Cell Structure And Function Flashcards
In microscopy sections of tissue must be
Thin enough for light to pass through, preferably single layers of cells
Staining for microscopy involves
Adding coloured dyes to slides to make biological specimens visible under the microscope, staining is necessary because most biological cell structures are colourless and otherwise invisible the stains bind to chemicals in specimens to give contrast so you can distinguish between different parts of the cell
Compare the resolution of a light microscope and an electron microscope
LM: Low as light has long wavelength so cannot distinguish objects close together.
EM: High as electron beam has short wavelength so can distinguish objects close together.
Compare the magnification of a LM and EM
LM: Low (X1500) so small objects can’t be seen.
EM:High (X1500000) so small objects can be seen.
Compare staining images in LM and EM
LM: Coloured dyes are used to give a coloured image.
EM: Heavy metals, denser objects absorb more electrons so appear darker, image is not coloured
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Describe the specimens used in LM and EM
LM can see living cells and can be used to follow some processes in living cells.
EM cannot look at living cells as the vacuum kills them.
Compare artefacts in LM and EM
LM: Not a problem
EM: Sample preparation complicated, and produces artefacts
Compare Scanning EM and Transmission EM
- In SEM electron beam bounces off surface of sample to produce a 3D image of surface, in TEM an electron beam penetrates the sample to show internal strictures of organelles.
- In SEM the specimen doesn’t need to be thin, in TEM Specimen must be very thin
- In SEM magnification and resolution is low compared to TEM, in TEM it is very high.
What is the formula for magnification
M=I/A
If a question gives you a photo with a scale bar drawn on it how do you work out the actual size of the object
Actual size = Length of object / Length of scale bar x Measurement of scale bar
What’s ultrastructure
The detailed structure of the internal components of cells as revealed by an EM
Describe the structure and function of the smooth ER
Single membrane cells which makes lots of lipids have lots of smooth ER, for example liver cells and fat cells
Function: makes and processes lipids
Describe function and structure of rough ER
Has a single membrane, the outer surface is covered in ribosome cells who itch make lots of proteins.
Function: Makes and processes proteins
Describe the structure and function of ribosomes
Structure: have no membrane and are found on rough ER or free in the cytoplasm and are made of RNA
Function: invited in translation of mRNA into protein.
Describe structure and function of a cell membrane
Structure: has a bylayer of phosphor lipids and is folded in some animal cells to form microvilli
Function: regulates movement of substances in and out of the cell
Describe the structure and function of mitochondria
Has a double membrane, the inner membrane is folded to form cristae
Function: aerobic respiration produces ATP
What is the structure and function of the nucleus
S: double membrane called nuclear envelope which has pores in it to let mRNA out.
F: controls activities of the cell and stores/protects the DNA
What is the structure and function of lysosomes
S: Has a single membrane which helps contain enzymes which would otherwise digest the whole cell.
F: contains digestive enzymes for destroying worn out organelles
What is the structure and function of Golgi apparatus
S: Has a single membrane and a stack of flattened sacks. Golgi vesicles transport protiens and lipids from the Golgi to the cell surface membrane for secretion.
F:modifies and packages proteins and lipids and also makes Golgi vesicles and lysosomes
What is the structure and function of peroxisomes
S: has a single membrane with a crystal core and is known as a micro body
F: involved in catabolism of lipids and reactive oxygen species. Also has a role in sugar metabolism and lipid biosynthesis
What is the structure and function of centrosome
S: composed of centrioles and microtubules which can be used as highways for vesicle transport or spindle fibres for centromere attachment during mitosis
What do mitochondria produce
ATP by aerobic respiration for processes such as active transport and protein synthesis
Mitochondria have a large surface area to volume ratio meaning
Oxygen can be absorbed for aerobic respiration by a short diffusing path to the centre
What are 2 important properties of stem cells
- They replace themselves by dividing by mitosis
- They are undifferentiated
What happens during differentiation
Some genes are expressed whereas other genes are not, the genes that are expressed are transcribed unto mRNA which is then translated into proteins, these proteins modify the cell so it becomes specialised
Name 4 different types of stem cells
Totipotent, pluripotent, multipotent, unipotent
Where is totipotent stem cells found and what are their properties
In the embryo during the first few divisions. Can produce any type of body cell, can even give rise to a whole other new organism
Where are pluripotent stem cells found and what are their properties
In the embryo after the first few divisions. Can mature into any type of body cell except the cells that form the placenta.
Where are multipotent stem cells found and what are their properties
Found in mature mammals. Can mature into a li,tied number of cell types (blood stem cells can make red blood cells)
where are unipotent stem cells found and what are their properties
Found in mature mammals. Can only mature into one type of cell
How is an epithelial cell specialised to carry out particular functions
- It has lots of microvilli which have large surface areas for diffusion and active transport of molecules into the cell.
- It has lots of Golgi vesicles, which transport proteins to cell surface membrane for active transport and facilitated diffusion.
- It has lots of mitochondria which produce ATP to supply energy to support active transport of molecules into cell.
What is the function and specialised features of a sperm cell
F: sex cell/gamete/haploid cell involved in sexual reproduction/fusion with egg cell
SF: has flagella tail to swim up the uterus. Has mitochondria to supply energy to swim and lysosomes for penetrating the egg cell.
What is the function and specialised features of a squamous epithelial cell
F: makes up alveoli walls and capillary vessel walls
SF: thin to allow exchange of substances over a short diffusion pathway. Has large surface area for efficient diffusion
What is the function and specialised features of an intestinal epithelial cell
F: lines the intestine to promote absorption of digested food products.
SF: Has a folded cell surface membrane to create microvilli which increases surface area to promote diffusion of substances. Has lots of mitochondria and Golgi for supplying ATP for active transport and vesicles for tracking absorbed products.
What is the function and specialised features of an erythrocyte
F: transports oxygen around the body in the bloodstream
SF: contains haemoglobin for binding to oxygen for transport in the bloodstream. Has a bi-concave shave and nucleated cells which increase the volume in the cytoplasm for more haemoglobin storage.
What is the function and specialised features of a leukocyte
F: protects body from foreign pathogenic invaders
SF: contains a dense lysosome content for digested engulfed pathogens. Capable of ruffling the cell membrane to bind to pathogenic antigens and trigger phagocytosis
What is the function and specialised features of a muscle cell
F: involved in contractile processes to move a body part or content
SF: actin and myosin contractile protiens are contained in the cytoplasm. Contains dense mitochondria for ATP and ER for calcium which is needed for muscle contraction.
What is the function and specialised features of a secretory gland cell
F: involved in synthesis and release of a product into a cavity or duct or into the blood stream
SF: contains dense ER for protein synthesis. Dense Golgi apparatus for vesicle information and secretion via exocytosis
What is the function and specialised features of a nerve cell
F: involved in the transmission of electrochemical action potentials for communications in the body
SF: contains mitochondria for ATP to maintain ion gradients across the axon and dendrite membranes. Has dense ER and Golgi apparatus to supply calcium and vesicles for exocytosis of vesicles containing neurotransmitters and synapses.
