Cells Flashcards
Eukaryotic vs Prokaryotic Cells?
Eukaryotic = animal/plant cell, has membrane bound organelles (nucleus, endoplasmic reticulum, golgi body, lysosome, mitochondra)
Prokaryotic = bacteria, has no membrane bound organelles
Structure of Nucleus?
contains DNA (made of genes, genes code for making proteins)
DNA wrapped around histones to form Chromatin
nucleus has a double membrane, called Nuclear Envelope, which contains pores
at centre of nucleus is Nucleolus – produces mRNA (copy of a gene)
rest of nucleus made of Nucleoplasm (contains the DNA/chromatin)
Endoplasmic Reticulum?
2 types = Rough and Smooth
Rough Endoplasmic Reticulum has ribosomes on it, makes proteins
Smooth Endoplasmic Reticulum has no ribosomes on it, makes lipids/carbohydrates
Golgi body?
modifies and packages proteins and lipids
packages them into vesicles for transport
digestive enzymes are placed into lysosomes (vesicles with membranes around them)
Mitochondria?
- site of aerobic respiration where ATP is produced
- They have a double membrane
- their inner membrane is folded to form cristae
- inside is the matrix- contains enzymes involved in respiration
Ribosomes?
attached to RER
site of protein synthesis
What is a Plant Cell made of?
Organelles (nucleus, endoplasmic reticulum, golgi body, lysosomes, mitochondria, chloroplast, vacuole, ribosomes) – all have membrane except the ribosomes
Cytoplasm (site of chemical reaction)
Cell Membrane (holds cell contents together, controls what enters/leaves cell, cell signalling)
Cell Wall (made of cellulose, prevents cell from bursting or shrinking)
Structure of chloroplast?
organelle for photosynthesis
has double membrane
contains discs called thylakoids
thylakoids contain chlorophyll
stack of thylakoids called granum
thylakoids surrounded by a fluid called stroma
Vacuole?
- Surrounded by a membrane called a tonoplast
- contains Cell Sap (water, sugar, minerals)
What is Bacteria made of?
No nucleus – loose DNA in the form of a single loop and plasmid
No membrane bound organelles: smaller ribosomes, mesosomes – infolding of cell membrane for respiration
Cytoplasm
Cell Membrane & Cell Wall (made of peptidoglycan/murein)
some have a Capsule (reduce water loss, protect from phagocytosis) and Flagella (movement)
What is Virus made of?
DNA or RNA (if RNA, also has a enzyme called reverse transcriptase to turn RNA into DNA)
Protein Coat called Capsid and Lipid Coat
Attachment proteins on outside
What is a Chromosome?
DNA in coiled form
formed during interphase of cell division (mitosis/meiosis) in Animals/Plants
made of 2 identical/sister chromatids joined by a centromere
carries 2 copies of the same DNA molecule
What is a homologous pair of chromosomes?
a pair of chromosomes: 1 maternal (from mother)/1 paternal (from father)
carries same genes but different alleles – there are 23 pairs in humans
What is Cell Division?
formation of new cells in multicellular organisms (animals & plants)
2 methods = mitosis & meiosis
mitosis = produces genetically identical cells for growth & repair of tissues
meiosis = produces genetically different haploid cells as gametes for sexual reproduction
What does Mitosis (cell cycle) produce?
2 genetically identical cells, diploid (have full set of chromosomes/DNA)
Interphase?
G1: protein synthesis
S: DNA replication (doubles set of DNA)
G2: organelle synthesis
Mitosis?
- Prophase: DNA coils to form chromosomes, nucleus breaks down, spindle fibres form
- Metaphase: chromosomes line up in middle of cell and attach to spindle fibre via centromere
- Anaphase: spindle fibres pull, centromere splits, sister chromatids move to opposite sides
- Telophase: chromatids uncoil, nucleus reforms (left with 2 genetically identical nuclei)
Cytokinesis?
separating cell into 2 (each receives a nucleus and organelles/cytoplasm)
What happens to DNA mass in mitosis?
halves
What happens to Chromosome number in mitosis?
stays the same (diploid)
What is Cancer?
formation of a tumour due to uncontrolled cell division (uncontrolled mitosis)
How does uncontrolled cell division occur?
due to mutation of DNA/cells forming cancer cells
mutation can occur randomly or due to mutagens (chemicals/radiation)
cancer cells are rapidly dividing cells (like hair cells, skin cells, red blood cells), they spend less time in interphase and more time in the other stages (mitosis)
Treatment for Cancer?
Surgery = aim is to remove tumour
Chemotherapy = - using drugs that inhibit mitosis in rapidly dividing cancer cells
- problem, also affect normal healthy cells (hair cell, skin cells, rbcs) causing side effects (hair loss, dry skin, tiredness)
- treatment given as regular doses to allow time for normal healthy cells to recover in number
Radiotherapy = radiation used to destroy cancer cells
How do Bacteria do Cell Division?
Binary Fission
Copy their DNA (Single Loop and Plasmids) and then separate into 2 new genetically identical bacteria [Asexual Reproduction]
Magnification?
how much larger the image size is compared to the actual size
Conversion for magnification?
1 mm = 1000 micrometre.
1 mm = 1,000,000 nanometre
Resolution?
minimum distance at which 2 very close objects can be distinguished
Why does electron microscopes have a higher resolution?
Electron microscope uses electrons which have a shorter wavelength (light microscope uses light which has a large wavelength)
Difference between TEM and SEM?
in Transmission the electrons pass through the specimen
in Scanning the electrons bounce off the specimen’s surface
Advantage and Disadvantage of TEM?
Advantage = highest magnification and highest resolution
Disadvantage = works in a vacuum so can only observe dead specimens, specimen needs to be thin, black and white image, 2D image, artefacts
Advantage and Disadvantage of SEM?
Advantage = produces 3D image
Disadvantage = works in a vacuum so can only observe dead specimens, black and white image, artefacts
Cell Fractionation?
Breakdown tissue into cells (cut, pestle & mortar)
add cold/isotonic/buffer solution (cold = reduce enzyme activity, isotonic = same water potential so organelle does not shrink or burst, buffer = maintains constant pH)
homogenate – breaks open cells releasing organelles
filter = removes large debris and intact cells
centrifuge – spin at low speed, largest organelle builds at bottom (nucleus), leaves supernatant, spin at higher speed, next heaviest organelle forms at bottom (chloroplast or mitochondria)
(organelle by size: nucleus, chloroplast, mitochondria, endoplasmic reticulum/golgi body/lysosomes, ribosomes)
How does a virus infect cells?
- infects host cells by attaching using their attachment protein
- send in their DNA which uses the cell to make the viruses components and uses the cell membrane to make the viruses lipid coat
- producing copies of the virus and destroying the host cell
how to calculate the mitotic index?
number of cells with visible chromosomes/ total number of cells observed
