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
What are some features of proteins in the plasma membrane?
- many membrane proteins are glycoproteins (proteins with carbohydrate groups attached to the ends that protrude into the extracellular fluid)
- the carbohydrate portions of glycolipids and glycoproteins form an extensive sugary coat called the glycocalyx
What is the glycocalyx?
acts as a molecular “signature” which allows cells to recognise one another
What are some examples of plasma membrane junctions? (3)
desmosomes, tight junctions and gap junctions
What are intergrins?
they are transmembrane proteins in the plasma membrane which bind to specific proteins in the extracellular matrix and link them to membrane proteins on adjacent cells
what are desmosomes?
they are accumulations of protein known as dense plaques along the cytoplasmic surface of the plasma membrane. they serve as anchoring points for cadherins
what are cadherins?
proteins that extend from then cell into the extracellular space where they link up and bind with cadherins from an adjacent cell
what is the function of desmosomes?
they hold adjacent cells firmly together in areas that are subject to considerable stretching, such as the skin
when are tight junctions formed?
when the extracellular surfaces of two adjacent plasma membranes join together so that no extracellular space remains between them
where are tight junctions located?
in a band around the entire circumference of the cell
what are some features of gap junctions?
- consist of protein channels linking the cytosols of adjacent cells
- connexins from the two membranes join, forming small, protein lined channels linking the two cells
- their diameter of 1.5nm limits what can pass between the cytosols of the connected cells to small molecules and ions, such as Na+ and K+, and excludes the exchange of large proteins
name 4 functions of cell membranes
- regulate the passage of substances into and out of cells and between organelles and cytosol
- detect chemical messengers arriving at the cell surface
- link adjacent cells together by membrane junctions
- anchor cells to the extracellular matrix
what is cytoplasm and what is its function?
fluid portion of cells that suspends the organelles and other components such as ions, proteins, lipids etc. site of many chemical reactions
what is the function of the cytoskeleton
- maintains shape of cell
- position organelles
- changes cell shape
what are some features of the cytoskeleton and what are their functions? (3)
- microfilaments: also known as actin filaments
- microtubules: both these and microfilaments can be assembled and disassembled rapidly, allowing a cell to alter these components of its cytoskeletal framework
- intermediate filaments: once assembled are less readily disassembled
what is the structure of a centrosome?
- two centrioles arranged perpendicular to each other: composed of microtubules, 9 clusters of 3
- pericentriolar material: composed of tubulin that grows the mitotic spindle
what is the function of a centrosome?
moves chromosomes to ends of the cell during cell division
what is the function of the cilia and flagella
specialised for movement
what is the structure of the flagellum
single tail like structure on sperm
where is the cilia found?
in groups in the respiratory system
what is the function of ribosomes?
-protein synthesis
what are some features of the ribosome?
- consists of ribosomal RNA
- contain large and small subunits
- can be attached to the ER or free in cytosol
what is the structure of the rough endoplasmic reticulum?
network of folded membranes studded with ribosomes
what is the function of the smooth endoplasmic reticulum? (4)
- lipid synthesis
- release of glucose in liver cells into bloodstream
- drug detoxification (especially in liver cells)
- storage and release of Ca2+ in muscle cells (sarcoplasmic reticulum)
what is the structure of the Golgi complex?
flattened membrane with bulging edges
what are the functions of the Golgi complex?
-modify proteins to glycoproteins and lipoproteins that:
.become parts of the plasma membranes
.are stored in lysosomes
.are exported by exocytosis
what is the structure of lysosomes?
- spherical or oval surrounded by single membrane
- typical cell may contain several hundred lysosomes
what are the functions of lysosomes?
- contain variety of digestive enzymes
- help in final process of digestion within cells
- carry out autophagy (destruction of warn out parts of cell) and death of old cells (autolysis)
what is tay-sachs?
a hereditary disorder where one missing lysosomal enzymes leads to nerve destruction
what is the structure of peroxisome?
a moderately dense oval bodies enclosed by a single membrane
what are the functions of peroxisomes?
- consumes molecular oxygen an undergoes reactions that remove hydrogen from organic molecules including lipids, alcohol and potentially toxic ingested substances
- it detoxifies and is abundant in liver
what is the structure of proteasomes?
tiny barrel shaped structure that contain proteases (proteolytic enzymes)
what is the function of proteasomes?
- digest unneeded or faulty proteins
- faulty proteins accumulate in brain cells in persons with Parkinson’s or Alzheimer diseases
what is the structure of the mitochondria?
- many folded membranes (cristae) and liquid matrix containing enzymes
- have some DNA, ribosomes (can make proteins)
what is the function of the mitochondria?
major site of ATP production, O2 utilisation and CO2 formation
-contains enzyme active in Krebs cycle and oxidative phosphorylation
what is the structure of the nucleus?
- round structure surrounded by nuclear envelope
- contains nucleolus: makes ribosomes that pass into cytoplasm through nuclear pores
- within the nucleus, DNA, in association with proteins, forms a fine network of threads known as chromatin
what is the function of cellulose in plants?
structure of the cell wall
what is the function of glycogen and starch?
storage
what is catabolism?
the breakdown of compounds into simpler molecules
why is catabolism useful? (2)
it releases energy and provides smaller building blocks
what is anabolism?
building a more complicated molecule from smaller units (eg amino acids->proteins)
what is cellular respiration?
the breakdown of glucose in many small steps to make ATP. it involves breaking bonds and moving electrons from one molecule to another
what do electrons ‘carry’?
energy
what is the balanced respiration equation?
C6H12O6+6O2–>6CO2+H2O+ATP
what does the process of oxidation include? (5)
- adding O
- removing H
- loss of electrons
- releases energy
- exergonic
what does the process of reduction include? (5)
- removing O
- adding H
- gain of electrons
- stores energy
- endergonic
what happens in the redox reaction?
glucose is oxidised and oxygen is reduced
how do electrons move in biology?
they cannot move freely, they move as part of a hydrogen atom
what is NAD+?
a coenzyme which regulates the activity of the enzyme it is bound to
what is NAD+ derived from?
the vitamin nicotinic acid/niacin
what molecules can NAD+ accept in order to be reduced? and what is it reduced to?
it accepts two electrons and two hydrogen atoms to be reduced to NADH
what is NADH used for?
making ATP in the electron transport chain
give an example of NADH production
formation of oxaloacetate from maltate in the Krebs cycle
what is FAD?
a cofactor that binds strongly to an enzyme
how is FAD synthesised?
from vitamin B2 oe riboflavin
how is FAD reduced and what is it reduced to?
it accepts two hydrogens and two electrons to be reduced to FADH2
how many electrons are transferred per hydrogen
two
give an example of FADH2 production
the formation of fumarate from succinate in the Krebs cycle
how does ATP provide energy?
the hydrolysis of the high energy phosphate bond
why is ATP structurally unstable?
due to the repulsion between ionised oxygen atoms which are all in close proximity
what are the 4 key stages of the complete oxidation of glucose?
- glycolysis
- pyruvate oxidation
- krebs cycle
- electron transport chain chemiosmosis
what occurs during the cori cycle?
lactate produced during anaerobic glycolysis is transported to the liver and converted to glucose
what does the cori cycle require to occur?
ATP
where does the glucose that is produced in the cori cycle go?
supplied back to the muscle
why do cancer cells use a low yield ATP generation system? (3)
lactate is thought to promote
- blood vessel formation
- metastasis and invasion
- immune escape
where does the oxidation of pyruvate occur?
in the mitochondria
