Week 12 - Nutrition and Metabolilsm Flashcards
1
Q
Metabolism
A
Sum of body’s chemical reactions. Series of enzyme-catalysed reactions, which include 4 basic processes
- Harnessing energy: in chemical bonds of molecules obtained from diet (nutrients); may be used to make adenosine triphosphate (ATP)
- Converting: one type of molecule into another for cell’s synthesis reactions
- Synthesising macromolecules: such as proteins, polysaccharides, nucleic acids, and lipids
- Breaking down macromolecules: into monomers or other smaller molecules
2
Q
Catabolism
A
- group of reactions where one substance is broken down into smaller parts
- EXERGONIC reactions, which releases energy
- cells can harness the energy released to drive other processes
- energy released by catabolic processes in the form of ATP
3
Q
Anabolism
A
- group of reactions which case smaller molecules to be combined to make a larger molecule
- ENDERGONIC reactions (USE energy)
4
Q
Metabolic rate
A
- total amount of energy expended by body to power all of its processes
- sum of all anabolic and catabolic reactions occurring in the body
5
Q
Basal metabolic rate (BMR)
A
- The body continues to use energy even when at rest. BMR is the minimal rate of metabolism for an awake individual at rest
Resting conditions:
- person has not eaten for the past 12 hours and has had a restful night of sleep
- person is not performing physical activity and has not performed strenuous physical activity for at least 1hr
- person is not under physical or emotional stress
- temp surrounding person is constant and comfortable
6
Q
Factors affecting total Metabolic rate and BMR
A
- pregnancy, anxiety, fever, eating, thyroid hormones, depression
- BMr varies between individuals, depending on factors such as gender and muscle mass ( skeletal muscle is a highly metabolically active tissue)
7
Q
Metabolic reactions - energy requirements
A
- energy is released from exergonic CATABOLIC REACTIONS
- this energy can be used to SYNTHESISE ATP
- when ATP is broken down, energy is released and is used to fuel endergonic ANABOLIC REACTIONS
8
Q
NUTRIENTS
A
A molecule obtained from food that body requires for its metabolic processes
WATER- essential component for multiple metabolic processes in body. broken down by enzymes through HYDROLYSIS
MACRONUTRIENTS - carbohydrates, proteins, lipids.
MICRONUTRIENTS- vitamins and minerals
9
Q
Carbohydrates
A
45-65%
humans cannot digest fibre
Polysaccharides:
- starch
- glycogen
- cellulose (fibre)
Disaccharides:
- lactose
- maltose
- sucrose
Monosaccharides:
- glucose
- galactose
- fructose
10
Q
Lipids
A
in diet includes triglycerides, cholesterol, certain vitamins
- Fats, mostly unsaturated =30% daily intake
- saturated fatty acids: mostly animal-derived products
- unsaturated fatty acids: commonly found in plant- derived products
- essential fatty acids: body is unable to sunthesize → must come from diet
11
Q
Proteins
A
Proteins & 20 amino acids
- 10-35% of daily intake is from protein-rich food
- 11 nonessential amino acids : can be synthesised
- 9 essential amino acids: must be obtained from dietary sources
12
Q
Vitamins
A
Fat-soluble: hydrophobic compounds, structurally similar to cholesterol → Vit A, D, E & K
Water-soluble: hydrophilic compounds featuring polar covalent bonds → Vit C & B
13
Q
Minerals
A
any element other than carbon, hydrogen, oxygen and nitrogen that is required by living organisms
- 7 major minerals are ions (in moderate amounts_ → calcium, chloride, magnesium, phosphorus, potassium, sodium and sulfur
10 trace minerals are ions (v small amounts) →iodine, iron & selenium
14
Q
ATP synthesis
A
- cells harness ATP energy by removing the 3rd phosphate group in a HYDROLYSIS reaction, bond between 2nd and 3rd is broken w/ a water molecule, releasing free phosphate and ADP (adenosine diphosphate)
15
Q
ATP phosphorylation
A
Process where released energy can by used by a cell
process where ATP donates a phosphate group to a reactant → reactant becomes more reactive →favours conversion of reactant to desired product
16
Q
Nutrients and ATP synthesis
A
- carbohydrates (glucose and glycogen) is the preferred source for ATP production
- breaking down glucose is a catabolic process known as GLYCOLYSIS resulting in the product PYRUVATE
- if carbohydrates in the diet do not meet metabolic demands for glucose, the body can produce glucose through non-carn sources → amino acids (proteins) & fatty acids (lipids)
- pyruvate can be used in the CITRIC ACID CYCLE (Kreb cycle) and the ELECTRON TRANSPORT CHAIN to yield more ATP molecules
17
Q
Stores and function of carbohydrates
A
- Stored in
1. muscle glycogen
2. liver glycogen
3. blood glucose - Most carbohydrate serves as FUEL for the body (ATP SYNTHESIS)
→Neurons, RBCs and kidneys depend on glucose - Sugars also serve as STRUCTURAL COMPONENTS
→ nucleic acids, glycoproteins and glycolipids, ATP
18
Q
regulation of blood glucose levels - rise
A
Stimulus: BGL rises after carb rich meal
→beta cells of pancreas release insulin into the blood
→ body cells take up more glucose & liver takes up glucose and stores it as glycogen
→ BGL declines
→ Homeostasis: BGL (70-110 mg/100ml)
19
Q
regulation of blood glucose levels- fall
A
Stimulus: BGL falls after skipping meal
→ alpha cells of pancreas release glucagon into blood
→ liver breaks down glycogen and releases glucose into blood
→BGL rises
Homeostasis: BGL (70/110mg/100ml)
20
Q
Carbohydrates absorption
A
- starts in oral cavilty when SALIVARY AMYLASE until pH drops to <4.5 in stomach
- final steps in carbohydrate metabolism in the small intestine:
→secretion of PANCREATIC AMYLASE
→ a number of enzymes from brush border of the small intestine breakdown carbohydrate into monosaccharides - in the liver excess glucose is stored as GLYCOGEN
21
Q
Glucose as a primary energy source
A
- glucose is a small, soluble molecule that is easily distributed through body fluids
- glycolysis provides a small amount of ATP ANAEROBICALLY
- unlike ATP, glucose can be efficiently stored as GLYCOGEN
- the break down of glycogen (GLYCOGENOLYSIS) occurs v quickly and involves only a single enzymatic step. mobilisation of other intracellular reserves involves much more complex pathways and takes considerable more time
22
Q
Glycolysis
A
- GLYCOLYSIs glucose is broken down in a series of 10 enzyme-orchestrated reactions that takes place in cytosol of all cells
- glucose is SPLIT into two 3-carbon sugar molecules called PYRUVATE
- the 10 reactions which take place dyring glycolysis can be condensed into two phases
1, energy investment phase
2. energy pay off phase
23
Q
Glycolysis - first phosphorylation
A
Reaction 1
glucose is phosphorylated by ATP, yielding glucose-6-phosphate and ADP
24
Q
Glycolysis - second phosphorylation
A
Reaction 2&3
- the carbon atoms in glucose -6-phosphate are rearranged and the molecule is then phosphorylated by another ATP, yielding fructose-1,6-biphosphate and ADP
25
Glycolysis - Cleavage
Reactions 4&5
- the six carbon fructose-1,6-biphosphate is split, and two three-carbon molecules are formed
26
Glycolysis - oxidation
reaction 6&7
- Glyceraldehyde-3-phosphate is phosphorylated and oxidised by NAD+ to hield NADH and 1,3-byphosphoglycerate, which then donates a Pi to ADP, producing ATP
27
Glycolysis - ATP synthesis
Reaction 8-10
- the carbon atoms in 3-phosphoglycerate are rearranged to form phosphoenolpyruvate, which donates a Pi to ADP, yielding ATP and pyruvate
28
Citric acid cycle (krebs)
2nd part of glucose metabolism
1. Citrate synthesis: Acetyl-CoA combines with oxaloacate to form citrate and CoA (reaction 1)
2. First oxidation: citrate is rearranged, then oxidized by NAD+ generating CO2 and NADH (reactio 2-4)
3. ATP synthesis: succinyl-Coa is converted to succinate and CoA, while forming ATP (reaction 5)
4. Second oxidation: succinate is oxidised by FAD and NAD+, generatinf FADH2 and NADH, and is converted back to oxaloacetate (reaction 6-8)
29
Protein function
- muscle contraction:movement of body, cells, cell structures
- cell membranes (receptors, cell identity, pumps)
- fibrous proteins (collagen, keratin): structural
- globular proteins (antibodies, myoglobin, enzymes) : functional
- plasma proteins: blood osmolarity and viscosity
30
protein absorption
In stomach:
- HCL denatures and unfolds proteins preparing them for easier chemical digestion, PEPSIN breaks proteins into small peptides
In Duodenum:
- PANCREATIC ENZYMES (trypsin, chymotrypsin and carboxypeptidase) continue breaking proteins into small peptides
In jejunum and ileum of small intestine:
- various PEPTIDASE ENZYME in intestinal lining brush border finish digestio of peptides into amino acids
31
amino acid catbolism
Dietary proteins are broken down into amino acid subunits in digestive tract; absorbed into bloodstream and delivered to liver
- AA consist of a carbon skeleton bound to a nitrogen containing amino group
- nitrogen is not used for energy so amino group is removed by TRANSAMINATION and the remaining carbon skeleton can be oxidised for fuel
32
Lipids - sources and finctions
- adipose tissue: helps protect tissues and organs and also provides fuel source
- plasma membrane and myelin sheath: composed of phospholipids and cholesterol
- cholesterol: precursor of steroids, bile salts and VIT D
- fatty acids: precursor of prostaglandins and other eicosanoids
- fat-soluble vits (ADEK)
33
Lipid absorption
- Begins in mouth with inguale LIPASE breaking down triglycerides into monoglycerides and fatty acids. continues in the stomach
- BILE SALTS from gallbladder emulsifies the large lipid droplet into smaller ones → greater access of PANCREATIC LIPASE
- most fats exist as triglycerides which contain three long hydrocarbon chains (FATTY ACIDS) linked to a modified sugar, (GLYCEROL)
34
Cholesterol
lipid which is not oxidised for duel; important to many anabolic processes in body
- Modified to produce Vit D, steroid hormones and bile salts
- Important structural molecule in plasma membranes
Packaged along w/ other lipids and proteins into stucutres called lipoproteins → provide transportation for cholesterol and other lipids in bloodstream
35
lipoproteins
Hydrophobic so protein carriers needed for transport in blood; complexes of lipids and proteins in blood.
categorised into 4 groups by DENSITY. the more protein content to lipid = higher density
1. chylomicrons: used for transport of dietary lipids to adipose tissue
2. v low-density (VLDLs): made in liver to transport triglycerides to all tissues; converted to LDLs after removal of some triglycerides
3. Low-density (LDLs): remnants of VLDL; carry cholesterol to cells; after they give away cholesteral they are repackaged into VLDL in liver as they are rich in cholesteral 'bad lipoproteins'
4. High-density (HDLs): HDL remove excess cholesterol from peripheral tissues and transport to liver for disposal 'good lipoproteins'
36
fatty acid catabolism, beta oxidation
LIPOLYSIS: enzyme-catalyzed process that liberates fatty acids and glycerol
- both fatty acids & glycerol can be used for energy generation, but overwhelming amount of energy is derived from fatty acid BETA OXIDATION
- glycerol is converted to clyceraldehyde-3-phosphate and enters glycolysis
- fatty acids are catabolides to acetyl-CoA by BETA OXIDATION and to KETONE BODIES by KETOGENESIS
37
Ketogenesis
- when body uses beta-oxidation of fats to make glucose, a by-product of incompletely oxidised fates is KETONES
- during extreme caloric restriction, carbohydrate restriction, or full starvation, liver begins to rapidly oxidise fatty acids for energy; leads to production of large quantities of ketone bodies
- ketone bodies cannot be further metabolised by liver cells to be appreciable amount enter bloodstream
- accumulation of ketone bodies in blood is cakked KETOSIS; can lead to a dangerous lowering of blood pH called KETOACIDOSIS
- people w/ diabetes who do not closely control BGL are at high risk of ketoacidosis. w/o insulin cells will switch fat oxidation for glucose production in order to meet metabolic demands
38
Metabolic absorptive state
occurs right after feeding and can last up to 4 hrs when ingested nutrients enter bloodstream
processes occur as nutrients are being absorbed from small intestine:
- OXIDATION: of nutrient molecules which provide energy to cells
- GLYCONEOGENESIS: stores excess glucose in skeletal muscle and hepatocytes
- LIPGENESIS: stores triglycerides in adipocytes and hepatocytes
- PROTEIN SYNTHESIS: provides structural materials for cells
39
Absorptive state regulation
pancreatic hormone INSULIN orchestrates many absorptive state processes
- Release of insulin is triggered by inc BGL
- oxidation of glucose, small amounts of AA & FA generates ATP for cells
- AA enter cells for protein synthesis; excess glucose enters muscle and liver cells and is stored by glycogenesis
- excess glucose, AA and FA are converted to triglycerides.
- lipgenesis stores triglycerides in adipocytes and hepatocytes
40
postabsorptive state
- body usually instate in late morning, late afternoon and most of night
- most body tissues switch from carbohydrate sources for energy to using FA ( stoed in adipose tissue)
processes in PAS:
- break down of proteins in muscle cells, releases glucogenic AA into blood
- KETOGENESIS in hepatocytes, converts fatty acids to ketone bodies and releases into blood
- GLUCONEOGENESIS & GLYCOGENOLYSIS in hepatocytes release glucose into blood → crucial for brain
- LIPOLYSIS in adipocytes releases fatty acids into blood
- oxidation of molecules such as Fa provides most cells w/ fuel
41
Pstabsorptive state regulation
Maintaining normal BGL is a challenge → gluvose enters blood from two major sources
- glycogen breakdown in liver
- gluconeogenesis using AA and glycerol
co-ordinated by:
- GLUCAGON: released from pancreas and stimulates glycogenolysis and gluconeogenesis in liver
- EPINEPHRINE: stimulates glycogenolysis in skeletal and cardiac muscle and liplysis in adipocytes
- GLUCOCORTICOIDS: stimulate mobilisation of lipid and protein reserves; enhanced by GH
- pancreatic hormone GLUCAGON released when BGL drops; triggers glycogenolysis & gluconeogenesis
42
neural regulation of feeding
Hypothalamus houses two nuclei that ontrol homeostatic variables associated w/ feeding
- SATIETY CENTRE: elicits feeling of fullness and inhibits desire to eat
- HUNGER CENTRE: (feeding centre)elicits feelings of hunger and stimulates desire to eat
43
endocrine regulation of feeding : long-term
primarily hormonal:
- LEPTIN: produced by adipocytes; stimulates satiety centre and inhibits neurons in hunger centre
- GHRELIN: produced by stomachl stimulates neurons in hunger centre to promote hunger
44
endocrine regulation of feeding: short term
can also inhibit or stimulate feeding
- INSULIN → decreases food intake
- feeding stretches stomach walls and initiates release of gastrointestinal hormones → both stimulate vagus nerve to indirectly suppress hunger centre
