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Flashcards in Metabolism Deck (10)
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1

WHY DO WE EAT AND DRINK?

- To make up for water we lose every day
- Supply building blocks for cells and tissues
- Supply atoms and molecules body can’t make and supply fuel to for energy (ATP)

2

ATP (Adenosine triphosphate)

- Breakdown of nutrients (glucose, fatty acids, some amino acids) releases energy used to make ATP from ADP
- ATP is major way that energy is stored in cells
- Breakdown of ATP to ADP releases energy the cells need to do work

3

DIGESTION AND ABSORPTION AND BLOOD NUTRIENT LEVELS

- Digestion/absorption of water and food occurs in GIT→ then water and individual nutrients go to circulatory system
- After a meal→ concentration of nutrients is elevated
- Don't eat all the time but cells are using nutrients all the time; without continual supply→ levels drop
- Body needs to ensure blood nutrient levels don't stay high but also don't drop below cell requirements

4

REGULATION OF BLOOD NUTRIENT LEVELS

- 2 metabolic states of body responses to changes in blood nutrient levels:
- Absorptive state→ first few hours after a meal
- Post- absorptive state→ hours before lunch, before dinner and overnight

5

THE ABSORPTIVE STATE

- Rise in blood nutrient levels (particularly glucose) stimulates insulin secretion→ leads to;
- Increases glucose uptake and consumption by cells
- Storage of excess glucose as glycogen (liver and muscles)
- Conversion of excess glucose to fatty acids that can be used for triglyceride production (adipose tissue)
- Increased amino acid uptake by cells for use in protein synthesis
- Net result→ restores blood glucose and other nutrients back to homeostatic level

6

BETWEEN MEALS→ WITHOUT MEALS

- Between meals→ body cells continue metabolising; body draws on fat reserves
- If time to next meal is extended; ration glucose available and make more glucose
- With prolonged fasting/starving→ ketones become major fuel

7

POSTABSORPTIVE (1) RAISING BGL AND GLUCOSE SPARING

- Glucose breakdown and reduced glucose consumption in liver→ rapid increase in blood glucose level (BGL)
- Increased amino acid uptake by liver→ used to make glucose→ further increases BGL

8

USING FATTY ACIDS TO MAKE ATP

- Glucose not immediately used by cells→ stored as glycogen
- Glucose used to form fatty acids→ can be stored as triglycerides
- When needed→ triglycerides can be broken down to fatty acids
- Some cells can consume fatty acids to make ATP
- Increased fatty acids supply as an alternative fuel for those organs which can use them

9

FATTY ACIDS AND KETONES

- During long periods of fasting or starvation→ ability to maintain BGL is lost
- In these circumstances→ fatty acids are used to make ketones/ketone bodies
- Organs that cannot use fatty acids to make ATP (e.g. brain) rely on ketone instead during fasting

10

USING GLUCOSE TO MAKE ATP

- Central to use of nutrients to make ATP is breakdown of glucose; 2 stage process
- Glycolysis produces some ATP and doesn't require oxygen
- Cellular respiration produces much more ATO and requires oxygen and generates CO2

This means a big demand for ATP that can only be provided by cellular respiration; which means
- Need for regular refuelling
- Constant demand for oxygen
- Constant need to remove excess carbon dioxide