Animal and Human Cell Biology 2 Flashcards
How much of our body is muscle?
40%, 12-15% is actin
Describe structure of muscle,
Sarcomere, muscle fibril, muscle cell
What are thick filament?
myosin - bridges are myosin hats that interact with actin
Myosin II cannot move by itself - held together by tail
Head doesn’t affect what the myosin does
What are thin filaments?
actin
What blocks interaction in relaxed muscle
Tropomyosin between myosin head and actin
How is contraction controlled?
stimulus from neutron spreads over the plama membrane of the muscle cell- its depolarised
Depolarisation released calcium from ER into the cytoplasm
Calcium binds to troponin complex changing the shape and released the block of myosin binding site on actin
Myosin binds actin and walks towards the Z disk
Actin uses ATP for this
How is contraction controlled?
Calcium is removed by pumps and myosin released the actin filament and troponin returns
Describe cardiac muscle
less ordered but the structural and mechanistic principles are the same
What do cardiac myocytes undergo?
spontaneous contractions
Flagellum
One or few per cell
Function in cell locomotion
10-40 beats
Propeller like motion
Cilium
Usually many per cell Function in fluid and particle transport Move liquid within the body 12-20 beats Back and forth motion
What is the axoneme
the core of the cilium/flagellum made from microtubules
What do centrioles participate in?
Microtubule formation in interphase
What do microtubules consist of
protofilaments
How many microtubules in the standard cilium?
9
What is the ultrastructure of cilium?
Outer (3 heads)and inner (1 or 2 heads) arm dynein, radial spoke
Which motor structure was first discovered?
dynein
Experiment for discovering dynein
Dyneine slide microtubules against each other
motor activity against the protein bridges between the tubules causing bending
Which cells form a non motile primary cilium?
enthotheicla cells
detect signals that govern proliferation
sense flow and bending - triggers various regulation pathways
primary cilia are essential
Non-motile cilia in human body?
Inner ear, kidney, bile duct, pancreas, bone, eye
Describe non-motile cilia
Don’t beat, done have dynein and don’t have central microtubule
sensing environmental cues
How do non motile cilia detect cues?
stimulus results in membrane depolarisation
Rods and cones
modified cilia
Actin organisation in a fibroblast
Stress fibre, cell cortex and filopodium
How actin nada actin binding proteins move a cell
Actin filaments push forward causing extension
Adhesion
Translocation by myosin contracting, cell body moves forward
De-adhesion so tail detaches
What does cell motility help?
Healing wounds, cells move inwards and close it through mitosis and cell growth
Organ development
Chromosome inheritance during mitosis (M phase)
Chromsome alignment, separation
Cell division (chromosome decondenses)
Microtubules make contact with chromosomes
Chromosomes are positioned in one plane
Prophase
Chromosomes condense, nuclear envelope disrupts
Spindle formed
Centrisomes duplicating
Anaphase
Microtubules and motors pull on chromosomes
Chromatids move to the poles
Rapid elongation of the spindle
Formation of a contractile ring
Telophase
Cell middle contracts and separates (cytokinesis)
Chromosomes decondense and nuclear envelope reforms
What forms the mitotic spindle?
Microtubules
What is the organisation of the mitotic spindle
Centrosome, Astral, kinetochore and polar microtubules
How can we test thet microtubules are required for mitosis
Nocodazole
Mechanisms for chromosome segregation
1: de/polymerisation of microtubules, exerts force on attached chromosomes
2: molecular motors that act on the microtubules
What are the role of motors in spindle function?
Kinesin in the middle, dynein at the end
Pulling on chromosomes exerts a polar ejection force
What is cytokinesis?
Cytoplasmic division
What are checkpoints in mitosis?
biochemical processes that recognise the status of cell and control transition from between cell cycle phases
Mitochondria
Double membrane with inner membrane folds (Cristae) and their own mitochondrial genome
Uses sugars fats and oxygen to produce ATP
Principle of oxidative phosphorylation
Uptake of food molecules from the cytosol in the matrix,
Sugar and fat metabolism
Oxidation of acetyl CoA into CO2 in Krebs cycle production of NADH
NADH transfers electrons to reparation chain at inner membrane electron flux - proton gradient
Back flow of protons drives ATP synthesis
What are acidified organelles?
end-somes and lysosomes
Describe mitochondrial own genome
DNA is circular, only 2 proteins of respiration, chain are encoded by the mitochondrial genome
Apoptosis
Cell death Multicellular organisms Followed by recycling of building blocks Stress triggers signalling Proteins cause damage to mitochondria releasing factors that activate enzymes Nucleus condenses Cells blebs Nucleus and DNA fragmentises, Phagocytosis
