Theme 1- Module 1 Flashcards
What’s so special about prokaryotic cells?
They do not contain a true nucleus
Do we have more eukaryotic cells or prokaryotic cells in our bodies?
Prokaryotic
What is the microbiome?
Population of microbes in our body
Do microbiomes contain only prok cells?
No also small eukaryotic cells
What does Strep. Salivarius do and where is it found?
Upper respiratory tract + oral cavity
Forms dental plaque
Colonize newborns germfree oral cavity and GI tract
What does Staph. Haemo do and where is it found?
When it’s on the skin it’s harmless
When it’s in the body it’s pathogenic
What does Bacteroides thetaiot. do and where is it found?
Intestines
Forms enzymes that breakdown ingested plant material
Define a cell
Membrane bound structure with macromolecules
What are the macromolecules?
Nucleic acids
Proteins
Polysaccharides
Phospholipids
What is the function of proteins?
Structure
Metabolic activities (enzymes, ribosome)
Do polysaccharides contribute to structural functions?
Yes
Are the tails of a lipid hydrophilic or hydrophobic? Polar or non polar?
Hydrophobic
Non polar
Phospholipids are amphipathic. What does that mean?
Have both hydrophobic and philic parts
Describe the structure of the fatty acid chains at the end of a phospholipid molecule.
16 or 18 carbons in a chain
Single or double bonds
Are single bonds saturated or unsaturated? Why is this important?
Saturated
The bond types change the shape and behaviours of the phospholipid and thus the membrane
True or false: Phospholipids are the only types of lipids found in cell membranes. If false, state the other lipids
False
Steroids
Describe the structure of steroids and give an example
4 hydrocarbon ring
Hydrophilic head
Phobic tails
Cholesterol
True or false: phospholipids only form lipid bilayers. If false, state what other structures they form
False
Can aggregate and form micelles
Do micelles need energy to form?
No
What role do micelles play in the human body?
Absorption of fat soluble vitamins and complex lipids
True or false: phospholipids are not stationary. Explain
True
Membranes are fluid
How do phospholipids typically move within membranes
Laterally within one layer
CANNOT flip from one layer to the other tho with a lot of energy
What are the 4 factors affecting the fluidity of membranes?
Number of carbons in the fatty acid tail
Unsat or sat fatty acids
Temperature (or other environmental factors)
Presence or absence of cholesterol/steroids
If there were 18 carbons in the carbon chain rather than 16, how would that change the membrane?
Longer chains pack together tighter and reduce fluidity
If there were double bonds in the carbon chain, how would that affect the structure and function?
Produce kinks
Push neighbouring phospholipids further apart
Increase fluidity
Affect permeability
What affect does temp have on the membrane?
High temp = more fluid
Low temp = less
Do cold adapted organisms have more unsat or sat phospholipids? Why?
Unsat
Maintain fluidity
What affect does chloresterol have on fluidity at normal temperatures? Why is this important?
Steroids pack closely to neighbouring phospholipids
Constrain fluidity (JUST phospholipids = TOO much fluidity)
Why are steroids important for fluidity at lower temperatures?
Phospholipids solidify at low temps
Cholesterol maintain fluidity by keeping apart
Is fluidity consistent throughout the entire membrane? Give an example of a domain that might be different
No
Lipid rafts
Are lipid rafts regions of high fluidity or low fluidity?
Low
What is the function of a lipid raft?
Hold macromolecules together in the membrane
Gather proteins involved in same metabolic pathway or a collection of receptors found on surface of cell
Why do lipid rafts have low fluidity?
1) Phospholipid tails are straight (saturated) –> pack together and lower fluidity
2) Higher conc of cholesterol
Why are lipid rafts taller than the rest of the membrane?
Carbon chains are longer
Why is low fluidity important in lipid rafts?
It allows them to hold the macromolecules
Macromolecules move _______ within the cell membrane
Laterally
Why is fluidity important in transmembrane movements?
Changing fluidity alters how much and how quickly a substance will move across the membrane (permeability)
Would regions of the membrane that have LESS unsat fatty acids and MORE cholesterol be less permeable or more?
Less bc less fluid membrane
Which substances can pass thru the membrane without additional energy?
Small, nonpolar (hydrophobic) molecules or ions
Which substances CANNOT pass thru the membrane without energy?
Large, charged polar molecules
How do small molecules cross the membrane?
Along a concentration gradient via diffusion
True or false: Cell membranes contain only lipids and proteins
False
Also contain carbs
How do hydrophilic molecules pass in and out of the cell?
Via transmembrane (integral membrane) proteins embedded within the cell membrane
What does the fluid mosaic model state?
Membranes consist of proteins and carbs embedded in a fluid bilayer
What does the fluid mosaic model predict?
Predicts certain properties of the cell membrane (i.e. The ability of membrane components to move laterally)
What are the three diff types of transport across cell membranes?
Passive diffusion
Facilitated diffusion
Active transport
What the difference between passive diffusion and facilitated diffusion?
Both involve the movement of molecules along a conc gradient but…
Passive = molecule coming into contact with the phospholipid layer
Facil = proteins embedded in the membrane allow the molecules thru
Does passive transport require energy?
No
What is active transport?
Movement of molecules AGAINST conc gradient
Embedded proteins require ATP (energy) to drive the transport
What is the most common way for substances (i.e. Water) to move passively across cell membranes?
Facilitated diffusion (passive transport)
How do transport proteins help large hydrophilic molecules pass the membrane?
Provide a hydrophilic core for them
What is osmosis?
Movement of water across a membrane (PASSIVE transport)
How does water diffuse across a selectively permeable membrane via a conc gradient?
From a less conc solution (HYPOTONIC) to a more conc solution HYPERTONIC)
If you placed a cell in a HYPERtonic solution what would happen?
Less water on outside so it would shrivel up as water goes out of it
If you placed a cell in a HYPOtonic solution what would happen?
It will become swollen (less water on inside compared to outside)
What are aquaporins and what are their functions?
Transmembrane proteins that allow water to move across membrane at a much faster rate than it could via simple diffusion
How do aquaporins allow water to move along so fast? (i.e. What structural components)
Allow ONLY water to pass thru a hydrophilic protein core thru the process of osmosis
True or false: the movement of water across a aquaporin does not requires energ
False
After placing a cell in a hypotonic solution, it bursts. What remains?
Ghost cells
Where does the energy for active transport come from?
The hydrolysis of ATP on the intracellular side of the cell
What is PRIMARY active transport?
Transmembrane transport protein is DIRECTLY affected by the hydrolysis of ATP
TT protein changes to pump the substance across
What is SECONDARY active transport?
INDIRECT expenditure of ATP entry
Neighbouring TTproteins use the electrochemical gradients established by primary active transport pumps to move their own solutes against a conc gradient
What are the similarities between primary and secondary active transport?
Both require energy
Both work against conc gradient
What kind of active transport does the sodium potassium pump use?
Primary active transport
True or false: in most cells, there is a greater conc of sodium in the interior fluid
False
Sodium greater on OUTSIDE
Potassium greater in INSIDE
How does the sodium-potassium pump work?
For every 3 sodium ions pumped OUT, 2 potassium ions pumped IN
Goes against conc gradient, so ATP gives up phosphate group to TTprotein
Phosphate group binds and causes a conformation change in shape of protein
Allows for release of sodium ions
Potassium from outside binds to TTprotein, causes original phosphate group to be released
Protein returns to original shape
Releases potassium into cytoplasm
What are hopanoids?
Five ringed structures in PROKARYOTES that serve a similar function to cholerestrol
True or false: most prokaryotes can synthesize sterols such as cholesterol
False
Synthesize hopanoids instead
Instead of a nucleus, what do prokaryotes have instead?
Nucleoid
= cell structure with multiple loops formed from supercoils of DNA
How are genes for antibiotic resistance commonly transferred thru bacteria?
Pili (threadlike structures that extend from one cell to another) transfer plasmids (and thus, genes) between bacteria
What is the function of the ER?
Synthesizes proteins and lipids
What is the function of the Golgi body?
Modifies proteins and lipids produced by ER
Sorts them out to destinations
What is the function of the Lysosome?
Contains enzymes that break down macromolecules
What is the function of Peroxisomes?
Contains enzymes involved in metabolism
- breakdown of fatty acids
- synth of certain types of phospholipids
What is the function of the mitochondria?
Produce most of the ATP/energy
What is the function of vacuoles (in plants)?
Maintain turgor pressure against cell walls and contribute to structural rigidity
What is the function of plasmodesmata (in plants)?
Connect neighbouring plant cells
