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GCSE Biology Edexcel > Key concepts in biology 1+2 > Flashcards

Key concepts in biology 1+2 Flashcards

1
Q

What sub cellular structures are found within animal cells?

A

nucleus
cell membrane
mitochondria
ribosomes

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2
Q

What sub cellular structures are found within plant cells?

A

nucleus
cell membrane
cell wall
chloroplasts
mitochondria
vacuole
ribosomes

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3
Q

What sub cellular structures are found within bacteria?

A

chromosomal DNA
Plasmid DNA
cell membrane
ribosomes
flagella

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4
Q

Is an Animal cell Eukaryotic or a Prokaryotic cell?

A

Eukaryotic

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5
Q

Is a plant cell Eukaryotic or Prokaryotic cell?

A

Eukaryotic

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6
Q

Are Bacteria Eukaryotic or Prokaryotic cell?

A

Prokaryotic

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7
Q

Nucleus

A

Contains genetic material which controls the activities of the cell

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8
Q

Cytoplasm

A

Most chemical processes take place here, controlled by enzymes

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9
Q

Cell membrane

A

Controls the movement of substances into and out of the cell

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10
Q

Mitochondria

A

Most energy is released by respiration here

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11
Q

Ribosomes

A

Protein synthesis happens here

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12
Q

Cell wall

A

Strengthens the cell - made of cellulose

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13
Q

Chloroplasts

A

contains chlorophyll, absorbs light energy for photosynthesis

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14
Q

Vacuole

A

filled with cell sap to help keep cell turgid

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15
Q

Chromosomal DNA

A

loop of DNA NOT found in the nucleus

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16
Q

Plasmid DNA

A

small ring of DNA, often used as a vector in genetic modification

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17
Q

Name 3 specialised cells

A

Sperm cells
Egg cells
Ciliated epithelial cells

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18
Q

How are sperm cells adapted to their fuction? Name function

A

Function - to transport male’s DNA to fertilise an egg

Tail - swim to egg
Acrosome (in head) - enzymes digest egg cell membrane
Mitochondria - Releases energy for movement
Haploid nucleus

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19
Q

How are egg cells adapted to their function? Name Function

A

Function - carry females DNA and to nourish the developing embryo in the early stages

nutrients in cytoplasm - respiration and cell division
Haploid nucleus - 23 chromosomes
Cell membrane changes structure - stops more sperm getting in for the right amount of DNA

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20
Q

How are ciliated epithelium adapted to their function? Name function

A

Function - movement of substances

Cilia on surface - sweep e.g mucus
mitochondria - release energy

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21
Q

What do light microscopes do?

A

pass light through the specimen

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22
Q

What do electon microscopes do?

A

use electrons rather than light

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23
Q

What cell structures and organelles are you able to see using a light microscope?

A

nuclei + chloroplasts
study living cells

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24
Q

What cell structures and organelles are you able to see using an electron microscope? + advantages of using electron rather than light

A

smaller things in more detail due to higher magnification + resolution
internal structure of mitochondria + chloroplasts
greater understanding of how cells work + role of sub cellular structures

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25
Q

Formula triangle for magnification

A

Image size
magnification x actual size

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26
Q

How do you find total magnification?

A

Eye piece lens magnification x objective lens magnification

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27
Q

Cell Units calculations + standard form

A

millimetre (mm) x10-3 m
x 1000
Micrometre (μm) x10-6 m
x 1000
Nanometre (nm) x10-9 m
x 1000
Picometre (pm) x10-12 m

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28
Q

Active site

A

The part of the enzyme to which a specific substrate will bind to to react

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29
Q

What are enzymes made of?

A

Proteins (amino acids joined together)

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30
Q

What are enzymes and where are they found?

A

they are biological catalysts - help reactions go faster without being changed in the reaction itself (reduce need for higher temperatures

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31
Q

Substrate

A

the molecule changed in the reaction

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32
Q

How many substrates do enzymes usually work with?

A

Only one - enzymes are said to have a high specificity for their substrate.

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33
Q

Why do enzymes have a high specificity for their substrate?

A

For the enzyme to work the substrate had to fit into the active site.
If the substrate’s shape doesn’t match the active site’s shape then the reaction won’t be catalysed.
This is called the “lock and key” mechanism or the enzyme substrate complex.

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34
Q

What is the “lock and key” mechanism/ the enzyme substrate complex?

A

That the substrate has to fit into the enzyme’s active site for the reaction to be catalysed because the substrate fits into the enzyme just like a key fits into a lock.

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35
Q

How do higher temperatures affect the rate of reaction of enzymes? + what is an enzymes optimum temperature?

A

increases the rate of reaction at first however if the temperature gets too hot then some of the bonds holding the enzyme together break.
This changes the shape of the enzyme’s active site so the substrate no longer fits.
The enzyme is denatured.
enzymes optimum temperature is 37/40

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36
Q

How does pH affect the rate of reaction of enzymes?

A

If the pH is too high or too low the pH interferes with the bonds holding the enzyme together.
This changes the shape of the active site and denatures the enzyme.

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37
Q

What is often the optimum pH for an enzyme?

A

7 (neutral)

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38
Q

What is pepsin?

A

An enzyme used to break down proteins in the stomach.

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39
Q

What pH does pepsin work best at? Why?

A

pH 2 because it is well suited to the acidic conditions in the stomach.

40
Q

How does substrate concentration affect the rate of reaction when enzymes are involved?

A

The higher the substrate concentration, the faster the rate of reaction.
This is because if the substrate concentration is higher then it is more likely that an enzyme will react with a substrate molecule.
However, once all of the enzymes’ active sites are full then increasing the concentration of substrate molecules doesn’t change the rate of reaction as there are no more enzymes to catalyse the reaction.

41
Q

Practical?

A
42
Q

How do you calculate rate of reaction? + units

A

Rate = 1000 / Time
OR Change / Time
S -1

43
Q

Name 3 types of enzymes

A

Proteins, Lipids, Carbohydrates

44
Q

What do plants store energy in the form of?

A

Starch

45
Q

What happens to starch in plants when plants need energy?

A

The enzymes break down the starch into smaller molecules (sugars) which can then be respired to transfer energy to be used by the cells.

46
Q

how can molecules be synthesised?

A

by using enzymes to catalyse the reactions needed for synthesis

47
Q

How can carbohydrates be synthesised?

A

joining together simple sugars

48
Q

Which enzyme catalyses the break down of starch to maltose + other sugars?

A

Amylase

49
Q

Which enzymes convert carbohydrates into simple sugars?

A

Carbohydrase (amylase)

50
Q

What is an example of a carbohydrase?

A

Amylase

51
Q

Which chemical solution is used to detect starch?

A

Iodine

52
Q

What colour will iodine change to if starch is present?

A

From browny-orange (the colour of iodine) to blue-black.

53
Q

What is the Test for reducing Sugars?

A

Benedict’s Reagent

54
Q

What is an example of a non-reducing sugar so therefore you couldn’t test for using the Benedict’s test?

A

Sucrose

55
Q

what is an example of a reducing sugar?

A

glucose

56
Q

Explain the test for Sugars.

A

By adding Benedict’s reagent (which is blue) to a sample and heating it in a water bath at 75°C. If the test is positive a coloured precipitate will be formed.

57
Q

What will be formed if the test for reducing sugars using Benedict’s reagent is positive?

A

A coloured precipitate

58
Q

What is a precipitate?

A

Solid particles suspended in solution

59
Q

What is the initial colour of the precipitate when testing for reducing sugars using Benedict’s reagent (for no sugar)?

A

Blue

60
Q

What is the second colour of the precipitate when testing for reducing sugars using Benedict’s reagent (for the lowest amount of sugar with some still present)?

A

Green

61
Q

What is the third /middle colour of the precipitate when testing for reducing sugars using Benedict’s reagent (for the intermediate amount of sugar)?

A

Yellow

62
Q

What is the fourth / penultimate colour of the precipitate when testing for reducing sugars using Benedict’s reagent (for the second highest amount of sugar)?

A

Orange

63
Q

What is the final colour of the precipitate when testing for reducing sugars using Benedict’s reagent (for the highest amount of sugar)?

A

Brick red

64
Q

What is the colour changing sequence for how the colour of the precipitate changes depending on the amount of sugar present in the test for reducing sugars?

A

Blue, green, yellow, orange, brick red

65
Q

Which enzyme converts proteins into amino acids?

A

Proteases (p + p)

66
Q

How are proteins made?

A

joining amino acids together - enzymes catalyse the reaction needed to do this

67
Q

What is the test used for proteins?

A

Biuret Test

68
Q

Explain Biuret Test

A

1) First, add a few drops of potassium hydroxide solution to make the solution alkaline.
2) Then add some copper (II) sulfate solution (which is bright blue)

Or you can use biuret solution which is a mixture of sodium/potassium hydroxide and copper sulfate.

69
Q

What conclusion would you draw if the solution went from blue to purple?

A

Protein is present

70
Q

Explain what you woukd see if there is protein present (positive result) + if no protein is present (negative result)

A

no protein then the solution will remain blue
if protein is present then the solution will turn purple.

71
Q

What enzyme converts lipids into glycerol and fatty acids

A

Lipase

72
Q

What will happen to the pH when lipids are broken down?

A

The fatty acids will lower the pH of the solution they are in

73
Q

What is the test for lipids?

A

Emulsion test

74
Q

Explain emulsion test + results

A

1) Shake the test substance with ethanol for about 1 minute until it dissolves, then pour the solution into water.
2) If there are any lipids present they will precipitate out of the liquid and show up as a milky emulsion.
3) The more lipid there is, the more noticeable the milky colour will be.

75
Q

What is an emulsion?

A

when one liquid doesn’t dissolve in another - it just forms little droplets

76
Q

What is calorimetry?

A

When food is burnt to see how much energy it contains

77
Q

how do you carry out a calorimetry experiment?

A

1) You need a dry food because it will burn more easily, for example dried beans or pasta will work best
2) weigh a small amount of the food and then skewer it on a mounted needle
3) next, add a set volume of water to a boiling tube (held with a clamp) - this will be used to measure the amount of energy that’s transferred when the food is burnt
4) measure the temperature of the water, then set fire to the food using a Bunsen burner flame, making sure that the Bunsen burner isn’t too near to the water because it may interfere with the results
5) immediately hold the burning food under the boiling tube until it goes out. then relight the food and hold it under the tube again - repeat this until the food won’t catch fire again
6) finally, measure the temperature of the water again and use the result to calculate the joules of energy the food contains using the formula
7) you can minimise the energy in the food being transferred to the environment by insulating the boiling tube e.g. with foil

78
Q

how do you work out the joules of energy in the food in calorimetry?

A

energy in food (in j) = mass of the water (in g (same as 1cm^3)) x temperature change of water (in °C) x 4.2

79
Q

how do you work out how many joules are in each gram of food in calorimetry?

A

energy per gram of food (in J/g) = energy in food (in J) / mass of food (in g)

80
Q

Diffusion

A

overall movement of particles from an area of high to an area of low concentration
down a concentration gradient

81
Q

What substances are transported in Diffusion?

A

only very small molecules can diffuse through cell membranes e.g. glucose, amino acids, water and oxygen

larger molecules such as starch and proteins cannot fit through the membrane

82
Q

Osmosis

A

net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration

83
Q

what is a partially permeable membrane?

A

a membrane with very small holes in it so only small molecules can pass through and not larger molecules

84
Q

in which direction do water molecules pass through the partially permeable membrane during osmosis?

A

The water molecules pass both ways through the membrane because the water molecules move about randomly all the time
But because there are more water molecules on one side than the other there’s a steady net flow of water molecules from one region to the other

85
Q

how do you carry out an experiment to investigate osmosis?

A

1) prepare sucrose solutions of different concentrations ranging from pure water to a very concentrated sucrose solution.
2) use a cork borer to cut a potato into the same sized pieces (the pieces need to be about 1cm in diameter and from the same potato.)
3) divide the potato cylinders into groups of three and use a mass balance to measure the mass of each group.
4) place one group in each solution
5) leave the cylinders in the solution for at least 40 minutes making sure that all of the cylinders get the same amount of time in the solution
6) remove the cylinders and pat them dry gently with a paper towel. this removes excess water from the surface of the cylinders so you get a more accurate measurement of their final masses.
7) weigh each group again and record your results
8) use your results to calculate the percentage change in mass for each group of cylinders before and after the time in the sucrose solution.

86
Q

Why is sucrose used in the solutions in the core practical test for osmosis?

A

The sucrose molecules are too large to diffuse through cell membranes so only the movement of water is being tested

87
Q

how do you calculate the percentage change in mass in an experiment?

A

percentage change in mass = (final mass - initial mass) / initial mass x 100

a positive result shows a gain in mass and a negative result shows a loss of mass

88
Q

What does calculating the percentage change in mass allow you to do in the core practical investigating osmosis?

A

To compare the effect of the sucrose concentration on cylinders that didn’t have the same initial mass

89
Q

What are some control variables for the core practical investigating osmosis?

A

The volume of solution in each group, the size of the potato cylinders, the type of potatoes used, the amount of drying

90
Q

What is the independent variable in the core practical investigating osmosis?

A

The sucrose solution concentration

91
Q

In the core practical investigating osmosis, what does it mean if the points plotted on the graph are above the x-axis?

A

The water concentration of the sucrose solutions is higher than in the cylinders. The cylinders gain mass as water is drawn in by osmosis

92
Q

In the core practical investigating osmosis, what does it mean if the points plotted on the graph are below the x-axis?

A

The water concentration of the sucrose solutions is lower than in the cylinders. This causes the cylinders to lose water so their mass decreases.

93
Q

In the core practical investigating osmosis, what does it mean where the curve crosses the x-axis?

A

The fluid inside the cylinders and the sucrose solution are isotonic - they have the same water concentration

94
Q

Active Transport

A

movement of particles across a membrane against a concentration gradient using energy transferred during respiration

95
Q

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

A

when there is a higher concentration of nutrients in the gut than in the blood, the nutrients diffuse naturally into the blood
however if there is a lower concentration of nutrients in the gut than in the blood active transport allows nutrients to be taken into the blood despite going against the concentration gradient.
essential to stop us starving

96
Q
A

GCSE Biology Edexcel (9 decks)

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