Topic 1 - Cell Biology Flashcards
Outline reasons for the therapeutic use of stem cells
- stem cells are unspecialised cells that can give rise to a wide range of body cells by differentiating along different pathways
- can divide indefinitely
- are accessible as can come from embryos/bone marrow/umbilical cord blood/adult tissue
- can repair damaged tissues
- such as in the case of stargardt’s disease - retinal cells derived from embryonic stem cells - restores sight
- drugs can be tested on stem cells to see if they are harmful
outline cell theory
- living things are composed of cells
- cells are the smallest unit of life
- cells come from pre-existing cells
magnification
magnification = size of drawing / actual size
describe the characteristics of stem cells that make them potentially useful in medicine
- can divide indefinitely
- can be used to produce a large number of identical cells
- can be used to repair damaged tissues
- are undifferentiated and can specialise in different ways
- used in the treatment of stargardts disease
compare and contrast the structure if a typical prokaryotic cell with that of a mitochondrion
differences:
- prokaryote has cell wall, mitochondria does not
- mitochondria has double membrane whereas prokaryote has single membrane
similarities
- both have 70S ribosomes
- both have naked DNA
explain how mitochondria could have been formed from free living prokaryotes
- endocytosis of prokaryote by a larger cell
- thus resulting in the double membrane of the mitochondria
- cell remained inside host cells and carried out respiration, thus providing energy to the host cell
- endosymbiotic theory
engulfed prokaryotic cell has its own DNA and 70S ribosomes
outline four different processes that allow substances to pass through the plasma membrane
- simple diffusion (movement of particles from a region of high concentration to a region of low concentration)
- osmosis (passive movement of water molecules from a region of lower solute concentration to a region of higher solute concentration across a partially permeable membrane)
- facilitated diffusion (diffusion of particles through transport proteins in the plasma membrane)
- active transport (movement of particles across membranes against a concentration gradient - requires ATP)
- endocytosis (process where cells take in molecules from outside the cell by engulfing them in cell membrane - vesicles)
- exocytosis (fusion of vesicles with membranes to release molecules)
explain how hydrophobic and hydrophilic properties contribute to the arrangement of molecules in a membrane
- hydrophilic attracted/soluble in water
- hydrophobic not attracted/insoluble in water
- hydrophilic heads of phospholipids face outwards
- hydrophobic tails of phospholipids face inwards
- integral proteins are embedded in the phospholipid bilayer/membrane due to hydrophobic properties
- peripheral proteins are on the membrane surface as they are hydrophilic
- phospholipids are amphipathic
- cholesterol is amphipathic, its hydroxyl group is hydrophilic and aligns towards the phosphate heads whereas the remainder of the molecule is hydrophobic and aligns with the phospholipid tails
state the property of amphipathic phospholipids that enables them to form a bilayer
- have both a hydrophilic and hydrophobic region
state the role of cholesterol in animal cell membranes
- reduces fluidity of membrane
- restricts the movement of phospholipids and other molecules
- reduces membrane permeability to hydrophilic molecules
describe how the structure of the membrane allows the formation of vesicles
- fluidity of membrane allows change of shape/formation of vesicles
- weak bonding between phospholipid tails
- kinks on the phospholipid tails prevent close packing
- cholesterol affects membrane fluidity
outline four different functions of membrane proteins
- channel proteins for facilitated diffusion
- pumps - active transport
- enzymes embedded in membrane
- electron carriers
outline four types of membrane transport including their use of energy
- simple diffusion is the passive movement of molecules along a concentration gradient
- facilitated diffusion is the passive movement of molecules along a concentration gradient through a protein channel
- osmosis is the passage of water through a partially permeable membrane from lower solute concentration to higher
- active transport is the movement of molecules against a concentration gradient with the use of ATP
- endocytosis is the formation of vesicles to bring molecules into the cell with the use of energy
- exocytosis is the formation of vesicles to release molecules from the cell with use of energy
describe the process of endocytosis
- plasma membrane engulfs particles
- allowed by the fluidity of the membrane
- plasma membrane pulls inwards and pinches off - edges fuse
- vesicle formed
- the inside of the plasma membrane becomes outside of the vesicle membrane
- vesicle breaks away from the plasma membrane and into the cytoplasm
- active process and requires energy
outline with example the process of exocytosis
- vesicles carry material to the plasma membrane
- vesicle fuses with membrane and expels material from the cell
