Animal and Human Cell Biology 2

Question 1

How much of our body is muscle?

Answer 1

40%, 12-15% is actin

Question 2

Describe structure of muscle,

Answer 2

Sarcomere, muscle fibril, muscle cell

Question 3

What are thick filament?

Answer 3

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

Question 4

What are thin filaments?

Answer 4

actin

Question 5

What blocks interaction in relaxed muscle

Answer 5

Tropomyosin between myosin head and actin

Question 6

How is contraction controlled?

Answer 6

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

Question 7

How is contraction controlled?

Answer 7

Calcium is removed by pumps and myosin released the actin filament and troponin returns

Question 8

Describe cardiac muscle

Answer 8

less ordered but the structural and mechanistic principles are the same

Question 9

What do cardiac myocytes undergo?

Answer 9

spontaneous contractions

Question 10

Flagellum

Answer 10

One or few per cell
Function in cell locomotion
10-40 beats
Propeller like motion

Question 11

Cilium

Answer 11

Usually many per cell
Function in fluid and particle transport
Move liquid within the body
12-20 beats
Back and forth motion

Question 12

What is the axoneme

Answer 12

the core of the cilium/flagellum made from microtubules

Question 13

What do centrioles participate in?

Answer 13

Microtubule formation in interphase

Question 14

What do microtubules consist of

Answer 14

protofilaments

Question 15

How many microtubules in the standard cilium?

Answer 15

9

Question 16

What is the ultrastructure of cilium?

Answer 16

Outer (3 heads)and inner (1 or 2 heads) arm dynein, radial spoke

Question 17

Which motor structure was first discovered?

Answer 17

dynein

Question 18

Experiment for discovering dynein

Answer 18

Dyneine slide microtubules against each other

motor activity against the protein bridges between the tubules causing bending

Question 19

Which cells form a non motile primary cilium?

Answer 19

enthotheicla cells
detect signals that govern proliferation
sense flow and bending - triggers various regulation pathways
primary cilia are essential

Question 20

Non-motile cilia in human body?

Answer 20

Inner ear, kidney, bile duct, pancreas, bone, eye

Question 21

Describe non-motile cilia

Answer 21

Don’t beat, done have dynein and don’t have central microtubule
sensing environmental cues

Question 22

How do non motile cilia detect cues?

Answer 22

stimulus results in membrane depolarisation

Question 23

Rods and cones

Answer 23

modified cilia

Question 24

Actin organisation in a fibroblast

Answer 24

Stress fibre, cell cortex and filopodium

Question 25

How actin nada actin binding proteins move a cell

Answer 25

Actin filaments push forward causing extension Adhesion Translocation by myosin contracting, cell body moves forward De-adhesion so tail detaches

Question 26

What does cell motility help?

Answer 26

Healing wounds, cells move inwards and close it through mitosis and cell growth Organ development

Question 27

Chromosome inheritance during mitosis (M phase)

Answer 27

Chromsome alignment, separation Cell division (chromosome decondenses) Microtubules make contact with chromosomes Chromosomes are positioned in one plane

Question 28

Prophase

Answer 28

Chromosomes condense, nuclear envelope disrupts Spindle formed Centrisomes duplicating

Question 29

Anaphase

Answer 29

Microtubules and motors pull on chromosomes Chromatids move to the poles Rapid elongation of the spindle Formation of a contractile ring

Question 30

Telophase

Answer 30

Cell middle contracts and separates (cytokinesis) | Chromosomes decondense and nuclear envelope reforms

Question 31

What forms the mitotic spindle?

Answer 31

Microtubules

Question 32

What is the organisation of the mitotic spindle

Answer 32

Centrosome, Astral, kinetochore and polar microtubules

Question 33

How can we test thet microtubules are required for mitosis

Answer 33

Nocodazole

Question 34

Mechanisms for chromosome segregation

Answer 34

1: de/polymerisation of microtubules, exerts force on attached chromosomes 2: molecular motors that act on the microtubules

Question 35

What are the role of motors in spindle function?

Answer 35

Kinesin in the middle, dynein at the end | Pulling on chromosomes exerts a polar ejection force

Question 36

What is cytokinesis?

Answer 36

Cytoplasmic division

Question 37

What are checkpoints in mitosis?

Answer 37

biochemical processes that recognise the status of cell and control transition from between cell cycle phases

Question 38

Mitochondria

Answer 38

Double membrane with inner membrane folds (Cristae) and their own mitochondrial genome Uses sugars fats and oxygen to produce ATP

Question 39

Principle of oxidative phosphorylation

Answer 39

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

Question 40

What are acidified organelles?

Answer 40

end-somes and lysosomes

Question 41

Describe mitochondrial own genome

Answer 41

DNA is circular, only 2 proteins of respiration, chain are encoded by the mitochondrial genome

Question 42

Apoptosis

Answer 42

``` 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 ```