SB1 - Key Concepts in Biology Flashcards
What are prokaryotic cells?
Small, simple cells without a nucleus
Give an example of a prokaryotic cell.
Bacteria
What are prokaryotes?
Single-celled prokaryotic organisms
What are eukaryotic cells?
A complex cell that contains a nucleus and other subcellular structures
Give an example of eukaryotic cells
Any animal or plant cell
What are eukaryotes?
Organisms that are made up of eukaryotic cells
What is contained within the nucleus of a eukaryotic cell?
Genetic material / DNA / Chromosomes
What is the role of the nucleus?
It controls the activities of the cell
Name the gel-like substance contained within the cell
Cytoplasm
What is the role of the cytoplasm?
It is where most chemical reactions happen
Name the subcellular structure that holds the cell together
The cell membrane
Give another role of the cell membrane
It controls what goes in and out of the cell
Name the subcellular structure where respiration takes place
Mitochondria
Which subcellular structures are involved in protein synthesis?
Ribosomes
Which stage of protein synthesis is ribosomes involved in?
The second stage (Translation)
Name three structures that plant cells usually have but animal cells do not
Cell wall, chloroplasts, large permanent vacuoles
Which plant subcellular structure is usually made from cellulose?
Cell wall
What is the function of the cell wall?
A rigid structure that supports and strengthens plant cells
Which plant subcellular structure contains cell sap?
Permanent vacuole
What is cell sap made from?
A weak solution of sugars and salts dissolved in water
What is the function of cell sap?
To maintain the internal pressure of a cell, to provide support
Which plant subcellular structure is only found in photosynthetic cells?
Chloroplasts
What chemical reaction takes place in the chloroplasts?
Photosynthesis
Name the green substance contained within chloroplasts
Chlorophyll
What is the function of chlorophyll?
To absorb the light energy needed for photosynthesis
Name the parts of a bacterial cell
A single circular strand of chromosomal DNA, cytoplasm, cell membrane, cell wall, plasmid DNA, flagellum, ribosomes
Name the part of a bacterial cell that controls the cells replication
Single circular strand of chromosomal DNA
Name the small loops of DNA found in many bacterial cells?
Plasmids
What type of information is contained within the plasmids?
Drug resistance
Name the part of some bacterial cells that rotates to make the cell move
Flagellum
Describe the flagellum
Long hair-like structures
Give two reasons why bacterial cells find it beneficial to have flagellum
- They can move towards areas of beneficial condition (e.g. those high in nutrients and oxygen)
- They can move away from areas of harmful conditions (e.g. chemicals, heat)
Fungal cells contain a nucleus, mitochondria, a cell membrane and a cell wall. What type of cell are fungal cells?
Eukaryotic
Give one way a fungal cell is similar to a plant cell and different to an animal cell
Fungal cells have a cell wall, like a plant cell, whilst animal cells do not have a cell wall
Explain why multicellular organisms contain many different types of cells
Each individual cell cannot carry out every life process so cells become specialised to do different jobs
What word is used to describe these different types of cells
Specialised
What is the structure of each type of cell related to?
Its specific function
Name the four types of animal cells that you need to know how their structure are linked to its specific function
Sperm cells, egg cells, small intestine cells and ciliated epithelial cells
Which cell is only found in males?
Sperm cells
Name four adaptations of sperm cells
Long tail / mitochondria concentrated area at base of tail / streamlined shape / acrosome / haploid nucleus of male DNA
Name the adaptation that propels sperm cells forward
The tail
Name the adaptation that provides the energy for sperm cells
Mitochondria concentrated area at base of tail
Name the adaptation that makes it easier for sperm cells to move
Streamlined shape
Name the part of a sperm cell that contains enzymes
Acrosome
What is the function of the enzymes found in sperm cells
To digest the cell membrane of the egg
Where is the acrosome found?
In the front tip of the head
What is the function of sperm cells?
To transport male DNA to the female DNA found in the egg
Which cell is only found in females?
Egg cells
Name three adaptations of egg cells
- High nutrient content
- Haploid nucleus / nucleus with only 23 chromosomes
- Cell membrane can change structure
Name one adaptation that both sperm cells and egg cells share
A haploid nucleus / nucleus with only 23 chromosomes
Explain why both sperm cells and egg cells have the adaptation of the haploid nucleus
To ensure that the resulting zygote has the correct number of chromosomes (46)
What adaptation happens straight after fertilisation?
The cell membrane changes structure
Explain why the cell membrane changes structure straight after fertilisation
To prevent any other sperm from entering the egg
Explain why egg cells are very large cells
They contain a large amount of nutrients in the cytoplasm to provide nourishment to the developing embryo
Name two functions of egg cells
- To carry the female DNA
2. To nourish the developing embryo
Name the two adaptations of egg cells that ensure a resulting embryo has the correct number of chromosomes
- Haploid nucleus
2. Membrane that changes structure after one sperm has entered
Which cell is found in the airways?
Ciliated cells
What is the main adaptation of ciliated cells?
Hair-like structures on the top surface of the cell
What is the function of the hair-like structures on the top surface of the cell?
To move substances in one direction along the surface of the tissue
Explain why ciliated cells contain a high number of mitochondria
To provide enough energy to move the cilia
Where in a female body are ciliated cells found?
Fallopian tubes / oviduct
What is the role of specialised cells found in the small intestine?
To absorb molecules through intestinal wall
Name the subcellular structures that increase the rate of the absorption of molecules through intestinal wall
Microvilli
Explain how the absorption of molecules through intestinal wall are adapted to their function
They increase the surface area of the cell
What is the study of very small objects?
Microscopy
Which piece of scientific equipment is used to study things that are too small to see with the naked eye?
Microscope
Name the first type of microscope
Light microscope
When was the first microscope developed?
1590’s
What can we see using a light microscope?
Individual cells and large subcellular structures
What is the maximum magnification of light microscopes?
X 1500
What is the maximum resolution (in mm) of light microscopes?
0.0001 mm
How would you write 0.0001 mm in standard from?
1 x 10^-4 m
How old you write 0.0001 mm in nanometers?
100 nm
How do light microscopes form an image?
Using light and lenses
Write one picometre in standard form
1 x 10^-12 m
Write one nanometre in standard from
1 x 10^-9 m
Write six micrometers in standard form
6 x 10^-6 m
Convert 6mm into nanometres
6,000,000 nm / 6 x 10^6 nm
Name the type of microscope that was developed in the 1930’s
Electron microscope
How does an electron microscope form an image?
Using beams of electrons passing through a specimen
What is the maximum resolution (in mm) of the electron microscope?
0.0000002 mm
What is the maximum magnification of an electron microscope?
X 2,000,000
Explain why an electron microscope has images that show more detail compared to a light microscope
They have a greater magnification and a greater resolution
When preparing a slide, what is first placed on a clean slide?
Drop of water
Explain the function of the drop of water on a clean slide during the preparation of the slide
To secure the specimen in place
Explain why a stain is usually added to a slide specimen
To add colour to objects in a cell so they are easier to see
What stain would you use when preparing a slide of onion skin?
Iodine
What stain would you use when preparing a slide of cheek cells?
Methyl blue
Once a slide is prepared, where on the microscope is it placed?
On the stage
What keeps the slide in place?
Clips
Which objective lens should be chosen first?
The lowest magnification
What part of the microscope would you use first to move the stage?
The coarse adjustment knob
Where should the stage be placed before looking down the eye piece?
Just below the objective lens
Which part of the microscope should be used to bring the image roughly into focus?
The coarse adjustment knob
What direction should the coarse adjustment knob be moved into to bring the image roughly into focus?
Downwards
What should be moved to bring the image into clear focus?
The fine adjustment knob
What should you do if you want to see the image at a higher magnification?
Swap to a higher powered objective lens and refocus
What is the equation for calculating magnification of a microscope?
Total magnification = eyepiece lens magnification x objective lens magnification
Calculate the total magnification used when viewing a specimen through a x4 eyepiece lens and a x50 objective lens
4 x 50 = x200
State the equation for calculating magnification if you do not know the power of the lenses used
Magnification = image size / real size
If you have a specimen that is 2.5 x 10^-2 mm wide and the image is 10 mm wide, calculate the magnification of the microscope
Magnification = 10 / 0.025 (2.5 x 10^-2) = x 400
An image of a cheek cell with a width of 60 um shows that the nucleus fits 8 times across the cell. Calculate the width of the nucleus
Width of nucleus = 60 / 8 = 7.5 um
A mitochondrion measured using an electron microscope has a width of 4.8 um and a height of 1.5 um. Estimate the area of the mitochondria
4.8 x 1.5 = 7.2 um^2
A ribosome with a width of 4 x 10^-5 mm is observed as being 900 um wide in an electron microscope image. Calculate the magnification of the image
Image size = 900 m / 1000 = 0.9mm
Magnification = 0.9 / 4 x 10^-5 = 0.9 / 0.00004 = x 22, 500
Compare today’s light microscope with Hooke’s
Hooke’s microscope: contains a barrel with two lenses, uses light, magnification up to x 30, resolution down to 0.002 mm
Modern light microscope: contains a barrel with two lenses, uses light, magnification up to x 1500, resolution down to 0.0001 mm
What do enzymes act as?
Biological catalysts
Give the definition of a catalyst
A substance that speeds up a chemical reaction without being changed or used up itself
What type of molecule are enzymes?
Proteins
What gives each type of enzyme a unique shape?
The way the chain of amino acids folds up
What is the model of enzyme action named?
The ‘lock and key’ model
What are the molecules that interact with the enzyme called?
The substrate
What is the uniquely shaped section of an enzyme called?
The active site
What happens at the active site?
The substrate fits into the active site
What does ‘high specificity’ for a substrate mean?
The enzyme will only interact with the specific substrate that matches the shape of its active site
Explain why increasing temperature will usually increase the rate of an enzyme-catalysed reaction
The reactants have more energy, so they move around more and collide more often with enough energy for a reaction to take place
Explain why enzymes will stop working if they get to hot (2 marks)
- Some bonds holding the protein structure of the enzyme in place will break and change the shape of the enzyme
- If the shape of the active site is changed it will stop working because the substrate will no longer fit into the active site
What is the scientific term for an enzyme that no longer works?
Denatured
What temperature do human enzymes work at?
37-38 degrees celsius
At what temperature do most human enzymes stop working?
45 degrees celsius
What is the definition of an enzyme’s optimum temperature?
The temperature at which the enzyme is most active
How does the concentration of a substrate affect the rate of reaction?
The higher the substrate concentration, the faster the rate of reaction
Explain why the higher the substrate concentration, the faster the rate of reaction
Higher the concentration, the more likely that the enzyme will collide with and interact with the substrate molecule
When does the concentration of a substrate no longer affect the rate of reaction?
When the number of substrate molecules is greater than the number of enzyme active sites / when all the enzyme active sites are full
How does pH affect an enzyme if it is too high or too low?
The pH affects the bonds holding the enzymes together therefore changing their shape at the active site. The enzyme becomes denatured
When investigating the effect of pH on the action of the enzyme amylase, what equipment would you need?
Spotting tile, dropping pipette, iodine solution, (bunsen burner, tripod, gauze, heatproof mat / water bath), 250ml beaker, boiling tube, 5ml syringes, test tube holder, stopwatch
Which piece of equipment is better at keeping the temperature of the amylase solution at a constant temperature compared to using a bunsen burner?
A water bath
What chemicals are used during the investigation of the effect of pH on the action of the enzyme amylase?
Iodine solution, pH buffers (pH1 to pH12), starch solution, amylase solution
How many times should the experiment on the effect of pH on the action of the enzyme amylase?
Three times
Why is doing an experiment three times important?
To produce a more accurate average time after removing outliers
How could the pH be accurately measured during the investigation of the effect of pH on the action of the enzyme amylase?
Using a pH meter
Name the independent variable in the investigation of the effect of pH on the action of the enzyme amylase
pH of buffer solutions
Name the dependent variable in the investigation of the effect of pH on the action of the enzyme amylase
Time taken for the starch to be digested / iodine solution to stay brown
State the control variables used during the investigation of the effect of pH on the action of the enzyme amylase
Use same volume of amylase solution, pH buffer and starch solution; same concentration of amylase solution, starch solution and iodine solution; same temperature of water in beaker / water bath
State the equation to calculate the rate of reaction of the enzyme used in the investigation of the effect of pH on the action of the enzyme amylase
Rate = 1000 / time
At pH6, it takes amylase 90 seconds to digest a starch solution. Calculate the rate of reaction
Rate = 1000 / 90 = 11 s^-1
State the equation used to calculate the rate of reaction of an enzyme
Rate = change / time
An enzyme reaction produces 24 cm^3 of a gas over 50 seconds. Calculate the rate of reaction
Amount of product formed = change = 24 cm^3
Rate = 24 / 50 = 0.48 cm^3 / s^-1
What is the function of the pH buffer in the investigation of the effect of pH on the cation of the enzyme amylase?
To maintain a constant pH throughout the reaction, therefore maintain constant conditions in the boiling tube
Name three main groups of big biological molecules that are essential for life
Carbohydrates, proteins, lipids
What do organisms need to do to use carbohydrates, proteins and lipids for life processes such as growth?
Break them down into their smaller components
Name the type of enzyme that digests carbohydrates
Carbohydrases
Name the type of enzyme that digests carbohydrates found in saliva
Amylase
What big molecule is digested by amylase?
Starch
What is starch broken down into?
Maltose and other simple sugars (e.g. glucose)
Describe the molecules produced by digestion
Small and soluble
Name the type of enzyme that digests proteins
Proteases
Where are proteases found in the body?
In the stomach / gastric juices
What are proteins broken down into when they are digested?
Amino acids
Name the type of enzyme that digests lipids
Lipases
What are lipids broken down into by lipases?
Three fatty acids and one glycerol
Where are lipases and carbohydrases found together in the body?
Intestines
In addition to breaking down molecules, name another function of enzymes in the body
Synthesis of new molecules
Name the two groups of sugars that can be tested for
Reducing sugars (e.g. glucose) and non-reducing sugars (e.g. sucrose)
Describe how you would prepare a solid food sample for testing its content of sugars, starch and proteins (4 marks)
- Break up food in a pestle and mortar
- Transfer the ground up food into a beaker and add some distilled water
- Stir the mixture vigorously
- Let mixture to settle and pipette out some of the liquid to use as the sample
Name the test for reducing sugars
Benedict’s test
What is a positive result for reducing sugars?
The solution changes from its normal blue colour to green, yellow to red. The higher the concentration of reducing sugar, the further the colour change goes
Explain why the water bath is set at 75 degrees celsius for the test for reducing sugars
To speed up the rate of reaction and therefore any colour change
Explain why each food sample should be heated for the same amount of time in the test for reducing sugars
So the results can be compared - to make it a fair test
Name the test for starch
Iodine solution
Describe a positive result for the food test for starch
In the presence of starch, iodine solution turns a blue / black colour
What colour is a negative result for the test of starch?
Yellow / brown colour
Name the test for proteins
Biuret test
Name the two chemicals used to test food for protein
Potassium hydroxide and copper (II) sulfate solution
Describe a positive result for protein in food
Colour changes from blue to purple / lilac / pink
Describe a negative result for protein in food
The solution remains blue
Name the test for lipids
Emulsion test
How do you prepare a sample of solid food to be tested for lipids?
Grind it up in a pestle and mortar
What substance is added to the food sample in a test tube?
Ethanol
After shaking, what is added after ethanol?
Distilled water
Describe a positive result for the emulsion test
Precipitate is seen as a milky emulsion
Name the type of experiments that can be used to work out the energy in different foods
Calorimetry
Some foods were burnt to find out how much energy they contained. Explain how this experiment shows how much energy a food contains (2 marks)
The higher the temperature rise of the water, the more energy is contained within the food
State the equation to calculate the total amount of energy in the burned food
Energy in food (J) = mass of water (g) x temperature change of water (degrees celsius) x 4.2
How do you calculate the energy per gram of food?
Divide the energy in the food by the mass of the food in grams
Explain why it is important to divide the energy in the food by the mass of the food in grams
To be able to compare the results of each food because the food samples are not exactly the same mass
Explain why the results from the experiment where you investigate some foods that were burnt and find out how much energy they contained are only an estimation
Energy is lost to the surroundings and the test tube instead of being transferred to the water
How do substances pass into and out of cells?
Diffusion, osmosis and active transport
How do smells spread?
Diffusion
What is the definition of diffusion?
The gradual movement of particles from an area of higher concentration to an area of lower concentration
What states of matter can be involved in diffusion?
Gases and liquids
Cells have partially permeable membranes. What does this mean?
The membranes only let some molecules through but not others
What type of molecules can move through partially permeable membranes?
Very small molecules
Describe the movement of particles in fluids
Random
If there is a higher concentration of oxygen inside a cell compared to the outside, describe the net movement of oxygen particles
Out of the cell
What is the net movement of water molecules called?
Osmosis
Give a definition for osmosis
The net movement of water molecules across a partially permeable membrane from an area of higher water concentration to an area of lower water concentration
State the net movement of water molecules across a partially permeable membrane separating distilled water on one side and sucrose solution on the other side
From distilled water into the sucrose solution
If a cell is short of water what happens to the concentration of the solution inside?
It becomes more concentrated
If the cell that is short of water is surrounded by a more dilute solution, describe the net movement of water molecules
Into the cell
What happens to cells that gain water by osmosis?
They expand
What happens to animal cells that gain too much water?
They burst
What happens to plant cells that gain too much water?
They become turgid
State the name for the process where particles can move against a concentration gradient
Active transport
Explain how cells can absorb ions from dilute solutions
Energy transferred from respiration is used to move ions from an area of lower concentration to an area of higher concentration / against a concentration gradient
Name a plant cell that relies on the absorption of ions from dilute solutions to absorb minerals
Root hair cell
Name an animal cell that relies on the absorption of ions from dilute solutions to absorb glucose
Small intestine epithelial cell
Using three different concentrations of sucrose solution, describe how you could investigate their effect on parsnip cells (6 marks)
- Use a cork borer to cut a parsnip into the same sized pieces (e.g. 1cm x 2cm cylinders)
- Divide the cylinders into groups of three and use a balance to measure the mass of each group
- Place 100cm^3 of each sucrose solution into separate beakers and place a group of cylinders into each solution
- Leave the cylinders in the solutions for one hour
- Remove the cylinders and gently pat dry with paper towels
- Use the balance to measure the new mass of each group
Name the independent variable in the experiment where you use three different concentrations of sucrose solution to investigate their effect on parsnip cells
The concentration of sucrose solutions
Name the dependent variable in the experiment where you use three different concentrations of sucrose solution to investigate their effect on parsnip cells
The cylinder mass
Name the control variables in the experiment where you use three different concentrations of sucrose solution to investigate their effect on parsnip cells
The volume of solution, the size of cylinders, the age and type of parsnips used, amount cylinders are dries, time cylinders are left in the sugar solutions
State the equation to calculate percentage change in mass in the experiment where you use three different concentrations of sucrose solution to investigate their effect on parsnip cells
Percentage change in mass = ((final mass - initial mass) / initial mass) x 100
A group of cylinders weighed 14.3g at the start of experiment and 17.4g at the end. Calculate the percentage change in mass
((17.4 - 14.3) / 14.3) x 100 = 22%
How do you find the concentration of a parsnip cell after plotting the percentage change in mass against the concentration of sucrose solution?
- Draw a line of best fit
2. Find the point at which the line of best fit crosses the x axis
Describe an adaptation of a fat cell
Large amount of fat stored in droplets in the cell
Explain how red blood cells are specially adapted to carry oxygen around the body
No nucleus makes more room for haemoglobin which combines with oxygen
Describe the special feature of muscle cells that allow them to contract
Contain proteins that contract to shorten the cell
Describe how the cells that line the gut are specialised to absorb nutrients
Microvilli increase their surface area, contain mitochondria to provide energy for active transport
Explain how nerve cells are adapted to their function
Long fibre that carries electrical impulses around the body, many short connections to link to other nerve cells, myelin sheath to insulate impulse as it travels along the axon
Explain why differentiation is important for organisms
It allows different parts of the body to become specialised for different functions so each function can be carried out effectively
