Key concepts of Biology

Question 1

What is the difference between a eukaryotic and prokaryotic cell?

Answer 1

Prokaryotes cell divide by binary fission
DNA single molecule found in the cytoplasm no mitochondria
Most are 0.2 ūm-2ūm
Eukaryotes divide by mitosis have a nucleus 5ūm-100ūm
Prokaryote is a single cell

Question 2

Function of sub cellular structures in an animal cell and how many it contains

Answer 2

Nucleus: contains genetic material which controls activities of the cell
Cytoplasm:jelly like material containing nutrients dissolved sugar and salts it is where many of the chemical reactions happen
Cell membrane:permeable to some substances not all so controls what goes in and out
Mitochondria:enzymes for respiration where most of energy is released in respiration
Ribosome:protein synthesis

Question 3

What extra sub cellular features does a plant cell have?

Answer 3

Cell wall:made from cellulose to protect the cell
Chloroplast:contains chlorophyll which absorbs light energy for photosynthesis and the enzymes needed for photosynthesis
Permanent Vacuole:filled with cell sap to keep the cell swollen

Question 4

Sub cellular features of bacteria

Answer 4

Chromosomal DNA:found loose in the cytoplasm w out nucleus
Plasmid DNA:small circles of DNA that can move between bacterium to another to give variation
Flagella: these rotate to or move to move the bacteria
Cell wall:protection only plant made from cellulose
Cell membrane
Ribosomes

Question 5

How is a sperm cell adapted to its function

Answer 5

Haploid nucleus sex cell contains one set of chromosomes acrosome in the head has enzymes so that the sperm can digest the egg middle piece packed with mitochondria for energy needed to swim and fertilise the egg.tail to swim

Question 6

How is an egg adapted to its function

Answer 6

Cytoplasm has nutrients for the early embryo to grow.haploid nucleus.cell membrane changes after fertilisation so no more sperm can enter

Question 7

How is the ciliated epithelial cell adapted to its function

Answer 7

Cilia on the surface beat to move fluids and particles up the trachea

Question 8

How have changes in the microscope helped us see sub cellular structures better and given us a better understanding

Answer 8

Electron microscopes were invented and instead of using light like the light microscope they fire electrons at samples they have a higher magnification and resolution so they let us see much smaller things in closer detail which has given us a better understanding

Question 9

Calculations microscope

Answer 9

Magnification is how many times bigger the image is
Total mag=eyepiece lens mag x objective lens mag
If you don’t know which lenses were used you can still work out the mag by
Mag=image size DIVIDE real size

Question 10

Convert the units Know then in order of size

Answer 10

Millimetres x10 to the -3
Micrometer um x10 to the -6
Nanometer -9
Picometer -12

Question 11

How do you use a microscope?

Answer 11

1)Place the slide on the stage
2)Set to the lowest magnification
3)Look through the eyepiece lens
4)Turn focusing wheel to increase resolution
5)Increase mag if you want
6)Increase focusing wheel if you want

Question 12

How do you prepare the microscope slide

Answer 12

1)place slide specimen on slide
2)stain with iodine so the organelles are visible
3)add water to prevent drying out
4)put on a coverslip so the specimen keeps flat and in place

Question 13

How do enzymes catalyse reactions(speed up)

Answer 13

Enzymes have an active site with a high specificity for a substrate so the substrate fits into the active site if the shape doesn’t fit the reaction won’t be catalysed

Question 14

How can enzymes be denatured?

Answer 14

Temperature: increases rate at first but if it gets to hot some of the bonds holding the enzyme together will break leads to change in active site substrate won’t fit any more
pH:interfere with bonds all enzymes have an optimum pH
Substrate:higher the faster Because it’s more likely that the enzyme will meet up and react but then the enzymes run out with all active sites full adding more won’t make a difference

Question 15

Describe how to investigate the effect of pH on the enzyme amylase

Answer 15

Place 1 drop of iodine onto each well in the spotting tile iodine turns blue black if starch is present
Then we get ons test tubes 2cm of starch amylase 2cm of buffer solution ph5 then we put it in a water bath for 10 mins to allow it to reach the correct temperature then we get a pipette and place a drop every 30 seconds to the spotting tile until the colour no longer turns blue/black which means starch is no longer present then you can try with diff buffers like pH 6 or 7

Question 16

Problem with this practical and how can it be solved

Answer 16

Only taking samples every 30 seconds means that we only have a approximate time for the reaction to complete can be fixed by taking it every ten seconds

Question 17

Another problem and how can it be solved?

Answer 17

Looking for the time the iodine will ho blue back is not obvious as it can be mixed with the orange so we might not know when the reaction has finished can be fixed by having a number of people look and decide

Question 18

Name the enzyme calculations for rate

Answer 18

Rate=1000 divide by time
Rate of reaction = change divide by time

Question 19

Why do enzymes break down bigger molecules

Answer 19

So they can be used for growth and other life processes

Question 20

What enzymes break down carbohydrates proteins and lipids

Answer 20

Carbohydrates(analyse) break down starch too maltose and other sugars
Proteases turn the protein to amino acids
Lipases turn them into glycerol and fatty acids

Question 21

How do you test for sugars

Answer 21

Add Benedict’s reagent which is blue to a sample and put it in water bath 75 degrees the higher the concentration the further the colour change
Blue-green-yellow-orange-brick red

Question 22

Test for starch

Answer 22

Use iodine to tear sample if starch is present changes to blue black If not stays browny/orange

Question 23

Test for lipids

Answer 23

Shake test substance with ethanol for about a minute till it dissolves then pour solution into water if there are lipids the colour of the liquid will be milky

Question 24

Test for protein

Answer 24

Biuret test
1)add potassium hydroxide to make the solution alkaline
2)add copper surface which is blue
Stayed blue no protein changes purple means protein is present

Question 25

How can food be burnt to see how much energy it contains?

Answer 25

Calorimetry
Food that will burn easily (dry) Weigh a small amount of the food and skewer to a mounted needle Next add a set volume of water held with a clamp Measure temp of water then set fire to the food using a Bunsen burner immediately hold the food under the boiling tube keep relighting the food until it can no longer catch on fire then measure the temperature of the water again

Question 26

How do you calculate amount of energy in food

Answer 26

Energy in food (joules)=mass of water g x temp change in water Celsius x 4.2
Energy per gram of food(g/j)=energy in food(j) divide mass of food

Question 27

What’s diffusion?

Answer 27

Overall movement of particles from an area of higher concentration to an an area of lower

Question 28

What’s osmosis??

Answer 28

Like diffusion but partially permeable membrane
Water

Question 29

What’s active transport

Answer 29

Opposite of diffusion uses energy

Question 30

Investigate osmosis
Core practical

Answer 30

Cut up potatoes into the same size piece place then in different sucrose solutions leave for 40 minutes remove from cylinder and pat them dryly with a paper towel removes excess water so the final measurements are more accurate

Question 31

Calculate percentage change

Answer 31

Percentage =final mass-initial DIVIDE Change Initial x 100