1.2 - Ultrastructure Of Cells Flashcards
History of electron microscopes/benefits/compared to light microscopes
Developed in Germany in the 1930’s
Allows images to be produced of things 200 times smaller than with light microscopes
Able to see the structure of eukaryotic cells - more intricate than expected
What electron microscopes revealed
The ultrastructure of cells
Size that the human eye can see unaided
0.1 mm
Size that the light microscope allows us to see
200 nano meters
Define resolution
Making the separate parts of an object distinguishable by eye
Why electron microscopes have a higher resolution than light microscopes
Because electrons have a much shorter wavelength than the wavelength of light
Main difference between Prokaryotes and Eukaryotes
Presence of a nucleus (in Eukaryotes - membrane bound nucleus, Prokaryotes - no nucleus)
Describe the cell wall
Much thicker and stronger than the cell membrane. It protects the cell, maintains the cells shape, and prevents the cell from bursting
Cytoplasm in Prokaryotes
One uninterrupted chamber - compartments not separated by membranes
Organelles in Eukaryotes
Present in the cytoplasm, have distinct structures with specialized functions
Size of ribosomes in Prokaryotes
70s
Define nucleoid
Region of the cell containing the DNA of the cell, usually in the form of one circular DNA molecule - DNA is not associated with proteins.
Is nucleus-like, but not a nucleus
The only way that living organisms can produce new cells is -
the division of pre-existing cells
Define Binary Fission
Cell division in prokaryotic cells, used for asexual reproduction
Describe Binary Fission
- Single circular chromosome is replicated
- The 2 copies of the chromosome move to opposite ends of the cell
- Cytoplasm divides
- -> Each of the daughter cells contain one copy of the chromosome so they are genetically identical
Products of Binary Fission
2 genetically identical daughter cells
Labels on a diagram of a prokaryotic cell
Ribosomes, cell wall, plasma membrane, cytoplasm, nucleoid, pilli, flagellum
Cytoplasm of Eukaryotes
Is compartmentalized with double membranes
Define organelles
The compartments in the cytoplasm
Advantages of the compartmentalized structure of Eukaryotes
Enzymes and substrates for processes can be concentrated
Potentially damaging substances can be kept inside the membrane of an organelle (eg. digestive enzymes in lysosomes)
Conditions like pH can be maintained at an ideal level for a particular process - different levels for different processes
Organelles and their contents can be moved around within the cell
Labels on a diagram of a eukaryotic cell
Nucleus, rough endoplasmic reticulum, Golgi apparatus, lysosome, mitochondria, free ribosomes, chloroplasts, vacuoles, vesicles, microtubules and centrioles, cilia, flagella
Describe Nucleus
Double membrane, with pores. Contains the chromosomes of DNA associated with histone proteins.
Describe Rough Endoplasmic Reticulum
Consists of flattened membrane sacs called cisternae, ribosomes attached on the outside of the cisternae. Classified as 80s.
Function of the Nucleus
Location of DNA replication and transcribing to form mRNA, which is exported via pores into the cytoplasm
Function of the Rough Endoplasmic Reticulum
To synthesize protein for secretion from the cell.
Describe Golgi Apparatus
Consists of flattened membrane sacs called cisternae. Cisternae are not as long as in the RER, are often curved, do not have ribosomes attached. There are many vesicles nearby.
Function of the Golgi Apparatus
Processing proteins which have been brought in by vesicles from the RER
Describe lysosome
Single membrane, spherical, contain high concentrations of protein - makes them densely staining in micrographs. Contain digestive enzymes.
Function of lysosome
digestive enzymes can be used to break down ingested food in vesicles, or break down organelles in the cell, or break down the whole cell
Describe mitochondria
double membrane, with inner structures called cristae, and fluid inside called matrix.
Function of mitochondria
Produce ATP for the cell by aerobic cell respiration, digests fat if it is being used as an energy source for the cell
Describe free ribosomes
Appear as dark granules in the cytoplasm, are not surrounded by a membrane
Function of free ribosomes
Free ribosomes synthesise protein, releasing it to work in the cytoplasm (as enzymes or in other ways)
Describe chloroplasts
Double membrane, stacks of flattened sacs called thylakoids, usually spherical or ovoid. Starch grains may be present inside if they have been photosynthesising rapidly.
Function of chloroplasts
Produce glucose and a wide range of other organic compounds by photosynthesis.
Describe vacuoles and vesicles
Organelles that consist of a single membrane with fluid inside.
Vesicles are very small vacuoles
Function of vacuoles and vesicles
Animals - some absorb food from outside and digest it inside vacuoles
Unicellular organisms - use vacuoles to expel excess water
Vesicles - used to transport materials inside the cell
Describe microtubules and centrioles
Microtubules - small cylindrical fibres in the cytoplasm of cells
Centrioles - in animal cells, two groups of nine triple microtubules
Function of microtubules and centrioles
Microtubules - variety of roles : including moving chromosomes during cell division
Centrioles - form an anchor point for microtubules during cell division, and for microtubules inside the cilia and flagella
Describe cilia and flagella
Whip-like structures projecting from the cell surface
Contain a ring of double microtubules plus two central ones
Flagella - larger than cilia, normally only one present (as in sperm)
Cilia - smaller than flagella, normally many are present
Function of cilia and flagella
Both used for locomotion
Cilia - can also be used to create a current in the fluid next to the cell
How do gland cells secrete substances?
Through their plasma membrane
What are the 2 types of gland cells in the pancreas?
Endocrine
Exocrine
What do the endocrine cells in the pancreas do?
Secrete hormones into the blood stream
What do the exocrine gland cells in the pancreas do?
Secrete digestive enzymes into a duct that carries them to the small intestine where they digest foods
What is the function of the organelles that are in exocrine gland cells in the pancreas?
Organelles which are needed to:
Synthesise proteins in large quantities
Process proteins to make them ready for secretion
Transport proteins to the plasma membrane
Release proteins through the plasma membrane
What are the organelles which are present in exocrine gland cells in the pancreas?
Plasma membrane Golgi apparatus Mitochondrion Vesicles Nucleus Lysosomes Rough ER
In a leaf, which cell type carries out the most photosynthesis?
Palisade mesophyll
What is the function of a leaf?
Photosynthesis - producing organic compounds from carbon dioxide and other simple inorganic compounds, using light energy.
What is the shape of palisade mesophyll cells?
Roughly cylindrical
What organelles are present in a palisade mesophyll cell?
Cell wall Plasma membrane CHLOROPLASTS - carrying out the most photosynthesis, so LOTS of these Mitochondrion Vacuole Nucleus
