Studied by 88 peopleWhat is the function of the nucleus?
Contains DNA to control the cell
What is the function of the cell membrane?
Controls entry and exit of substances
What is the function of the cell wall?
Provides structure and support
What is the function of mitochondria?
Carry out respiration to release energy
What is the function of ribosomes?
Protein synthesis
What is the function of chloroplasts?
Carry out photosynthesis
What is the function of a vacuole?
Contains cell sap
Define a prokaryote
A cell that does not have a nucleus
Define a eukaryote
A cell that has DNA in a nucleus
Name two cell structures that are in a eukaryote but not in a prokaryote
Nucleus, mitochondria, chloroplasts
What is a plasmid?
A small loop of DNA in bacteria
What is a plant cell wall made from?
Cellulose
How is DNA stored in a bacterial cell?
As a single, free-floating loop; also on plasmids
What is differentiation?
The process by which cells become specialised
What is the equation for magnification?
Magnification = Image Size ÷ Actual Size
A photograph of a cell is 15mm long. It has a magnification of 1100x. What is the actual size?
0.0136mm, or 13.6µm
A cell is 12µm wide. It is magnified by 450 times. How big is the image?
5400µm, or 5.4mm
If the image of a virus is 1.2mm, and its actual size is 0.2µm, how much has it been magnified by?
6000 times
Convert 38500µm into mm
38.5mm
How many µm are in 1mm?
1000
Write 17400m in standard form
1.74 x 10^4 m
Write 0.0034 in standard form
3.4 x 10^-3
How is a sperm cell adapted for its function?
It has a tail to swim to the egg
How is a nerve cell adapted for its function?
It has a long axon to conduct impulses over long distances
What and How is a muscle cell adapted for its function?
Specialsied to contract quickly or simply to squeeze to allow movement.
What is a root hair cell and how adapted for its function?
Specialised to take up water by osmosis and mineral ions by osmois and mineral ions by active transport from soil as tney are found on tip of roots.
It has a large surface area to increase osmosis of water
Mitocondria provide energy for respiration for active transport of mineral ions into root hair cells
How is a xylem cell adapted for its function?
It has hollow ends to transport water
How is a phloem cell adapted for its function?
It has sieve tubes to transport sugars
What is a stem cell?
An undifferentiated cell that can differentiate to become any type of specialised cell
Where are stem cells most commonly found in animals?
In embryos and in bone marrow
What is meristem tissue?
Plant tissue containing stem cells
When are plant cells able to differentiate?
Throughout the whole life of the plant
When do most animal cells differentiate?
At an early stage of development (as an embryo)
What is the "resolution" of a microscope?
Resolution is the smallest distance between two separate points
Why are electron microscopes better than light microscopes?
They have a higher resolution and higher magnification
Give an example of an organelle you could see with an electron microscope, but not with a light microscope?
Ribosomes
Describe the steps to prepare a slide [Required Practical]
Add a drop of water to the middle of a clean slide
Cut up an onion and separate it out into layers. Use tweezers to peel off some epidermal tissue from the bottom of one the layers
Using the tweezers, place the epidermal tissue into the water on the slide
Add a drop of iodine solution. Iodine solution is a stain which is used to highlight objects in the cell by adding colour to them
Place a cover slip on top. To do this, stand the cover slip upright on the slide, next to the water droplet. Then carefully tilt and lower it so it covers the specimen. Try not to get any air bubbles underneath it - they'll obstruct your view of the specimen
Describe the steps needed to use a light microscope to look at your slide [Required Practical]
Clip the slide you've prepared onto the stage
Select the lowest-powered objective lens
Use the coarse adjustment knob to move the stage up to just below the objective lens. Look from the side NOT IN EYPIECE as you may damage the slide.
Look down the eyepiece. Use the coarse adjustment knob to move the stage downwards until the image is roughly in focus.
Adjust the focus with the fine adjustment knob, until you get a clear image of what's on the slide
If you need to see the slide with greater magnification, swap to a higher-powered objective lens and refocus
What shape is DNA?
Double helix
What molecule is DNA stored as?
Chromosomes
How are chromosomes usually found in body cells?
In pairs
What is a gene?
A small section of DNA that codes for a specific protein
What is mitosis?
Cell division
What are the two main purposes of mitosis?
To grow and to replace cells
What must happen in a cell before mitosis can take place?
It must replicate its DNA to form two copies of each chromosome
Once DNA has been replicated, what happens next in mitosis?
One set of chromosomes is pulled to each end of the cell and the nucleus divides
What are the products of mitosis?
Two genetically identical daughter cells
What is the cell cycle?
The stages in a cell as it grows and goes through mitosis
What conditions may stem cells be able to help with?
Diabetes and paralysis
How are most blood cells formed?
From stem cells in bone marrow
What is therapeutic cloning?
When an embryo is produced with the patient's genes so that stem cells from the embryo can be used
Why are stem cells made by therapeutic cloning more useful for medical treatments?
They contain the same genes as the patient, so are not rejected by the patient's body
Give two ways using stem cells to clone plants may be useful
For preventing the extinction of rare plant species, and for producing large numbers of identical disease-resistant crops
Define diffusion
The movement of particles from a high concentration to a low concentration down a concentration gradient
What factors affect the rate of diffusion?
Temperature, surface area, difference in concentration
How is the small intestine adapted for diffusion?
There are lots of villi to give a large surface area, villi contain lots of capillaries close to the surface so there is a short diffusion distance and they have a good blood supply for quick absorbtion by blood increase concentration gradient
How are the lungs adapted for diffusion?
Lots of alveoli give a large surface area, they have thin wall/surface cells and capillaries are close so there is a short diffusion distance. they have good ventilation to show great air flow.
How are fish gills adapted for diffusion?
Gills have lots of filaments to give a large surface area, there are lots of capillaries with a short distance for diffusion
How are plant roots adapted to absorb water?
Roots have lots of long root hair cells to give a large surface area for osmosis
How are plant roots adapted to absorb mineral ions?
Root hair cells have mitochondria to release energy for active transport of mineral ions
How are leaves adapted for gas exchange?
Leaves have lots of stomata on the underside to allow carbon dioxide to diffuse in
Define osmosis
The movement of water from a high water potential to a low water potential across a partially permeable membrane
The difference in and out of cell determines how much osmois occurs red blood cell in differnet concentration of water
The difference in and out of cell determines how much osmosis occurs.
More concentrated than interanal cell envionment may cause cell to burst(turgid: swollen for plant cell) AS WATER MOVES IN
Same concentrstion as the cell so no net movement of water
Less concentrated than cells intenal envionment may cause cell to shrink(flaccid: shrink for plants) AS WATER MOVES OUT
Describe the steps to observe the effect of sugar solutions on plant tissue [Required Practical]
Cut up a potato into identical cylinders and get some beakers with different sugar solutions in them. One should be pure water and another should be a very concentrated sugar solution. Then you can have a few other with concentrations in between
Measure the mass of the potato cylinders, then leave one in each beaker for 24 hours
Then take them out, dry with a paper towel to remove any access water/solution and measure the masses again
If the potatoes have drawn in water by osmosis, they'll have an increase in mass. If water has been drawn out, they'll have a decrease in mass
The dependant variable is the chip mass and the independent variable is the concentration of the sugar solution
To reduce the effect of errors (e.g. from the potato cylinders not being fully dried or water being evaporated) complete the experiment three times and calculate the mean percentage change at each concentration
How would you calculate % change in mass of a potato chip in sucrose solution?
(Change in mass ÷ Starting mass) x 100
Why should you dry a potato chip dry before taking its mass?
To remove excess water, so it doesn't increase the mass
Why do you calculate %change in mass of a potato chip rather than just change in mass?
So that you can compare different chips, as the starting mass of each potato may not be the same
Define active transport
The movement of particles from a low concentration to a high concentration against a concentration gradient, using energy
Explain one example of active transport in plants
Absorption of mineral ions in root hair cells
Explain one example of active transport in animals
Absorption of glucose in the small intestine
Define a tissue
A group of cells with similar structure and function
Define an organ
A group of tissues working together to perform a function
Deine an organ system
A group of organs working together
Give two examples of tissues in animals
Epithelial tissue, muscle tissue, nerve tissue, glandular tissue
Give two examples of tissues in plants
Palisade tissue, spongy mesophyll tissue, xylem tissue, phloem tissue
Give two examples of organs in animals
Heart, lungs, stomach, brain, liver
Give two examples of organs in plants
Leaf, root, stem, flower
Define an enzyme
A biological catalyst that carries out metabolic reactions in living organisms
What is a substrate?
A substance that is broken down by an enzyme
Where does a substrate bind to an enzyme?
Active site
What is formed when an enzyme binds to a substrate?
Enzyme-substrate complex
Why are enzymes specific?
Each type of enzyme has an active site that only fits one specific substrate
What are enzymes made of?
Protein
What conditions cause enzymes to denature?
High temperatures or pH that is too high or low
Define denature
When an enzyme cannot work because its active site has lost its specific shape so the substrate no longer fits
What is human body temperature?
37oC
What is the Lock and Key Theory?
A substrate is specific to one enzyme because of the specific shape of its active site (like a key fitting a lock)
Enzymes are specific to the substrate they bind too.
Substrate binds with ACTIVE SITE
2.Enzyme breks down substrate into products after chemical reaction
Products released and enzyme doesnt change
What is the purpose of digestion
To break large, insoluble molecules into small, soluble molecules so they can be absorbed
Where is amylase made?
Where is protease made?
Where is lipase made?
Salivary glands and Small intestine and Small intestine Pancreas
Stomach and Small intestine and Pancreas
Pancreas and Small intestine
What is the substrate of amylase?
What is the substrate of protease?
What is the substrate of lipase?
What is the substrate of carbohydrase?
Starch
Protein
Lipids(Fat)
Carbohydrate
What are the products of amylase digesting starch?
What are the products of protease digesting proteins?
What are the products of lipase digesting lipids?
Glucose
Amino acids
Glycerol and fatty acids
What are the products of protease digesting proteins?
Amino acids
What are the products of lipase digesting lipids?
Glycerol and fatty acids
Give two functions of bile
To emulsify fats, and to neutralise stomach acid
What equipment is used to control temperature in an investigation?
Water bath
Define accuracy
Measurements that are close to the true value
What food does Benedict's test for?
Glucose(Sugar)
What food does Biuret solution test for?
Protein
What food does iodine test for?
Starch
What food is ethanol used to test for?
Fats
Note
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