Cell structure and division Flashcards
What are eukaryotic cells?
complex cells containing a nucleus and membrane bound organelles eg animal cells, plant cells, algal cells and fungal cells 80s ribosomes dna associated with histones + linear larger than pro no cell wall
Cell surface membrane
plasma membrane
membrane found on the surface of animal cells and just inside the cell wall of other cells
mainly made of lipids and proteins
regulates the movement of substances in and out of the cell
has receptor molecules which respond to chemicals
Nucleus
large organelle surrounded by a nuclear envelope which contains pores
nucleus contains chromosomes in nucleolus
nucleolus makes ribosomes
nucleus controls cells activities (transcription)
pores allow substances to move between nucleus and cytoplasm
Mitochondria
oval shaped
double membrane- inner is folded to form cristae which increases surface area for enzymes (to act)/respiration- oxidative phosphorylation
inside is matrix which contains enzymes and DNA
matrix stores substrates
site of aerobic respiration (produces ATP)
found in cells that are active and require energy
Chloroplasts
flattened structure found in plant and algal cells
surrounded by double membrane
has membranes inside called thylakoid membranes which are stacked up to form grana
grana are linked by lamellae
where photosynthesis takes place (grana or stroma)
Golgi apparatus
fluid filled membrane bound flattened sacs
vesicles are found on edge of sacs
processes and packages new lipids and proteins and makes lysosomes
transports proteins out of cells
Golgi vesicle
small fluid filled sac in cytoplasm
produces by golgi apparatus
stores lipids and proteins from golgi apparatus
transports them out of the cell by fusing with cell surface membrane
Lysosome
round organelle surrounded by a membrane- type of golgi vesicle
contains digestive enzymes called lysozymes
can be used to digest invading cells
Ribosome
small organelle made up of proteins and RNA with no outer membrane
site where proteins are made
Rough endoplasmic reticulum
system of membranes enclosing a fluid filled space
surface is covered with ribosomes
folds and processes proteins that have been made at ribosomes
Smooth endoplasmic reticulum
same as above but with no ribosomes
synthesises and processes lipids
Cell wall
rigid structure surrounding cells (plants, algae, fungi)
made of cellulose or chitin in fungi
supports cell and prevents them from changing shape
Cell vacuole (plants)
membrane (tonoplast) bound organelle found in cytoplasm
contains cell sap
helps to maintain pressure in cell and keep it rigid which stops plants wilting
What are prokaryotic cells?
small, simple, single celled organisms with no nucleus and no membrane bound organelles
70s ribosomes
dna not associated with histones / no chromosomes
replicate by binary fission
eg bacteria
cell wall of murien/ glycoprotein
Flagellum
long, hair like structure that helps the cell move
DNA
cells have single circular DNA molecule that floats freely in cytoplasm
Cell wall
supports cell, prevents cell from changing shape
made from glycoprotein
Capsule
made up of secreted slime
helps protect bacteria from attack
Plasmid
small loops of DNA that aren’t part of the main DNA molecule
contain genes for antibiotic resistance
How do prokaryotic cells replicate?
by binary fission- cell replicates its genetic material then splits into two daughter cells
1-circular DNA and plasmids replicate
2-cell gets bigger and DNA moves to opposite poles
3-cytoplasm divides
4-producing 2 daughter cells containing a copy of DNA
RODD
replicate, opposite poles, divide, daughter cells DNA
What are viruses?
they are acellular (not cells) and non living
they are nucleic acid surrounded by proteins
invade and reproduce inside host cells
What is the structure of viruses?
they havent got a membrane, cytoplasm or ribosomes
they have a lipid envelope
attachment proteins which allow them to cling onto a host cell
capsid which protect the nucleic acid from digestion
How does viral replication occur?
the virus attaches to the host cell surface using attachment proteins
they release their genetic material into the cell
the genetic material is replicated by host cell machinery
the viral components assemble
the replicated virus is released from the host cell
What is cell fractionation?
separating organelles in cells
homogenisation
filtration
ultracentrifugation
What is homogenisation?
breaking open of cells with a homogeniser to release organelles
solution must be ice cold to reduce activity of enzymes
solution must be isotonic to prevent organelles bursting or shrinking
a buffer solution should be added to prevent pH from fluctuating
Why is the homogenate filtered?
to remove large cell or tissue debris
organelles are much smaller so can pass through
What is ultracentrifugation?
the process used to separate organelle
filtered solution is poured into a tube and spun in a centrifuge
the heaviest organelles (nuclei) go to the bottom
the rest of the organelles stay suspended in the supernatant
this supernatant is drained off and spun again and the process is repeated at higher and higher speeds until all the organelles are separated out
How are the organelles separated?
through ultracentrifugation
they are separated in order of mass (heavy to light)
nucleus-(chloroplasts)- mitochondria- lysosymes - RER- ribosomes
the speed is faster for each round of centrifugation
mitosis
produces two genetically identical daughter cells
allows damaged tissues to be repaired and new tissue can grow
interphase
cell increases in mass and size, replicates DNA
g1 phase- growth phase
s phase- synthesis of DNA by dna replication
g2 phase- another growth phase, cell increases in size, cell replicates its organelles
become chromatids due to dna replication
prophase
chromosomes become short and fat (can be seen with microscope)
chromosomes are sister chromatids joined by centromere
nuclear envelope disappears
protein fibres form spindle in cell
metaphase
spindle fibres attach to centromere
chromatids line up on the equator of the cell
anaphase
centromere divides
spindle fibres shorten
chromatids move to opposite poles of the cell
telophase
chromosomes collect at opposite ends
new nuclear envelope forms around chromosomes
chromosomes become long and thin
cytokinesis
cytoplasm divides to form 2 daughter cells
genetically identical to eachother and parent
23 pairs of chromosomes
homologous chromosomes
chromosomes with same size/appearance
same genes at same loci present
mitotic index
number of cells undergoing mitosis/total number of cells
can be used to calculated time spent in certain stage
number of cells in stage x time / total number of cells
mass/number of dna and chromosomes
number of chromosomes= count no of centromere
m-4 a- 8 cy- 4
number of dna= count no of chromatids
m- 8 a- 8 cy- 4
dna increases in s phase due to replication
dna decreases when cell divides
chromosome number changes when sister chromatids separate
mitosis- anaphase
meiosis- anaphase 2
chromatids
homologous chromosomes ( one maternal and one paternal) divide and form sister chromatids
each chromosome is a chromatid and when they join by centromere they are sister chromatids
when mitosis ends, the chromatids end up as single chromosomes
1 paternal and 1 maternal chromosome in each cell
euk vs pro dna
similar- same nucleotide structure, joined by pd bonds different- linear vs circular associated with histones vs not in nucleus vs free floating plasmids vs no plasmids introns vs no introns
accurate calculations
repeat to calculate a mean
take a large sample to ensure it is representative
repeat to ensure there are no errors
bacteria
produce dipeptidases
to digest proteins
to use amino acids for growth/ protein synthesis
or to destroy a damaging protein
cancerous cells mitosis
more cells will be in mitosis stages eg PMAT
less cells will be in interphase
cells are dividing more rapidly, more mitosis is occurring
mitosis large number of cells
ensure sample is representative
