Download Final exam example - U of L Class Index

Final exam example
Test I & Final Exam
4. Which diet consists of whole-grain cereals and vegetables, a
small amount of fish, and no other meats and fruits?
A)
vegetarian
B)
macrobiotic
C)
ovo-vegetarian
D)
microbiotic
33.Taking
Taking supplements with folic acid will primarily help
A) pregnant and breastfeeding women
B) children
C) elderly people
D) women with heavy menstrual bleeding
1.A food that may provide a health benefit beyond basic nutrition
is known as a
A))
free radical
B)
functional food
C)
direct additive
D)
indirect additive
2.A substance continually produced in our cells that over time may
cause damage to DNA and other important cell structures is
known as a
A) free radical
B) functional food
C) direct additive
D) indirect additive
Test I & Final Exam
5. Lycopene is commonly found in
A)
garlic
B)
tomato sauce
C)
yogurt
D)
toothpaste
6. Abbreviation GRAS means
A) Generally Recognized as Suitable
B) Generally Recognized as Scientific
C) Generally Recognized as Safe
D) Generally Recognized as Supplement
7 True or false? Phytochemicals are complex plant chemicals that
7.
are essential for life.
A)
True
B)
False
8. True or false? Calcium-fortified orange juice, yogurt with live
cultures, and cereals with folic acid are examples of functional
foods.
A)
True
B)
False
Test I & Final Exam
9. The breaking apart of foods into smaller and smaller units is
called
A) digestion
B) absorption
b
ti
C) metabolism
D) molecular function
10. Which of the followingg is not one of the main p
processes that
allow nutrients to be absorbed from the GI tract into
circulation?
A) passive diffusion
B)) active diffusion
C) facilitated diffusion
D) active transport
11. Which of the following is not one of the three parts of the small
intestine?
A) duodenum
B) duodenal
C) jejunum
D) ileum
12. The primary organs of excretion are the
A)) heart and lungs
g
B) lungs and kidneys
C) kidneys and liver
D) liver and pancreasTest I & Final Exam
13. The main cause of diverticulosis is due to a diet
A)
high in fats and low in fiber
B)
high in seedlike products such as tomatoes and nuts
C)
low in fats and high in fiber
D)
low in seedlike products such as tomatoes and nuts
14. Which of the following are examples of heavy metals?
A) Iron and chromium
B) Carbon and cobalt
C) Lead and mercury
D) Fluoride
Fl
id and
d molybdenum
l bd
15. True or false? The lining of the GI tract is called the mucosa.
A)
True
B)
False
16. True or false? Bile prepares protein for absorption.
A) True
B)) False
17. True or false? Saliva and other fluids blend with food to form
lumen.
A) True
B) False
Test I & Final Exam
18. True or false? Nutrients in the lymphatic system must pass
g the liver before entering
g the bloodstream.
through
A) True
B) False
19. The most abundant form of complex carbohydrates ingested
should come from
A)
dietary fiber
B)
glycogen
C)
starch
D)
glucose
20. What are lignans?
A)
Plant cell structural components
B)
Phytoestrogens with estrogenic properties
C)
Plant carbohydrates
D)
Human form of healthy carbohydrate
21. The primary fuel in the body is
A) lactose
B) glucose
C) glycogen
D) maltose
Test I & Final Exam
22. Which organ stores and releases glucose as needed to maintain
g levels?
blood sugar
A)
liver
B)
kidney
C)
colon
D)
stomach
t
h
23. True or false? Legumes such as peas, lentils, and beans are low
g in p
protein.
in starch but high
A)
True
B)
False
24. True or false? Large amounts of glycogen can be consumed
through eating beef or chicken meats.
A) True
B) False
F l
25. True or false? The hormone epinephrine is released in response
to stress and raises blood glucose level.
A) True
B) False
Test I & Final Exam
26. Which type of fatty acid has two or more double bonds between
carbon atoms?
A) saturated
B) branched chain saturated
C) monounsaturated
D) polyunsaturated
27. Which one of the following is not a common source of
phospholipids?
A)
egg yolks
B)
egg whites
C)
soybeans
D)
peanuts
28 Whi
28.
Which
h lipoprotein
li
t i has
h the
th highest
hi h t percentage
t
off fat?
f t?
A) very low density lipoprotein
B) low-density lipoprotein
p p
C)) intermediate-densityy lipoprotein
D) high-density lipoprotein
29. Which is not a risk factor for heart disease?
A)
high blood pressure
B)
high blood cholesterol
C)
smoking
D)
high fiber intakeTest I & Final Exam
30. To reduce the risk of cancer, a person should decrease fat
consumption and increase consumption of all of the following
except
A)
f it
fruits
B)
fiber
C)
vegetables
processed ggrains
p
D))
31. Which of the following describes the role of Health Canada in the
monitoring of pesticides?
It samples
p all food shipments
p
for all p
pesticides.
A))
It samples all food shipments for some pesticides.
B)
C)
It samples random food shipments for some pesticides.
D)
It samples random food shipments for all pesticides.
32 Which
32.
Whi h nutrient
t i t contains
t i the
th mostt calories
l i per gram??
A)
vitamins
lipids
B)
carbohydrates
y
C))
D)
protein
33.Which of the following is not a primary factor influencing
decisions about what we eat?
A)
taste
B)
texture
C)
cost
Test I & Final Exam
D)
appearance
34. The typical American diet is usually high in
A) meats and potatoes
B) fruits and vegetables
C) fruits
f it and
d meats
t
D) sugars and vegetables
35. Carbohydrates, proteins, and lipids are considered
A) macrodiets
B) macronutrients
C) antioxidants
D) free radicals
36. Which of the following, is used the most widely as an
antimicrobial agent?
A))
Saccharine
B)
Sodium nitrite
C)
Sodium propionate
D)
Sugar
37. Which of the following is an inorganic nutrient?
A)
minerals
B))
vitamins
C)
carbohydrates
D)
lipids
Test I & Final Exam
38. Organic compounds needed in relatively small amounts for
reproduction, growth, and maintenance of the body are
A) minerals
B) lipids
C) vitamins
D) proteins
39. Your body is approximately _______ percent water.
A)
30
B)
45
60
C)
D)
75
40. Which of the following is likely to be a primary source for
nutritional information?
A)
newspapers
B)
nightly news
C)
professional journals
D)
magazine articles
41. What influence food choices that is most closely related to
religion, beliefs, and traditions?
A)
cultural
B)
cognitive
C)
sensory
D)
behavioral
Test I & Final Exam
42. Absorption of amino acids in GI tract is controlled by
A)
quaternary structure of proteins
B)
function of protein
C)
amino acid sequence
D)
bioavailability of proteins
43. Which of the followingg is one of the most commonlyy consumed
American vegetables?
A)
green beans
B)
corn
C))
broccoli
D)
iceberg lettuce
44. Which nutrient does not help supply structure to bone?
A)
lipids
B)
carbohydrates
b h d t
C)
minerals
D)
water
45. True or false? To a large extent, culture defines our attitudes.
A) True
B) False
46 True or false? An apple typically has a high amount of protein
46.
while being low in lipids.
A) True
Test I & Final Exam
B) False
47. Glycemic index is used to describe the following food properties.
A) The amounts of simple carbohydrates available for absorption
B) How fast carbohydrates are digested and absorbed from particular
food
C) How fast glucose is absorbed and transfer into glycogen
D) How fast complex carbohydrates will be digested into simple
sugars
48. Which of the following dietary guidelines is incorrect?
A)
Consume less than 2,300 mg of sodium per day.
B)
Choose fiber-rich fruits, vegetables, and whole grains often.
C)
Increase intake of fats and oils high in saturated or trans fatty
acids.
D)
Cook foods to safe temperatures to kill microorganisms.
49. The purpose of the Dietary Guidelines is to
A)
reduce the rates of overnutrition and undernutrition
B)
promote health and reduce the risk for chronic diseases
C)
increase caloric intake across the life-stage groups
D)
enco rage cons
encourage
consumption
mption of healthy
health trans
t
fats
50. Which of the following is not a mandatory requirement for a food label?
A)
statement of identity
B)
name and address of manufacturer
C)
nutrition information
D)
gross weight of content
Test I & Final Exam
51. True or false? Essential fatty acids are precursors to hormonelike substances
called eicosanoids.
A) True
B) False
52. True or false? Dietary fats supply the majority of the body's energy needs
during rest and low intensity exercises.
A) True
B) False
53. True or false? Cholesterol is considered essential because it cannot be
produced in the body.
body
A) True
B) False
54 Which of the following will not destabilize a protein's shape?
54.
A) cold temperatures
B) changes in acidity
C) changes in alkalinity
D) oxidation
55. The most abundant protein in mammals is
A) testosterone
B) estrogen
C) collagen
D) keratin
Test I & Final Exam
56. Once absorbed, amino acids travel from the small intestine via the portal
vein to the
A) pancreas
B) kidneys
C) liver
D) gallbladder
57 True or False? Dieting in place of changing eating habits is the best way to
57.
control body weight.
A) True
B) False
58. A severely ill person would likely have which of the following nitrogen
balances?
positive
A)) p
B) zero
C) negative
D) inactive
59. Which of the following foods is the poorest source of protein?
A) soy burger
B) chicken
C) kidney
kid
b
beans
D) milk
Test I & Final Exam
60. Excess dietary protein can cause
A) loss of vitamin C
B) kwashiorkor
C) loss of calcium
D) marasmus
61. True or false? The body will burn protein prior to carbohydrate as a source
off energy.
A) True
B) False
62. True or false? Taking protein supplements or eating high-protein diets is an
effective way to lose fat and gain muscle mass.
A) True
B) False
63. True or false? The majority of proteins in the bloodstream are dipeptides.
A) True
B) False
64. True or false? Proteins that are not digested in the small intestine travel to
the large intestine, where they are absorbed and utilized for energy.
A) True
B) False
Test I & Final Exam
65. Body fat levels of 6 to 10 percent for men and 12 to 19 percent for women
are considered
A) high
B) just right
C) low
D) morbidly obese
66 True or False? Limits for daily consumption of Nutrasweet are only set up
66.
for children.
A) True
B) False
67. Obesity is a risk factor for which of the following chronic diseases?
A) heart disease
B) diabetes
C)) cancer
D) all of the above
68. True or false? Skinfold measurements use the same principle as underwater
weighing to assess body fatness.
A) True
B) False
69. True or false? Body composition is an important factor in determining
disease risk.
A) True
Test I & Final Exam
B) False
70. Excess of fat-soluble vitamins typically accumulate in the
A) liver
B) muscle
C) small
ll intestine
i t ti
D) pancreas
71. Which is not considered an active form of vitamin A?
A) retinal
B) retinoic acid
C) retinol
D) retnalogic
72 True or False? Organic foods are entirely free from synthetic pesticides.
72.
pesticides
A) True
B) False
73. The active form of vitamin D is called.
A) coenzyme Q10
B) cholesterol
C) beta-carotene
D) calcitriol
Test I & Final Exam
74. Where is vitamin E primarily stored?
A) liver
B) kidneys
C) skin
D) body fat
75. A common deficiencyy associated with thiamin is called
A) scurvy
B) beriberi
C) rickets
D)) p
pellagra
g
76. Which vitamin is a component of acetyl CoA?
A) thiamin
B) vitamin C
C) folate
f l
D) pantothenic acid
77. Eating too many raw egg whites may adversely affect the absorption of
A) biotin
B) niacin
C) vitamin C
D) vitamin D
Test I & Final Exam
78. Which vitamin helps reactions to break down glucose, make RNA and DNA,
or produce energy-rich molecules that power protein synthesis?
A) thiamin
B) vitamin B6
C) riboflavin
D) vitamin D
79. True or false? Vitamins are found in every food group, including fats and
oils.
A) True
B) False
80. True or false? A healthy liver can store up to a year's supply of vitamin A.
A) True
B) False
81. True or false? Sources of riboflavin include dairy products, enriched grains,
eggs, and organ meats.
A) True
B) False
82. True or false? Signs of vitamin B12 deficiency include weakness and fatigue
and eventual nerve damage.
A) True
Test I & Final Exam
B) False
83. True or false? Only foods of animal origin contain retinoids, while some
foods of plant origin contain provitamin A carotenoids such as betacarotene.
A) True
B) False
84. In our body, which of the following is not a function of water?
A) carries
i food
f d through
h
h the
h di
digestive
i system
B) transports nutrients to cells and tissues
C) serves as a shock absorber and cleaning agent
provides energy
gy
D)) p
85. The majority of water lost from the body occurs through
A) exhaled air
perspiration
p
B)) p
C) feces
D) urine
86 Over 99 percent of calcium in the body is found within the
86.
A) liver and spleen
B) muscles and skin
C) bones and teeth
D) stomach and small intestine
Test I & Final Exam
87. Which mineral participates with over 300 types of enzyme-driven reactions,
including those in DNA and protein synthesis, blood clotting, muscle
contraction, and ATP production?
A) calcium
l i
B) boron
C) magnesium
D) sodium
88. Which mineral is known for transporting oxygen in blood?
A) iron
B) zinc
C) copper
D) calcium
89. True or false? Osmosis causes water to flow back and forth through the cell
membrane.
A) True
B) False
90. True or false? Foods low in fat and high in calcium, magnesium, and
potassium may reduce blood pressure
pressure.
A) True
B) False
91 T
91.
True or false?
f l ? Chloride
Chl id is
i nott a componentt off table
t bl salt.
lt
A) True
B) False
Test I & Final Exam
92. True or false? Wheat bran, phytate and oxalate increase calcium absorption.
A) True
B) False
F l
93. Which foodborne organism creates havoc within the gastrointestinal tract?
A) Campylobacter
B) Staphylococcus
St h l
aureus
C) Shigella
D) E. colites
94 Which of the following is not considered one of the major classes of drugs
94.
used in animals raised for food?
A) topical antiseptics
B) antiparasitics
C) genetically manufactured foods
D) antibodies
prevent spoilage
p
g and increase shelf life?
95. Which is added to foods to p
A) pasteurization
B) preservative
C) irradiation
D) microorganism
i
i
Test I & Final Exam
96. Which of the following is not typically used as a food preservative?
A) calcium citrate
B) sodium propionate
C) vitamin
it i E
D) potassium sorbate
97. True or false? Salmonella bacteria are prevalent in poultry and eggs that are
g y cooked.
not thoroughly
A) True
B) False
98. True or false? Genetic modification has appeared to be extremely successful,
especially in cases of insect-resistant varieties of corn, potatoes, and
soybeans.
A) True
B) False
99. True or false? Development of foodborne illnesses results from the
interactions between the pathogen, the host, and the environment in which
they exist and interact.
A) True
B) False
100. Two molecules of glucose when joined together form
A) maltodextrin
B) maltotriose
C) maltose
Test I & Final Exam
D) maltase
101. Providing above recommendation the best and complete protein supplements
or complete and highly bioavailable proteins leads to
A) the best way to develop body muscle mass
B) the
th b
bestt way tto control
t lb
body
d weight
i ht
C) the way to overload kidney and liver
D) effectively affect body hormonal system
p
in seeds,, nuts and vegetable
g
oils are?
102. The most common fattyy acids present
A) n-7
B) n-11
C) n-6
D)) n-3
103. The type of alcohol found in beer, wine, and liquor is called
A) methanol
B) ethanol
C) glycerol
D) isopropanol
104. Which of the followingg is not considered a distilled alcohol?
A) wine
B) rum
C) gin
D) whiskey
hi k
Test I & Final Exam
105. The majority of alcohol is metabolized in the
A) small intestine
B) stomach
C) bloodstream
D) liver
106. Which of the following vitamin deficiencies can be seen in alcoholics?
A) B6
B) B12
C) C
D)) common deficiencies for all vitamins
107. True or false? The breakdown of carbohydrates, fats, and proteins always
takes priority over alcohol.
A) True
B) False
108 True or false? Blood alcohol level rises faster in women due to their body size
108.
and composition, lower enzyme activity, and hormonal fluctuations.
A) True
B) False
Test I & Final Exam
109. Olive oil is one of the best nutritional oils because it contains
A) omega-9 fatty acids and specific antioxidants
B) n-3 fatty acids and polyphenolics
C) n-66 fatty
f tt acids
id as diglycerides
di l
id
D) most of fatty acids in the form of health diglycerides
110. True or False? In the small intestine triacylglycerides are hydrolized by
hydrolases into free fatty acids and glycerine.
glycerine
A) True
B) False
111 Triacylglycerides are anabolized by joining together
111.
A) glycerol with saturated fatty acids only
B) all groups of fatty acids
C) alcohols and short chain fatty acids
D) trihydroxy alcohol with fatty acids
112. Fats affecting positively our health should have
A) proper proportion of each group of fatty acids
B) only omega-3 and omega-6 fatty acids
C) specific proportion of omega-3 and omega-6 fatty acids
D) specific proportion of n-3, n-9 and n-6
Test I & Final Exam
113. True or false? Due to fluid loss and inadequate diet, alcoholics are
commonly deficient in minerals such as calcium, magnesium, iron, and zinc.
A) True
B) False
114. Which of the following completes the breakdown of acetyl CoA?
A) glycolysis
B) ketosis
k t i
C) endocytosis
D) citric acid cycle
115. Which hormone is initiating catabolism of glycogen in response to quick
needs of glucose as source of energy under stress?
A) epimolarine
B) epiglucerine
p p
C)) epinepherine
D) epidemic
116. True or False? Antibodies are proteins used by our body to fight specific
invader.
A) True
B) False
117. The body can make long-chain fatty acids though a process called
A) glycolysis
B) lipogenesis
C) ketogenesis
Test I & Final Exam
D) lipolysis
118. Prebiotics and probiotics are
A) alive bacterial cells and oligosaccharides
B) parts of our digestive tract
C) essential
ti l components
t to
t control
t l bacterial
b t i l microflora
i fl
in
i small
ll intestine
i t ti
D) specific carbohydrates and enzymes digesting them
119. Which of the following is not a main reason why direct additives are used in
foods?
A) to maintain or improve nutritional value
B) to neutralize flavor or color
C) to maintain product consistency
D)) to p
provide leavening
g or control acidity
y and alkalinity
y
120. Which of the following is not a good question to ask prior buying a
supplement?
A) Is the quantity enough to have an effect?
B) Is
I the
h product
d
new to me?
?
C) Who is selling the product?
D) All of the above are good questions.
121 The sugar alcohols include
121.
A) stanols and stanol esters
B) xylitol, sorbitol, mannitol, and lactitol
C) lutein
D) lycopene
Test I & Final Exam
122. Flaxseed is reach in the following phytochemicals
A) Oil and protein
B) Lignin and omega-6 fatty acids
C) Fiber
Fib and
d carbohydrates
b h d t
D) n-3 fatty acid and lignans
123. Most people survive total starvation for
y
A)) three days
B) two weeks
C) two months
D) one year
124. True or false? NAD+ is derived from vitamin C.
A) True
B) False
125 Which vitamin plays a primary role in vision and the development of body
125.
cells?
A) vitamin A
B) vitamin B6
C) vitamin C
D) vitamin D
126. Which of the following diseases is associated with a vitamin D deficiency?
A) scurvy
B) beriberi
C) rickets
Test I & Final Exam
D) pellagra
127. Which vitamin is primarily responsible for blood clotting?
A) vitamin A
B) vitamin C
C) vitamin E
D) vitamin K
128. Which vitamin the body needs to synthesize fatty acids?
A) riboflavin
B) niacin
C) thiamin
D) vitamin B6
129. A deficiency associated with inadequate levels of vitamin C is
A) scurvy
B) beriberi
C) rickets
D) pellagra
130. True or false? Water-soluble vitamins are stored in the body.
A) True
B) False
131. True or false? Ten to 15 minutes of daily sunshine will provide an adequate
supply of vitamin C.
A) True
B) False
Test I & Final Exam
132. True or false? Good sources of biotin include fruits and vegetable such as
broccoli and bananas.
A) True
B) False
F l
133. Which of the following is not a function of the GI tract?
A) transport of ingested food
B) secretion of digestive enzymes
C) exchange of oxygen within the blood vessels
D) movement of undigested material
134. When disease-causing bacteria are ingested what is killing them?
A) Pepsin
B) Bile
C) Gastrin
D) Hydrochloric acid
135. True or false? Most amino acids require active transport.
A) True
B)) False
136. True or false? Intrinsic factor is a substance necessary for the absorption of
vitamin B12.
A) True
B) False
Test I & Final Exam
137. Which of the following is used to help determine Estimated Energy
Expenditure (EER)?
A) age
B) height
h i ht and
d weight
i ht
C) physical activity level
D) all of the above
g body
y fat?
138. Which of the followingg methods is the least effective for measuring
A) the Bod Pod
B) underwater weighing
C) BMI index
D)) bioelectrical impedance
p
139. True or false? Our bodies store glucose as glycogen in the liver and muscles
for later use.
A) True
B) False
F l
140. True or false? Feasting stimulates anabolic processes such as glycogen and
fat synthesis.
A) True
B) False
141. True or false? Triglycerides are an excellent source of glucose the later can
b used
be
d iin llarge amounts
t as a source off energy.
A) True
B) False
Test I & Final Exam
142. Lecithin is a lipid component which
A) belongs to sterols group
B) has emulsifying properties
C) is the main lipid component in egg white
D) is the main component in plant cells only
143. Plants from Cruciferous family are source of
A) diverse group of cyclic phytochemicals
B) specifically offer diverse group of sulphur components
C) contains terpenes only
D) is a source of components helping with diabetes
144. The most sensible way to reduce the amount of body fat is
A) avoid consumption of carbohydrates
B) restrict daily energy intake to 1000 kcal
C) regularly
l l exercises
i att moderate
d t level
l l
D) limit the amounts of fat and carbohydrates in your diet
145. A grain product with added thiamin, riboflavin, niacin, folic acid, and iron to
replace those nutrients lost or diminished in food processing is
A) fortified
B) enriched
C) enhanced
D) processed
Test I & Final Exam
146. Which nutrient is not required to be posted on the Nutrition Facts panel?
A) carbohydrates
B) fats
C) water
D) vitamins
147. True or false? Health researchers have discovered links between diet and
high blood pressure, cancer, and heart disease.
A) True
B) False
148. True or false? The Recommended Dietary Allowance (RDA) is the daily level
that meets the needs of the majority of people (over 97 percent).
percent)
A) True
B) False
149. Most of poultry and pork meats are lighter in colour because they contain
A) lower amounts of myoglobin
B) lower amounts PUFA lipids
C) higher amounts of fats
D) higher amounts of protein
150. True or False? Glucose and fatty acids are not the main source of Acetyl
CoA.
A) True
B) False
Test I & Final Exam
151. True or false? Foods sweetened with sugar alcohol promote tooth decay.
A) True
B) False
152. All amino acids when catabolize for energy are directly involve in the
following metabolic processes
A) transamination and glycogenesis
B) glycolysis and acetyl CoA metabolism
C) TCA cycle, acetyl CoA metabolism and electron transfer chain
D) neither of the above metabolic processes
153. True or False? Omega-3 fatty acids have always first double bond on the
third carbon atom counted from methyl group.
A) True
B) False
154. True or False? The largest number of ATP molecules is produced during
lipogenesis of fatty acids.
A) True
B) False
155 Wh
155.
When water
t iintake
t k iis llow, spinal
i l cells
ll in
i the
th brain
b i signal
i
l the
th pituitary
it it
glands
l d
to release
A) epinephrine
B) antidiuretic hormone
C) thyroxin
D) insulin
Test I & Final Exam
156. Which mineral deficiency is the most common worldwide?
A) sodium
B) phosphorus
C) iron
i
D) calcium
157. True or false? Sodium and potassium are positively charged ions called
cations, and chloride and phosphate form negatively charged ions called
anions.
A) True
B) False
158. True or false? Water loss of 20 percent of body weight can cause coma and
death.
A) True
B) False
159. True or false? Vitamin D is needed for calcium absorption and should be
considered for the prevention of osteoporosis.
A)) True
B) False
160. True or False? Glucogenic amino acids are transformed into fatty acids by
t
transamination.
i ti
A) True
B) False
Test I & Final Exam
161. True or False? One of the main functions of the liver is storage and
anabolism of glycogen to keep proper blood glucose level.
A) True
B) False
162. True or False? Amino acids are metabolized by beta-oxidation to form long
chain fatty acids.
A) True
B) False
163. True or false? Manufacturers must have approval from Health Canada prior
marketing a supplement.
A) True
T
B) False
164. In the immune system antigen and antibody have the following functions
A) protect body from invaders by killing them
B) to
t mark
k iinvader
d and
dd
destroy
t
it
C) to destroy invader and produce proteins from it
D) to mark invader and remove it from body
165 Which metabolic process does not require oxygen when breaking down a
165.
glucose molecule into two molecules of pyruvate, yielding two molecules of
ATP and two molecules of NADH?
A) Metabolism
B) Acidity
C) Oxidation
Test I & Final Exam
D) Glycolysis