B1 - Cell level systems

Question 1

Converting units:

Answer 1

• Nanometers to micrometers (Divide by 1000)
• Micrometers to millimetres (Divide by 1000)
• Millimetres to centimetres (Divide by 10)
• Centimetres to metres (Divide by 100)
• Metres to kilometres (Divide by 1000)

Question 2

What are the two types of cells?

Answer 2

• Eukaryotic cells: Cells with a nucleus and are complex (plant and animal cells)
• Prokaryotic cells: Cells without a nucleus and are simple (Bacteria cells)

Question 3

What are the structures within an animal cell?

Answer 3

• Nucleus: Contains the genome (all the genetic information) of the organism
• Ribosomes: This is where protein synthesis occurs
• Cytoplasm: Where most of the chemical reactions occur.
• Mitochondria: Contains enzymes for respiration. It is where cellular respiration occurs
• Cell membrane: Controls what moves in and out of the cell

Question 4

What are the cells structures in a plant cell?

Answer 4

• All that is in the animal cell
• Vacuole: Regulates water potential in a plant
• Chloroplast: Contains chlorophyll which is were photosynthesis occurs
• Cell wall: Made of cellulose to support cell.

Question 5

What is the structures in a prokaryotic cell?

Answer 5

• Cell membrane: controls what moves in and out of the cell
• Chromosomal DNA: DNA which is not contained within the nucleus
• Plasmids: Circular shaped DNA separate from the chromosomal DNA

Question 6

What is the max resolution and magnification for a light microscope?

Answer 6

Max resolution: 200nm

Max magnification: 1500 times

Question 7

What is the max resolution and magnification of a electron microscope?

Answer 7

Max resolution: 0.2nm

Max magnification: 2,000,000 times

Question 8

Equation for magnification?

Answer 8

Magnification = Image size / actual size

Question 9

How do you prepare specimens for light microscope examination?

Answer 9

1) Specimen needs to be in thin slice in order to let light through
2) Take slide and use pipette to secure specimen by adding drop of water to it
3) Then add specimen to slide
4) If specimen transparent add drop of stain to make it easier to see
5) Place cover slip over and carefully lower it onto slide making sure there are no air bubbles

Question 10

Total magnification equation?

Answer 10

Total magnification = objective lens x eyepiece lens

Question 11

Basics of DNA:

Answer 11

• It is in a double helix shape
• It is a polymer made of monomers (nucleotides)
• DNA is organised into chromosomes (Long coiled up DNA).

Question 12

What is a gene?

Answer 12

• A gene is a small section of DNA which codes for a certain protein

Question 13

Why is genome important for science?

Answer 13

• Helpful in medicine

- Helps us think of evolution of humans overtime

Question 14

What is a nucleotide?

Answer 14

It is a monomer of DNA (A polymer).

• It is made of a sugar, phosphate and bases (A,T,G,C)
• The sugar and phosphate make the sugar phosphate backbone in DNA (strands of DNA)

Question 15

What is bases in DNA?

Answer 15

• A (Adenine)
• T (Thymine)
• G (Guanine)
• C (Cytosine)

A always pairs with T
G aways pairs with C

Question 16

What are proteins?

Answer 16

Proteins are coded by genes from animo acids

-The amino acids form peptide bonds becoming proteins

Question 17

What are proteins functions in the body?

Answer 17

-Enzymes
-Hormones
-Antibodies
Structural functions - muscle, hair and nails

Question 18

Protein synthesis in body?

Answer 18

1) DNA is too big to leave the nucleus therefore a messenger molecule (mRNA) is required
2) The DNA is unzipped and mRNA creates a complementary strand (Transcription)
3) mRNA leaves the nucleus to the cytoplasm where it attaches to a ribosomes for translation to occur.
4) tRNA molecules ferry in amino acids depending on the sequence of bases of DNA (each triplet code - three consecutive bases- code for an amino acid)
5) Another tRNA molecule ferries in another amino acid for the next triplet code and amino acids form peptide bonds
6) Once completed some amino acids repel and attract together folding the protein for its function.

Question 19

What are mutations?

Answer 19

Mutations are spontaneous changes in the sequence of DNA bases.

Question 20

What happens when mutations occur coding DNA?

Answer 20

The change in base sequences due to mutations can cause a different protein to be produced.
This may change the characteristic expressed
It can also alter shape of protein due to amino acid change therefore function is altered - eg enzyme may change shape so substrate can’t fit in active site.

Question 21

What happens when mutation occurs in non coding DNA?

Answer 21

This effects if the gene is turned on or off. This may cause characteristic to not be expressed at all.

Question 22

What are enzymes?

Answer 22

Enzymes are biological catalyst which speed up chemical reactions without being used up.

They function with the ‘lock and key’ hypothesis where a substrate must fit in the enzymes active site for enzyme to catalyse.

Question 23

Factors that effect rate of reaction for enzymes? How?

Answer 23

Temperature: As temperature increases, rate of reaction increases until it hits its optimum point (this is usually 37’c in enzymes in cells)
If temperature continues to increase, rate of reaction decreases as peptide bonds between amino acids break affecting shape of enzyme so substrate cannot fit.

PH: All enzymes have a specific optimum PH and if it is too acidic or alkali it can affect peptide bonds denaturing the enzyme

Enzyme and substrate concentration: As enzyme concentration increases rate of reaction increases until optimum point where the number of substates are the limiting factor. This is the same and opposite for the substrates.

Question 24

What is respiration?

Answer 24

Respiration is the release of energy from glucose.

There are two types of respiration: aerobic and anaerobic

Question 25

What is aerobic respiration?

Answer 25

-It is respiration with oxygen and it produces more energy from glucose than anaerobic respiration. Glucose + oxygen -> Carbon dioxide + water C6H1206 + 602 -> 6C02 + 6H20

Question 26

What is anaerobic respiration in animals?

Answer 26

Anaerobic respiration doesn't use oxygen and releases less energy than aerobic respiration. Glucose -> Lactic acid The lactic acid can build up in muscles causing muscle fatigue. Oxygen dept may also occur as oxygen is required to break down the lactic acid.

Question 27

What is anaerobic respiration in plants / yeast?

Answer 27

Glucose -> ethanol + carbon dioxide Anaerobic respiration in yeast cells is called fermentation used in bakery and alcoholic drinks.

Question 28

What is digestion?

Answer 28

Breaking insoluble food substances physically and chemically so it can reabsorbed into the blood.

Question 29

What are the types of extracellular enzymes?

Answer 29

Amylase -> pancreas -> breaks carbohydrates (polymer) into simple sugars Protease -> Stomach and pancreas -> breaks proteins (polymer) into amino acids Lipase -> pancreas -> lipids (not polymer) into fatty acids and glycerol

Question 30

How do you test for sugars?

Answer 30

-Use Benedict reagent test. TO TEST FOR REDUCING SUGARS (made from one unit) 1) Add Benedict reagent to sample and heat in a water bath at 75'c. If sugar present a coloured precipitate will form. 2)The higher concentration of sugars the further the colour change (Blue -> Green -> yellow -> orange -> Red) TO TEST FOR NON REDUCING SUGARS 1) add dilute hydrochloric acid in water bath set at 75'c 2) Add sodium hydrogen-carbonate (to neutralise it) then carry put Benedict reagent test 3) If solution stays blue then there is no sugar present and if there is a coloured precipitate the solution contains sugar

Question 31

How to test for starch?

Answer 31

Use iodine 1) If starch is present, sample turns from browny-orange to a blue-black colour 2) If not then it stays browny-orange

Question 32

How to test for lipids?

Answer 32

Use the emulsion test: 1) Shake substance with ethanol until it dissolves, then add water 2) If there is lipids, there is a milky emulsion 3) The more noticeable the colour is the more lipids there are

Question 33

How to test for proteins?

Answer 33

Use Biuret test 1) Add few drops of sodium hydroxide to make it alkaline 2) Then add some copper sulphate (Blue colour) - If present, solution turns purple - if not, solution stays blue

Question 34

What is photosynthesis?

Answer 34

Photosynthesis is the production of glucose in a plant using environments energy (energy from sun).

Question 35

What type of reaction is photosynthesis and respiration?

Answer 35

Photosynthesis: endothermic (absorbs energy from environment) Respiration: Exothermic (releases energy to the environment)

Question 36

Where in a plant cell does photosynthesis occur?

Answer 36

It occurs in the chloroplast which contain chlorophyll which absorb light

Question 37

Word and symbol equation for photosynthesis?

Answer 37

Carbon dioxide + water -> Glucose + oxygen 6CO2 + 6H20 -> C6H1206 + 6O2

Question 38

What are the two stages to photosynthesis?

Answer 38

1) Energy transferred by light is used to split water into oxygen gas and hydrogen ions (Oxygen is released here) 2) Carbon dioxide gas combines with hydrogen ions to form glucose

Question 39

How do you test for rate of photosynthesis?

Answer 39

Use an aquatic plant (like pondweed) in order to see the oxygen production. 1) While photosynthesising the aquatic plant will produce oxygen and bubble will rise. Counting bubbles can be used to see the rate of reaction 2) Or use capillary tube and syringe to collect oxygen gas in gas syringe measuring volume of gas produced.

Question 40

What is the factors affecting rate of photosynthesis?

Answer 40

Light intensity - when light intensity is increased the rate of photosynthesis increases until its optimum point where carbon dioxide concentration or temperature is the limiting factor (graph levels off) Carbon dioxide concentration - when CO2 concentration increases so does rate of photosynthesis until it hits its optimum point where temperature or light intensity is the limiting factor (graph levels off) Temperature - When temperature increases so does the rate of reaction until it hits its optimum point where if it keeps increasing the rate of reaction will decrease. This is because the enzymes required for photosynthesis denature - The peptide bonds between amino acids break, altering the shape of the enzyme consequently cause the substrate to not be able to fit in active site.

Question 41

How does light intensity and distance relate in photosynthesis?

Answer 41

Light intensity is indirectly proportional to the square of distance Light intensity = 1 / distance ^ 2