Topic 1- key concepts in biology Flashcards
What is osmosis?
Osmosis is net movement of water molecules across a partially permeable membrane from region of higher water concentration to region of lower water concentration
What is a partially permeable membrane?
it’s a membrane with small holes in it, tiny molecules (water) can pass through and bigger (sucrose) can’t
Which way do the water molecules pass through the membrane and why do they do this?
(osmosis step 1)
The water molecules pass both ways through the membrane during osmosis
(because water molecules move randomly all time)
What happens to the water molecules when there is more water molecules on one side? state which region the water molecules move to?
(osmosis step 2)
when there are more water molecules on one side of the membrane than the other there’s a net flow of water into the region with fewer water molecules
what happens to the solution in osmosis? And what happens to the water itself on what?
(osmosis step 3)
the solute solution gets more dilute, the water acts like it’s trying to equalize the concentration on either side of the membrane.
How do you calculate the percentage change in mass?
percentage change = final mass - initial mass/ initial mass x 100
What happens when the water concentration of the sucrose solutions is higher than in the potato bit?
The potato bit gains mass as water is drawn in by osmosis (hypertonic)
What happens when there is no change in mass?
The fluid inside the cylinders and the sucrose solution are isotonic (same water concentration)
What happens when the water concentration of the sucrose solutions is lower than the potato bit?
This causes the potato bit to lose water so their mass decreases (hypotonic)
What is Diffusion?
Diffusion is the net (overall) movement of particles from an area of higher concentration to an area of lower concentration
What states of matter does diffusion happen in?
Why?
Diffusion happens in both liquids & gases
because these substances are free to move about randomly
What types of molecules can diffuse in diffusion?
What types of molecules can and can’t go fit through the cell membrane?
Only very small molecules can diffuse through cell membranes
CAN-glucose, amino acids, water & oxygen
CAN’T- Starch and proteins
What is active transport? What is used in active transport?
Active transport is the movement of particles across a membrane against a concentration gradient from a area of lower concentration to an area of higher concentration using energy transferred during respiration
How is the movement particles different in active transport compared to diffusion? What does this process require?
Particles are moved up a concentration gradient rather than down
the process requires energy (diffusion = passive process)
What is calorimetry?
Food that can be burnt to see how much energy it contains
How do you calculate the energy in food? And the energy per gram of food?
energy in food (in J) = Mass of water (in g) x temp change of water (in C) x 4.2
energy per gram of food (in J/g) = energy in food (in J) / mass of food (in g)
How do you test for reducing sugars? What is a coloured precipitate?
1) Add benedict’s reagent to a sample (blue)
2) Heat it in a water bath (75 C)
3) If it’s positive–> coloured precipitate (solid particles suspended in solution)
What’s the order of precipitate concentration from low to high when benedict’s reagent is used in a sample?
blue —-> green —> yellow —-> orange —-> brick red
( low to high sugar concentration)
How does the biruet test work?
Why do you add the first solution? To make it what?
What colours does it turn if it contains & doesn’t contain proteins?
1) add potassium hydroxide to make the solution alkaline
2) then add copper (2) sulphate solution (bright blue)
3) no protein —> blue
2) protein (present) —> purple
What is biuret test is used for?
To find out if a substance contains proteins
How does the emulsion test work?
1) shake the substance with ethanol until it dissolves then pour it into water
2) any lipids present –> precipitates as a milky emulsion
3) more lipid –> more noticeable milky colour
What is emulsion test used for?
tests for any lipids in sample
How is starch tested for in a sample?
using an iodine solution
what colours does the iodine solution turn if starch is and isn’t present?
1) starch present
browny orange –> dark, blue-black colour
2) no starch
stays browny-orange
Why is it important that organisms need to break down big molecules into smaller components?
To use them from growth and other life processes
What are carbohydrases and what do they do?
Carbohydrases are any enzymes that convert carbohydrates into simple sugars
Give an example of a carbohydrase converting a carbohydrate into a sugar
starch ——–> maltose (and other sugars e.g dextrins)
(amylase enzyme)
What are Proteases and what do they do?
Proteases are enzymes that convert proteins into amino acids
What are Lipases and what do they do?
Lipases are enzymes that convert lipids into glycerol and fatty acids
What do organisms need to be able do to carbohydrates, proteins and lipids and what are used in this process?
synthesis carbohydrates, proteins and lipids from their smaller components
enzymes are used
How are carbohydrates synthesised?
by joining together simple sugars
What is glycogen synthase?
an enzyme used that joins chains of glucose molecules to make glycogen (molecule used to store energy in animals)
How are proteins synthesised?
What do enzymes do to reactions?
by joining amino acids together
They catalyse reactions
What are enzymes?
a protein that acts as a biological catalyst produced by living organisms that catalyse reactions
Why do living things produce enzymes?
reduces the need for high temperatures (high temperatures = quicker reactions)
only speed up the useful chemical reactions (wont speed up unwanted ones)
what is a catalyst?
a substance which increases the speed of reaction without being changed/used up in the reaction
what is the substrate?
the molecule changed in the reaction
What is the active site & what does every enzyme have?
part where it joins on to its substrate to catalyse reactions
an active site
what do enzymes only work with one of? What is this called?
only works with one substrate
high specificity for their substrate
What has to happen to make sure the enzyme catalyses the reaction?
substrate has to fit into the active site
what happens when the substrate’s shape doesn’t match the active site’s shape?
the reaction won’t be catalysed
what is the lock and key mechanism?
when the substrate fits into the enzyme (like a key into a lock)
where is amylase found?
saliva & small intestine
what reaction does amylase catalyse?
breaks down starch —–>small sugars (e.g maltose)
Where is catalase found?
most cells
but especially, liver cells
What reaction does catalase catalyse?
break down hydrogen peroxide (made in cell reactions) –> water & oxygen
Where is starch synthase found?
plant
what reaction does starch synthase catalyse?
synthesis of starch <—-glucose
Where is DNA polymerase found?
nucleus
What reaction does DNA polymerase catalyse?
synthesis of DNA <—-monomers
What is amylase, catalase, starch synthase, DNA polymerase?
enzymes
