Lecture 2: Cells, Tissues, Membranes

Question 1

Plasma membrane

Answer 1

• phospholipid bilayer

- polar head, non-polar tails

Question 2

Passive transport mechanisms

Answer 2

• simple diffusion = small, nonpolar solutes, e.g. oxygen
• facilitated diffusion = small, charged or polar solutes, moves with assistance of plasma membrane proteins
• osmosis = passive movement of water through membrane or aquaporin

Question 3

Types of facilitated diffusion

Answer 3

• channel mediated = water filled protein channel specific to one type of ion
• types = leak channel (always open), gated channel (stimulus to open)
• carrier mediated = carrier proteins to move small polar molecules (e.g. simple sugars, amino acids)

Question 4

Active transport mechanisms

Answer 4

• primary = against concentration gradient due to ion pumps
• secondary = moves against gradient due to movement of a second substance down gradient (symport - same direction, antiport - opposite direction)

Question 5

Vesicular transport mechanisms

Answer 5

• exocytosis = cell to interstitial fluid, vesicles from golgi apparatus fuse with membrane
• endocytosis = cell takes contents from outside

Question 6

Types of endocytosis

Answer 6

• phagocytosis = vesicle fuses with lysosome, lysosome breaks down particle
• pinocytosis = membrane folds inward and engulfs fluid
• receptor-mediated = receptors bind with molecules and folds inwards

Question 7

Function of a cell

Answer 7

• separate internal from external environment
• move molecules in and out (i.e. get nutrients, get rid of waste)
• communicate
• integrate into a tissue
• use energy, store energy
• make molecules, transform molecules
• move

Question 8

Elements of a cell

Answer 8

• cytoplasm = water (70-80%), ions
• organelles = proteins (10-20% - structure and function), lipids (insoluble, form membranes), carbohydrates (energy production)
• genetic material = nucleic acids

Question 9

Nucleus

Answer 9

• control centre for cell metabolism and reproduction

- stores genetic information (DNA → encodes genes → instructions for making proteins)

Question 10

Ribosomes

Answer 10

• made in the nucleolus
• form in the cytoplasm
• site of protein synthesis

Question 11

Endoplasmic reticulum

Answer 11

• rough ER (proteins)
• rough → ribosomes
• smooth ER (lipids)

Question 12

Golgi apparatus

Answer 12

• folding and packaging of proteins
• proteins packaged into vesicles
• located next to ER and near cell nucleus

Question 13

Transport vesicles

Answer 13

• transport proteins for cell membrane (receptors, transporters)
• constitutive secretion
• unregulated membrane fusion

Question 14

Secretory vesicles

Answer 14

• proteins released into extracellular space

- regulated → only preceding with a specific stimulus

Question 15

Lysosomes

Answer 15

• analogous to GI system → digestion of metabolites, debris, invades
• contains own plasma membranes
• encloses hydrolytic enzyme mixture (acidic environment can break down nucleic acids, polysaccharides)

Question 16

Mitochondria

Answer 16

• energy production → glucose + oxygen = ATP
• two membranes → inner folded membrane in interior matrix
• increases surface area for oxidative phosphorylation

Question 17

Cytoskeleton

Answer 17

• polymerization at one end, depolymerization at the other end
• provide tracks for vesicles and organelle transport
• microtubules = hollow, support compression
• intermediate → rope-like, flexible, mechanical strength in tension
• microfilaments/actin = mechanical support for maintaining/changing cell shape

Question 18

Types of junctions

Answer 18

• tight junctions = interlocking junctional proteins, impermeable barrier, e.g. sheets of epithelial tissues
• anchoring junctions = bind to adjacent cells through cadherins (e.g. skin, uterus, heart)
• gap junctions = allow ions and small molecules to pass for intercellular communication

Question 19

Extracellular matrix

Answer 19

• structural proteins = collagen (strength), proteoglycans (compliance, shock absorption), elastin (elasticity)
• adhesive proteins = bind matrix together (fibronectin, laminin)
• transmembrane proteins (integrins)

Question 20

Functions of ECM

Answer 20

• structural integrity
• growth factor regulation
• cell-matrix interactions
• proteolytic turnover
• cellular responses