosynthesis (5 reasons)

A
  • sucrose stored in fruit
  • stored as starch - can be used at night in respiration
  • ATP
  • cellulose - form cell walls
  • glucose + nitrogen = protein used for growth and repair
70
Q

describe the 2 stage process of photosynthesis

A

stage 1: light dependent (needs light)
- energy transferred from light is used to split water molecules into hydrogen ions and oxygen gas (chlorophyll absorbs light)
stage 2: light independent (doesn’t need light)
- carbon dioxide gas combines with the hydrogen ions to make glucose

71
Q

describe an experiment to investigate photosynthesis

A

Testing a leaf for starch:
- boil leaf - kills leaf + stops it photosynthesising
- boil ethanol in water bath - ethanol very flammable
- place leaf in ethanol - remove chlorophyll
- rinse leaf in water - remove ethanol + soften leaf
- add iodine to leaf - tests for starch

72
Q

what factors affect photosynthesis

A
  • light intensity
  • carbon dioxide concentration
  • temperature
  • these are also called limiting factors because if CO2 or light is in short supply or temperature is too low then the rate of photosynthesis is limited
73
Q

how can the rate of photosynthesis be measured

A

by measuring how much glucose or oxygen is produced over a certain amount of time

74
Q

what’s the rate of photosynthesis and how do you calculate it

A
  • this is a measure of how much photosynthesis occurs in a given time
  • rate = 1 / t
75
Q

how does light intensity affect the rate of photosynthesis

A
  • the higher the light intensity, the faster the rate of photosynthesis
  • this continues until photosynthesis reaches its maximum rate
  • in very low / no light, photosynthesis stops
76
Q

how does carbon dioxide affect the rate of photosynthesis

A
  • CO2 one of reactants for photosynthesis
  • greater the concentration of CO2 the faster the rate of reaction
  • atmosphere has only 0.04% co2 so often limiting factor
    > farmers artificially increase levels of CO2 in greenhouse, increasing rate of photosynthesis
77
Q

how does temperature affect the rate of photosynthesis

A
  • photosynthesis is a series of enzyme-controlled reactions
  • so higher temp = faster reaction
  • however too high of a temp can denature enzymes and reaction stops
78
Q

what 3 factors can you alter to see their effect on rate of photosynthesis and how

A
  • light intensity - vary distance of light from pondweed + count number of bubbles produced
  • CO2 concentration - add diff amounts of potassium hydrogen carbonate powder to water which releases co2
  • temperature - place apparatus in water baths at diff temps
79
Q

what is the inverse square law

A
  • when you double the distance from light source, the light intensity falls by a factor of 4
    light intensity (1) inversely proportional to 1 / distance (d)*2
80
Q

what is a limiting factor

A

when a factor is in short supply

OCR Gateway A GCSE Biology (7 decks)

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