eukaryotic, prokaryotic cells, viruses + nucleus structure Flashcards
examples of eukaryotic organisms
plant
animal
fungi
order of organisation
Specialised cells are organised
into tissues, tissues into organs and organs into systems.
In complex multicellular organisms, eukaryotic cells become
specialised for specific functions
example of prokaryotic organisms
bacteria
archaea
all living organisms can be divided into _____
eukaryotes/prokaryotes -> living organisms
Describe the general structure of eukaryotic cells
In all eukaryotic cells,
the DNA is contained in a membrane-bound (surrounded by a membrane) nucleus
The nucleus has a double membrane
the DNA is tightly wrapped/coiled around proteins called histones
Together, the DNA and histone proteins form chromosomes
By tightly coiling their DNA into chromosomes, eukaryotic cells can pack a lot of DNA into their nucleus
Their DNA is a linear molecule (the ends of the DNA molecule in a chromosome are not joined together to form a loop)
Eukaryotic cells contain other membrane-bound organelles - mitochondria, Golgi apparatus, endoplasmic reticulum
The same organelles are in plant cells, but in plant cells, there are also chloroplasts and a vacuole (also membrane-bound organelles)
The presence of membrane bound organelles
Contain other organelles that are not membrane-bound. For example, ribosomes which are involved in protein synthesis
Eukaryotic cells - surrounded by a cell-surface membrane (helps to control the molecules that can pass in and out of the cell)
In plants and fungi - cell membrane - surrounded by cell wall (the cell wall helps to maintain the structure of these cells)
plant cells - made from polysaccharide - cellulose
fungal cells - polysaccharide chitin
https://www.genome.gov/sites/default/files/media/images/tg/Chromosome.jpg
what does DNA and histone proteins form
Together DNA and histone proteins form chromosomes
The DNA in eukaryotic cells is a linear molecule
What does this mean
Their DNA is a linear molecule (the ends of the DNA molecule in a chromosome are not joined together to form a loop)
where are ribosomes found
eukaryotic and prokaryotic organisms/cells
what is the difference between the ribosomes in eukaryotic cells and prokaryotic cells
The ribosomes in eukaryotic cells are larger than those in prokaryotic cells
eukaryotic cells contain 80S ribosomes
prokaryotic cells contain 70S ribosomes
S - a unit showing how quickly organelles move in a centrifuge
describe how eukaryotic cells may lose their nucleus as they develop
what happens to most eurkaryotic cells
E.g. red blood cells in humans
most eukaryotic cells have a nucleus throughout their lifespan
draw an animal cell
https://s3.eu-west-2.amazonaws.com/elements.cognitoedu.org/a873ae44-8320-4da5-95d5-5cfa390ff0b5/animal-cell-organelles-diagram.png
draw a plant cell
https://s3.eu-west-2.amazonaws.com/elements.cognitoedu.org/2d24fe71-a463-47bf-8adb-09b05c963529/plant-cell-organelles-diagram.png
draw a fungal cell
plant cell without chloroplasts
https://s3.eu-west-2.amazonaws.com/elements.cognitoedu.org/2d24fe71-a463-47bf-8adb-09b05c963529/plant-cell-organelles-diagram.png
describe the structure of prokaryotic cells
Prokaryotic cells - much smaller than eukaryotic cells
Prokaryotic cells have no membrane-bound organelles
This means that in prokaryotic cells, the DNA is found in the cytoplasm rather than in a nucleus
Unlike in Eukaryotic cells, the DNA is arranged into a circular chromosome with no free ends and is not associated with
proteins
The DNA in prokaryotes is not bound to histone proteins
Sometimes bacterial cells contain small loops of DNA called plasmids
Plasmids usually contain a relatively small number of genes (these can include genes which make the bacterium resistant to antibiotics)
SO Plasmids are very important for bacteria (eukaryotic cells do not contain plasmids)
Prokaryotic cells contain ribosomes (70 S) -
prokaryotic cells - surrounded by a cell wall (in bacteria, this is made from peptidoglycan/murein - glycoprotein)
peptidoglycan - polymer formed between peptides and polysaccharide molecules
Cell wall helps to maintain the structure of the cells
Some bacteria produce a slime capsule on the outside of the cell wall - the slime capsule can help to protect the bacteria from phagocytosis by white blood cells
Some prokaryotic cells have a flagellum - helps them to move (flagellum - sperm -eukaryotic) - have different structures
pili - fine protein strands on their surface
these help bacteria to attach to surfaces/other bacteria
when two bacteria are attached, DNA can be transferred from one bacterium to another
bacteria also contain lipid droplets and glycogen granules - these act as nutrient stores for the bacterial cell
sometimes using the electron microscope - we can see infoldings in the cell membrane of prokaryotic cells - these are called mesosomes
initially scientists suggested that mesosomes played a role in respiration /// however scientists now believe that mesosomes are actually artefacts that are created when bacterial cells are prepared for electron microscopy
Importance of plasmids in prokaryotic cells
Plasmids usually contain a relatively small number of genes (these can include genes which make the bacterium resistant to antibiotics)
describe the importance of cell walls in prokaryotic/eukaryotic cells organisms
Cell wall helps to maintain the structure of the cells
E.g. if water moves into the bacteria cell by osmosis, the cell wall prevents the cell from bursting
draw a bacteria cell
https://s3.eu-west-2.amazonaws.com/elements.cognitoedu.org/f4d1b75a-2e5d-4038-aebc-607efbbf4ace/prokaryotic-organelles-illustration.png
describe the structure and life cycle of viruses
different types of viruses can have different shapes, but many viruses are broadly spherical
All viruses contain genetic material - this can be either DNA or RNA
The genetic material is contained inside a protein structure called a capsid
On the surface of the virus, are attachment proteins
These attachment proteins allow the virus particle to attach to and enter the host cell
In some viruses, the capsid is surrounded by a lipid envelope - lipid envelope formed from the host cell membrane
DRAW A VIRUS
https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTDvd7uBLPDxhB6jeqNm1HnC32aHW7thJTnsCdIPsqlY2PsOB-i
+ LIPID ENVELOPE - CIRCLE AROUND VIRAL PARTICLE
https://s3.eu-west-2.amazonaws.com/elements.cognitoedu.org/732822c4-1fa5-44f3-b4e9-e3c2966fb03e/virus-structure-diagram.png
what can viruses not do independently
Viruses cannot reproduce independently
Viruses can only reproduce inside a host cell
describe how viruses reproduce inside a host cell
A virus particle attaches to the surface of a host cell
Next the virus enters the host cell
Now, the virus uses the host cell’s enzymes to produce copies of itself
These virus particles now leave the host cell and can go on to infect new host cells and continue reproducing
compare the difference in size of a bacterial cell and a virus particle
A virus particle is much smaller than a bacterial cell
Viruses are not _____
Viruses are not cells
Viruses are acellular - which means not based on cells
explain how viruses are not living
Viruses cannot reproduce independently - in order to reproduce, a virus must invade a host cell and use the host cell’s enzymes to make copies of itself
So because viruses cannot reproduce on their own, viruses are not counted as living organisms
Draw the nucleus
https://studymind.co.uk/wp-content/uploads/2022/03/Screen-Shot-2022-03-29-at-3.54.23-PM.png
Rough Endoplasmic Reticulum
outer membrane
Inner membrane
describe the structure of the nucleus in cells
The nucleus contains a jelly-like `material called nucleoplasm
Nucleoplasm contains molecules such as nucleotides and enzymes - which are needed for DNA and RNA synthesis
Surrounding the nucleus, is a double membrane. This is called the nuclear envelope
Consists of two phospholipid bilayers
Within the nuclear envelope, there are nuclear pores - Function of nuclear pores - to allow molecules to enter and leave the nucleus
e.g. RNA nucleotides enter the nucleus through nuclear pores from the cytoplasm/ These nucleotides are used in the nucleus to synthesise messenger RNA The MRNA then leaves the nucleus via a nuclear pore and undergoes translation on a ribosome
The outer membrane of the nuclear envelope is continuous with the rough endoplasmic reticulum (RER plays a role in protein synthesis)
Nucleus contains a dark material - called chromatin
Chromatin - consists of DNA coiled around proteins called histones.
Together, the DNA and histone proteins form chromosomes (DNA in chromosome is a linear molecule)
Chromosomes are not visible inside the nucleus unless the cell is undergoing mitosis or meiosis.
In the nucleus, there is a region darker than the rest. This is called the nucleolus. The nucleolus is where are special type of RNA is produced called Ribosomal RNA ( or rRNA)
Ribosomal RNA forms part of the structure of ribosomes.
As well as forming rRNA the nucleolus is also where ribosome subunits are assembled
nucleus can contain one or more nucleoli
Chromosomes are not normally ______ inside the nucleus.
In what instant are they normally _______
Chromosomes are not visible inside the nucleus unless the cell is undergoing mitosis or meiosis.
explain the importance of proteins to living organisms
enzymes are proteins
enzymes (biological catalysts) are required for chemical reactions taking place in cells
other proteins play a structural role in cells e.g. moving organelles to where they are needed
some proteins act as transport molecules - e.g. haemoglobin - transports oxygen in mammals
so protein synthesis is one of the most important functions taking place in cells
describe protein synthesis
role of nucleus in protein synthesis
protein synthesis involves several different organelles
the instructions for encoding the amino acid sequence of a protein are contained within the gene for that protein
these genes are part of the chromosomes - which are found in the nucleus
to synthesise a protein, the genetic information encoded by that gene is converted to messenger RNA or mRNA - This process is called transcription
in nucleus (with pores)
gene –> mRNA (–> = transcription)
This mRNA then leaves the nucleus
now a ribosome reads the information contained in the mRNA and synthesises the protein molecule - called translation
mRNA –> protein (—> = translation by ribosome)
if the protein remains in the cytoplasm e.g. a cellular enzyme, then translation will take place on a free ribosome in the cytoplasm
However some proteins are secreted from cells e.g. digestive enzymes and antibodies
secreted proteins are translated on a ribosome attached to the rough endoplasmic reticulum
These proteins then make their way through the rough ER and the Golgi apparatus before leaving the cell
shows role of nucleus in protein synthesis
