Cell Structure Flashcards
Equation for magnification
M = I/A magnification = image size/actual size
Why are cells placed in a cold, isotonic, buffered solution?
cold - reduce enzyme activity
isotonic - prevent cell bursting by osmosis
buffered - maintain constant pH
Process of homogenation
Cells broken up inside solution to release organelles. Fluid then filtered to remove debris and whole cells.
List organelles in order they are separated during centrifugation
- nuclei + chloroplasts
- mitochondria + lysosomes
- RER + ribosomes
Light vs electron microscopes
- electron has high resolving power/magnification
- light has colour
- light does not require vacuum
- SEM 3D image
- specimen must be v thin for TEM
Why do electron microscopes have a better resolution?
Electrons have much shorter wavelength than light
Nucleus function
- stores DNA, produces mRNA, tRNA
- nuclear pores allow mRNA + ribosomes to pass through
Cell membrane function
- controls entry of substances into cell
- site of cell communication via receptors
Mitochondria function
- carry out aerobic respiration to produce ATP
Lysosomes function
- contains digestive enzymes to break down pathogens + cell debris
Endoplasmic reticulum function
rough -> large SA for ribosomes to carry out protein synthesis
smooth -> synthesise, store + transport lipids + carbs
Golgi apparatus function
- modifies proteins
- sorts, packages, + transports molecules around/out of cell in vesicles
Chloroplast function
Site of photosynthesis
- light absorption through thylakoid stacks
- sugar synthesis in stroma
How do cells specialise?
- no. of organelles each cell has depends on its function
- contain same genes, but only express ones they need
How are organisms organised?
Cells
Tissues
Organs
Organ systems
Structure of bacteria
- murein cell wall
- DNA circular, has smaller DNA in plasmids
- cytoplasm / enzymes + other soluble materials
- 70s ribosomes
- some have capsule of mucilaginous slime
- corkscrew flagellum
Viruses
- acellular, non living
- nucleic acids (RNA, DNA) + reverse transcriptase contained in protein capsid
- surrounded by lipid envelope w/ attachment proteins
Interphase
G1 - organelles synthesised + cell enlarges
S - DNA replicates
G2 - prep for mitosis, organelles grow + divide, energy stores increase
Prophase
- spindle apparatus forms from centrioles
- chromosomes visible, nuclear envelope disintegrates
Metaphase
- chromosomes line up at cell equator by spindle attaching to centromere of chromatids
Anaphase
- spindle contracts, separating individual chromatids by splitting centromere
- chromatids pulled towards poles
Telophase
- chromosomes become indistinct at poles
- spindle disintegrates, nuclear envelope reforms
- cytokinesis as cytoplasm splits
Product and uses of mitosis
Two daughter nuclei that have same no. of chromosomes as parent
Used for growth/repair of tissue, and asexual reproduction
Calculating mitotic index
no. of cells with condensed chromosomes/ total no. of cells * 100
Ho do drugs used in cancer treatment work?
Disrupt cell cycle
- prevent DNA replication
- inhibit metaphase by interfering w/ spindle formation
How do bacteria divide?
Binary fission, circular DNA divide, cytoplasm divides to produce two genetically identical daughter cells
Viral replication (summary)
- a. proteins on virus attach to host cell
- virus injects DNA/RNA into host cell
- host cell makes new copies of virus
- host cell bursts, releasing viruses
