Lecture 1 - Principles of cell function Flashcards
2 types of cells
Prokaryotic (Bacterial)
Eukaryotic (Animal)
5 unique features of a prokaryotic cell
Flagella
Pili
Cell Wall
Capsule
Endospores
What is the flagella?
Antennae of bacterial cell - tries to gauge external environment (is there something near that is important for nutrition purposes)
What is the pili?
The “hairs” that allow bacterial cells to attach to membranes to cause infection
Cell wall
Very thick
Role of Capsule
Prevents cell from drying out
Endospores are where, what, for? resistant to?
Within the cell wall
Walls very thick
For survival under harsh conditions
Resistant to various degrees to heat, desiccation (removal of moisture), freezing, toxic chemicals
Eukaryotic cells have no…
Pili, capsule
Eukaryotic cells have a
Well defined nucleus - contains nucleolus
Cytoplasm - number of organelles
DORA: Prokaryotes
D (DNA): DNA is naked, circular
O (Organelles): No nucleus, no membrane-bound
R (reproduction): Binary fission, single chromosome (haploid)
A (Average size): Smaller
What is binary fission?
Asexual reproduction where 1organism becomes 2, 2 becomes 4 and so forth
DORA Eukaryotes
D (DNA): DNA is bound to protein, linear
O (Organelles): Has a nucleus, membrane-bound, 80s ribosomes
R (Reproduction): Mitosis and meiosis, chromosomes paired (diploid or more)
A (Average size): Larger
In mitosis, daughter cells have … number of chromosomes as parent
Same
In meiosis, what happens with the cell?
Divides cell in 2 - 23 chromosomes each
DIfferent names for a membrane
Cell membrane, cytoplasmic membrane, plasmalemma, phospholipid bilayer, lipid bilayer
Cells are …permeable
semipermeable
if it wasn’t, anything could come in or out. only certain molecules are allowed in
Cells have the ability to…
Engulf
Another word for when a cell uses its plasma membrane to engulf a large particle
Phagocytosis
Interface of cells is between what kind of environments
Internal and external
3 Functions of the boundary in a membrane
- keeps nutrients in the cell,
- helps retain transported substances - useful substances are kept within the cell for use
- Excretion of unwanted substances
Interface between the environments
Cells respond to changes in the environment
Receptors help identify substances needed by the cell
Then, secretion of hormones or neurotransmitters
2 Major plasma membrane functions
- Receptors that have specific domains on it means only a certain molecule can attach on it e.g. if a mutation on the insulin receptors occur, the receptor may not be able to detect the insulin
- Anchors - hold certain proteins e.g. can trap mitochondria to cell membrane for energy purposes.
The cell membrane contains … that has a hydrophilic and hydrophobic part
Phospholipid bilayer
The reason why phospholipids have a hydrophilic and hydrophobic part to it is because…
Phospholipids
What is the protoplasm?
The cytoplasm and nucleus
The 2 faces/surfaces of the membrane
Protoplasm surface, face (P-face)
External surface, face (E-face)
The p-face and e-face contain what?
The intra-membranous particles that are proteins
Differences between the e-face or p-face and the e-surface or p-surface
The outside part of the cell membrane is the e-surface. It is hydrophilic
The inner part of a cell membrane when “unzipped” is the e-face. It is hydrophobic
P-face and e-face contain intramembraneous particles that are proteins
The cell membrane has 2 specific features - 2 dark lines and then a transparent zone in between them. What are these called?
The 2 dark lines are called the electron dense.
The transparent zone is called the electron lucid gap
Since the outsides of the cell membrane are hydrophilic, does a molecule that is soluble in water easily in water move freely into the cell?
Yes but since the e-face and p-face are hydrophobic, they will determine whether the entered molecule is important. If so, it will let it through. If not, it will repel it away.
Fluid mosaic model
States that membrane proteins are highly mobile - wherever the need for protein is, it can move there in 3 dimensions.
Many proteins are:
Glycoproteins (a component of glucose and protein)
What are amphipathic molecules
Those that are both hydrophilic and hydrophobic
A typical cell membrane is composed of:
Lipids and proteins in equal amounts
3 major types of lipids/proteins that you find in the cell membrane
- Phospholipids,
- Cholesterol
- Glycolipids
Phospholipids, Cholesterol and Glycolipids are
Amphipathic
Do red blood cells have high or low glycolipids
Low
Do myelin sheath cells have high or low glycolipids
High
Why do RBC’s have low glycolipids
Their function is to carry a lot of oxygen so if theres a lot of glycolipids it will take more effort to move and will be slower. Also, you want to have more hydrophilic molecules in the membrane as it easier for diffusion into cell.
Why is cholesterol important
It increases stability and prevents loss of membrane liquidity at a low degree.
It is less likely to be affected by significant changes in temperature. This is important since a change of 1 or 2 degrees can be very dangerous
50% of the plasma membrane is:
non-aqueous - used for transport receptors and anchoring sites
Hence, it is easier to move through here since it is ampipathic
Another name for RBC
Erythrocyte
2 main membrane transport mechanisms of Band 3 protein
Ion transport
Maintenance of protein to protein interactions
Under normal circumstances, sodium is… whereas potassium is…
Sodium is outside, potassium is inside
During action potential, Na moves… and K moves…
Na moves inside, K moves outside
Protein inside cell membrane does what during action potential
The protein inside the membrane pulls sodium in and pushes potassium out. This protein has electrochemical difference that allows it to do this.
What is the role of glycolipids?
They identify cells
Role of Band 3 protein
Ensuring that chloride goes into the cell, bicarbonate goes out (ANTIPORTER)
3 methods of transporting large substances
- Exocytosis - exits e.g. adrenaline around the body
- Endocytosis - inside of us
- Phagocytosis - bacteria engulfing
Fluid ingestion is called?
Pinocytosis
When a cell secretes something and it only affects itself, the form of chemical signalling is called?
Autocrine response
When a cell secretes something and activates another cell in the vicinity, it is called a
Paracrine response
When a cell secretes something and affects another cell far and wide within the body, it is called a
Endocrine response
Process of getting insulin into cell
The insulin receptors activates the GLUT-4 receptor which leads to the absorption of glucose into the cell
An absence of the GLUT-4 receptor leads to what disease?
Diabetes
5 types of transports of substances across cell membranes
- Passive diffusion - e.g. water
- Facilitated diffusion e.g. GLUT-4
- Selective facilitated diffusion e..g GLUT-4 only allow glucose to move through them
- Primary active transport - Sodium and potassium causing ATP (energy)
- Secondary active transport - Antiporter transport e.g. Band 3 protein
Movement of substance through diffusion is done by what
down concentration gradient (from a high concentration of a substance to low)
Does diffusion occur across cell plasma membranes?
Not necessarily
Does diffusion require energy?
No (passive transport)
Examples of diffusion
Diffusion of oxygen from the alveolus into blood capillaries
Movement of substance through osmosis
Down concentration gradient
Does osmosis occur across cell plasma membrane
Yes
Does osmosis require energy
No (passive transport)
Example of osmosis
Uptake of water by the root hair from the soil
Examples of substances used in active transport
Mineral ions, glucose, amino acids
Movement of substance through active transport
Against concentration gradient (low concentration to high concentration)
Does active transport occur across cell plasma membrane
Yes
Does active transport require energy
Yes
Example of active transport
Reabsorption of glucose into the kidney
What is osmolarity
Total solute concentration within a specific volume of a solvent.
Number of osmoles of solute per litre
Measured in osmoles per litre (Osm/L)
Osmolality
Number of osmoles of solute per kilogram of solvent
What’s an osmole
number of moles of a solute that contributes to the osmotic pressure of a solution
What are osmotically active substances
Substances that cause the movement of water across a membrane
Examples of osmotically active particles in biological systems
Ions e.g. Na - wherever sodium goes, water follows
Small molecules - glucose
Proteins - Albumin
Other organic molecules
Examples of osmotically active particles in clinical solutions
Saline solution (NaCl)
Dextrose solution (Glucose)
Ringer’s lactate (various electrolytes including lactate)
If osmolarity is equal to the molarity of glucose into a solution, glucose does not…
dissociate in a solution. hence, in a solution of 100mM of glucose, its osmolarity is 100mOsm/L
NaCl dissociates into:
Na+ and Cl-. Because of this, in a solution of 150mM of NaCl, its osmolarity increases to 300 mOsm/L since both sodium and chloride have 150mM each. THIS IS AN ISOTONIC SOLUTION - NO WATER
This is why energy drinks with NaCl in them will hydrate you more since the body’s natural osmolarity is 275- 295 mOsm/L
3 types of solution
Isotonic: no net movement of water
Hypotonic: water enters cell
Hypertonic: water leaves cell - leaves spikes leading to cells getting caught and causing a clot.
