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Biological Systems > Chapter 5 Cell membranes and Signalling > Flashcards

Chapter 5 Cell membranes and Signalling Flashcards

1
Q

What determines the structure and function of the cell membrane

A

Its contents - lipids, proteins and carbohydrates

Lipid molecules are phospholipids, which may vary in length, degree of saturation and kinds of polar groups present

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2
Q

What is the role of cholesterol it the cell membrane?

A

their hydroxyl groups interact with phospholipid head and modulate membrane fluidity

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3
Q

What factors affect membrane fluidity

A

Lipid composition - short unsaturated chains increase fluidity
Temperature - fluidity decreases with temperature

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4
Q

What are the two types of proteins present in the cell membrane

A

Peripheral membrane protein - lack hydrophobic group, not embedded in bilayer
Integral membrane protein - have hydrophobic lipid component (may have domains that function differently on inner and outer sides of membrane)

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5
Q

What factors restrict the movement of membrane proteins

A

Intracellular proteins and cytoskeleton attachments

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6
Q

What is the role of carbohydrates in the cell membare

A

Communication and cell adherence via carbohydrate + protein interactions

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7
Q

What are the three main types of proteins in thee cell membrne

A

Glycolipids - carbohydrate + Lipid
Glycoprotein - oligosaccharide and protein
Proteoglycan - Protein + longer carbohydrate

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8
Q

What are the differences between passive and active transport?

A

passive - does not require energy. Substance move down concentration gradient
Active- requires metabolic energy. Substances move against concentration gradient.

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9
Q

What are the 2 types of passive transport?

A

Simple diffusion through phospholipid bilayer

Facilitated diffusion through channel proteins or aided by carrier proteisn

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10
Q

What is diffusion?

A

process of random movement towards equilibrium. Net movement down a concentration gradient

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11
Q

What factors affect the speed of diffusion

A

Diameter of molecules
Temperature
Concentration gradient

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12
Q

What is osmosis and osmotic pressure

A

Osmosis - diffusion of water through special channels

Osmotic pressure - pressure that when applied to solution prevents water diffusion across a membrane

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13
Q

What molecules can pass via simple diffusion

A

O2, CO2, small, nonpolar, lipid soluble molecules

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14
Q

What is a hypertonic solution

A

Solution has higher solute concentration

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15
Q

What is turgor pressure

A

Internal pressure against a cell wall

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16
Q

What are the structures that allow faciliated diffusion?

A 
Channel proteins (less specific)
Ion channels (Specific ions)
Aquaporins (Water with concentration gradient)
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17
Q

What is the role of carrier proteins

A

speed up diffusion through channel proteins by binding to substances
Can become saturation, so rate of diffusion reaches maximum

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18
Q

Ion channels are mostly gates. What stimuli commonly activate?

A

Voltage gated

ligand gated

19
Q

What are the 2 types of active transport?

A

Primary active - involves direct hydrolysis of ATP for energy
Secondary active - uses energy from ion concentration gradient or electrical gradient

20
Q

How do cell smove large macromolecules in and out?

A

Exocytosis and Endocytosis

21
Q

How does exocytosis work?

A

Vesicle membrane fuses with the cell membrane and contents are released into the environment

22
Q

How does endocytosis work?

A

Cell membrane invaginates or folds around particles to form a vesicle that then separates from the cell membrane
- depends on receptors (integral proteins) that bind to ligand

23
Q

What is phagocytosis?

A

cellular eating
Process of specialised cell engulfing a larger particle or another cell - forms vesicle that then fuses with lysosome for digestion

24
Q

What is pinocytosis

A

cellular drinking

Smaller vesicles than in phagocytosis bring in fluids and dissolve substances

25
Q

What does receptor endocytosis do?

A

bring specific large molecules into cell via specific receptors - plays role in cell signalling and allows cells to control internal processes

26
Q

what are the receptors for endocytosis on the cell membrane called?

A

coated pits - when binds to ligand coated pit invaginates to form coated vesicle (coated with clatharin which stabilizes the vesicle, which is lost when the vesicle is inside the cell)

27
Q

What happens to receptors for endocytosis

A

recycled to cell membrane or degraded in a lysosome - controls abundance on the cell

28
Q

Cells can process external signals from their environment including:

A

heat, light and chemicals (ligands)

- Must have a receptor for the signal to respond

29
Q

What happens when a cell’s receptor is acrivated

A

Signal transduction pathway is initiated

30
Q

What are the types of signals that occur in animal cells?

A

Autrocrine - affect same cells that release them
Paracrine - diffuse to and affect nearby cells
Justacrine - requrie direct contact between signalling and responing cells

Hormones- travel to distant cells

31
Q

What are the components of a signal transduction pathway

A

signal + receptor + response

often include allosteric regulation

32
Q

What is allostreric regulation

A

Proteins change shape as a result of a molecule binding at a site other than the active site

33
Q

How are receptors classified?

A

Location

  • Intracellular (small ligands or nonpular and can diffuse across membrane)
  • Membrane (large or polar ligands)
34
Q

What type of bond is ligand-receptor bonding and why is this important

A

noncovalent and reversible

Allows for signal to stop

35
Q

How do Ion channel receptors work

A

Are ligand gated - change shape when ligand binds

36
Q

Describe the activation of protein kinase receptors

A

Ligand binds, exposes or activated cytoplasmic domain that has protein kinase acrivity - adds phosphate group to proteins

37
Q

Describe the activation of G protein-linked receptors

A

ligand binds, exposes site on cytoplasmic side that binds to mobile membrane protein (G protein)

  • Activated receptor exchanges GDP nucleotide bound to G protein for higher energy GTP protein
  • Activated protein activated effector protein à signal amplification
38
Q

What parts make up G proteins

A

receptor, effector protein and GDP and GTP (are used for energy transfer)

39
Q

Describe the process of signal transduction

A

Signal -> activated receptor -> cellular response: mediated by singal transduction pathway -> signal initiates protein interactions -> amplifies and distrubutes signal -> changes cell function

40
Q

What are the different cell responses to signals

A

Ion channels open
Altering gene expression
Enzyme activity alteration

Same signal can have different responses in different cells

41
Q

What is the role of secontary messengers for signals

A

regulate enzymes by non-covalently binding

Distribute the signal further (allow the cell to respond to single event with many events inside the cell)

42
Q

How do signal transduction pathways affect the original signal?

A

Amplify it at each step

43
Q

How is the signal transduction stopped?

A

End the signal after the cell response - transducer converted into precursor by enzymes
- Balance between regulating and signalling enzymes determines the cell’s response

44
Q

How do cells alter enzyme balance

A

Synthesis and breakdown of enzymes

activation and inhibition of enzymes

Biological Systems (20 decks)

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