Macro Exam 1

key role of the cell membrane

receptors sensitive to external stimuli and channels that regulate movement throughout the cell

hexokinase vs glucokinase

both glucose → glucose 6 phos

hexokinase: promotes glycolysis, negatively allosterically regulated by glu 6 pho

glucokinase: in liver, low affinity (low km), regulated by insulin

both take glucose away from the liver!!

key role of the cytoplasm

provides support and controls movement of organelles and connects cellular components with microtubules

key role of the nucleus and what does it contain

“chief executive officer”

contains DNA (instructions)

key role of the mitochondria

produce the most ATP used by cells (why its the powerhouse)

key roles of the oral cavity (3)

teeth: mastication

salivary glands: lubrication

swallowing

key role of the esophagus and two structures within

transportation

UES opens during swallowing - bolus slides to the stomach

LES allows food to enter the stomach - cannot return, prevents reflux (GERD)

key role of the stomach

digestion & passing food into small intestine

regulation of gastric secretions

mechanical: grinding food

chemical: gastric juice (producing chyme)

secretions of the stomach and their functions

Mucus & bicarbonate – neutralize HCl along tissue wall (protects mucosa)

HCl – protein denaturation

Intrinsic factor – binds vitamin B12 and carries to ileum for absorption

Gastric lipase – hydrolyzes triglycerides (mostly short and medium chain)

Pepsinogen – first converted to pepsin

Pepsin is an endopeptidase – direct digestion of protein within the protein chain

Gastrin – stimulates parietal and chief cells to release HCl and pepsinogen, respectively

key roles, portions, and cells (1) of the small intestine

main site for nutrient digestion and absorption

duodenum, jejunum (most), ileum

enterocytes (absorptive cells of the SI) turn over every 3-5 days

4 processes of absorption in the small intestine

diffusion – substances freely cross membrane

facilitated diffusion – requires a carrier

active transport – requires a carrier and ATP

pinocytosis – engulfed by cell membrane a released on the inside of the cell

key roles of the large intestine

ascending, transverse, and descending 

transportation and absorption

secretion of mucus (lubricant and protectant from bacteria) and bicarbonate (neutralize acids)

movement of material

key role of the pancreas

insulin and glucagon production

key roles of the liver

energy metabolism

produces bile to aid in digestion

emulsification of dietary lipids

• Brings fats into liquid suspension

• enzymes better able to break down lipids

• solubilization of lipid digestion products for absorption

• bile is a critical component of micelles – spherical structure that facilitates lipid absorption

key roles of the gallbladder

stores bile

CCK stimulates contraction and bile release

TCA cycle 

• location

• what is metabolized

• products

• main goal

• regulation

in the mitochondria (after molecules become acetyl coA)

carbohydrates, fatty acids, and amino acids metabolized

products from one cycle: 3 NADH (3 ATP later), 1 FADH2 (2 ATP later), 1 ATP, CO2 = 12 ATP total

produces a lot of electron carriers to make ATP later on

AMP, ADP= positively

end products, NADH, ATP = negatively

positive and negative regulators of the TCA cycle

positive: AMP or ADP (low energy)

negative: end products of certain reactions (citrate inhibits citrate synthase) or end products of the TCA cycle (NADH, ATP)

electron transport chain

• where it occurs

• what needs to happen before

• end goal

occurs in the mitochondria (inner membrane)

occurs after TCA cycle (because we have electron carriers NADH and FADH2)

• we need to extract the electrons and transfer to form a proton (H+) gradient

40% of energy is for ATP synthesis and 60% is heat

at the end, electrons are transferred to oxygen (producing H2O)

ETC complex 1

• end goal

accepts e- from NADH, leaks some e- generating free radicals

ETC complex 2

• what it does

• fun fact

accepts e- from FADH2

the only complex that isn’t a H+ pump

coenzyme Q

• what is it

• what does it do

lipid soluble molecule that diffuses within the lipid bilayer

transfers e- from complexes 1 and 2 to complex 3

ETC complex 3

• enzyme

• what does it contain

coenzyme Q cytochrome c oxidoreductase

contains 3 cytochromes and an Fe-S protein

cytochrome c

• what does it do

transfers e- from complex 3 to complex 4 within the inter-membrane

complex 9

• enzyme

• what does it contain

• function

cytochrome c oxidase

contains Fe and Cu dependent proteins

transfers e- from cytochrome c to oxygen producing H2O

after TCA cycle and ETC, what happens?

H+ flow down concentration gradient through ATP synthase

for every pair of e- through the complex, 3 ATP are generated

CHO digestion pathway

oral cavity → stomach → SI

what occurs during CHO digestion in the oral cavity

digests polysaccharides (starches) using salivary alpha amylase

disaccharides are not digested here

what occurs during CHO digestion in the stomach

starch: small amount of digestion via alpha amylase until inactivated

disaccharides are not digested here

what occurs during CHO digestion in the SI

duodenum and jejunum starch digestion via amylase

at the brush border, remaining things are hydrolyzed and glucose is absorbed

at the brush border, disaccharides are digested producing lactase, sucrase, maltase, trehalase

which of the following organelles are involved in protein synthesis and export? nucleus, smooth ER, rough ER, golgi apparatus

nucleus, rough ER, golgi apparatus

Allosteric enzyme regulation involves directly blocking the enzyme “active site.” T/F

False

Insulin binding the insulin receptor is an example of….

• Signals leading to a distinct event within the cell

• 2nd messenger signaling

• External stimuli

external stimuli

T or F: Taking a creatine supplement should improve marathon running by significantly contributing to ATP supply during the course of the race

False

Which of the following best describes the end result of the TCA cycle?

• Generates large amounts of ATP to be used for energy

• Generates large amounts of NADH and FADH2 to be used as energy

• Generates large amounts of NADH and FADH2 to be used as electron carriers

Generates large amounts of NADH and FADH2 to be used as electron carriers

T or F: NADH and FADH2 transfer their e- to the same ETC complex

false

Which stomach glands are most directly related to protein digestion?

• cardiac

• oxyntic

• pyloric

oxyntic

Most macronutrient absorption takes place in the ileum T/F

false

The PFK step in glycolysis is regulated by which of the following (select all that apply)?

• Protein Kinase A

• Glucagon

• AMP

• Fructose 2,6 bisphosphate

• Insulin

• ATP

glucagon, AMP, fructose 2,6 bisphosphate, insulin, ATP

Lactate is a waste product of intense exercise. T/F

false

The principal issue with all glycogen storage diseases is that the brain has an inadequate supply of glucose. T/F

false

what are the three monosaccharides

fructose glucose, galactose

T/F To the best of our current knowledge, the negative effects of HFCS are because it increases calorie intake.

true

the principal reason dietary fiber has a lower caloric value than starch is…

• Humans don’t have enzymes to digest the β-glycosidic bonds between monosaccharides within fiber

• Fiber has a faster gastric transit time and therefore is not well absorbed

• Fiber is a heteropolymer of monosaccharides, making it harder to digest

Humans don’t have enzymes to digest the β-glycosidic bonds between monosaccharides within fiber

At Thanksgiving, you eat so much turkey that the only other thing you eat is 0.5 slices of pie. The sugar from that pie will be absorbed by….

• GLUT4

• SGLT1

• GLUT2

• Amino acid receptors

SGLT1

Which of the following best describes beta cell failure?

• Early in type 2 diabetes, the pancreas secretes very little insulin

• Later in type 2 diabetes, the pancreas secretes a large amount of insulin

• Later in type 2 diabetes, the pancreas secretes very little insulin

• Early in type 2 diabetes, the pancreas secretes a large amount of insulin

Later in type 2 diabetes, the pancreas secretes very little insulin

T/F One must have obesity to develop type 2 diabetes.

false

What biomarker of glucose homeostasis would be best for monitoring the efficacy of a long-term (6 month) lifestyle intervention in people with type 2 diabetes?

A1c

Which of the following is NOT characterized by insulin resistance?

• PCOS

• Type 2 diabetes

• Type 1 diabetes

T1D

T/F there is one cause of lactose intolerance

false

Which of the following can enter the gluconeogenic pathway? (select all that apply)

• Acetyl CoA

• Fatty acids

• Lactate

• Amino Acids

• Glycerol

lactate, amino acids, glycerol

Which of the following are physiological actions of glucagon? (select all that apply)

• Promoting glucose uptake by skeletal muscle

• Promoting glucose uptake by adipose

• Activating glycogenesis

• Activating glycogenolysis

• Activating gluconeogenesis

activating glycogenolysis and activating gluconeogenesis

Between breakfast and lunch, which pathway supplies glucose to prevent hypoglycemia?

glycogenolysis

T/F When consumed in excess (positive energy balance), fructose contributes more to liver fat than glucose.

true

Avoiding dietary CHO at all costs could lead to which of these unfavorable effects (select all that apply)

• Avoiding many foods high in fiber

• Increasing many foods high in fiber

• Increasing saturated fat intake

• Avoiding many foods high in fiber

• Increasing saturated fat intake

T/F Overfeeding CHO and fat to the same degree induces similar weight gain.

true

Select all that are true.

• Non-celiac gluten sensitivity appears to be a real condition

• Non-celiac gluten sensitivity is present in 25% of the population

• There are good biomarkers for non-celiac gluten sensitivity

• Symptoms associated with non-celiac gluten sensitivity are definitely due to gluten (not another component of wheat)

non-celiac gluten sensitivity appears to be a real condition

pancreas digestion secretions:

• acinar cells: digestive enzymes

• duct cells: bicarbonate

pancreatic juice secretions contain:

• Electrolytes (Na+, K+, Cl-)

• Enzymes that act on all three energy nutrients:

  • Carbohydrases → hydrolyze carbohydrates (~50%)

  • Lipases → hydrolyze lipids (~90%)

  • Proteases → hydrolyze proteins (~50%)

• Bicarbonate: neutralizes the acidic chyme arriving in the small intestine from the stomach

cell membrane structure

sheet-like composed primarily of lipids and proteins

mostly phospholipid (PL), also cholesterol – regulates membrane fluidity

carbohydrate chains are often attached to membrane proteins

its dynamic (fluid mosaic model: lateral diffusion, proteins dispersed)

What mechanisms occur in the cytoplasm

glycolysis, glycogenesis, glycogenolysis, pentose phosphate pathway, fatty acid synthesis

what is the largest organelle

nucleas

what is embedded within the mitochondria

the ETC

what are cristae

protrusions that increase surface area of mitochondria - more room for proteins (important for metabolism)

what the general structure of the mitochondria

outer membrane (relatively porous) & inner membrane (selectively permeable)  

where does lipid and carb digestion begin

the oral cavity through digestive enzymes

where does protein digestion begin

the stomach

what are the 4 regions of the stomach

o   cardia - attaches to esophagus

o   fundus - holds food, gastric juice production

o   body - holds food, gastric juice production

o   antrum - majority of chyme formation

what are the 3 gastric glands and what do they contain

• cardiac: cardia - neck cells - mucus & bicarbonate

• oxyntic: body and fundus

  • parietal cells - HCl and intrinsic factor

  • chief cells - pepsinogen, gastric lipase

  • neck cells - mucus & bicarbonate

• pyloric: antrum

  • G cells - gastrin

  • neck cells - mucus & bicarbonate

dietary fiber vs functional fiber

dietary: component of plant foods resistant to human digestive enzymes, a sum of non-digestible oligosaccharides, resistant starch, cellulose, & lignans

functional: isolated, extracted, or manufactured non-digestible carbohydrates that have beneficial effects in humans, often added to foods and supplements

soluble fiber

• transit time

• satiety effects

• BG effects

• known in food or supplements?

generally accepted to slow gastric transit time via gel formation, increased satiety, favorable effects on blood glucose levels

insoluble fiber

• transit time

• stool effects

• food examples

Generally accepted to speed up gastric transit time

Increased fecal weight, loosens stool (laxation)

Whole grains, legumes and vegetables

what does elevated BG trigger

Insulin release (pancreatic β cell) → cellular uptake of glucose (and amino acids, lipids) and promotes their storage in muscle and adipose tissue

what does low BG trigger

Glucagon release (pancreatic α cells) → increases the breakdown of stored carbohydrates and lipid, and inhibits the synthesis of proteins

what mechanisms occur in response to low BG (fasted state)

• glycogenolysis

• gluconeogenesis

• ketogenesis

what mechanisms occur in response to high BG (fed state)

• glucose oxidation

• glycogen synthesis

• fat synthesis

• protein synthesis

allosteric regulation (ATP)

high energy state ➝ inhibits energy-producing pathways

allosteric regulation (AMP)

low energy state ➝ activates energy-producing pathways

what are the key organs in glucose homeostasis

liver, pancreas, muscle, adipose tissue, brain, kidneys, SI

what is the liver’s role in glucose homeostasis

Glucose storage, production, release: Glycogenesis, glycogenolysis, gluconeogenesis

what is. the role of the pancreas in glucose homeostasis

hormonal regulation: secreting insulin and glucagon

what can enter glycolysis

glucose, hexokinase, glucokinase, PFK, pyruvate kinase

what are the products of glycolysis

2 pyruvate

2 Net ATP (4 produced, 2 spent early on)

2 NADH

what can enter glycogenolysis

glycogen, glycogen phosphorolase, debranching enzyme, phosphoglucomutase, glu-6-phosphatase

what are the products of glycogenolysis

glucose

what is the cori cycle

a cycle of lactate between glycolysis (in the muscle) and gluconeogenesis (in the liver)

1. Lactate produced by anaerobic glycolysis in muscle is transported to the liver.

2. The liver converts lactate into glucose via gluconeogenesis.

3. This glucose is sent back to the muscle to be used again for energy.

what can enter gluconeogenesis

amino acids, lactate, and glycerol

what are the substrates of gluconeogenesis

amino acids, lactate, and glycerol

What are the gluconeogenic amino acids?

aspartate, asparagine, alanine, glycine, serine, cysteine, tryptophan, threonine, alpha ketoglutarate, succinyl CoA, fumarate

what are the products of gluconeogenesis

glucose

what can enter glycogenesis

glucose, ATP, branching enzyme, glycogen synthase

what are the products of glycogenesis

glycogen, ADP

what enzyme regulates gluconeogenesis

pyruvate carboxylase

what enzyme regulates glycogenolysis

glycogen phosphorylase

anaerobic glycolysis

• what is it

• end products

• ATP yeild

• where it occurs

• enzyme difference

• Breakdown of glucose into lactate without oxygen

• Lactate

• 2 ATP per glucose

• cytoplasm

• Lactate dehydrogenase

aerobic glycolysis

• what is it

• end products

• ATP yeild

• where it occurs

• enzyme difference

• Breakdown of glucose into pyruvate with oxygen present

• pyruvate

• 32 ATP

• cytoplasm & mitochondria

• Pyruvate dehydrogenase

flow of a glucose molecule

Step 1: Digestion of Starch → Glucose

• In the mouth:

  • Salivary amylase begins breaking down starch into smaller polysaccharides and maltose (a disaccharide).

• In the small intestine:

  • Pancreatic amylase continues starch digestion, producing maltose and other disaccharides.

  • Brush border enzymes (maltase, isomaltase, sucrase) break maltose into glucose monomers.

• Absorption:

  • Glucose is absorbed by intestinal epithelial cells via SGLT1 (sodium-glucose cotransporter 1) using secondary active transport.

  • Glucose then exits into the bloodstream via GLUT2 transporters.

Step 2: Glucose Transport & Distribution

• Glucose travels in the blood and is taken up by tissues via GLUT transporters:

• Muscle and adipose tissue: GLUT4 (insulin-dependent)

• Liver: GLUT2 (insulin-independent)

• Brain: GLUT1 and GLUT3 (insulin-independent)

Step 3: Cellular Metabolism of Glucose

• Glycolysis (in cytoplasm)

  • Glucose is phosphorylated → glucose-6-phosphate (G6P).

  • it undergoes a 10-step process, producing:

    • 2 pyruvate molecules

    • Net 2 ATP

    • 2 NADH

• Fate of Pyruvate

  • If oxygen is present (aerobic conditions):

    • Pyruvate transported into mitochondria.

    • Converted to acetyl-CoA by pyruvate dehydrogenase.

    • Enters TCA cycle for further oxidation → generates NADH and FADH₂.

  • If oxygen is limited (anaerobic conditions):

    • Pyruvate converted to lactate by lactate dehydrogenase.

    • Lactate can build up or be transported to the liver via the Cori Cycle.

• TCA Cycle and Electron Transport Chain (mitochondria)

  • Acetyl-CoA enters the TCA cycle → produces:

    • 3 NADH, 1 FADH₂, 1 GTP (per acetyl-CoA)

    • CO₂ as waste

  • NADH and FADH₂ donate electrons to the electron transport chain, generating a large amount of ATP via oxidative phosphorylation.

Step 4: Storage (when energy is abundant)

• Excess glucose → converted to glucose-6-phosphate → can enter glycogenesis.

• Stored as glycogen in liver and muscle.

• If glycogen stores are full and excess persists, glucose can be converted into fatty acids via lipogenesis and stored as triglycerides in adipose tissue.

Step 5: During Fasting or Energy Demand

• Glycogen can be broken down by glycogenolysis back to glucose-6-phosphate.

• In liver, glucose-6-phosphatase converts G6P to free glucose → released into bloodstream.

• Muscle uses G6P internally for energy.

how does insulin resistance effect gluconeogenesis

causes it to continue throughout the day

how does insulin resistance effect glycogenesis

causes it to occur even after we eat

glucose vs fructose metabolism

glucose

• highly regulated

fructose

• less regulated

what is the role of body fat storage in glucose homeostasis

ectopic fat accumulation causes insulin resistance

• Muscle doesn’t take up glucose out of the blood efficiently (low glycogenesis)

• Liver continuously releases glucose reserves (high gluconeogenesis

liver and muscle characteristics

liver: selfless 😇

muscle: greedy 😈