Cells Flashcards
What does the permeability of the membrane depend on
the nature of the molecule (polar , non polar)
size
What can polar molecules easily form
hydrogen bonds
What are polar molecules often called
hydrophilic
What are hydrophobic molecules
non- polar molecules that are unable to form hydrogen bonds
What molecules are lipids
hydrophobic
What three things do membranes consist of
lipids
proteins
glycolipids / glycoproteins
What does amphipathic mean
molecules with both hydrophobic and hydrophilic regions
what are the three major classes of lipids
phospholipids
glycolipids
sterols
what phospholipids are the most abundant
membrane
What does a phospholipids backbone composed mostly of
glycerol and a three carbon alcohol
What else is attached to the backbone
• negatively charged phosphate molecule forming polar hydrophilic head group
• two non -polar fatty acid chains forming the hydrophobic tails
What are the two fatty acids
unsaturated
saturate
what do the unsaturated fatty acids result in
kinks
Why can’t ions and lipid soluble molecules (polar) pass through the membrane
the interior of the bilayer is hydrophobic (non-polar)
Why can’t uncharged polar molecules like glucose pass through
they are hydrophilic
What can pass through the bilayer
small uncharged non polar lipid soluble molecules
example of large uncharged polar molecules that will be mostly impermeable to the bilayer
glucose
sucrose
Examples of small uncharged polar molecules that will be mostly permeable to the bilayer
water
urea
ethanol
glycerol
Examples of non polar lipid
molecules that will be permeable
Oxygen , Co2 , N2 , steroids
Where does oxygen diffuse from
air in the alveoli (high conc of oxygen) to blood in the capillaries (low conc of oxygen)
Where does carbon dioxide diffuse from in tissues
from cells (conc higher) to blood (conc is lower)
Where does the carbon dioxide diffuse from in the LUNGS
from the blood to the alveoli
What is a transmembrane protein
A protein that transfers molecules across the membrane
What are aquaporins
They are transmembrane proteins that allow water molecules to flow down their channels. From a region of higher concentration to lower
What are the two types of membrane proteins
integral
peripheral
What are integral proteins
embedded in the lips bilayer
difficult to isolate
amphipathic molecules
How are integral proteins embedded into the bilayer
The hydrophobic regions of the integral proteins interact with the hydrophobic interior of the lipid bilayer
What are peripheral proteins
•Hydrophilic
• found on the surface of the membrane
•interact only with the hydrophilic regions of the integral proteins
List the 4 functions of membrane (TRRE)proteins
- Transport
- Recognition
- Receptors
- Enzymes
Explain how membrane proteins help transport proteins
facilitate the movement of molecules in and out of the cell
channel and carrier proteins
What are channel proteins
Transmembrane proteins form channels for the passage of molecules
What are Carrier proteins
Undergo a conformational change to transfer the molecules from one side of the membrane to the other
Explain how membrane proteins help recognition
help in cell-cell recognition
Explain how membrane proteins act as receptors
for chemical signals and are burning sites for molecules like hormones and neurotransmitters
Explain how membrane proteins act as enzymes
catalyse reactions
Define osmosis
The diffusion of water across a selectively permeable membrane from lower to higher solute concentrations
How does water move in osmosis
From a region of lower water concentration to a region of higher water concentration
What are the factors that make facilitated diffusion
• molecules move down the conc gradient
• the movement is facilitated by transport proteins
What are channel proteins
transmembrane proteins that assemble to form channels for the passage of polar molecules
What is the selectivity of the ion channels due to
• the binding sites of hydrophilic amino acid side chains lining the channel
• the size of the pore
What are some reasons the channels open or close:
- changes in voltage across a membrane
- binding of small molecules to the channel proteins
- mechanical forces
What are carrier protiens
transmembrane transport proteins
What is the mechanism of carrier proteins
the carrier protein binds to the solute molecules, it undergoes a conformational change and transfers the molecules to the other side of the membrane
Define Active transport
the net movement of particles through a cell membrane from a region of lower conc to a region of higher suing energy
What are 3 things active transport helps to:
• takes up essential nutrients
• removes secretory
• maintain the right concentrations of ions in the cells
What are the two types of active transport
Indirect
Direct
Explain direct active transport
The energy released by an exergonic reaction is used to directly transport molecules across the membrane
Explain Indirect transport
The movement of one solute down its gradient drives the movement of the second solute against its concentration gradient
What factors are based on the movement of molecules by simple diffusion
• the size of the molecules
• hydrophobic or hydrophilic nature
What are the carbohydrates linked to creating what
lipids and proteins
forming glycolipids and glycoproteins
What forms glycolipids
covalent bonding of carbohydrates to lipids
What are the two factors of glycolipids
- amphipathic molecules
- external surface of the cell membrane
What are the carbohydrates and lipids like in glycolipids
carbs are polar and extend to the extra cellular environment
lipids are non polar and embedded into the bilayer
How do glycolipids contribute to membrane stability
They form hydrogen bonds with the water molecules surrounding the cell
What are the 4 (triple c g) functions of glycolipids and proteins
Cell recognition
cell adhesion
cell signalling
glycocalyx
Explain cell recognition in glycolipids and glycoproteins
They act as markers and help cells of the body recognise eachother.
They help immune systems recognise foreign cells
Explain cell adhesion
they help cells to attach and bind to other cells to form tissues
Explain cell signalling
They act as receptors for enzymes
What is glycocalyx
A sticky layer formed by the carbohydrate groups of the glycolipids and protiens that protrude form the cell surface .
Who proposed the fluid mosaic model and what year
Singer and Nicholson 1972
What does the fluid mosaic describe
the arrangement of the lipids and proteins
What 2 things does the Fluid Mosaic Model state:
• The lipid bilayer is fluid
• The proteins are embedded in the fluid bilayer which resembles a mosaic
What is the benefit of the fluid nature of the membrane
That most lipids and proteins are able to move laterally , parallel to the membrane surface
What are organelles
discrete structures in cells adapted to perform specific functions
what 5 organelles have no membranes
ribosomes
centrioles
microtubules
proteasomes
nucleoli
what organelles have a single membrane
smooth er
rough er
golgi
vesicles / vacuoles
lysosomes
what organelle has a double membrane (5)
nuclei
mitochondria
chloroplasts
what does compartmentalisations allow
it allows the development of specialised cell structures
where are membrane bound organelles found
eukaryotic
what is an advantage of compartmentalisation in cells
the cell can separate chemical reactions and other cellular processes, this allows the cell to increase rate of chemical reactions
What two factors should you have to be an organelle
enclosed by a membrane
have a specific function
what is a disadvantage of compartmentalisation
it can delay a cells ability to respond to the environment
What are the 4 types of stem cell
Totipotent
Pluripotent
Multipotent
Unipotent
What are the differentiated cells produced in totipotent cells
• Can differentiate into any type of cell
• Can give rise to a complete organism
What are the differentiated cells produced in pluripotent t cells
Can differentiate into all body cells , cannot give rise to a whole organism
What are the differentiated cells produced in multipotent cells
Can differentiate into a few closely related type of body cell
What can unipotent cells differentiate into
Can only differentiate into their associated cell type
What are the stem cells at the morula stage
Totipotent
Are stem cells specialised or unspecialised
unspecialised
What is the morula
solid ball of totipotnet cells formed soon after fertilisation
What’s the function of the stem cell niche
The micro environment in which stem cells reside and receive their instructions
What is a micelle
formed when phospholipids are shaken with water
What are the two main components of animal cell plasma membranes
Phospholipids
Cholesterol
What makes Cholesterol (lipid) amphipathic
• majority hydrophobic
• the hydroxyl group of cholesterol molecule is hydrophilic
What does cholesterol help with
regulation of membrane fluidity and permeability
What happens in the interaction between cholesterol and phospholipids tails (temperature)
stabilises the plasma membrane at higher temperatures by stopping the membrane from becoming too fluid
What does cholesterol do at cold temperatures
increases fluidity of membrane, stopping it crystallising
What type of proteins are plasma membrane
globular proteins
What is cholesterol
lipid
As a whole what is the job of a transport protein
creates hydrophilic channels to allow ions and polar molecules to travel through the membrane
What is cell adhesion
allows tight junctions to form between cells
What organ and organ system do epithelial cells make up
Organ: Stomach
Organ system : digestive
What organ and organ system do muscle cells make up
Organ : bladder
Organ system : Urinary system
What organ and organ system do nerve cells make up
Organ : Brain
Organ system: CNS
What organ and organ system do rod and cone ells make up
Organ : Eye
Organ system : Visual system
What do structural adaptations include
shape of cell
the organelles the cell contains
What is a stem cell
a cell that can divide by mitosis an unlimited number of times
What is potency
the ability of stem cells to differentiate into more specialised cell types
What are the 4 types of potency
Totipotency
Pluripotentcy
Multipotentcy
Uni potency
Explain totipotency
stem cell that can differentiate into any cell type found in an embryo
Explain pluripotentcy
Embryonic Stem cells that can differentiate into any cell type found in an embryo but are not able to differentiate into any extra - embryonic cells
Explain multipotentcy
Adult stem cells that can differentiate into closely related cell types
Explain unipotency
adult cells that can only differentiate into their own lineage
What embryonic stem cell would it be if taken 3-4 days after fertilisation
Totipotent
What embryonic stem cell would it be if taken 3-4 days after fertilisation
Totipotent
What embryonic stem cell would it be if taken 3-4 days after fertilisation
Totipotent
What embryonic stem cell would it be if taken 5days after fertilisation
pluripotent
What is one treatment of Stargardts disease
Injection of retina cells derived from embryonic stem cells into patients eyes
Ethics : Arguments for Embryonic stem cells
• Totipotent and pluripotent can differentiate into any cell type thus giving patient a higher chance of living a healthy life
• Embryonic stem cells are not differentiated therefore less chance of genetic damage due to accumulation of mutations
Arguments against embryonic stem cells
• cells have a higher risk of developing tumours
• process involves the creation and destruction of embryos
Arguments for cord blood stem cells
• can be easily obtained and stored
• fully compatible either tissues of adult - reduce risk of rejection
Arguments against Cord blood stem cells
• The cells are multipotent and therefore have a limited capacity to differentiate into different cell types
Arguments for Adult stem cells
- donor able to give permission - less controversial
- lower chance of rejection patients own adult stem cells are being used to treat them
- lower chance of developing tumours
- can be removed without any long lasting side effects ffecfs
Arguments against adult stem cells
- difficult to obtain painful to extract
- are multi potent limited capacity to differentiate into different cell types
