Cell systems - HM Flashcards
What is mycoplasma?
The simplest cells, mainly bacteria, that cause disease
What helps to control stability in the fluid mosaic model?
Phospholipids having one straight leg and one kinked leg
Cholesterol
Why do animals in colder climates have more kinks in their phospholipid tails?
Because they make the membranes more fluid as they destabilise the ordered structure of the membrane
What do enzymes do to the transition states that lowers the activation energy?
Makes the transition state more stable so needs less energy to reach it
How does penicillin act as a competitive inhibitor?
It mimics the transition state of bacteria
It fits into the active site of beta lactamase enzyme
Bacteria cant bind to make cell walls
What makes up antifreeze?
Ethylene glycol
How does giving alcohol or fomepizole treat antifreeze poisoning?
ADH enzyme converts glycolic acid to oxalic acid which is toxic. These compete to bind to the ADH enzyme and inhibit it
How can enzymes be used in diagnosis?
They shouldn’t be in blood so can indicate cell damage and can show specific places
WHat are the different types of plasma membrane proteins?
Channels Voltage-gated channels Transporters Active transporters Receptors Adhesion proteins
What makes it hard or bacteria to become a complex organism?
Cell wall
What are the subunits of intermediate filaments?
Alpha protein molecules
What are the names when intermediate filaments come together?
Dimers - two strands come together head to head
Tetramers - when the dimers come together head to tail
What are 2 examples of intermediate filaments?
Keratin
Actin
What are desmosomes?
They stick/connect cells together
What are hemidesmosomes?
Connect the cells with the connective tissue
What is the function of keratin?
Supports epithelial cells
Where is keratin found in the cell?
Links organelles to the desmosomes
Provides supports and transfers stresses between all the cells
What happens when there are defects in keratin?
Causes epidermolysis bullosa simplex
Skin rips and blisters easily
What is the structure of an actin filament?
Double stranded helix
What does actin that’s not in muscles do?
Can disassemble and move to different places and then reassemble and change the shape of the plasma membrane
What is actin involved in?
Moving
Phagocytosis
Cell division/cytokinesis
Provides strength to the membrane
What is the cortical actin cytoskeleton?
Mesh of actin under the plasma membrane that makes it strong eg. for RBCs
What are microtubules made of?
Tubulin subunits that from a helical structure with a hollow middle
What are the functions of microtubules?
Move and position things in the cell - ‘Railway network’
Mitotic spindles form centrosomes
Where are microtubules made?q
In the MTOC - microtubule organising centre
These also split in mitosis to form centrosomes
What is the structure of collagen?
3 collagen protein chains wound into a triple helix for strength
What does collagen 1 make up?
Skin, tendons, organs, bone, scar tissue
What does collagen 2 make up?
Cartilage
What does hydroxylation of collagen do?
Strengthens the links between the collagen chains
What is the repeating motif in collagen?
Glycine - proline - X
What is a cofactor for the hydroxylase enzymes?
Vitamin C
What happens in hydroxylation?
Prolyl hydroxylase converts proline to hydroxyproline
Lysyl hydroxylase converts lysine to hydroxylysine
What does vitamin C deficiency cause?
Weakened collagen structures so scurvy
What is glycosylation of collagen and when does it happen?
The addition of carbohydrates to hydroxylysine to form procollagen. It happens after hydroxylation.
What happens after glycosylation of collagen?
A triple helix of procollagen if formed
What happens after the triple helix of procollagen is formed?
The structure is secreted in a vesicle and collagen peptidase cuts off the ends
Why is the procollagen structure secreted in a vesicle?
To stop procollagen forming inside the cell
How are collagen fibres arranged?
In skin - different direction
In tendons - same direction
What is the main protein in milk?
Casin
What do osteoblasts do?
Turn cartilage to bone
What causes growth plate ossification?
Puberty
Mechanical jarring
What is chondrodysplasia and why does it occur?
A form of dwarfism, caused by FGF3 gene converting growth plate to bone too fast
What do osteoclasts do?
Degrade bone
How do osteoclasts attach to the bone surface and why?
Integrin interactions
Prevents digestive enzymes leaking
How do osteoclasts degrade bone?
They release lysosomes and H+ and Cl- ions
Why degrade bone?
In healing when an overgrowth occurs
To make sure the osteons are all facing the right way for impact
How does the parathyroid hormone control bone density?
It controls blood Ca2+ levels by increasing osteoclast activity to release more Ca2+ form the bones
What is the hormone that antagonises PTH and how does it control bone density?
Calcitonin, it decreases osteoclast activity
How does vitamin D affect bone density?
Increases osteoclast numbers and promotes calcium uptake from the intestines
How does oestrogen affect bone density?
It inhibits osteoclast activity and promotes osteoblast activity
What causes osteoporosis?
Less oestrogen so less osteoblasts so loss in bone density
What is the equation for animal size?
Animal size =(cell size x cell number) + amount of ECM
What are the hormones that control growth?
Hypothalamus releases GHRH (growth hormone releasing hormone)
Pituitary releases GH
Liver releases IGF-1
(insulin like growth factor)
What causes giantism?
Overproduction of growth hormone in childhood
What causes growth hormone deficiency dwarfism?
Damage to the pituitary gland
Can now be treated
What is IGF-1?
A growth hormone that binds to receptors
How does IGF-1 control cell growth?
Binds to receptor
Triggers conformational change
Activates Akt
Akt activates mTORC1
What is quiescent?
Resting phase of cell cycle - G0
What triggers cells to exit G0?
Mitogens
What is increased cell size called?
Hypertrophy
What is increased cell number called?
Hyperplasia
What hormone antagonises cell growth by inhibiting Akt?
Myostatin
What else can reduce growth?
Limited amino acid availability in childhood
Epigenetic changes in maternal nutrition
What is apoptosis?
Controlled cell death
What is the enzyme that digests the cell contents in apoptosis?
Caspase
What are the cell contents packaged into in apoptosis?
Blebs
What happens to the plasma membrane in apoptosis?
The lipid phosphatidylserine is flipped to the outside
