Cell Structure and Cellular Respiration Flashcards
What are stem cells?
Undifferentiated biological cells that can differentiate into specialised cells and divide (mitosis) to produce more stem cells.
In a developing embryo, what can stem cells differentiate into?
Ectoderm, endoderm and mesoderm (germ layers)
In adults, stem cells act as a repair system for the body alongside what other cells?
Progenitor cells.
What is potency?
Potency specifies the differentiation potential of a stem cell
What are totipotent stem cells?
Stem cells that can differentiate into embryonic and extraembryonic cell types.
How are totipotent stem cells formed?
From the fusion of an egg cell and a sperm cell.
What is a pluripotent stem cell?
They are the descendants of totipotent cells and can differentiate into nearly all cells, i.e cells that are derived from any of the 3 germ layers
What are multipotent stem cells?
Stem cells that can differentiate into a number of cell types, but only those of a closely related family of cells
What are oligopotent stem cells?
stem cells that can differentiate into only a few cell types, such as lymphoid or myeloid stem cells.
What are unipotent cells?
Cells that can only produce one type, their own, but have the property of self-renewal, which distinguishes them from non-stem cells.
What are some features of prokaryotic cells?
- no nucleus or membrane bound organelles
- singular, circular chromosomes
- cell membrane and cell wall (peptidoglycan)
- contains ribosomes
what’s the difference between bacterial and Archaean cell walls?
Archaean cell walls lack peptidoglycan
What is a gram-positive cell?
They have a thick mesh-like cell wall made of peptidoglycan which takes up 50-90% of the cell wall, which stains purple
What is a gram-negative cell?
have a thinner layer (10% of cell wall), which will stain pink
What are some features of eukaryotic cells?
- Membrane bound nucleus
- compartmentalise many cellular functions within organelles and the endomembrane system.
- have a cytoskeleton for support
- examples include fungi, plant and animal cells and protozoa.
What makes up a plasma membrane?
- phospholipid bilayer
- cholesterol
- proteins (internal and peripheral)
- attached carbohydrates (glycolipids and glycoproteins)
What are the functions of the plasma membrane?
- barrier between inside and outside of cell
- controls entry and exit of materials
- receives chemical and mechanical signals
- transmits signals between intra- and extra- cellular spaces
What are some features of the phospholipids in the plasma membrane?
- phospholipids are amphipathic
- organised into a bilayer with the non-polar fatty acid chains in the middle
- the polar regions of the phospholipids are orientated toward the surface of the membrane
- hydrophobic fatty acid tails
- hydrophilic phosphate group head
Why are the polar regions of the phospholipids orientated toward the surfaces of the membrane?
this is due to their attraction to the polar water molecules in the extracellular fluid and cytosol
What are some features of cholesterol in the plasma membrane? (6)
-cholesterol associates with certain classes of plasma membrane phospholipids and proteins, forming organised clusters
-cholesterol molecules are weakly amphipathic.
-the polar -OH group of the cholesterol forms hydrogen bonds with the polar heads of phospholipids and glycolipids
-stiff steroid rings and hydrocarbon tail are nonpolar
-cholesterol has a temperature dependent effects on membrane fluidity
-warm temp=restrains phospholipid movement
cold temp=maintains fluidity by preventing tight packing
What do the clusters of cholesterol, proteins and phospholipids do?
they work together to pinch off portions of the plasma membrane to form vesicles that deliver their contents to various intracellular organelles
What are some features of glycolipids in the plasma membrane?
- carbohydrate groups form a polar head and their fatty acid tails are nonpolar
- glycolipids appear only on the extracellular side of the membrane, making the bilayer asymmetrical
what are some features of integral proteins in the plasma membrane?
- closely associated with the membrane lipids and cannot be extracted from the membrane without disrupting the lipid bilayer
- they are amphipathic
- also referred to as transmembrane proteins
- some form channels where water and ions can cross the membrane, some form channels for chemical signals
What are some features of peripheral membrane proteins in the plasma membrane?
- they are not amphipathic and do not associate with the nonpolar regions of the lipids in the interior surface if the membrane
- located at the membrane surface where they are bound to polar regions of the integral membrane proteins