Cell Structure and Cell Cycle Flashcards
Eukaryotic vs Prokaryotic
- Eukaryotic = animal/plant cell, has membrane bound organelles
- prokaryotic = bacteria, has no membrane bound organelles
Tissue definition
A group of specialised cells
Organ definition
Made of different tissues
Organ System definition
Different organs working together
What is an animal cell made of?
- Organelles - all have membrane except the ribosomes
- Cytoplasm - site of chemical reaction
- cell membrane (holds cell contents together, controls what enters/leaves cell, cell signalling)
Structure of nucleus
- contains DNA
- DNA wrapped around histones to form chromatin
- nucleus has a double membrane, called nuclear envelope, which contains pores
- at centre of nucleus in nucleolus - produces mRNA
- rest of nucleus made of nucleoplasm (contains the DNA)
Endoplasmic Reticulum
- 2 types = rough and smooth
- Rough ER has ribosomes on it, makes proteins
- Smooth ER has no ribosomes on it, makes lipids/carbohydrates
Golgi body/apparatus
- modifies and packages proteins
- packages them into vesicles for transport
- digestive enzymes are placed into lysosomes
Mitochondria
- site of respiration, releases energy, produces ATP (energy carrier molecule)
- has a double membrane, inner membrane folded into Cristae (increases SA for enzymes of respiration)
- middle portion called matrix
Ribosomes
- attached to RER
- site of protein synthesis
What is a plant cell made of?
- organelles - all have membrane except the ribosomes
- cytoplasm
- 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 is called geranium
- 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 plasmid
- No membrane bound organelles: smaller ribosomes, mesosomes 0 unfolding 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 an enzyme called reverse transcriptase to turn RNA into DNA)
- Protein coat called capsid and lipid coat
- Attachment proteins on outside
- (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, hence, producing copies of the virus and destroying the host cell)
What is cell division?
- formation of new cells in multicellular organisms (animals & plants)
- 2 methods = mitosis and 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 produce?
2 genetically identical cells, diploid (have full set of chromosomes?DNA)
Benefit of mitosis
Growth and repair of tissues
Stages of mitosis
interphase
Mitosis
Cytokinesis
Interphase
G1: protein synthesis
S: DNA replication
G2: organelle synthesis
Mitosis
Prophase: DNA coils to form chromosomes, nucleus breakdown, spindle fibres form
Metaphase: chromosomes line up in the middle of the 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
Cytokinesis
Separating cell into 2
What is cancer?
formation of a tumour due to uncontrolled cell division
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, they spend less time in interphase and more Tim din the other stages
Treatment for cancer
Surgery
Chemotherapy
Radiotherapy
How do bacteria do cell division?
- Binary fission
- copy their DNA and then separate into 2 new genetically identical bacteria
2 types of microscopes
Light and Electron (transmission and scanning)
How to judge a microscope
Magnification and Resolution
Magnification
how much larger the image size is compared to the actual size
Which has higher magnification?
SEM, LM or TEM
TEM > SEM > LM
Formula for magnification
magnification = image size/actual size
conversions
1mm = 1000 micrometre, 1 mm = 1,000,000 nanometre
Why can organelles appear different in images?
viewed from different angles and at different levels/depths
Resolution
Minimum distance at which 2 very close object can be distinguished
Which type of microscope has the higher resolution?
TEM > SEM > LM
Why does electron microscope have higher resolution?
Electron microscope uses electrons which have a shorter 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, black and white images, artefacts
Advantage and Disadvantage of SEM
- advantage = produces 3D image
- disadvantage = works in a vacuum so can only observe dead specimens, black and white images, 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 a t low speed, largest organelle builds at bottom (nucleus), leaves supernatant, spin at higher speed, next heaviest organelle forms at bottom (chloroplast or mitochondria)
