NS 1150 Exam 2

Cornell University NS1150 Exam 2

1st law of thermodynamics

Energy can change forms but is neither created nor destroyed

Catabolic

Breaking down larger molecules into smaller one

Anabolic

Synthesis of smaller molecules into larger ones

Glycolysis

Breaking down of glucose into 2 pyruvate

Beta Oxidation

Breaking down of fatty acids into acetyl-CoA. remove 2 carbon units and generate electron carriers

Lipolysis

Breakdown of triglycerides to fatty acids and glycerol

Proteolysis

Breakdown of protein to amino acids

Gluconeogenesis

Glucose synthesis from noncarbohydrate sources

Glycogenesis

Formation of glucose

Lipogenesis

Synthesis of fatty acids and triglycerides. Excess glucose are converted to fatty acids and then are combined with glycerol to form TGs and stored in fat cells

Catabolic & Anabolic reactions…

Can be coupled in a complex metabolic pathway to be able to do work

Adenosine Triphosphate

The energy that is released from the body during catabolic breakdown. Energy is stored between phosphate bonds.

Energy from ATP is used for…

Powering anabolic reactions

Acetyl CoA Routes

Synthesis of fats for storage (lipogenesis, anabolic pathway) or oxidative phosphorylation (generates ATP)

Glucose storage form

Stored as glycogen in the liver and muscle

Lipids/fats (free-fatty acids) storage

Stored as Triglycerides in the adipose tissue, muscle, and serum

Protein storage

Simple form is amino acids used in the muscles. Does NOT get stored for later use

Oxidative Phosphorylation

The primary source of ATP at rest and during steady exercise. Uses carbs and fats as substrates. In Mitochondria.

Mitochondria

TCA cycle and ETC. Inner compartment: pyruvate to acetyl CoA, fatty acid oxidation, TCA cycle. Inner membrane: site of ETC reaction

Aerobic glycolysis

CHO —> Glucose —> Pyruvate —> Acetyl CoA

Glycolysis (cytosol), Tricarboxylic acid cycle, ETC (mitochondria)

Aerobic Lipolysis

Fatty acids —> Acetyl CoA

TCA Cycle

Produces high-energy electron carriers (NADH, FADH₂)

Oxidative System

Series of electron carriers mounted in the mitochondrial intermembrane space. Hydrogen ions are pumped across the membrane to the outer compartment of the mitochondrion

Oxidation of Fats: Aerobic Lipolysis

Fat is stored as triglycerides inside muscle fibers and in adipocytes within adipose tissue. Broken down into 1 glycerol molecule and 3 fatty acids. Fatty acids must be converted to acetyl CoA to be used for energy.

Takes place in mitochondria matrix. Beta oxidation occurs.

Basal metabolic rate

energy needed to perform normal bodily functions (respiration, circulation, digestion). Can be increased with more muscle.

Thermogenesis

The energy cost of food processing (ingestion, digestion, absorption, transport, storage)

Physical activity

Body movement determining activity-induced

Direct Calorimetry

A bomb calorimeter is used to determine the E content of nutrients

Respiratory exchange ratio

CO₂ made / O₂ used

Simple sugars

Mono & Di Saccharides

Complex Carbohydrates

Oligo & Poly Saccharides

Monosaccharides

Single unit sugars that differ in their arrangement of atoms. Glucose, fructose, galactose

Disaccharides

Pairs of monosaccharides. Put together via condensation reactions and taken apart by hydrolysis

Oligosaccharides

3-10 monosaccharides. We cannot digest some but the gut bacteria can

Polysaccharides

Chains of monosaccharides, including glycogen, starches, and fiber. Made almost exclusively by glucose

What food sources are NOT a good source of carbs (CHO)?

Fats and animals

Glucose

Consumed as a component of disaccharides and polysaccharides. Is used as fuel, stored as glycogen, or converted to fatty acids and stored in adipose tissue

Galactose

found mostly in milk as part of lactose

Fructose

Occurs naturally in fruits and honey

Disaccharides

Sucrose (glucose + fructose), lactose (glucose + galactose), maltose (glucose + glucose)

Complex Carbohydrates

Starch, glycogen, fiber

Starch

Varying levels of amylose and amylopectin

Rich in plant products including gains, root crops and tubers, and legumes

Glycogen

Main storage of glucose for animals. Found in a limited extend in meats, not a significant source of CHO

Fiber

Structural components of plants that are indigestible by humans

Complex CHO

Grains, legumes, root vegetables.

Refined grains

Endosperm: starchy portion

Bran

fiber-filled outer layer

Germ

nutrient-packed core with vitamins and healthy fats

Endosperm

Starchy carb middle layer with some proteins and vitamins

High fructose corn syrup

Made from corn. Part fructose and glucose

Once consumed, fructose is…

Converted into glucose, glycogen, and/or fatty acids and is stored in the liver. Excess fructose can lead to health concerns

Salivary amylase

breaks down starch in the mouth

pancreatic amylase

breaks down starch in the small intestine

Maltase

breaks down maltose to the monosaccharide glucose

Sucrase

breaks down sucrose to the monosaccharide glucose and fructose

Lactase

Breaks down lactose to glucose and galactose

Enterocytes

Absorptive cells where monosaccharide absorption across intestinal wall occurs

Functions of carbohydrates

use excess glucose to make glycogen when blood glucose is high

decreases gluconeogenesis

prevents protein catabolism

Recommended dietary intake for CHO

45-65% DRI

130g/day. Added sugar should be no more than 25% of total kcals

Fiber DRI

Not set due to insufficient data

AI: 21-25 female, 30-38 male

Dental cavities

sugar can contribute to dental decay. Also drinks with sugar and low pH

Nutrient deficiencies

Added sugars contribute to nutrient deficiencies by displacing nutrients

Obesity

Syndromic Forms

Non-syndromic Forms

biological and social factors.

Syndromic: chromosomal rearrangements, pleiotropic

Non-syndromic: polygenetic, monogenetic

GLUT

14 in the body

Primarily facilitate glucose transport via facilitated diffusion

GLUT4 receptors are the most abundant of the GLUT receptors

Pancreas

primary player in glucose homeostasis

produces key hormones

Acinar cells, pancreatic juice 95%

Islet of Langerhans: hormone producing cell 2.5%

liver

stores and releases energy

Insulin/Beta cells

promotes energy storage

serves as a signal for rapid transfer of GLUT4

Glucagon/Alpha cells

promotes mobilization of stored energy

Glucose homeostasis after a meal

blood glucose levels increase, releasing insulin

insulin enables glucose transporters to take up glucose from the blood into cells

insulin promotes the formation of glycogen in the liver and the conversion of excess glucose into fat for storage

Glucose homeostasis in between meals

low blood glucose stimulates the release of the hormone glucagon from the pancreas

glucagon stimulates the breakdown of glycogen in the liver and the release of glucose into the blood

Diabetes

Elevated levels of glucose in blood, hyperglycemia

Causes of T1D

autoimmune disease

destruction of pancreatic beta cells leading to failure to produce and secrete insulin

Causes of T2D

chronically elevated levels of blood glucose can lead to increased insulin production but receptors are not responsive. insulin resistance

Complications of Diabetes

cells produce sugar alcohols and glycoproteins

Structure of blood vessels and nerves becomes damaged, loss of circulation and blood flow

Diagnosing diabetes

Hemoglobin A1C: avg blood sugar levels over past months

GTT: blood sugar before and after glucose drink

Recommendations for preventing diabetes

whole foods, fiber rich, non-starchy vegetables, minimize added sugars, lose weight, limit saturated fat, 2 or more servings of fish per week, limit alcohol intake

Fatty acids

Most abundant lipid

composed of CHO

Omega CH₃ end *left

Alpha COOH end *right

Short chain fatty acid

2-5 carbons, predominant

Medium chain fatty acid

6-12 carbons

Long-chain fatty acid

more than 12 carbons

Saturated fatty acid

SOLID at room temp

ALL single bonds

Unsaturated fatty acid

LIQUID

monounsaturated: One DB

Polyunsaturated: many double bonds

Cis Unsaturated fatty acid

H atoms are positioned on the same side of the double bond

LIQUID at room temp

Trans Unsaturated fatty acid

H atoms on opposite sides of DB

SOLID at room temp

Triglycerides

Primary dietary lipid and a major source of energy

composed on 1 glycerol + 3 fatty acids bound together via ester linkages

Phospholipids

Found naturally in most foods

Composed of 1 glycerol + 2 FA bound via ester linkages

Phosphate-containing a polar head group

Amphipathic molecules

Sterols

Lipids with multi-ring structures

Cholesteroyl ester

Can be synthesized endogenously

Needed to synthesize bile acids and steroid hormones

Digestion and absorption of lipids

TGs are broken down into monoglycerides

Form micelles

Absorb to enterocytes

MAGs back into TAGs then packed to chylomicrons

Lipoproteins

Chylomicrons, VLDL, IDL, LDL, HDL

Transport lipids

Apoproteins

Proteins associated with lipoproteins, play a key role in the transport of lipids

Lipid absorption

Chylomicrons transport diet-derived lipids from the small intestine via the lymph system

Lipid transport

As chylomicrons circulate the blood, they encounter Lipoprotein Lipase which is found within capillaries of adipose, liver, and muscle tissue. LPL stimulates TG into FA to enter the cells

Low Density Lipoproteins LDL

BAD

transports cholesterol

deposit cholesterol into the blood vessels

High Density Lipoproteins HDL

GOOD

Removes cholesterol

Main functions of lipids

Energy reservoirs, prevent protein catabolism, insulation and protection, structural components, hormones

Lipid metabolism after a meal

Increase insulin, decrease glucagon

Insulin stimulates lipogenesis

Lipid metabolism in between meals

Decrease insulin, increase glucagon

Glucagon stimulates lipolysis

Exogenous pathway lipids after a meal

The exogenous pathway refers to the process by which dietary lipids are absorbed in the gastrointestinal tract, incorporated into chylomicrons, and transported to tissues for utilization or storage.

Digestion occurs in SI, aided by bile salts and pancreatic lipases, which emulsify fats and break them down into fatty acids and monoglycerides.

FFA are absorbed by enterocytes and re-esterified and packed into CM

CM released into lymph capillaries and eventually into the blood stream

Endogenous pathway in a post-absorptive state

Start at the liver

Newly synthesized FA arrive from extrahepathic tissues

Reverse Cholesterol pathway/HDL purpose

Lipoprotein form in both the liver and small intestines

Transports cholesterol esters from peripheral tissues to the liver, converted to bile