Cell systems - HM Flashcards by Mary Tilling

What is mycoplasma?

The simplest cells, mainly bacteria, that cause disease

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What helps to control stability in the fluid mosaic model?

Phospholipids having one straight leg and one kinked leg

Cholesterol

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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

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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

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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

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What makes up antifreeze?

Ethylene glycol

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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

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How can enzymes be used in diagnosis?

They shouldn’t be in blood so can indicate cell damage and can show specific places

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WHat are the different types of plasma membrane proteins?

Channels
Voltage-gated channels
Transporters
Active transporters
Receptors
Adhesion proteins

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What makes it hard or bacteria to become a complex organism?

Cell wall

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What are the subunits of intermediate filaments?

Alpha protein molecules

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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

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What are 2 examples of intermediate filaments?

Keratin

Actin

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What are desmosomes?

They stick/connect cells together

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What are hemidesmosomes?

Connect the cells with the connective tissue

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What is the function of keratin?

Supports epithelial cells

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Where is keratin found in the cell?

Links organelles to the desmosomes

Provides supports and transfers stresses between all the cells

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What happens when there are defects in keratin?

Causes epidermolysis bullosa simplex

Skin rips and blisters easily

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What is the structure of an actin filament?

Double stranded helix

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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

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What is actin involved in?

Moving
Phagocytosis
Cell division/cytokinesis
Provides strength to the membrane

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What is the cortical actin cytoskeleton?

Mesh of actin under the plasma membrane that makes it strong eg. for RBCs

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What are microtubules made of?

Tubulin subunits that from a helical structure with a hollow middle

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What are the functions of microtubules?

Move and position things in the cell - ‘Railway network’

Mitotic spindles form centrosomes

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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

Cell systems - HM Flashcards

(67 cards)