Week 2 Lecture 4 Cell Physiology

Question 1

Active transport

Answer 1

Moving solutes against there concentration gradient

Requires energy
-primary active transport- hydrolysis of ATP
-secondary active transport - energy in an ion concentration gradient

Question 2

Primary active transport

Answer 2

Energy from ATP hydrolysis

Change the shape of a carrier protein

Pump the solute across the membrane against its concentration gradient

40% of the ATP in a cell is generated on primary active transport.

Question 3

Sodium-potassium pump

Answer 3

• Move Na+ into the extracellular fluid
• Pump against 3 Na+ gradient
• Move 2 K+ into the cytosol
• Pump against K+ gradient
• Leak back down their electrochemical gradients
Open on inside so sodium can bind

Question 4

Na+- K+- ATPase

Question 5

Secondary active transport

Answer 5

-Uses the energy stored in a Na+ or H+ concentration gradient
• Move solutes against their concentration gradient
• Indirect use of ATP
Ions in high concentration have high kinetic energy
N
• Steep Na+ concentration gradient (sodium-potassium pump)
• Na+ ions have potential energy
• Na+ ions leak back in
—Stored energy converted to kinetic energy
— Moves substances against their concentration gradient

Question 6

Secondary active transport pt 2

Answer 6

• Carrier protein binds Na+ and other substance simultaneously
• Protein changes shape so both substances cross the membrane simultaneously

Question 7

SYMPORTERS

Answer 7

Move substances in same direction

Carrier proteins, specific binding sites, a comfermational change in shape to allow transport

Question 8

ANTIPORTERS

Answer 8

Move substances in opposite direction

Question 9

Clinical relevance

Answer 9

• Digitalis [medication] for heart failure
• Slows the sodium-potassium pump, not at steep concentration gradient
• Na+ accumulates in the heart muscle – decreased concentration gradient
• Na+ - Ca2+ antiporters slow and calcium accumulates
• Increases force of muscle contraction

Question 10

Vesicle transport

Answer 10

• Endocytosis
—Movement into a cell
—Vesicle from plasma membrane- pull it into cell

• Exocytosis
—Movement out of a cell
—Intracellular vesicles fuse with plasma membrane
Release something out of the cell
• both Active process requiring ATP

Question 11

Endocytosis

Answer 11

• Receptor-mediated endocytosis
• Highly selective
• Specific ligands
• E.g. LDLs, transferrin, some vitamins

• Old cells, viruses, bacteria
• Phagocytes (macrophages or neutrophils)

Question 12

Phagocytosis

Answer 12

• Old cells, viruses, bacteria
• Phagocytes (macrophages or neutrophils)

Question 13

Bulk-phase endocytosis

Answer 13

• Pinocytosis
• Take up of extracellular fluid

Question 14

Exocytosis

Answer 14

• Release material from a cell
• Secretory cells – enzymes,
hormones, mucus
• Nerve cells – neurotransmitters
• Waste
• Intracellular secretory vesicles

Question 15

Transcytosis

Answer 15

• Transport molecules across a cell
• Endocytosis and exocytosis
Eg GI tract for absorbotion

Question 16

Cytoplasm pt1

Answer 16

Cytoplasm – cell contents between membrane and nucleus
• Cytosol
—Intracellular fluid
—55% of cell volume
—75 – 90% water with dissolved/suspended contents

• Organelles
—Specialised structures
—Characteristic shapes
—Specific functions in growth, maintenance and reproduction

Question 17

Cytoplasm pt 2

Answer 17

• Cytoskeleton
Hold organelles where they need to be
• Protein filament network
• Cell shape and organisation
• Movement

• Microfilaments =smallest
• Intermediate filaments= middle
• Microtubules=largest

Question 18

Cytoplasm pt 3

Answer 18

• Microfilaments edge of the cell
• Actin and myosin
• Most prevalent at the cell edge
• Movement and mechanical support
Micro Lili = increase SA

• Intermediate filaments, hold different organelles in shape
Internal structure
• Thicker than microfilaments
• Stabilise position of organelles
• Cell to cell attachment keeping cells together

Question 19

Cytoplasm pt 4

Answer 19

• Microtubules
• Largest cytoskeleton components
• Unbranched hollow tubes
• Tubulin
• Cell shape and organelle movement
Hold entire cell shape
Much stronger

Question 20

Ribosomes

Answer 20

• Sites of protein synthesis
• High content of ribonucleic acid
• Two subunits large and small subunits
• Attached to the endoplasmic reticulum

Question 21

Endoplasmic reticulum

Answer 21

• Network of membranes as flattened sacs

Increase sa = more ribosomes = efficiency
• Rough ER
• Ribosomes embedded
• Secretory, membrane and organellar proteins
• Glycoproteins and phospholipids

Smooth ER
• Enzymes
• Fatty acids and steroid synthesis
• Detoxify drugs
• Repeated exposure to drug leads to tolerance

Question 22

Golgi complex

Answer 22

-3 to 20 saccules
• Modify, sort and package proteins
• Entry face – receives & modifies proteins from RER
• Intermediate saccules add carbohydrates or lipids
• Exit face – further modification, sorts and packages for destination

Question 23

Lysosomes

Answer 23

• Digestive & hydrolytic enzymes
• Digest substances that enter via endocytosis
Old organelles or entire cells
• Autophagy
• Autolysis
• Extracellular digestion
• Acidic pH 5

Question 24

Peroxisomes

Answer 24

• Contain oxidases (remove H atoms)
• breaking down Amino acids, fatty acids into component parts
• Toxic substances e.g., alcohol

Question 25

Mitochondria

Answer 25

• ATP generation through respiration
• High number in muscles, liver and kidneys
• High surface area
• Apoptosis cell death