SB1: Key Concepts in Biology Questions Flashcards
What are prokaryotic cells?
Small, simple cells without a nucleus.
Give an example of a prokaryotic cell.
Bacteria.
What are prokaryotes?
Single-called 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 a cell:
Cytoplasm.
What is the role of cytoplasm?
It is where most chemical reactions happen.
Name the subcellular structure that holds the cell together:
The cell membrane.
Give the role of the cell membrane:
- It controls what goes in and out of the cell.
2. It’s a subcellular structure that holds the cell together.
Name the subcellular structure where respiration takes place:
Mitochondria.
Which subcellular structures are involved in protein synthesis?
Ribosome.
Which stage of protein synthesis is the ribosome 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 sugar and salts dissolved in water.
*sheet said slats
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 chloroplasts?
Photosynthesis.
Name the green substance contained within photosynthetic cells:
*may be chloroplasts not photosynthetic cells, double check
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 plasmids?
Drug resistance.
Name the part of some bacterial cells that rotates to make the cell move.
Flagellum.
Describe 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 as e.g. those high in nutrients and oxygen.
- They can move away from areas of harmful conditions eg 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 cell:
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?
It’s specific function.
Name the four types of animal cells that you need to know how their structure are linked to their specific function:
Sperm cells, egg cells, small intestine cells and ciliates epithelial cells.
Which cell in the answer to the previous question 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 the sperm cell forward:
The tail.
Name the adaptation that provides the energy for the tail:
Mitochondria concentrates area at base of tail.
Name the adaptation that makes it easier for the sperm cell to move:
Streamlined shape:
Name the part of the sperm cell that contains enzymes:
Acrosome.
What is the function of the enzymes found in the acrosome?
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 the sperm cell?
To transport male DNA to the female DNA found in the egg.
Which cell is only found in females?
Egg cells.
Name 3 adaptations of the egg cell:
- High nutrient content.
- Haploid nucleus/ nucleus with only 23 chromosomes.
- Cell membrane can change structure.
Name an adaptation that the egg cell and speed cell share:
A haploid nucleus/ nucleus with only 23 chromosomes.
Explain why the egg cell and sperm cell have a 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 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 of the following cell is found in the airways: Sperm cells, egg cells, small intestine cells and ciliates epithelial cells.
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 ciliated cells:
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 absorption molecules through intestinal wall:
Microvilli.
How are specialised cells 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?
1590s.
What can we see using microscopes?
Individual cells and large sub-cellular structures.
What is the maximum magnification of a microscope?
X 1500.
What is the maximum resolution (in mm) of a microscope?
0.0001mm.
How would you write in 0.0001mm standard form?
1x10^-4m.
How would you write 0.0001mm in nanometres?
100nm.
How do microscopes form an image?
Using light and lenses.
Write one picometre in standard form:
1x10^-12m.
Write one nanometre in standard form:
1x10^-9m.
Write six micrometres in standard form:
6 x 10^-6 m.
Convert 6mm into nanometres:
6,000,000nm / 6x10^6m.
Name the type of microscope that was developed in the 1930s:
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 an electron microscope?
0.0000002mm.
What is the maximum magnification of an electron microscope?
x 2,000,000.
Explain why electron microscopes images show more detail than light microscopes:
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 microscope:
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 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 x 4 eyepiece lens and a x 50
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) = x400.
An image of a cheek cell with a width of 60μm shows that the nucleus fits 8 times across the cell. Calculate the width of the nucleus:
Width of nucleus = 60 / 8= 7.5μm.
A mitochondrion measured using an electron microscope has a width of 4.8 μm and a height of 1.5 μm. Estimate the area of the mitochondria:
4.8 x 1.5= 7.2μm^2.
A ribosome with a width of 4 x 10^-5 mm is observed as being 900 μm wide in an electron microscope
image. Calculate the magnification of the image:
Imagesize=900m/1000=0.9mm
Magnification = 0.9 / 4 x10-5) = 0.9 / 0.00004 = x22,500.
Compare today’s light microscope with Hooke’s:
Hooke’s microscope: contains a barrel with two lenses, uses light, magnification up to ×30, resolution down to 0.002 mm.
Modern light microscope: contains a barrel with two lenses, uses light, magnification up to ×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?
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 too hot.:
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.
W What temperature do human enzymes work at?
37-38 degrees c.
W At what temperature do most human enzymes stop working?
45 degrees c.
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 to 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,) or (water bath), 250ml beaker, boiling tube, 5 ml 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 investigating 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 investigating the effect of pH on the action of the enzyme amylase be repeated?
Three times.
Why is repeating investigations important?
To produce a more accurate average time after removing outliers.
How could the pH be accurately measured during investigating the effect of pH on the action of the enzyme amylase?
Using a pH meter.
Name the independent variable in investigating the effect of pH on the action of the enzyme amylase:
pH of buffer solutions.
Name the dependent variable in investigating 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 investigating 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 investigating 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 = 11s^-1.
State the equation used to calculate the rate of reaction of an enzyme:
Rate = change ÷ time.
An enzyme reaction produces 24 cm3 of a gas over 50 seconds. Calculate the rate of reaction:
Amount of product formed = change = 24cm^3. Rate = 24 ÷ 50 = 0.48cm^3 s^-1.
What is the function of the pH buffer in investigating the effect of pH on the action 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, 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:
- 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 C 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 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 for 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 for the test for lipids?
Ethanol.
After shaking, what is added after the ethanol has been added in the test for lipids?
Distilled water.
Describe a positive result for the test for lipids:
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:
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 C) 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 calculate the energy per gram of food:
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 burning food to find out how much energy they contain are only an estimation.
To be able to compare the results of each food because the food samples are not exactly the same mass.
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.
A cell is short of water. If the cell is surrounded by a more dilute solution, describe the net movement of water molecule
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 energy transferred from respiration to absorb minerals:
Root hair cell.
Name an animal cell that relies on energy transferred from respiration to absorb glucose:
Small intestine epithelial cell.
Using three different concentrations of sucrose solution, describe how you could investigate their effect on parsnip cells:
- Use a cork borer to cut a parsnip into the same sized pieces eg 1cm x2cm cylinders.
- Divide the cylinders into groups of three and use a balance to measure the mass of each group.
- Place 100 cm3 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 investigating the effect of different concentrations of sucrose solution on parsnip cells:
The concentration of sucrose solutions.
Name the dependent variable in investigating the effect of different concentrations of sucrose solution on parsnip cells:
The cylinder mass.
Name the control variables in investigating the effect of different concentrations of sucrose solution on parsnip cells:
The volume of solution, the size of cylinders, the age and type of parsnips used, amount cylinders are dried, time cylinders are left in the sugar solutions.
State the equation to calculate percentage change in mass in investigating the effect of different concentrations of sucrose solution on parsnip cells:
Percentage change in mass = ((final mass – initial mass) ÷ initial mass) x 100.
An investigation into the effect of different concentrations of sucrose solution on parsnip cells is carried out. A group of cylinders weighed 14.3 g at the start and 17.4 g at the end. Calculate the percentage change in mass:
(17. 5–14.0) ÷ 14) x 100 = 0.25 x 100 = 25%.
* ans had ((17.5
An investigation into the effect of different concentrations of sucrose solution on parsnip cells is carried out.
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.
