Molecular Cell Biology- Cells and their Organelles: stem cells Flashcards Preview

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Flashcards in Molecular Cell Biology- Cells and their Organelles: stem cells Deck (36)
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1
Q

Single celled organisms

A

Bacteria, some free-living eukaryotes such as yeast and protozoa

2
Q

Apical

A

Oriented towards the lumen

3
Q

Basal/basolateral

A

Oriented away from lumen

4
Q

What does it mean when it is said that cells are polarised?

A

They have apical and basal polarity

5
Q

Differences between eukaryotic and prokaryotic cells

A

Eukaryotic cells have membrane-bound organelles in cytoplasm, eukaryotic cells are larger, eukaryotes have their DNA in the form of chromatin, eukaryotes have no cell wall and no chloroplasts (except plants)

6
Q

Microtubule

A

Gives cell structure

7
Q

Intermediate Filaments

A

Gives cell structure

8
Q

Phospholipids. Structure of hydrocarbon tails.

A

Hydrophilic heads and hydrophobic tails cause them to spontaneously arrange themselves into bilayers. Tail has a bend which is important to function of lipid

9
Q

Membrane lipid compositions and the importance of the effects of lipid composition

A

Varying lipid composition of membranes varies the physical properties of the membrane. Important because membranes fulfill many different roles in a cell so properties must vary

10
Q

Flip Flop movement (transverse diffusion) and example. How fast is the process

A

When a lipid moves from one surface to another e.g. phospholipid changing layer it is in in the bilayer. Very slow, often needs an enzyme

11
Q

Flippase

A

Aids Flip-Flop movement

12
Q

What kinds of molecules is the membrane fully permeable and slightly permeable to? Give examples where necessary

A

Fully permeable to gases and small uncharged polar molecules like ethanol. Slightly permeable to small uncharged polar molecules like urea and water.

13
Q

What kinds of molecules is the membrane impermeable to? Give examples

A

Large uncharged polar molecules like glucose/fructose. Ions like K+. Charged polar molecules like proteins and amino acids.

14
Q

Cytosol

A

The aqueous component of the cytoplasm of a cell. Contains many metabolic pathways and is site of protein synthesis

15
Q

Types of proteins in a membrane and their function

A

Transporters (involved in movement of molecules across membrane), Anchors (mediators of membrane associations), receptors (for recognition and receiving chemical signals) and enzymes

16
Q

Use of H+ ions to provide energy

A

Electron transport drives pump that pumps protons across mitochondrial membrane and the proton gradient is used by ATP synthase to make ATP

17
Q

Golgi apparatus

A

Modifies, packages and sorts proteins and lipids destined for another organelle or for secretion via exocytosis

18
Q

Lysosomes, give function too

A

Cytoplasmic vesicles packed with degradative enzymes; the main sites of intracellular degradation/digestion

19
Q

Peroxisomes, give function too

A

Cytoplasmic vesicles which provide a contained environment for reactive H2O2 generation. Uses oxidation reactions. The main function of oxidation reactions in peroxisomes is the breakdown of fatty acids and toxic molecules. Detoxifies toxic substances like ethanol via catalase

20
Q

Endosomes

A

Responsible for sorting of endocytosed material

21
Q

What does the cytoskeleton consist of and what does it do?

A

Consists of actin filaments, intermediate filaments and microtubules. Pulls chromosomes apart during mitosis, supports plasma membrane, controls cell shape, enables some cells to move and drives/guides the intracellular traffic of organelles, proteins and RNA

22
Q

Actin filaments

A

Polymer of actin monomer,filament is 7 nm in diameter . Necessary for movement, can form contractile bundles and microvilli. May associate with myosin to form powerful contractile structures, carry cargo-bearing motor proteins e.g. myosin. Can grow, dissolve and reform.

23
Q

Intermediate Filaments

A

10nm diameter, made of various fibrous proteins depending on cell type (keratin in epithelial, vimentin in smooth muscle cells and white blood cells, neurofilament proteins in neurones, Lamins in nucleus). Twisted into ropes, providing tensile strength. Needed to maintain cell shape

24
Q

Microtubules

A

20nm diameter. Polymers of tubulin dimers. Organised from structures such as the centrosome. Form the spindle in mitosis. Important in cell shape and movement. Carries cargo-bearing motor proteins. They are molecular motorways, allowing proteins etc to be transported from one end of cell to the other

25
Q

Name two motor proteins and discuss how they move along microtubules

A

Dynein and kinesin. These motor proteins walk along microtubules using energy from ATP. Dynein walks towards the negative end of the microtubule and kinesin towards the positive end.

26
Q

Stem cells defining properties

A

It is not itself terminally differentiated. Immortal. It can divide without limit, when stem cell divides daughter cells can choose to either remain a stem cell or begin journey to terminal differentiation. Division slows as one gets older.

27
Q

Where are stem cells particularly needed and how do they stay undifferentiated

A

Stem cells are especially needed in areas where there is a recurring need to replace differentiated cells that cannot themselves divide. To keep stem cells undifferentiated, keep the stem cells near their stem cell niche. A stem-cell niche is an area of a tissue that provides a specific microenvironment, in which stem cells are present in an undifferentiated and self-renewable state.

28
Q

Pluripotent

A

Can differentiate into all body cells but not placental cells

29
Q

Totipotent

A

Can differentiate into any type of body cell AND placental cells. Only embryonic cells after first few divisions are considered to be totipotent

30
Q

Multipotent

A

Can differentiate into a few types of cell. More limited. Adult stem cells are multipotent. Multipotent cells only differentiate to make a specific specialised tissue

31
Q

Stem cells in the skin

A

Important in skin replacement and wound healing

32
Q

Haemopoietic stem cells

A

Differentiate into all sorts of blood cells

33
Q

Induced Pluripotent Stem Cells (IPS)

A

Adult stem cells that have been modified to behave like embryonic pluripotent stem cells

34
Q

Advantages and disadvantages of IPS

A

Cells taken from a patient should not elicit an immune response. Fewer ethical issues. Theoretically any cell type could be replaced. But more research needs to be done on developmental pathways. Transplanted stem cells may develop into cancer cells

35
Q

Necrosis (lysis)

A

A form of cell death. Cells lyse (CM ruptures) and burst. CM integrity destroyed and soluble contents are released into tissue fluids. Cell components degraded by the actions of extracellular enzymes and phagocytic cells engulf fragmentary remains. Triggers immune response (inflammation)

36
Q

Apoptosis

A

A form of cell death. The normal pathway. Signalling processes in cell activate intracellular suicide proteases which degrade intracellular structures and organelles, collapse cytoskeleton and fragment the cell into mini-cells to be engulfed by phagocytes for degradation. Apoptotic cell dies without damaging neighbours