Lecture 2: The Cell Flashcards
What is the cell theory
• All cells come from preexisting cells [currently being proven wrong in a lab, so we can say in nature]
- all organisms are composed of cells
- cells are the smallest structural and basic unit of life
therefore a mitochondria itself is not life unless within a cell
DNA in prokaryotic vs eukaryotic cells
Prokaryotic – one circular double strand DNA
Eukaryotic – many linear double stranded DNA
- one strand per chromosome
Why are eukaryotic cells larger than prokaryotic cells??
Surface to Volume Ratios its volume grows faster than its surface area, leading to a lower SA:V ratio.
This determines the efficiency of nutrient uptake, waste removal, and overall cellular function.
Eukaryotes also have membrane-bound organelles
Important components of prokaryotes
Cell wall: provides structural support especially from external environment
Made up of carbohydrate: peptidoglycan
Capsule: defence mechanism secretes slimy liquid to remove toxins and provide support
The ‘stickiness’ of the capsule promotes cell adhesion to surfaces, a survival advantage. In addition, the capsule protects the cell from phagocytosis.
No nucleus or membrane-bound organelles
• Plasma membrane for respiration and
photosynthesis because they lack other organelles
• Flagella for movement and pili that transfer DNA and are used for cell signaling
Ribosome function
Synthesize proteins, via translation
Where is most of the DNA stored in prokaryotes?
No nuclear membrane, hence no nucleus
They have a nucleoid where circular DNA is stored
Diversity of Prokaryotes how do they survive in extreme environments?
Use variety of substances as energy and carbon sources and to synthesize almost all required organic molecules
Vastly outnumber all other types of organisms
Versatile
Types of Eukaryotic cells
1) protists: like algae are similar to plants
2) fungi: like plant cells but have chitin to compose cell wall
3) animal
4) plant
The function and structure of the Nucleus
The nucleus contains most genes
• The nuclear envelope encloses the nucleus
• Nuclear pore complex
• DNA and proteins form genetic material called chromatin
• Chromatin condenses to form discrete chromosomes
• The nucleolus is located within the nucleus and is the site of ribosomal RNA synthesis
Nuclear pore complex
Pores allow certain molecules (proteins and RNAs) to come in and out
Highly regulated
Chromatin: what is it?
DNA and proteins form genetic material called chromatin
• Chromatin condenses to form discrete chromosomes
Where and what is the nucleolus
- located within the nucleus
- site of ribosomal RNA synthesis
Nuclear envelope
- double membrane: outer and inner membrane is made up of a phospholipid bilayer
Function of ribosomes
- ribosomes are used to build nuclear proteins and transport them into the nucleus
- main function: protein synthesis via translation
What are ribosomes made up
rRNA and protein
Where are free ribosomes
- in cytosol with no attachment to membrane
- bound ribosomes are on the outer surface of ER or nuclear envelope
Endomembrane system
a group of membranes and organelles in eukaryotic cells that works together to modify, package, and transport lipids and proteins.
Why can eukaryotes grow larger than prokaryotes
endomembrane system
- by allowing for compartmentalization of cellular functions it allows for biochemical
processes such as protein synthesis and transportation
what is the endomembrane system made up of
- nuclear envelope
- endoplasmic reticulum
- Golgi apparatus
- lysosomes
- vesicles
- plasma membrane
- These internal membranes is how we transport nutrients and waste in and out
- allow eukaryotes to grow larger
endoplasmic reticulum (RER vs SER)
Rough ER: ribosome-studded
- makes proteins that become part of the cell
- membranes or are secreted from the cell
Smooth ER:
- synthesize lipids and breaks down toxic substances
No ribosomes attached
Rough vs Smooth ER (based on their anatomy)
the RER is directly connected to nuclear envelope
What is the Golgi complex
- flattened membranous sacs
are indirectly connected to each other and the ER
Function of the Golgi complex
- chemically modifies proteins made in the RER
- by adding chemical groups to accessorize proteins that affect if it goes to different places
- sorts finished proteins into TRANSPORT VESICLES to be secreted from cell or embedded in plasma membrane or lysosomes
where are the four places the Golgi could send the proteins
1) membrane
2) lysosome
3) golgi
4) just leaves the cell
vesicles from the ER and their pathway
1) vesicle from the ER about to fuse with the Golgi apparatus, they are here to deposit proteins to the Golgi
2) attach and fuse with the cis face (closer to ER)
3) vesicles budded (pinched off from membrane) from Golgi containing finished product
4) trans face: vesicles leave Golgi from this side for the 4 other cell locations
what is the cisternae in the Golgi
membrane-bound sacs that stack to form the structure of the Golgi.
These sacs are where proteins and lipids are modified, sorted, and packaged for transport
lysosomes
- membranous sac of hydrolytic enzymes (digestive enzymes that break down macromolecules) that can digest macromolecules
- recycle the cells own organelles (if they’re too old/cant function) and macromolecules=autophagy
- involved in phagocytosis: eating of large macromolecules
how are ribosomes moved across from RER to GA
- ribosomes are shuttled via vesicles from RER to GA
exocytosis vs endocytosis (vesicles)
exocytosis:
- circle within moves towards plasma membrane
- membranes fuse (which replenishes the plasma membrane)
- contents of secretory vesicles are sent out
endocytosis:
- macromolecules collect on the outside
- moves down as membrane create a pocket and cirlce goes in
- endocytic vesicle: use plasma membrane
- usually go to lysosomes and get recycled
plasma membrane in endocytosis and exocytosis
endocytosis: membranes fusing replenishes the plasma membrane
exocytosis: pocket is created by membrane
- vesicles are processed and membrane components return
mitochondria
- the site for cellular respiration
- have their own DNA
- make mitochondrial proteins from FREE RIBOSOMES
- double membraned
- cristae (folds increase SA, enhancing ATP production)
- matrix (krebs takes place here)
theory of endosymbiosis
theory that mitochondria from eukaryotic cells evolved from prokaryotic cells
- since circular DNA has its own ribosomes
how does the theory of endosymbiosis explain double membranes
The inner membrane is thought to be the original membrane of the engulfed prokaryote, while the outer membrane is derived from the host cell’s membrane
the cytoskeleton
supportive structure
built from: microtubules, intermediate filaments, microfilaments
function:
- support and shape cells
- interacts with motor proteins=motility (movement)
-monorails for vesicle trafficking
- regular biochemical activities
major components of cytoskeleton
microtubules
- thickest/largest
- made up of tubuli
- circular and stacked
filaments
- made up of diff proteins, mostly keratin
microfilament
- heavily used when cell moves
- thinnest
- make up of actin
centrosomes and centrioles
- microtubules grow out from a centrosome which (in animal cells) has a pair of bundled centrioles (perp)
- the centrosome is a microtubule organizing centre
motor protein
kinesin
- connects to cell structure such as vesicle
- holds vesicle as it walks along microtubule
- allows components of cell to move
structure of a eukaryotic flagellum
(9+2 system): nine doublet microtubules surround a central pair of singlet microtubules.
microtubules: come together to form flagellum
dynein protein: motor protein
- whip-like action, same movement that a sperm cell has
what’s a prokaryote flagellum
Flagella
- propeller motion
what’s the only cell with flagellum in people
sperm cell
what is the ciliary beating pattern
-allow things to continuously move to avoid toxins from building up
- produced from dynein motor proteins
peroxisomes
- specialized metabolic compartments bounded by a single membrane
- converts H2O2 to water:
major metabolic process
toxic to cells and convert to water with catalase enzyme quickly
chloroplasts
- type of plastid
- chloroplast is the site for photosynthesis
- have own DNA
- make protein with free ribosomes
- double membrane
- grana
what is plastid
double-membrane organelles which are found in the cells of plants and algae
vacuoles
- food vacuoles formed via phagocytosis
- contractile vacuoles pump excess water out of cells
- central vacuoles hold organic compounds and water
cell wall
provides: support, protection, perforated with plasmodesmatas
- allow chemicals to move between adjacent cells to allow for cellular communication
cell adhesion molecules
- glycoproteins (on surface of animal cells) embedded in plasma
- maintain body form and function (help make tissues, etc)
- attach and detach during development (via adhesion molecules)
- cell recognition molecule
- adhesion site for pathogens (may attach on glycoproteins to enter cell)
cell junctions
TIGHT JUNCTIONS
- membranes of neighbouring cells ar expressed together to prevent leakage of extracellular fluid (skin cells)
ANCHORING JUNCTIONS
- fasten cells together into strong sheets (muscle cells)
GAP JUNCTIONS
provide cytoplasmic channels between adjacent cells (cellular communication)
extracellular matrix
- allows animal cells to attach through adhesive proteins
collagen: animal cells are the only ones that can secrete collagen (broken down into gelatin)
- important because it provides support and influence cell behaviour
network of proteins that support, regulates behavior, and communicate
Ribosomes use what to assemble amino acids into proteins
mRNA
What is the cell wall coated with in prokaryotes
- polysaccharide: glycoalyx
- loosely associated: slime layer
- gelatinous and firmer: capsule
Increased interlinked glycoproteins
Increase fluidity
Another class of glycoproteins is called the..
fibronectins
- bind to receptor proteins called integrins that span the pm
example of anchoring junction
desmosomes, maintain the integrity of tissues
- intermediate filaments help anchor them
microfilaments anchor with which junctions
adherens junctions
What are the motor proteins that walk across microfilaments
Myosins
What are the motor proteins that walk across microtubules
Dyneins and kinesins
What are intermediate filmanets responsible for
- structural support in cells/tissues
ex. they compose the network for nuclei in epithelial cells (made up of certain-filaments)
trace the organelle pathway for proteins
1) nucleus
2) rough er
3) transport vesicle
4) golgi
5) secretory vesicle
6) plasma membrane
why are cells small
- volume of a cell increases to the cube of the linear dimension
Function of pilli
Attaches the cell to other surfaces and other cells
Tonoplast
Transport proteins in and out of vacuole
