Physiology Flashcards
What does it mean by the plasma membrane being fluid?
It can change its shape easily. Many proteins in the membrane can diffuse laterally, but many are anchored so it is important to realise that many proteins are not distributed equally within the cell membrane.
What is the structure of a plasma membrane ?
It is a bio-molecular layer of amphipathic phospholipid molecules with their hydrophilic heads at the outer and inner surfaces and their hydrophobic fatty acid chains facing towards the middle
What are found in the plasma membrane ?
Cell attachment proteins
Receptors
Enzymes
Channels
Transporters
What is cytosol made of?
Proteins
Carbohydrates
Electrolytes
It has fluid and gel-like properties
What are the common features of a eukaryotic cell?
Outer membrane
Cytoskeleton
Cytosol
Membrane bound organelles
Inclusions
What is the cell membrane permeable and non-permeable to ?
It is permeable to oxygen,water, hydrophobic molecules and small molecules and non-permeable to charged molecules like sodium and potassium.
What is the function of the plasma membrane ?
It separates the cytoplasm from the outside environment.
How can an organelle be defined?
Small membrane bound organ that has a specific function and structural organisation that is important to maintain life.
What are examples of membrane bound organelles?
Mitochondria
Rough endoplasmic recticulum
Smooth endoplasmic recticulum
Golgi apparatus
Lysosomes
Nucleus
What are inclusions?
Inclusions in a cell are small, non-living substances or particles found inside the cell.
Name some Inclusions in the cell?
Glycogen granules
Lipid droplets
Pigments
What is the cytoskeleton?
The cytoskeleton is a network of protein fibers inside a cell that gives the cell its shape, supports it, and helps it move. It acts like the cell’s “skeleton” and “muscles,” providing both structural support and flexibility.
What does the cytoskeleton do?
The cytoskeleton also plays a role in transporting materials within the cell and helps organize its internal components.
What is the cell membrane permeable to?
small hydrophobic molecules
water
oxygen
What defines a eukaryote?
Any cell or organism that possesses a clearly defined nucleus
What is a plasmalemma?
It separates the cytoplasm from the outside environment , that forms a selectively permeable barrier
What is cell membrane impermeable to?
charged ions
What can be found in cytoplasm ?
organelles and inclusions
What does the mitochondria do?
produces energy production(energy house)
What does the rough ER do?
synthesises proteins
What does smooth ER do?
synthesise lipids and cholesterol
and detoxifies
What does Golgi apparatus do?
modification and packaging of secretions
What do lysosomes do?
hydrolytic enzyme for intracellular digestion
What does the nucleus do ?
contains genetic code
What is an example of inclusions?
adipose cells in brown fat
What are microfilaments composed of?
2 actin strands
What are microtubule composed of ?
alpha and beta tubular that form protofilaments -> form microtubule
What are MAPS?
Microtubule associated proteins
What is dynein and what does it do?
It is an ATPase, that moves toward the cell and drags the membrane of organelles and vesicles along the microtubule
What is kinesin and what does it do?
It is an ATPase, that moves toward the cell periphery and drags the membrane of organelles and vesicles along the microtubule
What is Euchromatin?
DNA that is more dispersed and undergoing transcription
What is heterochromatin?
DNA that is highly condensed and not undergoing transcription
Where does mRNA and tRNA synthesis take place ?
in nucleus
Where does rRNA take place?
in nucleolus(within nucleus)
What do nuclear pores do?
allow the transport of molecules across the nuclear envelope
Where are ribosomes formed?
in nucleolus
What do cristae do and where can they be found?
In mitochondria, they increase the surface area
What does the mitochondria do?
produce ATP through oxidative phosphorylation, and is involved in creating certain lipids and proteins
What do intracellular junctions do?
connect cells to other cells, happens mainly in epithelial cells
What are occluding(tight) junctions?
links cells to form a diffusion barrier and prevents diffusion
aka Zona occludens
What is an anchoring junction?
aka adherens junction, it anchors cells together and prevents separation
What are desmosomes?
they link sub-membrane intermediate filaments of adjacent cells
aka macula adherens
What does a communicating (gap) do?
allow movement of molecules between cells (selective diffusion)
How do communicating gaps look like?
each junction is studded with several pores, these pores are produced by connexion proteins
What are communicating gaps used for?
ions and cytokines pass between cells-> rapid communication
Where can communicating gaps be found?
smooth muscle
cardiac muscle
epithelia
-> used for spread of excitation
How can material move across the cell membrane ?
Diffusion
transport proteins(pumps and channels)
Incorporation into vesicles(requires ATP)
How does vesicular transport occur?
Endocytosis
Exocytosis
Phagocytosis
What is endocytosis?
It is a receptor mediated process that incorporates extracellular material into the cell
What is exocytosis?
it expels intracellular material out of the cell
What is phagocytosis?
Bacteria binds to the cell surface and the cell engulfs it to the phagosome that then binds with lysosome containing digestive enzymes which produce a phagolysosome
How long does a cell cycle last for skin cells?
for days
How long does the cell cycle last for liver cells ?
for years
How long does the usual cell cycle last?
about 12 hours
What are the stages of a cell cycle?
G1, S ,G2
What parts is the cell cycle divided into?
Mitosis and Interphase
What phases are in the interphase?
G1, S, G2
What are cyclins?
cyclins are proteins and their concentration increases and decreases throughout the cell cycle
What are the cell cycle proteins called?
cyclins A, B and E
What is the role of cyclins during the cell cycle?
cyclins activate cyclin dependant kinases(CDKs)
What happens to cyclin and CDKs when cell cycle is complete?
cyclins and CDKs are degraded and absorbed by ubiquitin(cytoplasmic care taker protein)
What phases is the interphase made up of?
G1, S, G2
What does the nucleus contain?
It is inside a nuclear envelope and contains network of chromatin threads, granules and nucleolus
Where does replication of DNA take place ?
In the nucleus
Where are the two paired centrioles located?
In the cytoplasm
What is the G1 phase about?
GROWTH PHASE
Also called the growth phase or gap phase
What happens in G1 phase?
It is the time when the cell initiates another cycle
most of the molecular machinery is created during G1 that will be needed in the next phase of the cycle
Organelles synthesise proteins and make energy
How is the G1 phase controlled?
it is controlled through cyclin E and CDKs
What happens at the end of G1 phase?
It is also the check point for DNA damage which would result in apoptosis
What is the S phase about ?
DNA REPLICATION
DNA replication happens in this cycle
Explain what happens in S-Phase?
DNA is synthesised
What is S phase promoted by?
promoted by cyclin A and CDKs
What does the S phase end with?
Two identical daughter copies
What is the G2 phase about ?
cell prepares for division and this period ends with the breakdown of nuclear membrane and onset of chromosome condensation
What is G2 phase controlled by?
Cyclin B and CDKs
What happens after G2 phase?
Mitosis and cytokinesis
Name the different phases of Mitosis?
Prophase
Prometaphase
Metaphase
Anaphase
Telophase
(Cytokinesis)
What happens in Prophase?
Nuclear membrane disintegrates
chromosomes first visualised and split into longitudinally into 2 chromatids
What happens in the Prometaphase?
Nuclear membrane and nucleolus disappear
Chromosomes are entangled in a meshwork of continuous microtubules
What happens in Metaphase?
Chromosomes align at the metaphase plate.
Colchicine arrest: cell division at metaphase prevents the formation of microtubules of the spindle
What is the role of colchicine?
arrests the cell division at metaphase
prevents the formation of microtubules of spindle
What can colchicine be used for?
karyotyping
cytotoxic drugs in cancer therapy
What happens in Anaphase ?
Spindle fibres contract, causing the sister chromatids to separate and reach the opposite poles of the cell
What is the end result of Anaphase?
Two identical complete chromosomes
What is non-disjunction?
when one or more chromosomes fail to migrate properly in anaphase, so one daughter cell receives extra chromosomes and the other is deficient in chromosomes
What are Isochromosomes?
the formation of two daughter cells of unequal length due to the centromere splitting transversely instead of longitudinally
What happens in Telophase?
nuclear membrane reforms and nucleolus appears
Cytoplasm divides and two complete cells are formed
What is cytokinesis?
the cleavage furrow develops around the equator region and daughter cells separate
What happens in the G0 phase?
The cell is resting
What is the role of the nucleus?
Store DNA
Protect DNA
Regulate what enters and exits cells
Plays a role in DNA processes
Regulate cell division
Regulate immune response
What does the cytoskeleton do?
allows movement of organelles and of the cell itself, gives shape and can change shape
involved in cellular movement
involved in cell division and muscle contraction
What is the cytoskeleton?
a network of proteins within the cell that determines shape and fluidity of cell
What is the result of the mitotic cell division?
Two genetically identical daughter cells
Describe the different stages in mitosis in short form?
Prophase: Chromosomes condense and spindle fibers form.
Metaphase: Chromosomes align in the center of the cell.
Anaphase: Sister chromatids are pulled apart to opposite sides of the cell.
Telophase and Cytokinesis: The cell divides its cytoplasm, forming two new daughter cells.
What are the 4 basic tissue types?
Epithelial
Connective
Muscle
Nervous
What are common features of epithelial cells?
strong adhesion between epithelial cells
minimal intercellular space
formation of sheets of cells
What other features do epithelial cells have ?
have a basal surface(basal laminae) which is a layer of the extracellular matrix components
What do cells attach to?
cells attach to the basal laminae and vary in size, shape, orientation and function
What do epithelial cells cover ?
cover surfaces of the body, lines, hollow organs and forms glands
