Book 1- cells Flashcards
What is a cell?
the basic unit of living organisms
What is a tissue?
a smaller group of similar cells, which carry out a specific function
What is an organ?
a group of different tissues
What does unicellular mean?
its made up of 1 cell only
How are eukaryotes characterised?
by the presence of a nucleus and other cell organisms
What do plant cells have that animal cells don’t?
- ) a cellulose wall providing support and shape
- ) starch grains present in the cytoplasm
- ) chloroplasts containing chlorophyll
- ) vacuole containing sugars, salts and sometimes pigment
What are plasmadesmata?
channels for exchanging substances between adjacent plant cells
What do prokaryotes contain?
DNA, cell membrane, ribosomes, cytoplasms
what structures may a prokaryote be?
capsule, plasmid, flagella
explain virsues
they are accelular. they are not alive by themselves, therefore must enter the human and take over a cell to multiply. consists of DNA or RNA, capsid, lipid envelope and attachment protein
The function of the nucleus?
contains DNA, which codes for proteins
The function of chloroplast?
carries out photosynthesis, producing glucose
The function of the mitochondria?
carries out aerobic respiration, which releases energy
The function of ribosomes?
Carries out protein synthesis by joining amino acids together
The function of SER
produces fats and transports them around the cell
The function of RER
has ribosomes attached, which makes proteins. transports proteins to the Golgi body
The function of Golgi body?
modifies and packages proteins, produces vesicles and lysosomes
The function of lysosomes?
digest unwanted materials, such as bacteria
Why do muscle cells contain many mitochondria?
mitochondria respire, more means more respiration, more energy released for muscle contraction
Where are epithelial cells found?
lining the inside or outside of organs
How are epithelial cells suited to its purpose?
- )folded into microvilli providing a large SA for diffusion.
- ) lots of microvilli meaning higher rate of respiration providing more ATP for the active uptake of digested foods.
How is a palisade mesophyll cell adapted to photosynthesis?
- ) possess numerous chloroplasts
- ) have thin cell walls providing a short diffusion pathway
- ) columnar providing a large SA
- )vertically arranged so there are fewer cell walls for light to pass through
What is differential Centrifugation?
a technique that is used to separate organelles according to their density.
Explain Centrifugation (6)
1.) The cells are broken by homogenising a tissue in an ice cold, isotonic, buffer solution using a blender.
Ice cold- prevents enzyme action that might cause digestion of the organelles,
Isotonic- allows water to move in and out of organelles equally preventing organelles bursting.
Buffer solution- maintains the PH so that proteins aren’t denatured.
2.) the homogenate us then filtered to remove debris and any remaining whole cells.
3.) homogenate is poured into a tube and spun in a centrifuge at a low speed, causing the heaviest organelle to form a sediment at the bottom.
4.) the supernatant contains lighter organelles. it is poured into another tube and spin for longer at a higher speed
What order do organelles separate in in centrifugation?
nuclei, chloroplasts, mitochondria, ER, ribosomes
Magnification equation??
size of image/ size of real image
What is the resolution?
how detailed the image is
2 types of electron microscopes?
transmission electron and scanning electron microscope
How does TEM work?
uses electromagnets to focus a beam of electrons through a thin specimen and then focusing the electrons to form an image on the screen.
how does SEm work?
scans a beam of electron onto a specimen which collects the electrons scattered by the surface
Advantages and disadvantages of SEM
A- 3D, can be used on thick specimens
D- gives lower resolution images, can only be used on dead specimens due to the vacuum
Advantages and disadvantages of TEM
A- high resolution images
D- can only be used on think specimens, can only be used on dead specimens due to the vacuum
Why is electron microscopy better than light?
- electrons have a shorter wavelength, providing a better resolution.
- a higher magnifications images blurs using light due to poor resolution
How’s a microscope slide prepared?
- ) pipette a small drop of water onto the centre of the slide
- ) use twezers to place a thin specimen on top if the water drop
- )add a drop of a stain to highlight the object.
- ) add the cover slip. standing it upright and lowering to avoid bubbles
