Human Nutrient Use and Metabolism Flashcards
1
Q
Energy through eating
A
Eat food –> Digest food –> Food molecules are transported to cells, where cellular respiration takes place –> Energy currency is produced
2
Q
Carbohydrates
A
- Digested into small pieces, either glucose or a sugar that is easily converted to glucose, then absorbed into blood
- Can only be stored in limited quantities, o the body is eager to use them for energy
3
Q
Storage of carbohydrates
A
- liver stores some of the excess (as glucose and glycogen) for distribution between meals
- Also stored in muscle and nervous tissues
4
Q
Function of fats
A
Long-term energy storage and insulation
5
Q
Function of Sterols
A
Regulate growth and development
6
Q
Function of phospholipids
A
Form the membranes that enclose cells
7
Q
Fats/Lipids
A
- Broken down into fatty acids, which can travel in the blood freely or associated with protein
- If not needed, stored as triglycerides in fat cells
- Typically provide more than half of the body’s energy needs
- Excess carbs also stored as fatty acids
8
Q
Proteins
A
- Broken down into amino acids that are then used to build new proteins
- When there is a shortage of fats or carbs, proteins can also yield energy
9
Q
Nutrients
A
- Carbs and fats will be used primarily for energy
- Proteins from food are broken down to provide amino acids for proteins
10
Q
Anabolism
A
-Synthesizing large molecules from small ones
11
Q
Catabolism
A
Breaking down complex molecules to simpler ones
12
Q
Gluconeogenesis
A
Synthesis of glucose from a non-carb precursor
13
Q
Glycogenesis
A
Synthesis of glycogen from glucose
14
Q
Lipogenesis
A
Excess glucose converted to fat
15
Q
Lipolysis
A
Breakdown of stored fats into glycerol and fatty acids
16
Q
Ketogenesis
A
Production of ketone bodies from breakdown of fatty acids (from acetyl CoA)
17
Q
Catabolic-Anabolic Steady state
A
Dynamic state in which organic molecules (except DNA) are continuously broken down
18
Q
Nutrient pools
A
- Stores of amino acids, carbs, and fats
- Pools are interconvertible because pathways are linked by common intermediates
- Amount and direction of conversion are directed by liver, adipose tissue, and skeletal muscle
19
Q
Amino acid pools
A
-Bodys total supply of free amino acids
-Pool is the source for:
-Resynthesizing body proteins
-Forming amino acid derivatives
Gluconeogenesis
20
Q
Carbohydrate and fat pools
A
-Carbs and fats are easily interconverted through key intermediates
- Two major differences between carb/fat pools and amino acid pool:
- Fats and carbs are oxidized directly to produce energy in mitochondria
- Amino acids must be first converted to a citric acid cycle keto acid
-Excess carb and fat can be stored as such (amino acids are not stores as proteins)
21
Q
Absorptive state (fed state)
A
- Youve just eaten a meal, you want to use what you need for energy production and save the rest
- last for about four hours after eating, when absorption of nutrients from digestive tract to cells is occurring
- Anabolism exceeds catabolism
- Excess nutrients are stored as fats, and to a lesser extent carbs, if not used
22
Q
Postabsorptive state
A
Youre in between meals but still need energy, now you want to use what youve stores
23
Q
Absorptive state Carbs
A
- glucose is major cellular energy fuel
- Can be converted in liver to glycogen or fat
- Glycogen remains in liver, but fat joins protein to form very low density lipoproteins (VLDLs) released to blood for storage by adipose (fat) tissue
- Glucose in blood enters cells; excess stored as glycogen in muscles or fat in adipose cells
24
Q
Absorptive state Triglycerides
A
- Triglycerids are used for energy by adipose tissue, liver, and skeletal and cardiac muscle
- Most glycerol and fatty acids are converted back to triglycerides for storage
25
Absorptive State Amino acids
- Some absorbed amino acids are de-aminated in liver
- Removal of amino group produces keto acids that can be used in citric acid cycle for energy
- Most amino acids are used for protein synthesis
26
How is homeostasis maintained/How is everything integrated
Nervous system - Autonomic system
27
Sympathetic nervous system
- Arouses body for "fight or flight"
| - Neurotransmitter released by sympathetic neurons is norepinephrine (similar to adrenaline)
28
Parasympathetic Nervous system
- Predominates during relaxation, "rest and digest"
| - Neurotransmitter is acetylcholine, same neurotransmitter used at neuromuscular junction
29
Endocrine system
- Hormones involved in blood glucose regulation
- Insulin and glucagon
- Both produced by pancreas
30
Hormonal control of the absorptive state
-Primarily by insulin
- Insulin secretion by beta cells of pancreas is stimulated by:
- Elevated blood levels of glucose and amino acids
- Parasympathetic stimulation
- When insulin binds to membrane receptors, it facilitates diffusion of glucose into muscle and adipose cells (GLUT-4 transporter)
- Brain and liver take up glucose without insulin
- Consider why this is important
31
Pancreas
-Produces insulin to allow cells to take up glucose
32
Hormonal control of the absorptive state
- Insulin is a hypoglycemic hormone that enhances:
- Glucose oxidation for energy
- Glycogen and triglyceride formation
- Active transport of amino acids into cells
- Protein synthesis
-It also inhibits glucose release from liver and gluconeogenesis
33
Post-Absorptive state (Fasting state)
- When GI tract is empty and energy sources are supplied by breakdown of body's reserves
- Catabolism exceeds anabolism
- Goal is to maintain blood glucose between meals by:
- Making glucose available to blood
- Promote use of fats for energy
- Glucose sparing saves glucose for organs that need it most, such as brain
- Modulation of insulin effects after a high protein, low-carbohydrate meal
- Insulin responds to high amino acid blood levels; if high-protein meal is consumed, hypoglycemic conditions may result-not good for brain
- Glucagon modulates effect ensuring adequate blood glucose
34
Sources of blood glucose
- Glycogenolysis in liver: first resuerve used
- Glycogenolysis in skeletal muscle: before glucose from liver is exhausted, glycogen stores in skeletal muscles start to break down
- Lipolysis in adipose tissues and liver
- Glycerol used for gluconeogensis in liver
- Catabolism of cellular protein
- Major source during prolonged fasting, glycogen and fat stores exhausted; limited amount of protein can be broken down before damage
- Amount of fat in body determines how long a person can survive without food
35
Glucose sparing
- During prolonged periods of fasting, body uses more non-carbohydrate sources to conserve glucose
- More fat and protein are converted to intermediates that can enter citric acid cycle
- Brain uses bulk of glucose while other body cells switch to fatty acids as fuel source
- Results in production of ketone bodies
- After 4-5 days without food, brain will start to also use ketone bodies as fuel
36
Hormonal and neural controls of the post-absorptive state
- sympathetic nervous system interacts with several hormones to control events of post-absorptive state
- More complex than absorptive state, which only uses one hormone, insulin
-Triggered by reduced insulin release as blood glucose levels drop
37
Glucagon
Hyperglycemic hormone whose release is stimulated by:
- Declining blood glucose levels
- Rising amino acid levels
- Glucagon promotes:
- Glycogenolysis and gluconeogenesis in the liver
- Lipolysis in adipose tissue, causing fatty acids and glycerol to be released
38
Post-absorptive state, sympathetic nervous system
- Adipose tissue is innervated by sympathetic nervous system
- --can quickly supply glucose if blood levels are low
- Low plasma glucose, fight-or-flight response, or exercise can trigger fat mobilization and glycogenolysis
- --initiated by sympathetic nervous system and epinephrine from adrenal medulla
39
Diabetes Mellitus
-Inadequate insulin production (Type 1) or abnormal insulin receptors (Type 2)
Results in:
- -Unavailability of glucose to most body cells
- Excessively high blood glucose levels (hyperglycemia)
- Glucose loss in urine
Fats and proteins are used for energy instead
- Can lead to metabolic acidosis, protein wasting, and weight loss
- May lead to coma and death
40
Type 2 Diabetes
- Insulin resistant diabetes
- Insulin levels often normal (sometimes high) but insulin receptors do not respond to it
- May be some genetic association but more related to lifestyle
