Cells Flashcards
(111 cards)
1
Q
Fluid Mosaic Model
A
This model suggests biological membranes are a two- dimensional liquid where all lipid and protein molecules diffuse more or less freely
2
Q
Plasma Membrane Surface Components
A
Phospholipids (75%) Cholesterol (20%) Glycolipids (5%) Flippases Scamblases
3
Q
What Phospholipid is on the inner plasma membrane?
What ones have a negative charge?
Which Enzyme is associated?
A
PI (negative)
PE
PS (negative)
Enzyme: Flippase
4
Q
What Phospholipid is on the outer membrane?
Which enzyme is associated?
A
PC
Sphingomyelin
Enzyme: Scramblase
5
Q
What are the roles of Glycolipids in the Plasma membrane and where are they concentrated?
A
ONLY found on the outer membrane
Role is to provide energy and also serve as markers for cellular recognition
6
Q
What role does Cholesterol play on the plasma membrane?
A
increases membrane stability and maintains fluidity
(structural stability)
permeable to sodium and potassium
7
Q
Functions of Membrane Proteins
A
transport Enzymatic activity receptors for signal transduction intercellular adhesion cell-cell recognition attachment to cytoskeleton and extracellular matrix
8
Q
Anchoring Membrane Junctions (desmosomes)
A
Mediate cell-cell and cell-matrix adhesions; linked to cytoskeleton to transmit and distribute stress (e.g. skin and heart muscle)
9
Q
Occluding Membrane Junctions: tight junctions and the proteins that form them
A
Impermeable junction that encircles the cell to form seals between epithelial cells (e.g. intestinal wall)
Each cell has a set of proteins that form the tight junction – the proteins interact or make the membrane impermeable
- Zipper-like interactions
- Localize to one part of the cell (to the top of the cell)
- Interacts with actin filaments to maintain the orientation and position of the tight junction
Transmembrane proteins to form tight junctions:
occludin
Claudins
10
Q
Channel-forming Membrane Junctions (gap junctions)
A
allow diffusion of small molecules
Cell to cell communication
- Free movement of small molecules (very small proteins, ATP, GTP, or other small molecules)
- To interact with components on the other side of the cell
- Cells can exchange nutrients through gap junctions
- Connexon: Channel between cells
11
Q
Signal relaying membrane junctions
A
ligands on or released from cell transmit signals to
receptors on adjacent cell (e.g. synapses)
12
Q
Desmosomes
A
2 cells interact with each other
Each cell has a set of desmosomes that interact with each other
- Plaque is what holds them together
- Linker proteins interact with the 2 desmosomes to provide strength
13
Q
Intermediate filaments (keratin)
A
Skin cells have a lot of keratin
Skin cells are very strong as the linker proteins have a lot of keratin
14
Q
Connexon: gap junction
A
made up of connexin
the channel remains closed until another cell comes and then it opens to interact
6 connexin interact from each cell to form a channel
- 12 connexins interacting
- only open when interacting with different cell
15
Q
Passive Membrane Transport: Diffusion
A
- Move components across the membrane without energy
- Down the concentration gradient
16
Q
Simple Diffusion
A
lipid soluble molecules can freely move across the plasma membrane
- They are hydrophobic
- Nonpolar and lipid soluble substances
- Oxygen, carbon dioxide, fat soluble vitamins
17
Q
Facilitated diffusion
A
Transport of glucose, amino acids, and ions
Transported substances bind carrier proteins or pass through protein channels
Transport of ions via a
protein channel
-Carrier proteins must bind to the molecule and then conformational change allows the molecule to be released and go to the interior of the cell
18
Q
Osmosis
A
- Movement of water (main solvent)
- Aquaporin – allows for free movement of water down the concentration gradient
- High to low concentration
- Water can move across the plasma membrane without any help but not all the time
19
Q
Osmolarity definition
A
total concentration of ALL solute particles in a solution
20
Q
Isotonic
A
cell and cytosol have same concentration
- No effect on cell size
- Water is flowing in and out nicely
21
Q
Hypertonic and what happens to the cell
A
the cell has a lower concentration than the solution, so water will move out of the cell
(cell loses water) **SHRINKS
-Water wants to even the concentration between the cell and solution, so since the cell has a high concentration, it will lose water to the solution, therefore shrinking
-Pulls water out of the cell to go into different compartments
22
Q
Hypotonic and what happens to the cell
A
the cell has a higher concentration than the solution, so water will move into the cell, making the cell get larger ***CELL SWELLS
- Giving a hypotonic solution can cause the cells to swell as extra water is entering
- Cause damage to cells
23
Q
Active Transport
A
Uses ATP to move solutes across a membrane (direct and indirect)
Requires carrier proteins
24
Q
Symport vs Antiport
A
Symport: moving in the same direction
- Antiport: moving substances in the opposite direction
25
Primary Active Transport and an example
hydrolysis of ATP phosphorylates the transport protein causing conformational change
Example: sodium potassium pump
Sodium out, potassium in
Sodium is high in extracellular fluid (3 sodium)
Potassium is low in the extracellular compartment but HIGH in the intracellular compartments
26
Secondary Active Transport
uses an exchange pump (such as the primary active transport protein Na+-K+ pump) to indirectly to drive the transport of other solutes
- Indirect system that does not directly use ATP
- moving down the concentration gradient (carrier protein to bind to protein)
27
Primary Active Transport Process
Cytoplasmic side – picks up 3 sodium molecules
- ATP then donates a phosphate so it becomes ADP
- Provides the energy for the conformational change
- Then the conformational change happens, and releases sodium into the outside
- The channel is now facing the extracellular fluid
- Binds potassium to the inside
- Conformational change happens and releases the potassium into the inside of the cell
- Phosphate (from ATP) gets released
- Unequal distribution of charge (3 positive charged sodium out, for 2 positive charged potassium)
28
Vesicular Transport: Exocytosis
moves substance from the cell interior to the extracellular space
EXocytosis (exit)
29
Exocytosis: t-SNARE and v-SNARE
- t-SNARE – target-SNARE (where the vesicle needs to go)
-Identifies plasma membrane as the plasma membrane
-EX:Syntaxin/ SNAP-25
Provide identification of the target sites (plasma membrane)
v-SNARE – vesicle-SNARE (found only on vesicles)
-Help provide identification markers
-Only provide t-SNARE on the plasma membrane
-EX: Synaptobrevin and Synaptotagmin
These work together to make a v-SNARE
30
SNARE steps
- The vesicle (has v-SNARE on it)
- Needs to be targeted to show where to go
- The t-SNARE targets it so it can be docked
- The t-SNARE and v-SNARE interact together
- The prime step requires ATP
- Then there is the fusion of the vesicle into the extracellular compartments
31
Endocytosis and examples
from plasma membrane to the inside of the cell
ex. phagocytosis, macropinocytosis, clarthrin-dependent endocytosis, caveolin-dependent endocytosis
32
Phagocytosis: Bacteria
Uptake of larger particles
- Bacteria taken up by immune cells to be destroyed
- Actin pushes the cell membrane around the bacteria to engulf it
- Microtubule depolymerization – help remodel the membrane
33
Phagocytosis: Viruses
Macropinocytosis – takes the virus in
- Cell drinking or gulping
- Non-specific what it takes in
- Takes some of the extracellular environment into a vesicle to see what is surrounding
- Phagocytosis – engulf the virus in
- Includes Clathrin, Dynamin, Caveolin, Flotillin
34
Clathrin-mediated endocytosis steps
AP2 is the adaptor protein come along the membrane
- Clathrin will interact with the AP2 and causes the membrane to bend
- Dynamin is a motor protein that interacts with the membrane bending to separate it from the cell
- Squeezes/pinches it off
- AP2 and Clathrin then fall off
35
Receptor-mediated endocytosis
Still involves Clathrin
- Clathrin interacts with the receptor
- Bends the cell membrane again to form a vesicle again
36
Non-clathrin-coated vesicles
Caveolae – caveolin vesicles are smaller than Clathrin
- High in lipids (sphingolipid and cholesterol)
- Lipid rafts are high in the same lipids
- Coatomer (COP1 and COP2) – intracellular trafficking
- COP1 goes back to the ER
- COP2 from the ER to the Golgi apparatus
37
Lipid Rafts
- Lipid rafts are microdomains
- Involve modification of the lipid
- Stabilized structure that is much less moveable than other structures
- Planar lipid raft – high in sphingolipid and cholesterol (reduces membrane fluidity)
- Caveola – modification of planar lipid rafts
- These act as signaling platforms for receptors
- Concentrate the receptors in these areas to cause the microdomain
- Too much signaling cause membrane pinching with dynamin
- Saves the receptor from degradation
38
Electrochemical Gradient
- Ions move down the concentration gradient: potential
- If the inside of the cell has a negative charge, and outside has a positive charge, a flow of positive ions (chemical gradient) goes into the cell (opposites attract)
- If the outside of the cell is negative, and the inside is positive, there will be a flow of positive ions but not nearly as much
- The charges inside and outside the cell cause the electro-gradient
39
Potassium and Chloride and the Electrochemical gradient
Channels in the membrane cause potassium-leak channels
- Let’s potassium in and out whenever
- Potassium is positive
- High concentration of potassium inside the cell, and high concentration of sodium outside the cell
- Permeability for sodium through the plasma membrane is very low (and calcium)
- Chloride is high outside the cell, because it is being repelled out of the cell due to the inside being negative and chloride is also negative
- Chloride is highly permeable, but the negative charge repels it out
40
Anionic
negative charged proteins (inside of the cell)
41
Cationic
positive charged proteins
42
Roles of Membrane Receptors: Contact
2 proteins interact with each other (1 protein from the membrane of one cell, and another from the membrane of the other cell)
43
Roles of Membrane Receptors: Electrical
popular in nerve and muscle cells (action potentials)
| -Regulated by VOLTAGE
44
Membrane Receptors: Chemical
ligands in the extracellular matrix that bind to the receptors
- Acetylcholine binds to ligand gated ion channel receptors called nAChR
- Nicotinic-Acetylcholine-Receptor
- Regulated by IONS
45
GPCR (G-Protein-Coupled-Receptor)
20-30% of all drugs are used against this system
- Membrane protein: receptor protein (GPCR)
- Inactive G protein: GDP bound to the receptor causes an inactive protein
- GDP binds to alpha-subunit
- This then causes the alpha-subunit to interact with beta and gamma
- Beta and gamma are attached to the plasma membrane, but alpha is NOT
- When a ligand binds to the receptor and activates the receptor to signal to the G protein that there is an activation of the GPCR
- The receptor binds to the alpha subunit of G-protein to promote the exchange of GDP to GTP
- Dissociation of the alpha-subunit from the beta and gamma
- This is now an active G-protein
- The active GTP-alpha-subunit then can go on to activate other proteins
- Interact with target protein to cause signaling in the cell
- The only way to stop the signaling is GTP to be deactivated
- This would cause hydrolysis of a phosphate from the GTP to cause it to be GDP
46
PKA Pathway
When the GTP becomes activated, it can go on to activate adenylyl cyclase
- This causes the adenylyl cyclase to utilize ATP to form cyclic AMP
- Interacts with inactive-PKA (4 subunits – blue and grey)
- Grey parts are the regulatory subunits
- Blue is the active enzyme parts of the enzyme
- PKA: protein-kinase-a
- AMP binds to the PKA then releases the active enzyme components of PKA
47
PLC Pathway
PLC: phospholipase-C pathway (beta)
- Gq – type of alpha subunit of the G-protein that becomes active and activates the PLC
- Takes a lipid from the membrane and grabs the phosphate (PI) groups attached
- Phosphatidylinositol-4,5-bisphosphate (PI(4,5)P2) gets cleaved
- One products gets converted to inositol-1,4,5-trisphosphate (IP3) which then binds to the lumen of the endoplasmic reticulum
- Opens a channel, and releases the calcium from the ER
- The other product is diacylglycerol – leads to activation of protein-kinase-C
48
Cytoplasm
- Liquid component of the cells (not a lot of it)
- Consists of cytosol, inclusions, and cytoplasmic organelles
- Membranous: mitochondria, peroxisomes, lysosomes, ER, Golgi apparatus
- Nonmembraneous: cytoskeleton, centrioles, ribosomes
49
Mitrochondria
- Key players of all the energy of the cell
- Generates ATP
- Double membrane structure
-Outer-mitochondrial membrane
-Inner-mitochondrial membrane (a lot of invaginations)
-The curved parts are the cristae (increase surface area)
-Contain their own mitochondrial DNA
- Circular in shape
- Ability to generate RNA
mDNA
50
Ribosomes
- Protein synthesis
- Ribosomes are made of protein and RNA itself (rRNA)
- Free ribosomes: form cytoplasmic proteins
- Membrane-bound ribosomes: form the proteins that are for membranes
- Insulin is made of membrane-bound ribosomes
51
Rough Endoplasmic Reticulum
Lots of ribosomes
Makes phospholipids and integral membrane proteins
Continuous with the nuclear envelope
52
Smooth ER
- Tubular in structure
- No ribosomes associated with it
Liver: lipid and cholesterol metabolism, breakdown glycogen, detoxification of drugs
- Testes: synthesis of steroid-based hormones
- Intestinal cells: absorption, synthesis, and transport of fat
- Skeletal/cardiac: storage and release of calcium
53
Lysosomes
- Large vesicles that can be abundant in all cell types
- Phagocytes – large number of lysosomes
- Phagocytes – take up foreign bacteria and destroy them (immune)
- Degrading non-functional organelles is critical for all cells
54
Golgi Apparatus
- Downstream of the ER
- Stack of membrane sacs
1. Transport of vessels from the ER, to fuse with the cis face of the Golgi apparatus
2. Proteins pass through the stack of the GA to the trans face
3. Leave the trans face and move to designated parts of the cells
- Cis face – receives non-modified vesicles from the ER
- As it moves through the smooth ER, it gets shipped out by the trans-face
- THINK: trans-face – transport
55
Pathways of the Golgi Apparatus
1: Secreted vesicles to release the products by exocytosis to the extracellular membrane
2: Renewal of a new protein
3: Involves vesicles to be delivered to other organelles like the lysosome and the phagosome
56
Peroxisomes
Catalases remove free radicals – which are highly reactive chemicals
- O2- can be very damaging to DNA
57
Cytoskeleton
- Rods running through the cell
- Regulating overall cellular function
- Found within the cell to operate as a highway system
- Gives shape to plasma membrane
- Consists of microfilaments, intermediate filaments, microtubule
- Membrane structural stability and strength
58
Microfilaments
- Made of actin subunits
- Constantly following apart and being put back together again
- Found associated with plasma membrane to provide shape and strength
- CAM: Cell Adhesion Molecules
- Dynamic: always falling apart but then building back together (remodelled)
- Form cellular extensions (microvilli)
59
Intermediate filaments
- Not dynamic – once they are formed, they stay formed
- Associated with desmosomes or plaques
- Strength for cell (rigid structure)
- Interact with plasma membrane
- Come off the desmosomes
- 6 or 8 intertwined fibrous subunits
60
Microtubules
- Dynamic – constantly remodelled depending on cell needs
- Made of tubulin subunits (tube structure with nothing in middle)
- Organization for the highway system of the cell
61
Motor molecules
Myosin molecules play a role in muscle contraction, also interacts with actin
- Kinesin
- Powered by ATP
- Protein structure allows them to look like they are walking on the muscle cell
- Organelles interact with a receptor and use ATP to walk along the microtubule
- Organelles it can interact with:
- Mitochondria
- Secretory vesicles
- Lysosomes
- Motor proteins interact with a target vesicle and cause movement
- Plasma membrane to the interior – Dynein (positive pole of microtubule to the negative side)
- Interior to the plasma membrane – Kinesin (negative side to positive end of microtubule)
62
Centrioles
- Usually 2 centrioles together, with 3 rods that are duplicated 9 times to form the barrel shape
- Centrosome matrix - Monomer proteins of tubulin surrounding it
- Tubulin is made and produced in the areas around the centrioles
63
Cilia and Flagella Functions
- Movement of fluids around the cell
- Ex. Move fluid from the interior part of lungs to the exterior
- Flagella are larger and move whole cells
- Basal body is made of centriole (9 triplets)
- Forms the basis of the cilia and flagella
Exterior: made up of centrioles with motor proteins
Interior: made of 2 microtubules without motor proteins
- Each motor protein interacts with the microtubules that are next to it
- Radial spokes: other proteins that create structure of the cellular tubes
64
Cilia
- Move fluid in one direction with coordinated activity
| - Power stroke and Recovery stroke
65
Flagella
- Create a circular propelling motion
| - Allows cells to move through being propelled
66
Microvilli
- Have no tubulin in it
- Microfilaments in cellular extensions
- Made of actin (no contraction or movements of fluid)
- Increase surface area of PM of the intestinal cell to increase nutrient absorption
- No power strokes and unable to move things in the body
67
Nucleus
- Each cell has its own copy of the genetic library (in the nucleus)
- Nucleus is filled with sticky fluid: the DNA
- Darker part: Nucleolus – smaller structure found in the nucleus, associated with high volume of cellular transcription
- Generation of rRNA
68
Nuclear Envelope
– double membrane structure
- Holds everything together
- Perinuclear space: - the space in between the 2 walls of the nuclear envelope
- There are some breaks in the membrane that are called pores
69
Nuclear pore complex
Specialized structure to allow for communication of mRNA molecules or new protein that are forming
70
Nuclear Lamina
provide structure to the nucleus and regulates cell division and replication
71
Chromatin
- Found in the nucleus
- 30% DNA, 60% histones, 10% RNA
- Histones interact with DNA to stabilize it and organize the DNA
- Nucleosomes – condense the DNA and only become visible during cell division
- DNA is the fundamental component of chromosomes
- DNA winds around the histone molecules to form the functional unit of the nucleosome
- Nucleosomes interact with each other and become more tightly bound
- Chromatin is protein and DNA
72
Metaphase Chromosome
highly condensed DNA molecule, that cannot participate in transcription because it is too tightly wound on itself
73
Chromosomes
- We each have 23 pairs of chromosomes, so 46 individual ones
- Specifically, 22 pairs of chromosomes and then the sex chromosomes
- Chromosome 1 has the most genes associated with it
- We can encode up to 32,000 different proteins (genetic diversity)
74
Interphase
- No real cell division, but a lot of activities associated with growth
- The longest phase
75
Growth Phase
o Gap 1
| o Metabolic activity
76
Synthetic Phase
DNA replication
| Need to unwind the DNA to release the histones to create the exact copy
77
Helicase
untwists the helix to allow for access of the enzymes required for replication
78
Replication bubble and fork
bubble: separation of the strands
fork: the fork in the road of the DNA
79
Topoisomerase
interacts on the other side of the helix, to relieve stress and allow for easier unwinding
80
DNA polymerase 3
– creates the exact copy of the DNA by going along the leading and lagging strand
Works in 5’ to 3’ direction ONLY
81
RNA primase
primes the DNA to allow for the DNA polymerase to interact
| - 5’ to 3’ of a few nucleotides to help start polymerase off
82
DNA polymerase 1
remove the primer and go along to duplicate
83
DNA ligase
connects the broken pieces
84
leading strand
replicated continuously in the 5’ to 3’ direction
85
lagging strand
replicated in the opposite direction so okazaki fragments form (discontinuous strands)
86
Growth Phase 2
Gap 2
Final preparation
Production of proteins associated with mitosis
87
G0
cells that have permanently stopped dividing and going into a quiet phase
Neurons
Not dividing
88
Prophase
EARLY PROPHASE
Condensation of the chromatin to form chromosomes
Get 2 sister chromatids that are connected at the centromere
Centrosomes go to opposite poles of the cell (Separate)
Mitotic spindles are microtubules that push the 2 centrosomes away from each other
89
Kinetochore microtubules
Bind to centromere molecules and draw them and bring them into the middle of the cell
Interact with the chromosomes
90
polar microtubules
Push the 2 poles apart from each other
Spread and separate the poles as well
Do not interact with the chromosomes
91
Late prophase
Disappearance of nuclear envelope
Fragments and separates and goes into the ER
Centrosomes (asters) go to the opposite poles
92
Metaphase
Alignment of the chromosomes at the centre plate
Metaphase plate – in the middle
On either pole, there are the asters and microtubules
Separase – enzyme that cleaves the sister chromatids at the centromere
93
Anaphase
Separation of the sister chromatids to become daughter chromosomes
94
Telophase
Nuclear envelope starts to reform
Nucleolus forms – generation of the rRNA
Cleavage furrow – contraction starts to form to pull the membrane in
95
Cytokinesis
Actual separation of the sister cells
96
Cell Division Control: Internal
As the cells get bigger, the cell division gets activated
Cyclins and cyclin-dependent kinases: regulate cell division
Checkpoint 1 – if the cell is ready or not go to the S phase (enough components)
Checkpoint 2 – have M-phase promoting factor to be present
97
Cell division control: External
-Growth hormones (we need more hormones)
-Contact inhibition
Cell contact can prevent the division
Increased cell division causes cancer
98
mRNA
-Carries genetic information
-Coding region is the part that encodes the new protein
-UTR – untranslated region
5’ UTR – untranslated region that also consists of the cap
3’ UTR – poly(A)tail
A long stretch of A nucleotides
99
tRNA
-Allows the amino acid to bind and interacts with mRNA
-Amino acid at the top of it through an ester bond
-Anticodon – specific sequence that recognizes the specific sequence on the mRNA
oThe mRNA has a codon (interacts with the anticodon)
100
rRNA
-Forms the basis for ribosomes
-Ribosomes are both protein and RNA
-Large subunit
-Small subunit
Both subunits come together to form protein translation
101
Transcription
A lot of regulators associated with it
- Uses RNA polymerase 2
- Uses RNA triphosphates to form a complementary DNA
- Binding to the template strand to make an exact copy
- Coding strand – the strand being formed
- Template strand – being used as the basis of the transcription
- TATA box – part of initiation of the transcription
102
Initiation of Transcription
- Histones interact with the molecule
| - 60% of the DNA structure is associated with the proteins
103
HAT (histone acetylase)
Acetylates molecules to the histones
Loosen the binding of the histones to the DNA
Gene repression
- DNA is tightly wound and has no easy access to any genes
- Activate the genes using HAT
- CBP, p300, PCAF
- Once the DNA get loosened up, RNA polymerase 2 can come in
Gene deacetylation
- DNA compaction with its nucleosomes and histones
- Turning it off
104
Chromatin remodeling complex
Helps loosen up the DNA as well
105
Promotor/Enhancer Region
The promotor is found close to the TATA box
- Proximal to the TATA
- Regulates gene expression
Enhancers are found upstream or downstream
- DNA can bend and twist so that the enhancer region is closer to the promotor
- Enhancer is further away
106
Sigma factor/RNA polymerase
RNA polymerase separates the 2 molecules and copies the template strand
Sigma factor – improves the function of the RNA polymerase
107
Elongation of transcription
- Multiple RNA polymerases can work on the template
- Goes along and replicates and unwinds the DNA strand
- Forms a pre-mRNA molecule
- Needs to add 5’ cap
- Polyadenylation – adding the poly A tail
108
Splicing: Exons and Introns
Exons
- Parts of the mRNA that codes for protein
Introns
- Do not code for proteins
- Splicing takes the introns out so that the molecule only consists of exons
109
Starting codon
AUG is the starting codon
Small ribosomal subunit interacts with it at the P-site
Brings a fMET (amino acid)
110
Elongation of transcription: further along
Uses GTP as energy source
- GTP to GDP + P
Large subunit then comes onto the molecule to form the large and small subunit together
The large subunit has a E, P, A section
A section – accepts a new tRNA
P section – allows the bonding of the amino acids that the RNA molecule brings (codon and anticodon)
E section – exit – the tRNA goes away
The ribosome moves along the codons of the template strand and continuously pairs the codons and anticodons with the subsequent amino acid
- Peptide bond forms
- tRNA come in at the A site
111
Membrane bound proteins
-ER signal sequences found within the growing polypeptide
-Signal recognition particle (SRP)
- Slow down or almost stop protein translation
- Won’t begin again until a receptor is found
SRP receptor
The receptor is on the ER, so the SRP has to find the receptor on the ER
The peptide grows and pinches off the ER
