2 - Cells Flashcards
Describe the function of the nucleus
- site of DNA replication & transcription
- contains genetic code for each cell
Describe structure of mitochondrion
- double membrane: inner membrane forms cristae which is site of electron transport chain + has large surface for enzymes needed for oxidative phosphorylation.
- fluid matrix contains mitochondrial DNA, respiratory enzymes, lipids, proteins
Describe structure and function of Golgi apparatus
- modifies and processes proteins from the rER and combines them with triglycerides
- packages them into vesicles for release
- produces lysosomes
Describe structure and function of a lysosome
Bags of digestive enzymes
Contain hydrolytic enzymes (lysozymes) which:
- break down pathogens
- digest worn out organelles
Describe structure and function of a ribosome
Formed of protein & rRNA, free in cytoplasm or attached to ER
Site of protein synthesis via translation:
- large subunit: joins amino acids
- small subunit: contains mRNA binding site
Describe structure & function of endoplasmic reticulum (ER)
Cisternae: folded membranes (rough & smooth ER both have them)
- rough ER: many ribosomes attached for protein synthesis
- smooth ER: lipid synthesis
Describe structure of cell wall
- provide structural strength
Plants: made of cellulose
Bacteria: murein
Fungi: chitin
Plasmodesmata join cytoplasms of plant cells + allow molecules to pass between
Describe structure & function of cell vacuole in plants
- has a tonoplast which maintains pressure and rigidity inside the plant cell
- contains cell sap which can act as a temporary food storage for the cell
What are some common cell adaptations
- folded membrane or microvilli increase surface area eg for diffusion
- many mitochondria = large amounts of ATP for active transport
- walls 1 cell thick for short diffusion pathway
What are similarities between prokaryotic & eukaryotic cells?
both have:
- cell membrane
- cytoplasm
- ribosomes
Why are viruses “particles” & not cells?
They are A-cellular & non living:
- no cytoplasm
- cannot self reproduce
- no metabolism
Describe the structure of a viral particle?
- DNA or RNA & viral enzymes
- surrounded by capsid
-no cytoplasm
Describe the structure of an enveloped virus
- simple virus surrounded by matrix protein
- matrix protein surrounded by envelope derived from cell membrane of host cell
- attachment proteins on surface
What is the function of mitochondria ?
- site of aerobic respiration
- site of ATP production
What is structure and function of cell membrane:
- partially permeable, controls the entrance & exit of molecules
- formed from phospholipid bilayer
What are the structures that all prokaryotic cells have?
- a cytoplasm that lacks membrane bound organelles
- circular DNA
- Ribosomes
- no nucleus
- cell wall that contains murein - a glycoprotein
What are the structures that some prokaryotic cells have?
- plasmids = small loops of DNA
- slime capsule
- flagellum
What is a virus?
A cellular and non - living
What is a bacteria’s cell wall made of ?
Murein
What structures do bacteria have?
- murein cell wall
- plasmid dna
- naked circular dna
- capsule
- flagella
How many ribosomes in prokaryotic cells?
70s ribosomes
How many ribosomes in eukaryotic cells?
80s
How do prokaryotic cells divide?
By binary fission NOT mitosis
What are properties of optical/light microscopes?
- quick simple preparation
-2D image - colour image
- lower resolution
- larger field of view
What are properties of electron microscopes?
- higher resolution
- black n white images
- expensive
- magnifies objects more
- 2 types: TEM/SEM
What are properties of SEMs (scanning electrons)?
- high resolution due to short wavelength of electrons
- 3D (can see external structures)
- can’t see inside cell
- used on thick specimens
What are properties of TEMs (transmission electrons)?
- electrons have short wavelength so give high resolution
- denser parts absorb more electrons so appear darker
- can only be used on dead/thin specimens (bc have to be in vacuum sealed conditions so electrons don’t collide)
- can see INSIDE specimen
- complex/lengthy preparation
Before cell fractionation begins what are the tissue conditions?
Cold - reduced enzyme activity
Isotonic - same water potential to prevent organelles from damage from osmosis/bursting
buffered - to prevent denaturing of enzyme
What is the method of cell fractionation?
- blend cells and filter
- In cold, isotonic, pH controlled solution centrifuge and remove cell debris
- centrifuge again at higher speeds till desired organelle settles out
What are the 3 stages of interphase
- G1 - growth
- S - DNA synthesis
- G2 - growth & preparation for mitosis
What happens in gap phase 1 (G1)?
Cell is very active: 
- biggest increase in size
- transcription of genes to make RNA
- synthesis of proteins
What happens in DNA synthesis (S)?
DNA is replicated
- chromosomes duplicated & ready for divisions by mitosis
What happens in gap phase 2 (G2)?
Cell continues to grow
- mitochondria & ribosomes are made
- Proteins needed for cell division are made
What are the three stages of the cell cycle?
- Interphase (G1,S,G2)
- Mitosis
- Cytokinesis - division of cytoplasm to create the new cells
What happens during prophase in mitosis?
- chromosomes condense
- chromosomes appear as two sister chromatids joined at the centromere
What happens during metaphase in mitosis?
- chromosomes line up on the equator
- chromosomes are attached to spindle fibres by their centromere
What happens during anaphase in mitosis?
- centromere splits
-chromatids are pulled to the opposite ends of the cell
What happens during telophase in mitosis?
- chromosomes unwind
- cytokinesis (cytoplasm splits)
What is simple diffusion?
- a passive process (no ATP needed)
small lipid soluble/non polar substances going through the cell membrane
How do fatty acids effect the membrane’s fluidity?
Saturated: less fluid
Unsaturated: more fluid (can’t pack as close)
What are globular proteins ?
Proteins inserted in the phospholipid bilayer which can move through the membrane structure
What’s the function of glycolipids in the cell membrane?
cell signalling and recognition
What’s the function of cholesterol in the cell membrane?
- make the membrane less fluid
- connect phosplipids
- add strength to the membrane