Topic 3 Flashcards
what is a nucleus?
a large organelle surrounded by a NUCLEAR ENVELOPE (double membrane), which contains many PORES.
the nucleus contains CHROMATIN (made from DNA and proteins) and a NUCLEOLUS.
what is the function of a nucleus?
controls the cell’s activities by controlling the transcription of DNA. the pores allow substances such as RNA to move between the nucleus and the cytoplasm.
the nucleolus makes ribosomes.
the DNA in the chromosomes contain the genes that control the synthesis of proteins.
describe a lysosome.
a round organelle surrounded by a membrane with no clear internal structure.
what is the function of a lysosome?
contains DIGESTIVE ENZYMES.
these are kept separate from the cytoplasm by the surrounding membrane, and can be used to digest invading cells or to break down worn out components of the cell.
the acrosome is a specialised lysosome.
describe a ribosome.
a very small organelle that either FLOATS FREE in the cytoplasm or is attached to the ROUGH ENDOPLASMIC RETICULUM.
it is made up of proteins and RNA.
it is not surrounded by a membrane.
what is the function of a ribosome?
the site of protein synthesis
describe the rough endoplasmic reticulum (RER).
a system of membranes enclosing a fluid-filled space. the surface is covered with ribosomes.
what is the function of the rough endoplasmic reticulum (RER)?
folds and processes proteins that have been made at the ribosomes.
proteins made at these ribosomes are transported through the ER to other parts of the cell in vesicles.
describe the smooth endoplasmic reticulum (SER).
a system of membranes enclosing a fluid-filled space.
similar to the RER but with no ribosomes.
what is the function of the smooth endoplasmic reticulum (SER)?
synthesises and processes lipids.
describe the golgi apparatus.
a group of fluid-filled, membrane-bound, FLATTENED SACS.
vesicles are often seen at the edges of the sacs.
what is the function of the golgi apparatus?
processes and packages new lipids and proteins in vesicles.
also makes lysosomes.
describe a mitochondrion.
oval-shaped.
have a double membrane - the inner one is folded to form CRISTAE.
inside is the MATRIX, which contains enzymes involved in respiration.
what is the function of mitochondria?
the site of aerobic respiration where ATP is produced.
they are found in large numbers in cells that are very active and require a lot of energy.
describe a centriole.
small, hollow cylinders, made of MICROTUBULES (tiny protein cylinders).
found in animal cells but only some plant cells.
what is the function of a centriole?
involved with the separation of chromosomes during cell division.
involved in the formation of a spindle during nuclear division.
what are the signs that a cell is metabolically active?
lots of mitochondria
extensive RER
many golgi apparatus
what are the steps of protein trafficking (the production of proteins and their route through the cell) ?
1) transcription of DNA to mRNA.
2) mRNA leaves the nucleus through the nuclear envelope.
3) protein made on ribosomes enter rough ER.
4) protein moves through the rough ER assuming three-dimensional shape en route (tertiary protein structure).
5) vesicles pinched of the rough ER contain the protein.
6) vesicles from the ER fuse to form the flattened sacs of the golgi apparatus.
7) proteins are modified within the golgi apparatus.
8) vesicles pinched of the golgi apparatus contain the modified protein.
9) vesicle fuses with cell surface membrane releasing protein.
describe the role of the RER and golgi apparatus in the formation of extracellular enzymes.
extracellular enzymes such as digestive enzymes move to the cell surface membrane and are secreted.
describe the cell wall in a prokaryotic cell.
the cell wall supports the cell and prevents it from changing shape.
it is made of MUREIN (a glycoprotein).
describe the capsule in a prokaryotic cell.
a mucilaginous layer of slime.
helps to protect bacteria from attack by cells of the immune system.
describe the plasmid in a prokaryotic cell.
small loops of DNA that are not part of the main circular DNA molecule.
contain genes for things like antibiotic resistance and can be passed between prokaryotes.
plasmids are not always present.
describe the flagellum in a prokaryotic cell.
a long hair-like structure that rotates to make the prokaryotic cell move.
not all prokaryotes have a flagellum and some have more than one.
describe the pili in a prokaryotic cell.
short hair-like structures.
help prokaryotes stick to other cells and can be used in the transfer of genetic material between cells.
