Week 7: Cellular Respiration/Energy Metabolism

why cells need energy

• metabolism

• movement

• growth

• cell division

• action potentials

ATP

• universal energy currency

cellular respiration

process of nutrient breakdown with accompanying ATP synthesis

redox reactions

• reduction

• oxidation

reduction

• gain in electrons

oxidation

loss of elections

NADH+

becomes reduced to NADH

• picks up 1 hydrogen

FAD

becomes reduced to FADH2

• picks up both hydrogen

summary reaction for cellular respiration

C6H12O6 + 6O2+ 32 ADP + 32 Pi

→ 6CO2 + 6H2O + 32 ATP

glycolysis

• stage 1 of glucose catabolism

• in cytoplasm

• converts glucose molecule (6C) into two pyruvic acid (pyruvate) molecules (two 3C)

• NET TOTAL FROM 1 GLUCOSE: 2 PA, 2 ATP, 2NADH + 2H+

pyruvate oxidation

• stage 2 of glucose catabolism

• formation of acetyl coA in mitochondria

• pyruvic acid is transported and oxidized further

• ea. p molecule → acetyl coA

• in ea. process of pyruvic acid oxidation, 1 CO2 and 1 NADH is produced

• NET TOTAL FROM 2 PYRUVIC ACID: 2 acetyl coA, 2 CO2, 2 NADH + H+

kreb’s cycle

• stage 3 of glucose catabolism

• also known as citric acid cycle

• circular pathway

• occurs in mitochondria

• citrate is formed, oxoloacetate is regenerated

• acetyl coA is converted into 2 carbon dioxide molecules

• NET TOTAL FROM 2 ACETYL COA: 4CO2, 2 ATP, 6NADH + 6H, 2FADH

electron transport chain

• stage 4 of glucose catabolism

• located on the inner mitochondrial membrane

• NADH passes its electrons at the beginning of ECT (complex I) → yields 2.5 ATP

• FADH2 passes its electrons later down the chain (complex ii) → yields 1.5 ATP

• oxygen = final electron acceptor

chemiosmosis

the use of a hydrogen ion gradient to make ATP

anaerobic respiration

• conversion of pyruvate to lactate regenerates NAD+, allowing glycolysis to continue

• 2 ATP molecules produced

postabsorptive state

fasting state

absorptive state

shortly after eating, nutrients are being absorbed and glucose is used for energy

glucose

→ glycogen

triglycerides

excess glucose, lipids

proteins

→ used for protein synthesis

carbohydrate metabolism

• first and usual energy source for most tissues

• blood glucose and glycogen sufficient for one day

when glucose is in excess

• glycolysis: glucose broken down to make energy

• glycogenesis: making glucose from noncarbohydrate sources

when glucose is at low levels

• gluconeogenesis (liver only)

• glycogenolysis: breaking down glycogen into glucose

lipid metabolism

• triglycerides are primarily long term energy storage molecules

• used when glucose levels fail

  • except for the brain, which cannot use fatty acids

liver

brain relies on glucose, so when glucose runs low:

makes glucose for the brain during gluconeogensis

also makes ketone bodies (during ketogenesis) - provides energy for the brain

what organ is responsible for this?

protein metabolism

• not stored in the body for energy (used for something)

• can be catabolized for energy

  • acetyl coA, gluconeogenesis

• stored as fat

fasting

glycogen is first broken down to glucose

• lipids are then broken down into glycerol and fatty acids, which are oxidized for energy

• protein breakdown starts to occur

ketone bodies

• acidic, increases acidity of blood

• accumulation leads to ketoacidosis, can be deadly

ketoacidosis

• result of starvation

• lack of carbohydrates in the diet

• uncontrolled diabetes mellitus