Nucleus, ER, Ribosomes and Golgi body Flashcards
Ultrastructure
The detailed structure revealed by the electron microscope.
A nucleus is the…
largest organelle.
A nucleus is surrounded by…
two membranes called the nuclear envelope.
The outer membrane of the nuclear envelope is…
continuous with the endoplasmic reticulum.
The nuclear envelope has many small…
pores called nuclear pores. This allows and controls exchange between the nucleus and the cytoplasm.
Examples of substances leaving the nucleus:
mRNA and ribosomes for protein synthesis.
Examples of substances entering the nucleus:
proteins to help make ribosomes, nucleotides, ATP and hormones such as thyroid hormones T3
ATP stands for…
adenosine triphosphate.
Chromatin
The chromosomes are in a loosely coiled state known as chromatin(except nuclear division)
Chromosomes contain…
DNA which is organised into functional units called genes.
Genes control the…
activities of the cell and inheritance, so the nucleus controls the cell’s activities.
Nucleolus makes…
ribosomes, using information in its own DNA.
Endoplasmic Reticulum (ER)
Is an extensive system of membranes running through the cytoplasm.
(ER)The membranes form…
an extensive system of flattened compartments called sacs, spreading through the cell.
(ER) The sacs can be…
interconnected to form a complete system (reticulum). The ER is continuous with the outer membrane of the nuclear envelope.
Rough ER
It is covered with many ribosomes. Visible as black dots.
Ribosomes consist…
of two subunits. A large and small subunit.
On the rough ER, the ribosomes are…
small only about 25nm in diameter. Made of RNA (ribonucleic acid) and protein.
Proteins made by the ribosomes on the rough ER…
enter the sacs and move through them. The proteins are often modified on the journey.
Small sacs called…
vesicles, which can break off from the ER and these can join together to form the Golgi body.
The Golgi body forms a part of…
the secretory pathway, as the proteins can be exported from the cell via the Golgi body.
Smooth ER
It lacks ribosomes and has a completely different function.
A function of smooth ER
It makes lipids and steroids such as cholesterol and the reproductive hormones oestrogen and testosterone.
Golgi body is…
a stack of flattened sacs.
More than one Golgi body can…
be present in the cell.
(Golgi body) The stack is constantly…
being formed at one end of the vesicles which bud off from the ER and broken down again at the other end to from Golgi vesicle.
The stack of sacks together with…
associated vesicles is referred to as the Golgi body.
The Golgi body collects…
processes and sorts molecules (mainly proteins form rough ER), ready for transport in Golgi vesicle either to other parts of the cell or out of the cell-secretion.
(glycoprotein)Example of protein processing in Golgi body is…
the addition of sugars to proteins to make molecules of glycoproteins.
(functioning protein)Example of protein processing in Golgi body is…
the removal of the first amino acid, methionine, from newly formed proteins to make a functioning protein.
In plants, enzymes in Golgi body…
concert sugars into cell wall components.
Golgi vesicles are also used to make…
lysosomes.
