Topic 1 - Key Concepts in Biology Flashcards
What can organisms be?
Eukaryotes and prokaryotes
All living things are made up of tiny ____
All living things are made up of tiny cells
What are eukaryotic cells?
Complex cells
Give examples of types of organisms with eukaryotic cells
Plants and animals
What are prokaryotic cells?
Smaller and simpler cells
Give examples of types of organisms with prokaryotic cells
Bacteria
What are eukaryotes?
Organisms made of eukaryotic cells
What are prokaryotes?
Prokaryotic cells (single-celled organism)
What are the differents parts of a cell?
Subcellular structures
Give examples of subcellular structures in animals cells?
A nucleus Cytoplasm A cell membrane Mitochondria Ribosomes
What is a nucleus?
A subcellular structure that contains genetic material that controls the activites of the cell
What is cytoplasm?
A gel-like substance where most of the chemical reactions happen
What can be found in the cytoplasm?
Enzymes
What is the cell membrane?
The membrane around the cell which holds the cell together and controls what goes in and out of the cell
What are mitochondria?
The place where most reactions for respiration take place
What are ribosomes?
The structure involved in the translation of genetic material in the synthesis of proteins
What are the subcellular structures found with plant cells?
A nucleus, cytoplasm, a cell membrane, mitochondria, ribosomes, a cell wall, a vacuole and chloroplasts
What is the cell wall?
A wall around the cell made of cellulose which supports and strengthens the cell
What is the vacuole?
A structure which contains cell sap, a weak solution of sugar and salts.
It also helps maintain internal pressure of the cell
What are chloroplasts?
Structures where photosynthesis occurs which makes glucose for the plant
What do chloroplasts have inside them?
A green substance called chlorophyll
Bacterial cell’s have no _____
Bacterial cell’s have no nucleus
Bacterial cell’s have ____ nucleus
Bacterial cell’s have no nucleus
Compare the size of bacterial cells to animal and plant cells
Bacterial cells are a lot smaller than plant and animal cells
What are the subcellular structures found within bacterial cells
Chromosomal DNA Ribosomes A cell membrane Plasmid DNA A flagellum
What is chromosomal DNA?
One long circular chromosome which controls the cell’s activities and replication
It floats free in the cytoplasm (not in a nucleus, as there is no nucleus)
What is plasmid DNA?
Small loops of extra DNA that aren’t part of the chromosome
What does plasmid DNA contain genes for?
Drug resistance
True or False? Bacteria can’t pass genes as there are no genes?
False, plasmid DNA can be passed between bacteria
What is a flagellum?
A long, hair-like structure that rotates to make the bacterium (enables cell movement)
What is the use of a flagellum for a bacterium?
To move the bacteria away from harmful substances like toxins and towards beneficial things like nutirents or oxygen
Describe the function of the nucleus
Contains the genetic material that controls the activity of the cell
Describe the function of the mitochondria
Where most of the reactions for respiration take place
Describe the function of ribosomes
The structure involved in the translation of genetic material in the synthesis of proteins
True or false? Multicellular organisms contain lots of different types of cells?
True
What are specialised cells?
Cells that have a structure which makes them adapated to their function
Give examples of specialised cells?
Egg, sperm and ciliated epithelial cells
What are sperm and egg cells specialised for?
Reproduction
Why is it important the egg and sperm clel have the right number of chromosomes?
So the fertilised egg has the normal amount for a human
If not, the offspring will have a disabillity
What is the main function of an egg?
To carry the female DNA and to nourish the developing embryo in it’s early stages
How is the human egg cell adapted to its function?
By containing nutrients in the cytoplasm to feed the embryo
By having a haploid nucleus
Straight after fertillisation its membrane changes structure to stop any more sperm getting in. This makes sure the offspring ends up with the right amount of DNA
What is the main function of a sperm cell?
To transport the male’s DNA to the female’s egg
How is the sperm cell adapted to its function?
By having a long tail so it can swim
By having a lots of mitochondria in the middle section to provide the energy needed to swim
By having an acrosome at the front of the head where it stores enzymes needed to digest through the membrane of the egg cell
By having a haploid nucleus
What are ciliated epithelial cells specialised for?
Moving materials
Where can ciliated epithelial cells be found?
On the lining of organs
What do ciliated epithelial cells often have on the surface?
Cillia
What are cillia?
Hair-like structures
How is ciliated epithelial cells adapted to its function?
The cillia beat to move substances in one direction
Found in areas of high traffic (lining of the airways)
What are cells often studied using?
Microscopes
How do microscopes work?
They use lenses to magnify images
What are the main goals of microscopes?
To magnify and increase the resolution of the image
Define resolution
How well a microscope can distinguish between two points that are close together
How do light microscopes work?
By passing light through the specimen
What can you see with a light microscope?
Nuclei and chloroplasts
True or False? You can’t look at living specimens through a light microscope because the light will kill them?
False, you can use it to view living specimens
How do electron microscopes work?
By firing electrons through the specimen
What can you see with an electron microscope?
The internal structure of mitochondria and chloroplasts
What can you see with an electron microscope?
The internal structure of mitochondria and chloroplasts
What are the rules of scientific drawing?
Use a sharp pencil Draw outlines Don't colour or shade Label all the important features Include the magnificaton used Include the scale
What is magnification?
How many times bigger the image is
What is the total magnification equation?
Total magnification = Eyepiece lens magnification x Objective lens magnification
What is the magnification equation?
Magnification = Image size / Real size
State the way to remember the magnification formula?
I AM
I = A x M
What is the standard form for milli?
x10^-3
What is the standard form for micrometre?
x10^-6
What is the standard form for micro?
x10^-6
What is the standard form for nano?
x10^-9
What is the standard form for pico?
x10^-12
Calculate the length of a cell which has an image size of 7 x 10^-1mm under a magnification of x400
Write you answer in μm
7 x 10^-1mm x 10^3 = 7 x 10^2
Actual size = Image size / Magnification
AS = 7 x 10^2 / 400
AS = 1.75 μm
What are enzymes?
Catalysts produced by living things
Why do organisms need enzymes?
Because the reactions need to be carefully controlled, to get the right amount of substances
And the reactions that need to take place require extremely high temperatures which would be impossible within the body
And if you were to raise the temperature, other less useful and sometimes harmful reactions would take place
Enzymes have _________ so they can catalyse reactions
Enzymes have special shapes so they can catalyse reactions
What do chemical reactions usually involve?
Things being split apart or joined together
What is the substrate?
The molecule changed in the reaction (reactant)
What does every enzyme have?
An active site
What is an active site?
The part where an enzyme joins onto its substrate to catalyse the reaction
Enzymes usually only work with ___ substrate
Enzymes usually only work with one substrate
What are enzymes said to have for their substrate?
A high specificity
Why do enzymes have a high specificity to its enzyme?
Because for the substrate to be catalysed it must fit into the unique enzymes’ active site which means that the active site on the enzyme will only fit that substrate
What three factors affect the rate of reaction?
Temperature
pH
Substrate concentration
How does temperature affect the rate of reaction?
Heating it at first increases the rate, however, too high of temperature will denature the enzyme
How does pH affect the rate of reaction?
Too high or too low of a pH will break the bonds holding the enzyme together
There will be an optimum pH at which the enzymes rate is at its fastest
How does substrate concentration affect the rate of reaction?
As you increase the concentration of the substrates, the rate of reaction also increases, however, there will be a point where the limiting factor is no longer substrate concentration instead it is now number of open active sites
Explain why enzymes have an optimum pH?
If the pH is too high or too low, it can interfere with the bonds holding the enzyme together. This changes the shape of the active site leading to the denaturing of the enzyme
When investigating the effect of pH on enzyme activity, what enzyme is used?
Amylase
What is amylase?
An enzyme which catalyses the breakdown of starch to maltose (sugar)
How do you test for starch?
By using iodine solution
What is the colour change when testing for starch?
Browny-orange to blue-black
When investigating the effect of pH on enzyme activity, what temperature should you use?
Around 35*c
When investigating the effect of pH on enzyme activity, what must you add to a test tube?
Amylase solution Buffer solution (pH of 5)
When investigating the effect of pH on enzyme activity, why shouldn’t you use the same syringe?
Some of the previous chemicals may of not fully left the syringe meaning the reaction will begin early if you were to mix the reactants causing in accurate results
When investigating the effect of pH on enzyme activity, what is the main method used?
Continous sampling
When investigating the effect of pH on enzyme activity, how do you know when all the starch has been converted?
The iodine solution doesn’t change (remains browny-orange)
When investigating the effect of pH on enzyme activity, how do you know when all the starch has been converted?
The iodine solution doesn’t change (remains browny-orange)
When investigating the effect of pH on enzyme activity, what do you change when doing repeats?
The pH of the buffer solution
When investigating the effect of pH on enzyme activity, what is the independent variable?
The pH of the buffer solution
When investigating the effect of pH on enzyme activity, what is the dependent variable?
Time taken for amylase to break down all of the starch
What is the rate of reaction equation?
1000/time
What are the units of rate of reaction?What are the units of rate of reaction?
s^-1
What is a rate?
A measure of how much something changes over time
Examples of big molecules that the body use are ____, ____ and ____
Examples of big molecules that the body use are carbohydrates, lipids and proteins
Why is it important that organisms break the larger molecules into smaller molecules?
So they can be used for growth and other life processes
And some are too big to be moved around the body
Give an example of a use that a plants uses starch for
Storage of energy
What does a plant do when it needs stored energy?
It’s enzymes break down the starch into sugar which can be respired to release
What enzymes break down carbohydrates?
Carbohydrases
What do carbohydrases break down?
Carbohydrates
What do carbohydrates get broken down into?
Simple sugars
Give an example of a carbohydrase
Amylase
What enzymes break down proteins?
Proteases
What do proteases break down?
Proteins
What do proteins get broken down into?
Amino Acids
What enzymes break down lipids?
Lipases
What do lipases break down?
Lipids
What do lipids break down into?
Glycerol and fatty acids
An enzyme-controlled reaction was carried out at pH 4
After 60 seconds 33cm^3 had been released
Calculate the rate of reaction cm^3 s^-1
33/60=0.55 cm^3 / s^-1
Name the molecules that result from the breakdown of carbohydrates
Simple sugars
Name the molecules that result from the breakdown of proteins
Amino Acids
What do you use to test for sugars?
Benedicts reagent
How do you test for sugars?
Add benedicts reagant to the sample and heat it in a water bath thats set to 75*C
If the test is positive a coloured precipitate will form
What colour is benedicts reagant before contact with sugar?
Blue
State the colour change order for benedicts reagent?
Blue -> Green -> Yellow -> Orange -> Red
What is the test for starch?
Iodine
How do you test for starch?
Add iodine to the sample
Describe the colour change for a positive iodine starch test
From browny orange to bluey black
What is the name of the test for lipids?
The emulsion test
How do you test for lipids?
Shake the test substance with ethanol for about a minute until it dissolves then pour the solution into water
If lipids are present there will be a milky emulsion
Describe the positive test for lipids
Milky precipitate
What solutions do you add to proteins?
Potassium hydroxide and copper(ii) sulfate
How do you test for proteins?
Add drops of potassium hydroxide to make the solution alkaline
Then add some copper sulfate solution
Describe the positive result for the biuret test
If protein is present, solution will turn purple
If protein not present, solution will remain blue
What colour is copper(ii) sulfate?
Blue
During the biueret test why do you add potassium hydroxide?
To make the solution alkaline
A solution was mixed with potassium hydroxide and copper(ii) sulfate solution turns purple
What conclusion do you draw from this test?
Proteins are present
When calculating energy in food, what type of food must you have?
Dry
When calculating energy in food, what must you do first?
Weigh the food
When calculating energy in food, after weighing the food what must you do?
Add a set volume of water
When calculating energy in food, what must you measure?
The temperature of the water before and after
When calculating energy in food, where do you hold the burning food?
Underneath the water in the tube with the thermometer
How do you calculate the energy in food?
E = M x T x 4.2 Energy = Mass x Temperature x 4.2 Joules = g x *c x 4.2
How do you calculate the energy per gram of food?
Energy per gram of food = Energy in food / Mass of food
J/g = J / g
A student burned 0.2g of popcorn under 20cm^3
During the experiment the temperature of the water increased by 28.6*C when the popcorn was burnt
Calculate the energy per gram of food?
E = M x T x 4.2 E = 0.2 x 28.6 x 4.2 E = 2,402.4 J
Energy per gram = 2402.4 / 0.2
Energy per gram = 12,012 J/g
A student burned 0.5g of popcorn under 20cm^3
During the experiment the temperature of the water increased by 38.7*C when the popcorn was burnt
Calculate the energy per gram of food?
E = M x T x 4.2 E = 0.5 x 28.6 x 4.2 E = 3250.8 J
Energy per gram = 3250.8 / 0.5
Energy per gram = 6,501.6 J/g
A student performed a calorimetry experiement on a small piece of bread
Why is it important to record the increase in temperature as soon as possible after the bread is burnt in this experiment?
To minimise the amount of energy loss to the surroundings
Define diffusion
The net movement of particles from an area of higher concentration to an area of lower concentration
Diffusion happens in both ______ and ____
Diffusion happens in both liquids and gases
Define osmosis
The net movement of water molecules across a partially permeable membrane from a region of higher water concentration to a region of lower water concentration
What is a partially permeable membrane?
A membrane with very small holes in it
Define active transport
The movement of particles across a semi-permable membrane from an area of lower concentration to an area of higher concentration through the use of energy
True or False? All three; diffusion, active transport and osmosis are passive?
False, active transport requires energy
Give two differences between the processes of diffusion and active transport
Diffusion is passive whilst active transport requires energy (is active)
Diffusion goes down a concentration gradient, whereas, active transport goes up a concentration gradient
When investigating osmosis, what do you put in the sucrose?
Potato cylinders
When investigating osmosis, how long do you leave the cylinders in the solution?
For atleast 40 minutes
When investigating osmosis, what do you record?
The mass of the potatoes before and after
When investigating osmosis, what is the independent variable?
The sucrose solution concentration
When investigating osmosis, what is the dependent variable
The mass of potato cylinders lost
When investigating osmosis, what are some examples of control variables?
Volume of the sucrose, size of the potato cylinders and type of the potatoes
What do we call it when both solutions have the same concentration of water?
Isotonic
When investigating osmosis, on the graph what does a positive percentage change in mass represent?
The sucrose solutions concentration is higher than in the cylinders so the chips gain mass as water through osmosis
When investigating osmosis, on the graph what does a negative percentage change in mass represent?
The sucrose solutions concentration is lower than in the cylinders so the chips lose mass as water through osmosis
When investigating osmosis, on the graph what does no percentage change in mass represent?
That the solutions are isotonic (same water concentration)
A group of potato cubes were placed in a sucrose solution and left for one hour
The cube weighed 13.3g at the start and 11.4g at the end
Calculate the percentage change in mass
% = (Change / Original) x 100 % = (11.4-13.3 / 13.3) x 100 % = -14.3%
What is the function of the cell membrane?
Hold the cell together and control what goes in and out
Give three structures found in plant cells but not in animal cells
Vacuole
Cell Wall
Chloroplasts
Name the subcellular strucutre in plant cells where photosynthesis takes place
Chloroplasts
Name two structures that are found in both prokaryotic cells and eukaryotic cells
Ribosomes and cell membrane
What does the term haploid mean?
Half the number of chromosomes of that respective organism
Give three way in which a human egg cell is adapated to its function
Membrane locks after fertilisation to ensure offspring has correct number of chromosomes
Contains nutrients to nourish early stages of embryo
Haploid nucleus to ensure offspring has correct number of chromosomes
What are cilia?
Hair-like structures on the top surface of ciliated epithelial cells
Give an advantage of an electron microscope over a light microscope
An electron has a bigger magnification than a light one whilst also having a better resolution
Why is it necessary to use thin samples with a light microscope?
The light microscope relies on shining light through the specimen
Therefore, if the specimen is too thick the light won’t be able to get through the specimen
Write the equation you would use to find the size of a specimen using the magnification used and the size of the image seen through a microscope lens
Image Size / Magnification = Actual Size
Describe how you would convert mm to μm?
x 1000
What part of an enzyme makes it specific to a particular substrate?
It’s active site
Why can denatured enzymes no longer catalyse chemical reactions?
Because the substrate will no longer be able to fit into the enzyme
Explain how temperature affects enzyme activity
As temperature increases enzyme activity increases until the bonds between the enzyme begin to break further denaturing the enzyme
Describe how you could investigate the effect of pH on the rate of amylase activity?
Every 10 seconds add a sample of a solution mixed with a buffer solution with a pH, amylase and starch.
Time how long it takes for the starch to be broken down fully
Repeat with different pH solutions
Which two molecules are produced when lipids are broken down?
Fatty and glycerol molecules
Name a big molecule that’s formed from simple sugars
Starch
Describe the colour change that occurs when benedicts reagent is added to a substance containing sugars
Blue -> Green -> Yellow -> Orange -> Red
What chemical reagent is used to test for the prescence of starch?
Iodine
How would you test for the presence of lipids in a sample?
Shake the substance whilst pouring ethanol until it dissolves then pour the solution into water
Milky water as positive
Describe briefly how you could use calorimetry to measure the energy content of a peanut
Add a set volume of water to a test tube
Heat dry food
Calculate temperature change of water
Use equation: E=MxTx4.2
If a potato cylinder is placed in a solution with a very high sucrose concentration, what will happen to the mass of the potato cylinder over time?
Explain why?
Mass of potato will decrease
As there will be higher concentration of water in potato than the solution so the water will move down the concentration gradient
