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biology paper 1 > B1 > Flashcards

B1 Flashcards

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1
Q

What is a light microscope used for?

A

A light microscope is used to observe small objects like cells by magnifying them using visible light and lenses.

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2
Q

How does a light microscope magnify objects?

A

Light passes through the specimen and is magnified by the objective and eyepiece lenses.

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3
Q

Name the main parts of a light microscope.

A

Eyepiece lens, objective lenses, stage, light source/mirror, coarse focus knob, fine focus knob.

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4
Q

What are the steps to observe cells using a light microscope?

A
  1. Lower the stage.
  2. Place the slide and secure it.
  3. Select the lowest-power objective lens.
  4. Use the coarse focus knob to move the stage up.
  5. Adjust the fine focus knob for clarity.
  6. Switch to a higher-power lens if needed and refocus.
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5
Q

How do you calculate total magnification?

A

magnification= eyepiece lens x objective lens

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6
Q

Why do scientists stain cells?

A

Many cell structures are transparent. Stains help highlight different parts of the cell for better visibility.

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7
Q

What are common stains used for cell observation?

A

• Iodine solution – Stains starch in plant cells.
• Methylene blue – Stains the nucleus in animal cells.

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8
Q

What are the steps to prepare a stained microscope slide?

A
  1. Place a drop of water or stain on a clean slide.
  2. Place the specimen on the slide.
  3. Gently lower a coverslip to avoid air bubbles.
  4. Use tissue paper to remove excess stain.
  5. Observe under the microscope.
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9
Q

What is the difference between low and high-power magnification?

A

Low power (e.g., ×10) – Wider field of view, useful for locating specimens.
High power (e.g., ×40) – More detail but a smaller field of view, requiring careful focusing.

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10
Q

What is a useful tip for using a microscope effectively?

A

Always start with the lowest magnification, focus, then increase magnification for detailed observation.

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11
Q

What is an example of something observed under a light microscope?

A

The image on the page shows magnified plant cells with visible cell walls.

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12
Q

Why do we use stains when observing cells under a microscope?

A

Many cell structures are transparent. Staining makes different parts of the cell more visible under a microscope.

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13
Q

What is a resolution?

A

Defined as the smallest distance between two points that can be seen as separate entities.

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14
Q

Up to what distance can light microscopes see?

A

You can’t see structures smaller than 0.2 micrometers (2x10-2m)

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15
Q

What is an electron microscope?

A

They use elections instead of light to produce an image.

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16
Q

When was EM developed?

A

At about 1930 to allow scienctists to see in greater detail.

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17
Q

How is the greater resolution in an EM achieved?

A

It’s achieved by using high energy electrons as the light source.

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18
Q

What is the 2 types of electron microscope?

A

Transmition electron microscope
scanning electron microscope

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19
Q

What’s a transmission electron microscope?

A

Produce the most magnified image. They work in a similar way to a light microscope.

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20
Q

How does a TEM work?

A

A beam of electron passes through a very thin slice of the sample. The beam is focused to produce an image.

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21
Q

What is a SEM?

A

It produces a 3d image of a surface.

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22
Q

How does SEM work?

A

They send a beam of electrons across the surface of a specimen. The reflected electrons are collected to produce an image.

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23
Q

Advantages of a light microscope

A
  1. cheap to buy and operate
  2. Small and portable
  3. Simple to prepare a sample
  4. specimens can be living or dead
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24
Q

Disadvantages of electron microscope

A
  1. Expensive to buy and operate
  2. Large and difficult to move
  3. Sample preparation is complex
  4. specimens are dead
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25
What has the development of electron microscope allowed scientists to see?
The detail within sub cellular structures such as chloroplast.
26
What is a chromosome?
Each long molecule of dna is a chromosome
27
How much chromosomes do people have? And chickens?
Most people have 46 chromosomes. Chickens have 78
28
What are genes?
Short sections that code for a characteristic.
29
How can you determine your blood group or weather you have freckles or dimples.
1. Haemoglobin binds to oxygen allowing red blood cells to transport it around the body. 2. The combination of genes in an organism controls how an organism functions and what it looks like
30
What is the structure of DNA
DNA is made of 2 stands which are joined together by bases. The strands are twisted together to form a double helix.
31
What is DNA made from?
It’s made of many small units called nucleotides which are joined together. This means DNA is a polymer
32
What do DNA nucleotides contain?
Phosphate- circle Deoxyribose- pentagon base- rectangle
33
What are each bases pair?
A(denine) - T(hymine) C(ytosine) - G(uanine)
34
What is mRNA and how is it formed?
DNA can’t leave the nucleus of the cells as it is too big. Instead a copy of the DNA is made called mRNA. This is a single stand of DNA.
35
What is the process of Transcription?
The dna around a gene unzips so that both strands are seperated. One of the DNA strands acts like a template. Complementary bases attach to the strand being copied. Instead A binds with U instead of T.
36
What happens when transcription is complete?
The strand of mRNA detaches itself from the DNA template. The DNA zips back up. mRNA is small enough to move out of the nucleus. It travels to subcellular structures called ribosome in the cytoplasm. This is where protein will be made.
37
How are proteins made?
Proteins are made from amino acids. Different amino acids join to form proteins. The order of nucleotides determines the type and order of amino acids and this determines which proteins are produced.
38
What process makes proteins?
Made by a process called translation.
39
What happens in translation
The mRNA attaches to a ribosome. Here the nucleotide sequence is interpreted and a new protein is made
40
Explain the steps of protein synthesis (making protein)
.The ribosome reads the nucleotides on the mRNA in groups of 3. These groups are base triplets. Each triplet codes for a specific amino acid . The ribosome continues to read the triplet codes adding more and more amino acids . The amino acids join together in a chain this is a protein.
41
What are enzymes?
They are biological catalysts- this means they speed up reactions without being used up
42
What reactions are enzymes involved in?
1. Building larger molecules from small ones such as protein synthesis 2. break down large molecules into smaller ones such as digestion
43
What is the active site?
Where molecules of other substances bind to the enzyme.
44
What is the substrate?
The molecule that binds to the enzyme is called the substrate. When it binds to the active site it fits inside the enzyme.
45
Explain the lock and key hypothesis
Enzyme is the lock and the substrate is the key. Only one type of key will fit and be able to open the door.
46
What factors affect enzymes?
1. Temperature 2. Ph 3. enzyme concentration 4. substrate concentration
47
How does temperature affect enzyme controlled reactions?
At higher temps, the enzyme and substrate molecules collide more often increasing the rate of reaction
48
What happens if the temperature is too high?
The amino acid chains in the protein begin to unravel changing the shape of the active site. The enzyme is now denatured and now the substrate can no longer bind and so the rate of reaction decreases until all the enzyme molecules denatured and the reaction stops
49
How does PH affect enzyme controlled reactions?
Affects the interactions between amino acids in a chain. This makes the enzyme unfold changing the shape of the active site
50
how does substrate concentration affect enzyme controlled reactions ?
At a certain substrate concentration all the enzymes are bound to substrate molecules. The rate of reaction is at its maximum. Any further increase in the number of substrate molecules will not increase as there is no enzymes for it to bind to.
51
How does enzyme concentration affect enzyme controlled reactions?
The higher the enzyme conc the faster the rate of reaction.
52
Why is enzyme concentration limited by substrate concentration?
If no new substrate molecules are added the reaction will stop.
53
Why do you need certain types of food?
fats + carbohydrates= energy to move and stay alive Protein= growth and repair of body tissues
54
What is metabolic rate?
The more active you are the more energy you need. Chemical reactions in your cells transfer energy from its chemical stores in food. The speed at which it happens is your metabolic rate.
55
What are carbohydrates?
They are polymers.They are made from smaller carbohydrates molecules like sugar. Inside your body the carbohydrate enzymes bread down carbohydrates.
56
What enzyme breaks down starch?
Amylase
57
Examples of carbohydrates
Sucrose sugar to make cake. Starch is a carbohydrate polymer. It’s synthesised from glucose monomers. Plants often convert glucose to starch. Starch is a chemical energy store.
58
What are protiens?
Protiens are also polymers. They are formed from amino acids. Protease enzymes break down proteins in amino acids.
59
What are lipids?
They are the fats and oils you eat. They are a good store of energy. However some animals use them for insulation and buoyancy. Liapase enzymes break down lipids into fatty acids
60
Explain lipids
Lipids are synthesised from three fatty acid molecules and glycerol molecules. Once food molecules are fully digested, they are absorbed into the bloodstream and then they travel to the cells that need them.
61
What’s the process of respiration?
To produce energy in the form of ATP from larger molecules (like sugars)
62
What type of reaction is respiration?
Respiration is an exothermic reaction
63
When does aerobic respiration take place?
When there’s plenty of oxygen available
64
What’s the word equation for aerobic respiration?
Glucose+oxygen—-> co2+ water +(energy)
65
What’s the symbol equation for respiration?
GLUCOSE. +. Oxygen C6 H12 O6. 602
66
What does aerobic respiration in animals produce?
Lactic acid and energy
67
What does anaerobic respiration in yeast produce?
Ethanol carbon dioxide and energy
68
What respiration produces more ATP?
aerobic respiration= 36ATP anaerobic respiration= 2ATP
69
What’s oxygen debt?
The extra oxygen that is needed to break down the lactic acid formed in anaerobic respiration.
70
What breaks down carbohydrates?
carbohydrases
71
What types of enzymes break down lipids and what are they broken down into?
Lipids are broken down by lipases into glycerol and fatty acids
72
what type of reaction is photosynthesis?
it’s an endothermic reaction
73
Where does photosynthesis take place?
In the chloroplasts
74
What is the word equation for photosynthesis?
C02+H20—-> c6h12o6 + o2
75
What’s the symbol equation?
add a 6 infront of everything but glucose
76
What is the effect of temperature on photosynthesis?
As temperature increases, so does the rate of photosynthesis Once the temperature exceeds the optimum the rate of photosynthesis decreases as enzymes begin to denature.
77
What is the inverse square law?
As the distance from the light source doubles, the light intensity quarters. Light intensity is inversely proportional to light intensity = 1/ distance^2
78
What’s a limiting factor?
A factor that limits the rate of a reaction when there’s not enough of it.
79
What is the word equation for photosynthesis?
C02+H20—-> c6h12o6 + o2

biology paper 1 (3 decks)

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