Biology paper 1 Flashcards
When were the first light microscopes developed?
In the mid 17th century
Pros of light microscopes
Relatively cheap, can magnify live specimens, can be used almost anywhere.
Pros and cons of transmission electron microscopes
2d images - high magnification + resolution.
But scanning electron microscopes give dramatic 3D images but lower magnifications. Electron microscopes are large, expensive, and have to be kept in special temperature conditions.
1km =… metres
1m =.. cm
1cm =.. mm
1mm =.. micrometres
1pm = …. Nanometres
1000metres
100cm
10mm
1000micrometres
1000nanometres
Define resolution (microscopes )
The ability to distinguish between 2 separate points and it is the resolving power of a microscope that affects how much detail it can show.
How do you calculate magnification with a light microscope?
Magnification of eye piece lens x magnification of objective lens.
Equation for magnification
Magnification = size of image divided by size of real object.
Evaluate the use of an electron microscope and a light microscope, giving one example where each type of microscope might be used.
The electron microscope and light microscope are both important tools in biology, but they are suited to different tasks. The electron microscope uses a beam of electrons to achieve much higher magnifications and resolutions, allowing us to see tiny structures like viruses that can’t be observed with a light microscope. However, it requires complex sample preparation, meaning live specimens can’t be studied. On thr other hand, the light microscope used visible light and is much simpler to use. It has lower resolution and magnification, making it suitable for observing larger structures, like plant cells, and it FSH dtufynlive specimens in their natural state. Overall, electron microscopes are best for detailed studies of small objects, while light microscopes are ideal for observing larger, living cells or tissues.
What are the two types of cells?
Eukaryotes and prokaryotes
What is the difference between eukaryotes and prokaryotes?
Eukaryotes = complex , animal and plant cells , big
Prokaryotes = smaller, simpler, single - called organism, bacteria.
What subcellular structures do animal cells have and what are their functions?
Nucleus - contains genetic material that controls the activities of the cell.
Cytoplasm - gel-like substance where most of the chemical reactions happen. The organelles are suspended. It contains enzymes that controls these chemical reactions.
Cell membrane - hold the cell together and controls what goes in and out.
Mitochondria - these are where most of the reactions for aerobic respiration take place.
Ribosomes - these are where proteins are made in the cell and where protein synthesis takes place.
What do plant cells have that animal cells don’t?
Rigid cell wall - made of cellulose. It supports and strengthens the cell.
Permanent vacuole - contains cell sap which keeps the cells rigid to support the plant.
Chloroplasts - where photosynthesis occurs, making food for the plant. They contain a green substance called chlorophyll which absorbs the light needed for photosynthesis.
Why don’t root cells have chloroplasts..
As they are underground and don’t photosynthesise.
List the main structures you would expect to find in a human cell.
Nucleus , cell membrane , mitochondria, cytoplasm , ribosomes
Suggest why the nucleus and the mitochondria are so important in all cells? (4marks)
The nucleus and mitochondria are vital for cell function because the nucleus houses the cell’s genetic information (DNA), controlling cell activities and reproduction, while mitochondria, the “powerhouses” of the cell, generate energy through cellular respiration.
Chloroplasts are found in many plant cells but not all of them. Suggest two types of plant cells that are unlikely to have chloroplasts and in each case explain why they have none. (4marks)
Root hair cells and petals
Petals and other flower parts are involved in attracting pollinators, not in photosynthesis.
Their vibrant colors and fragrances are adaptations for attracting insects, birds, or other animals to aid in pollination, not for capturing light energy.
Root cells, especially root hair cells, are located underground and are not exposed to sunlight, which is necessary for photosynthesis.
Their primary function is to absorb water and nutrients from the soil, not to produce food through photosynthesis.
Where is the bacterial chromosome found in prokaryotic cells?
It’s a single dna loop found free in the cytoplasm.
What are plasmids in prokaryotic cells?
Extra small rings of DNA.
They code for very specific features such as antibiotic resistance
What is flagella and its function?
A long protein trans they lashes about. The bacteria use their flagella to move themselves around.
What is the order of magnitude
When something is 10x bigger.
A small animal cell has a length of around 10um. A large plant cell has a length of around 100um.
100 divided by 10 is 10. A large plant cell is an order of magnitude or 10 to the power of 1 bigger than a small animal cell.
Define diffusion.
The spreading out of particles of any substance, resulting in a net movement from an area of higher concentration to an area of a lower concentration, down a concentration gradient.
