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GCSE OCR Biology- Triple > B1- Cell Level Systems > Flashcards

B1- Cell Level Systems Flashcards

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1
Q

Name two types of cells:

A
  • Eukaryotes (all animals and plants) are made from complex cells called eukaryotic cells.
  • Prokaryotes (bacteria) are smaller and simpler cells called prokaryotic cells.
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2
Q

What are sub-cellular structures?

A

Sub-cellular structures components of the cell that each have a specific function.

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3
Q

Name the function of the nucleus:

A

The nucleus is the ‘control centre’ of the cell, which contains DNA (genetic info) in the form of genes, and also information for the formation of proteins.
Genetic info is carried on chromosomes, which are a form of DNA.

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4
Q

Name the function of the cell membrane:

A
  1. The cell membrane keeps the cell together by containing the organelles within it.
  2. Cell membranes are partially permeable (selective barrier), allowing selected chemicals only to move both into and outside of the cell.
  3. It contains receptor molecules that are used for cell communication.
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5
Q

Name the function of the cytoplasm:

A

The cytoplasm includes all the contents of the cell, within the cell membrane, but outside of the nucleus of the cell. Jelly-like substance that contains salts, sugars and enzymes. Chemical reactions take place here.

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6
Q

Name the function of the mitochondria:

A

The mitochondria is the power house of a cell. They generate chemical energy in the form of ATP during aerobic respiration. Generally, the mitochondria numbers vary by cell type (muscle cells need more).
They are the site of cellular respiration and contain the enzymes needed for the reactions involved.

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7
Q

Name the function of the ribosomes:

A

The ribosomes interpret nuclear information (mRNA) and use it to build proteins (protein synthesis). Extremely small can only only be seen using an EM.

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8
Q

Name the function of the cell wall:

A

The cell wall gives cell shape and support. It is made up of cellulose which provides strength.

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9
Q

Name the function of the chloroplasts:

A

The chloroplasts allow plants to make their own food by carrying out photosynthesis. They contain the green pigment chlorophyll that traps the sun’s energy. Some cells contain more than 50.

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10
Q

Name the function of the vacuole:

A

The vacuole is filled with cell sap. They are permanent in plant cells. Fluid filled space in membrane. Controls osmosis. Keeps plant upright.

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11
Q

Name all the sub-cellular structures found in prokaryotic cells:

A
  • Cytoplasm
  • Cell Wall
  • Loop of DNA (also called chromosomal DNA)
  • Ribosomes
  • Flagellum
  • Cell membrane
  • Plasmids
  • Slime Capsule
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12
Q

Name the function of the Loop of DNA (also called chromosomal DNA):

A

The Loop of DNA (One long circular chromosome) controls the cell’s activities and replication. It floats free in the cytoplasm (not in nucleus)

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13
Q

Name the function of the Plasmid:

A

The plasmid is small loop of extra DNA that aren’t part of the chromosome. Plasmids contain genes for things like drug resistance and can be passed between bacteria.

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14
Q

What is resolution?

A

The minimum distance at which two distinct points of a specimen can still be seen - either by the observer or the microscope camera - as separate entities.

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15
Q

What is magnification?

A

Magnification is the ability to make small objects seem larger, such as making a microscopic organism visible.

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16
Q

Describe the differences between Light Microscope and Electron Microscope:

A

Light Microscope…

Magnification: 1500x
Resolution: Low (250nm)
Type of radiation used: Light
Focussed by: Objective lens
Type of material that can be viewed: Living/moving
Size of microscope: Small
Preparation and cost of material: Cheap/Easy

Electron Microscope…

Magnification: 500,000x
Resolution: 0.25nm
Type of radiation used: Electron Beam
Focussed by: Electromagnetic lens
Type of material that can be viewed: Dead
Size of microscope: Large
Preparation and cost of material: Difficult and Expensive.

Also not portable and can’t be used to look at living tissue, unlike light microscopes.

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17
Q

A light microscope is good for…

A
  • Looking at live samples quickly
  • Looking at living samples
  • Inexpensive for high magnification
  • We can use it to see nuclei and chloroplasts
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18
Q

A scanning electron microscope (SEM) is good for…

A
  • High magnification (x500,000)
  • High resolution
  • 3D
  • lets us see smaller things in more detail like the internal structure of a mitochondria.
  • We can see plasmids and viruses.
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19
Q

A transmission electron microscope (TEM) is good for…

A
  • High magnification (x500,000)

- High resolution

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20
Q

Name the parts of a light microscope:

A
  • Eyepiece lens (looked through to see the image and also magnifies the image)
  • Objective lens (magnifies the image. Usually there are three different objective lenses (x4, x10, x40)
  • Stage (supports the slide)
  • Clip (holds the slide in place)
  • Handle (to carry the microscope with)
  • Lamp (shines light through the slide so the image can be seen more easily)
  • Focussing knobs (moves the stage up and down to bring the image into focus) includes Coarse adjustment knob and Fine adjustment knob.
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21
Q

Explain how to prepare a specimen before investigation:

A
  • If specimen is thick, make a thin slice of it
  • Take a clean slide and use pipette to put on drop of water or mountant in the middle- this will secure the specimen in place.
  • Use tweezers to place your specimen on the slide.
  • Add a drop of stain if needed- so if specimen is colourless or transparent, a drop of stain is added to make the specimen easier to see.
  • Different stains are used to highlight different structures or tissues.
  • Place a cover slip at one end of the specimen, holding it at an angle with a mounted needle.
  • Carefully lower the cover slip onto the slide. Press it down gently with the needle so that no air bubbles are trapped under it.
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22
Q

What is the formula for calculating total magnification:

A

total magn. = eyepiece lens mag. x objective lens mag

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23
Q

What is the general formula for magnification?

A

magnification = image size
—————-
real size

24
Q

What are chromosomes?

A

Chromosomes are long molecules of coiled up DNA.

25
Q

What are genes?

A

The DNA is divided up into small sections called genes..

A section of DNA that codes for a particular protein is called a gene.

26
Q

Describe the DNA structure/molecule:

A
  • DNA is a double helix
  • Each of the two DNA strands is made up of lots of nucleotides joined together in a long chain- this make DNA a polymer.
  • Each nucleotide contains a small molecules called a base.
  • DNA has four bases.
  • Adenine, Thymine, Cytosine and Guanine.
  • Each base forms cross links to a base on the other strand.
  • This keeps the two DNA strands tightly wound together (hydrogen bonds between nucleotides)
  • A is complementary with T
  • C is complementary of G
  • 2nd nucleotide strand is inverted upside down.
27
Q

Describe what each nucleotide contains:

A
  • Each DNA nucleotide has the same pentose sugar and phosphate (acid) group.
  • The base on each nucleotide is the only part of the molecule that varies (its either A,T,C or G)
  • The base is attached to the sugar.
28
Q

How is DNA a polymer?

A

Polymers are large, complex molecules composed of long chains of monomers joined together.
Monomers are small basic molecular units.
DNA is a polymer made up of nucleotide monomers.

29
Q

How does our body try and avoid corruption of genetic information?

A

The genetic information is kept inside protein coats to protect it from corruption.

30
Q

How many chromosomes do Humans have?

A

46 (23 paris).

31
Q

What does DNA stand for?

A

Deoxyribonucleic Acid

32
Q

What are enzymes?

A

Enzymes act as biological catalysts.
A catalyst is a substance that speeds up a reactions without being changed or used up in the reaction itself.
Enzymes reduce the need for high temperatures (too high temperature can denature both cells and enzymes so increasing temp has a limit) and we only have enzymes to speed up the useful chemical reactions in the body.
Each enzyme is a protein coded for by a different gene, and has a unique shape which it needs to do its job.
The enzyme and substrate are complementary of each other.

33
Q

What is a substrate?

A

The substrate is a molecule changed in the reaction.
It fits into the active site of the enzyme (the part where substrate joins the enzyme to catalyse reaction).
A substrate is complementary to its enzyme.
The substrate is specific to the enzyme, e.g.
A lipase enzyme will only catalyse lipids into fatty acids and glycerol.

34
Q

What enzyme breaks down starch?

A

Amylase and other carbohydrase enzymes break down starch into sugar.

35
Q

What enzyme breaks down protein?

A

Protease breaks down protein into amino acids.

36
Q

What enzyme breaks down lipids?

A

Lipase breaks down lipids into fatty acids and glycerol.

37
Q

How does temperature affect the rate of reaction for enzymes?

A
  • Changing the temperature changes the rate of an enzyme-controlled reaction.
  • At first, the higher the temperature is, the faster the rate of reaction is.
  • The enzyme and substrate move more, so are more likely to collide and react or catalyse.
  • However, if the reaction gets too hot, some of the bonds holding the enzyme together break or the shape of the active site changes, causing the enzyme to become denatured.
  • Since the active site shape has changed, it is no longer complementary to the substrate, so the reaction will not catalyse effectively or at all, so the reaction stops.
  • This is irreversible.
  • Each enzyme has it optimum temperature (when the reaction occurs the fastest and doesn’t denature the enzymes) - 37.5Cº, same temperature as our bodies.
38
Q

How does pH affect the rate of reaction for enzymes?

A

-If the pH is too high or too low, it interferes with the bonds holding the enzyme together.
This changes the shape of the active site and can irreversibly denature the enzyme.
All enzymes have an optimum pH that they work best at, it’s often neutral pH 7, however not always.
For example, pepsin is an enzyme used to break down proteins in the stomach.
It works best at pH 2, which means it’s well suited to the acidic conditions in the stomach.

39
Q

How does enzyme conc^n affect the rate of reaction for enzymes?

A
  • The more enzyme molecules there are in a solution, the more likely a substrate molecule will meet up with one and join with it.
  • So increasing the concentration of the enzyme increases rate of reaction.
  • But if the amount of substrate is limited there comes a point when there are more than enough enzyme molecules to react with the available substrate, so adding more enzymes will have no further effect.
  • The graph would level off at some point.
  • The substrate then becomes the LIMITING FACTOR.
40
Q

How does the substrate conc^n affect the rate of reaction for enzymes?

A
  • The higher the substrate concentration, the faster the reaction, its more likely the enzyme will meet up and react with a substrate molecule.
  • This is only true up to the point- after that there are so many substrate molecules and not enough free active sites on the enzymes, and adding more will not increase the rate of reaction.
41
Q

What is Respiration?

A

Respiration is the process of transferring chemical energy from the breakdown of glucose (a sugar).
It goes on in every cell in all living organisms, 24/7.
It is said to be a universal chemical process.
The energy transferred by respiration can’t be used directly by cells- so its used to make a substance called ATP (Adenosine triphosphate).
ATP stores the energy needed for many cell processes.
Respiration is controlled by enzymes, so the rate of respiration is affected by both temperature and pH.
It is an exothermic reaction, it transfers energy to the environment (by heat).
Cells can respire using glucose as a substrate (also can use other organic molecules like lipid, proteins carbohydrates) for respiration.

42
Q

What is aerobic respiration?

A

Aerobic respiration occurs when there is sufficient oxygen.
It is the most efficient way to transfer energy from glucose.
Produces 32 ATP molecules per molecule of glucose.
You use this type of respiration most of the time.
Oxygen is a limiting factor.

43
Q

What is the word equation for aerobic respiration?

A

glucose + oxygen -> ENERGY + carbon dioxide + water

44
Q

What is the symbol equation for aerobic respiration?

A

C6H12O6 + 6O2 -> 6CO2 + 6H2O

45
Q

What is anaerobic respiration?

A

Anaerobic respiration occurs without oxygen.
It is not the most efficient way to transfer energy from glucose because it transfers much less energy per glucose molecule than aerobic.
Just 2 molecules of ATP are produced.
During vigorous exercise, you body cannot supply enough oxygen for aerobic respiration. (OXYGEN DEBT)
So your muscles have to respire anaerobically.
All animals that respire anaerobically produce lactic acid.
The glucose is only partially broken down.
When lactic acid builds up, it gets painful and makes your muscle fatigued.
To get rid of the lactic acid, you need to ‘repay’ the oxygen debt.
Advantage- you can keep using your muscles without oxygen being a limiting factor.

46
Q

What is the anaerobic respiration word equation and symbol equation for yeast?

A

Fermentation equation:

Glucose -> Energy + Ethanol + Carbon Dioxide.

C6H12O6 –> Energy + 2C2H5OH + 2CO2.

47
Q

What is the word equation for anaerobic respiration in animals?

A

glucose –> lactic acid + energy (2ATP)

48
Q

How can you test for sugars? (reducing and non reducing)

A

Reducing sugars include simple sugars made from one unit, e.g. glucose.
Add Benedict’s reagent (which is blue) to a sample and heat it to 75Cº in a water bath.
If test is positive it will form a coloured precipitate.
The higher the concn of reducing sugar the further the colour change goes (blue-green-yellow-orange-brickred)

Non-reducing sugars- if there aren’t any reducing sugars in sample, you can test for non-reducing, sucrose.
Using a new sample of test solution, add dilute HCl and heat solution to 75Cº in water bath.
Then add sodium hydrogen carbonate to neutralise it and carry out Benedict’s test as above.
A coloured precipitate means there are non reducing sugars present.
If solution remains blue, the test did not contain any sugar at all.

49
Q

How can you test for starch in a test solution?

A

You can test for starch by:
adding iodine solution to test sample.
If starch is present, the sample changes from browny-orange to blue-black.
If there is no starch, it stays brown-orange.

50
Q

How can you test for lipids?

A

Use the emulsion test for lipids:

  • shake the test substance with ethanol for a minute until it dissolves, then pour the solution into water.
  • if there are any lipids present, they’ll show up as a milky emulsion.
  • the more lipid there is, the more noticeable the milky colour is.
51
Q

How can you test for proteins?

A

The biuret test is used for proteins:
First add a few drops of sodium hydroxide solution to make the solution alkaline.
Then add some copper(II) sulfate solution (which is bright blue).
If there’s no protein, the solution will stay blue.
If there’s protein present, the solution will turn purple.

52
Q

Explain how photosynthesis contributes to a plant’s biomass:

A

Photosynthesis produces glucose, which is used to make larger, complex molecules that make up the mass of the plant’s living material/the plant’s biomass.

53
Q

What is photosynthesis?

A

-the process by which green plants and some other organisms use sunlight to synthesise nutrients from carbon dioxide and water.
-Photosynthesis occurs inside the chloroplasts.
They contain chlorophyll which absorbs light.
Energy is transferred to the chloroplasts from the environment by light.
-It is an endothermic reaction.
-First, energy transferred by light is used to split water into oxygen gas and hydrogen ions.
-Carbon dioxide gas then combines with the hydrogen ions to make glucose.

54
Q

What is the word equation and symbol equation for photosynthesis?

A

light
carbon dioxide + water ————-> glucose + oxygen
chlorophyll

6CO2 + 6H2O ——-> C6H12O6 + 6O2

55
Q

What are the limiting factors that affect the rate of photosynthesis?

A

Light intensity, concentration of CO2 and temperature.

GCSE OCR Biology- Triple (3 decks)

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