Chapter 4: Carbohydrates Flashcards
Photosynthesis (2)
- carbohydrates produced
- plants use energy from sun to create energy
Humans convert plant foods from..
carbohydrates to glucose
Glucose (2)
- most abundant carb and monosaccharide
- preferred source of energy for brain and red blood cells
Simple carbohydrates (4)
sweeter than complex carbs
- monosaccharide
- disaccharide
- mix with saliva and react with taste buds
Oligosaccharides (4)
contain 3-10 monosaccharides
- fewer sugar units
- similar in length to monosaccharides
- food sources: legumes, beans, cabbage, Brussels sprouts, broccoli, breast milk
Complex carbs
polysaccharides
Monosaccharides (definition, structure and 3 kinds)
one unit of sugar structure is a hexose - glucose - fructose - galactose
Fructose (3)
- sweetest natural sugar
- found in fruits
- part of high-fructose corn syrup
Galactose
part of the disaccharide, lactose
Disaccharides (definition and 3 kinds)
two monosaccharides join together through condensation
- sucrose, lactose, and maltose
Sucrose (2)
table sugar
- glucose + fructose
Lactose (2)
milk sugar found in dairy products
- glucose + galactose
Maltose (2)
formed from digestion of starches
- glucose + glucose
Polysaccarides and oligosaccharides similarities
both make up cellulose in plant cell walls and escape digestion like fiber
Structure of oligosaccharide
raffinose = galactose + sucrose (glucose and fructose)
Starch (definition and examples)
- repeated units of glucose
- plants store glucose in chains of starch
ex. amylose
amylopectin
Amylose (4)
straight chain of polysaccharides in starch
- 40% of starch
- resistant starch not digested in GI tract
- improves health of digestive tract, glucose tolerance, and intestinal bacteria growth
Amylopectin (3)
branched chains of polysaccharides found in starch
- 60% of starch
- easier to digest
Fiber (4)
non-digestible polysaccharides
- structural component in cellulose
- straight chain of glucose held together with glycosidic bond
- plant foods contain soluble and insoluble fibers, animal products do not contain fiber
Functional fiber (2)
fiber extracted or isolated from a plant, or manufactured by the food industry
- has health benefits
Soluble fiber (4)
- dissolves in water
- easily fermented by bacteria in intestine
- ex. pectins, mucilages, betaglucans
- health benefits: lowers cholesterol and blood glucose, controls appetite
Insoluble fiber (4)
- does not dissolve in water
- not easily fermented by bacteria in intestine
- ex. cellulose, ligins, hemicelluloses
- health benefits: increases stool bulk, relieves constipation
Glycogen (5)
- stored form of glucose in animals
- long, branched chains of glucose
- stored in liver and muscle
- muscle glycogen broken down for energy in muscle
- animal products do not contain glycogen
Liver glycogen response to blood glucose levels (3 steps)
blood glucose decrease > glycogen breaks down > blood glucose increases
Lactose intolerance
deficiency of lactase, the enzyme that digests lactose
- nausea, cramps, bloating, flatulence, diarrhea
Lactose maldigestion
inability to digest lactose due to low levels of lactase
Dietary recommendations for lactose intolerance (7)
Create tolerance
- depends on individual’s threshold
- consume small amounts of dairy (milk, cheese, yogurt)
- whole milk better tolerated than skim milk
- cheese has less lactose than milk (hard cheeses)
- consume yogurt with live, active cultures
- consume lactose-reduced products or take lactose pills
Disaccharides and starches digestion
digested to monosaccharides
Monosaccarides digestion
absorbed by small intestine
Fiber digestion
passes through GI tract undigested
Digestion of carbs (4)
- teeth grind food and mix with saliva (salivary amylase)
- food travels down esophagus to stomach (amylase continues breaking down starch)
- pancreas releases pancreatic amylase when carbs enter small intestine (starches break down into maltose, disaccharides converted to monosaccharides)
- Large intestine, all starch and simple sugars have been broken down and absorbed (only indigestible fiber remains)
Carbohydrate absorption (4)
absorbed as monosaccharides
- absorbed through intestinal cell mucosa
- transported to liver via portal vein
- metabolic needs direct fate of monosaccharides
Galactose and fructose function (2)
- used by liver for energy
- converted to glucose
Glycogenesis (2)
glucose converted to glycogen
- excess glucose converted to glycerol and mostly fatty acids for storage in adipocytes
Carbohydrates functions (4)
- provide energy (4 kcal/g)
- maintain blood glucose levels: glucose primary fuel for brain, glycogenesis occurs 4 hours after meal, muscle glycogen cannot raise blood glucose levels
- spare protein: prevent gluconeogenesis (occurs mainly in liver and sometimes kidney)
- prevents ketosis
Gluconeogenesis
forms new glucose from amino acid proteins
Normal blood glucose levels (2)
70 mg/dl to 110 mg/dl
- insulin and glucagon maintain level
Insulin (6)
lowers blood glucose levels
- needed for glucose to enter the cell from bloodstream
- liver, kidney, and brain cells can use glucose without insulin
- stimulates glycogenesis
- stimulates lipogenesis
- inhibits lipolysis
Lipogenesis
glucose to fat
Lipolysis
form lipids
Glucagon (5)
increases blood glucose levels
- release of glucose into blood
- glycogenolysis (breakdown of glycogen)
- glucose production
- conversion of lactic acid to glucose
4 hormones that regulate glucose metabolism
- epinephrine
- norepinephrine
- cortisol
- growth hormone
Epinephrine and Norepinephrine hormones (3)
raise blood glucose
- stimulate glycogenesis and gluconeogenesis
- released from adrenal glands
Cortisol (3)
increases blood glucose
- stimulates gluconeogenesis
- reduces uptake of glucose by muscle cells
Growth hormone (4)
conserves blood glucose
- fat breakdown for energy
- reduce uptake of glucose by muscle cells
- increase glucose production in liver
Hypoglycemia (4)
blood glucose level less than 70
- occurs with excess insulin production
- signs and symptoms: hunger, dizziness, light headedness, confused, weak, sweat
- treatment: eat/drinking carb rich foods, eating smaller well-balances meals
Dietary fiber importance (6)
lower risk of:
- bowel irregularity
- constipation and diverticulitis
- obesity
- heart disease
- cancer
- diabetes
Constipation (3)
- caused by slow muscle contractions in colon that mov poop too slowly causing excessive water absorption
treatment: - insoluble fiber reduces transit time of food in colon
- soluble fiber makes poop easier to pass
Diverticulosis
increased pressure in colon causes weak spots along wall, forming pouches called diverticula
Diverticulitis
infection of the diverticula
Fiber and heart disease (5)
- viscous, soluble fiber helps lower blood cholesterol levels
- soluble fiber interferes with reabsorption of bile acids
- fiber and bile acids secreted in feces
- slow, viscous, soluble fiber may reduce rate at which fat and carbohydrate are absorbed
- decreasing fat in blood and improving insulin sensitivity may decrease risk of heart disease
Fiber reduces blood cholesterol levels (3)
- cholesterol in blood taken up by liver
- liver uses cholesterol to synthesize bile (released into small intestine to emulsify fat)
- viscous fiber in small intestine binds bile in small intestine preventing it from being reabsorbed and reused by liver (bile-fiber complex eliminated)
Good and bad cholesterol
good: HDL
bad: LDL
Fiber in diabetes (2)
- viscous soluble fiber slows digestion and absorption of glucose; controls blood glucose levels
- higher consumption of fibers reduces risk of diabetes
Fiber in cancer (3)
decreases amount of time cancer-promoting substances spend in intestinal lining
- encourages growth of colon-friendly bacteria and their fermentation by-products
- reduces concentration of bile acids in colon
Fiber and obesity
increases satiety, reducing food intake
Cautions about fiber
- introduce fiber into diet slowly
- can cause flatulence and bloating
- may reduce absorption of iron and zinc
Carbohydrate recommendations (DRIs and AMDR)
DRIs recommend 130 grams/day
AMDR recommends 45-65% kcal/day
MyPlate daily recommendations (4)
- 6 servings grain
- 3 servings vegetables
- 3 servings of dairy
- 2 servings fruit
Fiber recommendations (DRI and AI)
DRI: 14g/1000 calories
AI: 25 to 38 g/day
Best sources of carbs
nutrient-dense, low-saturated fat foods, low amounts of simple carbs (more fiber and complex carbs)
Whole grains (3)
abundant in complex carbs, starch and fiber
- reduced risk of chronic diseases
- 3 servings per day
Low-fat and fat-free dairy products
1 to 17 grams of lactose
Fruits and vegetables (4)
provide simple sugars, starch, and sugar
- flesh of fruits contain simple sugars and pectin
- skin of fruits contains cellulose
- vegetable contain starch and fiber
Wheat kernel to flour (3 layers)
- bran = fiber
- endosperm = starch (rich)
- germ = small
no fiber in wheat flour = enriched source of fiber
Fortification
added vitamins and minerals
Legumes, nuts, and seeds (2)
- legumes provide 4g fiber per serving
- nuts and seeds contain little starch but are good sources of fiber
Glycemic index (GI)
rating scale of how much a food increases blood glucose and insulin
Glycemic load (GL)
amount of carbohydrate in a food multiplied by GI of that food
Standard measure of GI
white bread
Naturally occurring sugars (3)
fructose and lactose
- nutrient dense
- found in fruit and dairy products
Added sugars (3)
- sugar added to processed foods and sweets
- empty calories
- number of source of added sugar: sweetened drinks
Added sugars in food processing (5)
- keep products moist
- brown color for pastries
- preservative and thickener
- works with yeast to make bread rise
- make food sweet
Dental caries (cavities) (4)
- sugar and starches
- energy source for bacteria in mouth
- bacteria grow > produce acids that ruin teeth enamel
- sugarless chewing gum reduces dental caries
Sugar substitutes (7)
- polyols
- sacchrin
- aspartame
- acesulfame-K
- sucralose
- rebaudioside A
- neotame
Sugar alcohols (5)
- polyols
- chemical structure of sugar with alcohol component added
- found in plants and synthetically produced
- found in gum, candy and baked goods
- causes diarrhea
Aspartame (4)
- most-used
- composed of two amino acids: aspartic acid and phenylalanine
- 4 kcal/g
- 200x sweeter than sugar
Individuals with PKU should avoid..
aspartame
- unable to metabolize phenylalanine
Acesulfame-K (3)
- 200x sweeter than sugar
- tabletop sweeter
- body does not metabolize it so its exerted through urine
Sucralose (3)
- Splenda
- developed by changing structure of sucrose molecule
- not digested or absorbed by body; pass through GI tract and is excreted
Diabetes
- condition where individual doesn’t have enough insulin or is resistant to effects of insulin
- rise in blood glucose levels
- pancreas can’t keep up with blood glucose levels
Type 1 Diabetes (6)
- immune system destroys beta cells of pancreas
- no insulin produced
- begins in childhood or early adulthood
- insulin injection dependent
- 5 to 10% of diabetes
- symptoms of elevated blood sugar: polydipsia, polyuria, and polyphagia
Polydipsia
uncontrollable thirst
Polyuria
excessive urination
Polyphagia
strong desire to eat
Type 2 Diabetes (5)
- overweight/obesity increases risk
- 90 to 95% of diabetics
- produce insulin but have become insulin resistant
- pancreas overproduces insulin and decrease production from overuse
- can go undiagnosed for some time (damages vital organs)
Prediabetes (3)
- impaired glucose intolerance
- fasting blood sugar between 100 mg/dl and 125 mg/dl
- high risk of diabetes and heart disease
Blood glucose levels (3)
- less than 100 mg/dl»_space; normal
- 100 to 125 mg/dl»_space; prediabetic
- 126 mg/dl»_space; diabetic
Gestational diabetes (3)
- diagnosed when women gets diabetes during diabetes
- cause is ineffectiveness of insulin due too pregnancy hormones
- uncontrolled glucose can cause large newborn baby and complications
Long term damage of diabetes (8)
- nerve damage
- leg and foot amputations
- eye diseases
- blindess
- tooth loss
- gum problems
- kidney disease
- heart disease
Benefits of physical activity (3)
- increases insulin sensitivity
- reduces body fat
- lowers blood pressure and lipids
Preventing type 2 diabetes (3)
- shed some excess weight
- exercise regularly
- eat balanced, high-fiber, healthy diet
Glycogenolysis
- breakdown of glycogen
- occurs 4 hours after a meal
Ketosis
excess number of ketone bodies in the blood