GCSE Biology: Flashcards
What are the two types of cells?
Prokaryote and Eukryote.
What is a eukaryote?
Complex.
Animal and plant cells.
What is a prokaryote?
Smaller and simple bacteria.
What are different parts of the cell called?
Subcellular structures.
Name the structures in a animal cell:
Nucleus, Cytoplasm, Cell Membrane, Mitochondria, and Ribosomes.
What is a Nucleus?
Genetic material and control cell activity.
What is a Cytoplasm?
Gel substance, chemical reactions happen and has enzymes that control reactions.
What is a Cell Membrane?
Holds cells together and controls what goes in and out.
What is a Mitochondria?
Reactions for aerobic respiration take place and transfers energy.
What is Ribosomes?
Proteins are made.
Name the structures in a plant cell:
Cell wall, Permanent vacuole and Chloroplasts.
What is a Cell wall?
Made of cellulose and supports the cell.
What is a Permanent vacuole?
Has cell sap and a weak solution of sugar and salts.
What is Chloroplasts?
Photosynthesis occurs.
What is Chlorophyll?
Green substance that absorbs the light needed for photosynthesis.
[ In a Chloroplasts. ]
In a bacterial cell what cells aren’t included?
Chloroplasts or mitochondria.
What kind of nucleus does a bacterial cell have?
A single circular strand of DNA that floats freely in the cytoplasm.
Name the cells that might be in a bacterial cell:
Cytoplasm, Cell Membrane and a Cell Wall.
What are Plasmids?
Small rings of DNA that might be in bacterial cells.
Why are microscopes important?
To study cells that can’t be seen by the human eyes. Also, developed over years of technology and improved.
What is a Light Microscope?
The light and lenses to form an image of a specimen and magnify it.
Why do you use Standard Form in Science?
Because of the tiny objects which could be very big or small numbers with a lot of zeros so. Using standard form is useful and manageable.
What is an Electron Microscope?
Using electrons instead of light to form an image, a higher magnification and a higher resolution. See the internal structures of mitochondria and chloroplasts.
What is the formula of Magnification?
Magnification= Image size ÷ Real size
A specimen is 50um wide. Calculate the width of the specimen under a magnification of x100. [In mm]
Image size= Magnification x real size
Image size= 100 x 50
=5000um
=5mm [um= 1000÷ =mm]
Which mircroscopes do you look at a specimen?
A light microscope.
How do you prepare a slide to view an onion cell?
- Add a drop of water on a clean slide.
- Cut up the onion and seperate them into layers. Use tweezers to peel off some epidermal tissues from the bottom of one of the layers.
- Place the epidermal tissue into the water on the slide.
- Add a drop of iodine solution [Stain] to highlight objects.
- Then put a cover slip upright on the slide next to the water droplet. Carefully, tilt and lower it so it covers the specimen.
While you prepare your slide what do you try not to do?
Get any air bubbles under the slide because they’ll obstruct your view on your specimen.
Name the six things that a light microscope has:
Eyepiece, Coarse adjustment knob, Fine adjustment knob, High and Low power objective lenses, Stage and Light.
How do you use a light microscope?
- Clip the slide you’ve prepared onto the stage.
- Select the lowest-powered objective lens.
- Use the cosarse adjustment knob.
- Look at the eyepiece then move the stage downwards until the image is roughly in focus.
- Adjust the fine adjustment knob when you get a clear image.
- [If you need to see the slide with greater magnification swap to a higher-powered objective lens.]
When drawing your observations what do you need to use?
A pencil with a sharp point and at least half a page with clear unbroken lines.
When drawing your observations what do you not do?
No colouring or shading.
When drawing your observations what do need to include?
A title, write down the magnification that it was observed under, label important features and using straight uncrossed lines.
What is an Enzyme?
Proteins that help speed up metabolism, or the chemical reactions in our bodies.
Name 2 facts about cells:
Cells don’t look the same and have different structures to suit their different functions.
What is the definition of Differentiation?
The process of a cell changes to become specialised for its job.
What happens when cells changes?
They develop different subcellular structures and turn into different types of cells. This allows them to carry specific functions.
Where does differenation mostly occur?
As an organism develops.
Explain the differentiation in most animal cells:
Lost at an early stage after they become specialised.
Explain the differentiation in most plant cells:
They don’t ever lose this ability of being lost at an early stage.
The cells that differentiate in mature animals are mainly used for?
Repairing and replacing cells such as skin or blood cells.
Name the scientific word for this phrase;
‘Undifferentiated cells’…
Stem Cells.
What is the function of a Sperm Cell?
Is to get the male DNA to the female DNA.
What does a sperm cell looks like?
It has a long tail and a streamlined head to help it swim to the egg.
Name two facts about a Sperm Cell:
- Lots of mitochondria in the cell to provide the energy needed.
- Carries enzymes in its head to digest through the egg cell memberane.
What is the Sperm Cell spicialised for?
Reproduction.
What is the function of a Nerve Cell?
Carry electrical signals from one part of the body to another.
Describe what a Nerve Cell looks like:
The cells are long [to cover up distance] and have branched connections at their ends to connect to other nerve cells to form a network throughout the body.
What is a Nerve Cell specialised for?
Rapid Signalling.
What is the function of a Muscle Cell?
To contract quickly.
Describe what a Muscle Cell looks like:
These cells are long [for space to contract] contain lots of mitochondria to generate energy needed.
What is a Muscle Cell specialised for?
Contraction.
Describe what a Root Hair Cell looks like?
On surface of plant roots which grow into long ‘hairs’ out into the soil.
Why does a plant need a big surface area?
For absorbing water and mineral ions from the soil.
What is a Root Hair Cell specialised for?
For absorbing water and minerals.
What is the funtion of Phloem and Xylem Cells?
Form Phloem and Xylem tubes which transport substances such as food and water around plants.
How are the Phloem and Xylem tubes formed?
The cells are long joined end to end.
Name a fact about Xylem cells:
Hollow in the centre.
Name a fact about Phloem cells:
Very few subcellular structures so that stuff can flow through them.
What are Phloem and Xylem cells specialised for?
Transporting Subtances.
What happens to cells in the human body when we grow in order to surrive?
The cells divide and DNA.
What does Chromosomes contain?
DNA
In your body most cells have what in it?
A nucleus that conntains genetic material in form of chromosomes.
What do Chromosomes look like?
Coiled up with lenghts of DNA molecules.
What does each Chromosomes carry?
A large number of genes. Different genes control the development of different characteristics.
Give an example of a characteristics:
Hair colour.
In Body Cells there are two copies of Chromosomes from whom?
One of the organism’s “mother” and one from its “father”.
In a human cell how many pairs of Chromosomes are there?
23 pairs of Chromosomes.
What does a Cell Cycle do?
Makes new cells for growth, development and repair.
What happens in Body Cells in multicellular organism?
They divide to produce new cells as part of a series of stages called The Cell Cycle.
What is the definition of Mitosis?
The stage of the cell cycle when the cell divides.
In multicellular organisms what do they use?
They use Mitosis to grow or repalce cells that have been damaged.
What happens at the end of the Cell Cycle results?
Two new cells identical to the original cell with the same number of Chromosomes.
What are the two main stages of the Cell Cycle:
Growth and DNA Replication.
Mitosis.
In Growth and DNA Replication what happens in a cell that’s not dividing?
The DNA is all spread out in long strings.
In Growth and DNA Replication what happens before the cell divides?
The cell has to grow and increase the amount of subcellular structures such as mitochondria and ribosomes.
In Growth and DNA Replication when its DNA duplicates what is formed?
The DNA is copied and forms X-shaped chromosomes. Each ‘arm’ of the chromosome is an exact duplicate of the other.
In a X-shaped chromosome what does each ‘arm’ represent?
The left arm has the same DNA.
The right arm has chromosomes.
What happens next once the DNA has been copied?
The chromosomes line up at the centre of the cell and cell fibres pull them apart. The two arms of each chromosome goes to opposite ends of the cell.
What happens next when chromosomes go to the opposite ends of the cell?
Membranes form around each of the sets of chromosomes. These become nuclei of the two new cells [the nucleus has divided].
Finally what happens next once the nucleus has been divided?
The cytoplasm and cell membrane divide. The cell has now produced two new daughter cells. The daughter cells contain exactly the same DNA [they’re identical].
The daughters DNA is also identical to whom?
The parents cell.
Whats the type of simple cell division that can reproduce Prokaryotic Cells?
Binary Fission.
In binary fission, the cell…
Splits into two.
What is the method of Binary Fission?
What is the circumstance of each of the daughter cell having one copy of the circular DNA?
- Circular DNA and plasmid(s) replicate.
- Cell gets bigger. The circular DNA strands move to opposite “poles” (ends) of the cell.
3.Cytoplasm begins to divide. New cell walls begin to form. - Cytoplasm divides. Two daughter cells are produced. Each daughter cell has 1 copy of the circular DNA.
What is the circumstance of each of the daughter cell having one copy of the circular DNA?
Can have a variable number of copies of the plasmid(s).
How long does bacteria divide and why?
Very quickly by the right conditions.
Give an example of a condition that can make a bacteria divide quickly:
Warm environement.
What happens when the conditions become infavourable to a bacteria?
Stop dividing and eventually die.
What is Mean Division Time?
A method of how many times a bacteria cell has divided in a certain amount of time and the number of cells it has been produced in that time.
Bacteria (and some other microganisms) are grown in a “Culture Medium”. What does a Culture Medium contain for the need to grow?
Carbohydrates.
Minerals.
Proteins.
Vitamins.
The Culture Medium used can be a…
Nutrient broth solution.
Solid agar jelly.
Bacteria grown on agar “plates” will form visible…
Colonies on the surface of the jelly or spread out to give an evening covering of bacteria.
To make an agar plate what gets poured into the shallow round plastic?
Hot agar jelly.
What are the “plates” called when testing Culture Medium?
Petri Dishes.
Name the correct scientific term of “wire loops” in a Petri Dish:
Inoculating Loops.
When the jelly’s cooled and set, what can the inoculating loops be used for?
Transfer microorganisims to the cluture medium.
Alternatively, a sertile dropping pipette and spreader can be used to get an even covering of bacteria.
In Labs at School cultures of microorganisms aren’t kept above 25*c. Why?
Harmful pathogens are more likely to grow.
What kind of conditions does the Cultures Medium grow a lot faster at higher temperatures?
Industrial conditions.
After the evening covering of bacteria what does the microorganisims do?
Multiply.
(Investigate the effect of antibiotics on bacterial growth:)
Step 1-Preparation:
Place paper discs soaked in different types or concentrations of antibiotics on an agar plate with an even covering of bacteria.
Why is an even covering of bacteria important in the peperation step?
An even covering ensures consistent results by providing a uniform environment for the antibitics to act upon.
(Investigate the effect of antibiotics on bacterial growth:)
Step 2-Diffusion:
Antibiotics will diffuse into the agar around the paper discs, creating areas where bacteria may have died.
What happens during the diffusion step?
Antibiotics diffuse into the agar from the paper discs, potentially killing or inhibiting bacteria around the discs.
(Investigate the effect of antibiotics on bacterial growth:)
Step 3-Control Setup:
Use a control disc soaked in sertile water instead of an antibiotic to ensure the results are due to the antibiotic.
Why is a control disc used in the experiment?
To ensure any observed effects on bacterial growth are due to the antibiotic and not other variables.
(Investigate the effect of antibiotics on bacterial growth:)
Step 4-Incubation:
Leave the plate for 48 hours at 25*C.
What are the conditions for the incubation step?
Incubuate the plate for 48 hours at 25*C to allow sufficient time for bacterial growth and antibiotic action.
(Investigate the effect of antibiotics on bacterial growth:)
Step 5-Observation:
Measure the inhibition zone (clear area) to determine the antibiotic’s effectiveness. Larger inhibition zones indicate more effective antibiotics.
What does the inhibition zone represent?
The clear area around the disc where the bacteria have not grown, indicating the effectiveness of the antibiotic.
How do you measure the effectiveness of an antibiotic?
By measuring the size of the inhibition zone around the paper disc.
Larger inhibition zones indicate more effective antibiotics.
What does a larger inhibition zone indicate?
The antibiotic is more effective at inhibiting bacterial grwoth.
What is the purpose of using a control in the antibiotic effectiveness test?
The control disk (soaked in sertile water) ensures that the observed effects on bacterial growth are due to the antibiotic and not other factors.
What are the potential consequences of contamination by unwanted microorganisms in mircobiology experiments?
Contamination can skew experimental results and lead to the growth of harmful pathogens which could affect the accuracy and safety of the experiment.
Describe the process for preparing petri dishes and culture medium to ensure they are uncontaminated before use.
Petri dishes and culture medium must be sterilized, typically by heating them to a high temperature to kill any existing microorganisms that might be present.
What is the recommended method for sterilizing an inoculating loop before transfering bacteria to the culture medium?
The inoculating loop should be sterilized by passing it through a hot flame to eliminate any potential contaminants.
Explain why is it necessary to lightly tape the lid of a petri dish after inoculating it with bacteria.
Taping the lid helps to secure it and prevnt unwanted microorganisms, from entering the dish. Thereby reducing the risk of contamination.
What is the reason for sstoring petri dishes upside down after inoculation?
Prevents condensation droplets from falling onto the agar surface, which can otherwise cause contamination and effect the growth of the bacteria.
(Culturing Microorganisms:)
Purpose of comparing inhibition zones:
It’s important because of the effectiveness of antibiotics.
(Culturing Microorganisms:)
Methods for comparison:
By eye vs calculating the area.
(Culturing Microorganisms:)
Formula for the calculation:
Area = PieR*2
(Culturing Microorganisms:)
Application to bacterial colonies:
Area = PieR*2
But to measure the diameter first.
What is the process called when a cell changes to become specialized for its job?
Differentation.
What are stem cells?
Undifferenetiated cells that can divide to produce more undifferenetiated cells and can differentiate into different types of cells.
Where are stem cells found in the early stages of human development?
In early human embryos.
Why are stem cells from embryos exciting to doctors and medical researchers?
Because they have the potential to turn into any kind of cell at all.
