Structure and functions in living organisms Flashcards
What is an enzyme?
a biological catalyst which speed up reactions. They are made of proteins. They lower the activation energy of a reaction.
What is a catalyst?
a substance which increases the speed of a reaction, without being changed or used up in the reaction.
What are the chemical reactions in the body that enzymes speed up called?
metabolic reactions
How do enzymes catalyse a specific reaction?
They catalyse a specific reaction due to the shape of the active site. The substrate has to fit into the active site of the enzyme in order for the reaction to take place. This is called the ‘lock and key’ model.
What conditions speed up enzyme reactions?
- Temperature
- Concentration of enzymes
- Optimum pH
- Concentration of substrates
How does temperature change the rate of an enzyme-catalysed reaction?
high temps increase the rate at first
the enzymes have more kinetic energy
they move more and more likely to collide and form enzyme-substrate complexes.
if too hot, violent collisions break bonds in active site changing its shape so substrate cant fit. Enzyme is denatured
How does pH affect the rate of an enzyme-catalysed reaction?
If pH is too high or low, it interferes with bonds holding enzymes together. Changes shape of the active site and denatures the enzyme. All enzymes have an optimum pH they work best at. Optimum pH is often neutral 7 pH.
Explain the investigation of how temperature affects enzyme activity.
The enzyme catalase catalyses the breakdown of hydrogen peroxide into water and oxygen.
Can collect the oxygen and measure how much is produced in a set time.
Use pipette to add a set amount of hydrogen peroxide to a boiling tube. Put tube into water bath at 10ºC
Set up measuring cylinder so its underwater with delivery tube going into it.
Add source of catalase (eg 1 cm³ of potato)to hydrogen peroxide and quickly attach bung
record how much oxygen is produced in first minute
repeat 3 times an calculate mean
repeat at 20ºC, 30ºC, 40ºC
Control variable = pH, potato used, size of potato pieces
Describe investigation of temperature affecting enzymes when measuring how fast a substrate disappears
Enzyme amylase catalyses breakdown of starch to maltose
Easy to detect starch using iodine solution - if starch present iodine will turn from browny-orange to blue-black
Put starch solution and amylase enzyme into boiling tube and heat in waterbath at correct temperature
Put a drop of iodine solution into each well on spotting tile
Every ten seconds drop a sample of mixture into a well using a pipette
when iodine solution remains browny-orange record total time taken
repeat with water bath at different temperatures to see how it affects time taken for starch to be broken down.
Explain investigation of how pH affects enzyme activity.
use enzyme catalase
set up same apparatus but no water bath
add buffer solution with different pH level to a series of different tubes containing hydrogen peroxide
record how much oxygen is produced in first minute
repeat three times, calculate mean
repeat at different pH
control variables = same temp, volumes, concentration
What is diffusion?
the net movement of particles from an area of high concentration to low concentration, down a concentration gradient
Explain the diffusion of oxygen from cell to cell.
Oxygen particles are moving from an area of high to low concentration, down a concentration gradient. This means particles will spread out more by moving through the cell membrane, particles will move faster if the cell membrane is thin
Why does diffusion happen in liquids and gases?
particles are free to move about randomly
What is Osmosis?
The net diffusion of water molecules across a selectively permeable membrane, from a region of higher water potential to lower water potential
What is water potential?
the ability of water molecules to move freely
How does solute concentration affect water potential?
solutes (eg glucose or salt) bond with water molecules. Thus meaning there are less free water molecules that could move.
the more solute present, the fewer water molecules can move freely and the lower the water potential
What is a solution with a low solute concentration known as?
hypotonic - weak solution
What is a solution with a high solute concentration known as?
hypertonic - strong solution
Why is a barrier needed during osmosis
(selectively permeable) to measure movement of water
Why does increasing temperature increase diffusion?
Increasing temperature, increases kinetic energy
particles move around faster and spread out faster
diffusion therefore takes place faster at high temperatures
Use CORMS to outline investigation of Osmosis in living systems.
(Potato Cylinders)
Change - salt concentration
Organism - same species of swede
Repeat - Do each concentration 10x
Measure - change in mass
Same - temp, time, SA of potato
What is active transport?
The movement of particles against a concentration gradient using energy released in respiration
How is active transport used in the digestive system?
If lower concentration of nutrients in gut than blood, active transport allows nutrients to be taken into the blood, despite concentration gradient being wrong way. Essential to stop us starving. Needs energy from respiration to happen.
How does SA:Volume affect movement of substances?
Rate of diffusion, osmosis, active transport is higher in cells with larger SA:Volume. Substances move into and out of smaller cube faster.
How does Distance affect movement of substances?
Short distances increases rate
as substances can move in and out of cells quicker
eg thin cell membrane
How does Temperature affect movement of substances?
Increasing temperature, increases rate
particles have more kinetic energy
so they move faster
so move in and out of cells faster
How does Concentration Gradient affect movement of substances?
Doesn’t affect rate of active transport
Bigger difference in concentration increases rate of diffusion and osmosis
If lots more particles on one side, more to move across so substances move in and out faster
Outline investigation of Diffusion in non-living systems.
Independent - amount of jelly/ size of cell (SA:Volume)
Dependent - Time taken to change colour (pink - colourless as acid diffuses into jelly and neutralises sodium hydroxide)
Control - Same volume of hydrochloric acid, temperature of acid, concentration of acid
Risks - getting acid in someones eye
Do multiple repeats
Equipment:
Measuring cylinder
Stop watch
Teaspoon to handle agar cube
100cm³ glass beaker
Hydrochloric acid
Agar cubes containing alkali and cresol red indicator
What is respiration?
the process of transferring energy from glucose, which happens constantly in every living cell
How is energy transferred by respiration?
Used to make ATP which stores the energy needed for many cell processes
What is ATP?
adenosine triphosphate, releases energy quickly
How is ATP used?
ATP molecules are broken down and energy is released.
What is the word and chemical equation for aerobic respiration?
glucose + oxygen -> carbon dioxide + water ( + energy)
C₆H₁₂O₆ + 6O₂ -> 6CO₂ + 6H₂O
How many molecules of ATP are produced during aerobic respiration?
32 molecules per molecule of glucose
(most efficient way to transfer energy from glucose)
What is the word equation for anaerobic respiration in animals?
glucose -> lactic acid (+energy)
Why do we anaerobically respire?
doing vigorous exercise means your body can’t supply enough oxygen to working muscles for aerobic respiration. Instead muscles respire without oxygen
How many molecules of ATP are produced during anaerobic respiration?
2 molecules per glucose molecule
What happens when lactic acid is produced?
glucose is only partially broken down and lactic acid is produced which builds up in muscles - painful and leads to cramp
How is lactic acid removed?
by blood flowing through muscles
What is the word equation for anaerobic respiration in plants?
glucose -> ethanol + carbon dioxide (+ energy)
What is the role of diffusion in gas exchange?
Blood passing next to the alveoli has returned from lungs and rest of body so contains carbon dioxide and very little oxygen. Oxygen diffuses out of the alveoli and into the blood which is a lower concentration. Carbon dioxide is diffused out of the blood and into the alveoli which is a lower concentration so it can be breathed out. Oxygen released from red blood cells once it reaches body cells via diffusion. Carbon dioxide diffuses out of body cells and into blood at same time to be carried back to lungs.
What is the structure of a leaf?
Waxy cuticle - reduces water loss
Upper epidermis - contain no chloroplasts and are transparent to allow light in
Palisade mesophyll - cells tightly packed near top of leaf to get lots of sunlight, contain many chloroplasts, most photosynthesis happens
Spongy Mesophyll - contain air spaces to allow movement of gases throughout leaf
Lower epidermis - cells contain no chloroplasts apart from guard cells
Guard cells - help regulate movement of gases in and out of leaf, help control water vapour loss.
How are leaves adapted for gas exchange?
Leaves are broad - large SA for diffusion
Thin - gases travel a short distance
Air spaces inside leaf - lets gases move easily between cells. Increases SA for gas exchange
What is the role of the stomata in gas exchange?
Stomata close as it gets dark. Photosynthesis cant happen in dark, so don’t need to be open to let in CO₂
water can’t escape when closed, stops plant drying out
Opening and closing is controlled by guard cells. do this by changing their shape and volume (increase in volume to open up, decrease to close)
