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The Digestive System and Body Metabolism Ch 14 Part D

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Title: The Digestive System and Body Metabolism Ch 14 Part D


1
The Digestive System and Body MetabolismCh 14
Part D
2
Metabolism
  • Chemical reactions necessary to maintain life
  • Includes 2 phases
  • Catabolism substances are broken down to
    simpler substances
  • Energy within chemical bonds of food is released
    captured to make ATP
  • Anabolism larger molecules are built from
    smaller ones
  • Major nutrient catagories used for various
    cellular body needs
  • Carbohydrates used for ATP
  • Fats used for cell membranes, myelin
    insulation, to make ATP when no carbohydrates
  • Proteins for structures

3
Carbohydrate Metabolism
  • Carbohydrates are the bodys preferred source to
    produce cellular energy (ATP)
  • Glucose (blood sugar) is the major breakdown
    product and fuel to make ATP

Figure 14.17
4
Cellular Respiration
  • Oxygen-using events take place within the cell to
    create ATP from ADP
  • Carbon leaves cells as carbon dioxide (CO2)
  • Hydrogen atoms are combined with oxygen to form
    water
  • Energy produced by these reactions adds a
    phosphorus to ADP to produce ATP
  • ATP can be broken down to release energy for
    cellular use

5
Carbohydrate Metabolism
Figure 14.18
6
Stages of Cellular Respiration
  • Cellular Respiration includes
  • Glycolysis
  • Krebs Cycle
  • Electron Transport Chain

7
Metabolic Pathways Involved in Cellular
Respiration
  • Glycolysis energizes a glucose molecule so that
    it can be split into two pyruvic acid molecules
    and yield ATP
  • Occurs in cytoplasm
  • Citric Acid (Krebs) Cycle
  • Produces virtually all the carbon dioxide and
    water resulting from cell respiration
  • Yields a small amount of ATP
  • Occurs in mitochondria

8
Metabolic Pathways Involved in Cellular
Respiration
  • Electron Transport Chain
  • Hydrogen atoms removed during glycolysis and the
    Krebs cycle are delivered to protein carriers
  • Hydrogen is split into hydrogen ions and
    electrons in the mitochondria
  • Electrons give off energy in a series of steps to
    enable the production of ATP

Figure 14.19a
9
Cellular Respiration
Figure 14.19
10
Metabolic Pathways Involved in Cellular
Respiration
Figure 14.20a
11
Metabolism of Carbohydrates
  • Hyperglycemia
  • Excessively high levels of blood glucose
  • Excess glucose is stored in liver as glycogen
  • If blood glucose levels are still too high,
    excesses are converted to fat

12
Metabolism of Carbohydrates
Figure 14.21a
13
Metabolism of Carbohydrates
  • Hypoglycemia
  • Low levels of glucose in the blood
  • Liver breaks down stored glycogen and releases
    glucose into the blood

14
Fat Metabolism
  • Handled mostly by the liver
  • Use some fats to make ATP
  • Synthesize lipoproteins, thromboplastin (clotting
    factor), and cholesterol
  • Release breakdown products to the blood
  • Body cells remove fat and cholesterol to build
  • membranes and steroid hormones
  • Used for myelin sheaths of neurons

15
Fat Metabolism
Figure 14.21b
16
Use of Fats for ATP Synthesis
  • Stored fats energy
  • 9 kcal of energy in 1g of fat
  • 4 kcal of energy in 1g carbohydrates or proteins
  • Fats must first be broken down to acetic acid
  • Within mitochondria, acetic acid is completely
    oxidized to produce water, carbon dioxide, and
    ATP
  • When low glucose, use fat for ATP

17
Use of Fats for ATP Synthesis
  • Acidosis (ketoacidosis) results from incomplete
    fat oxidation in which acetoacetic acid and
    acetone accumulate in the blood
  • Breath has a fruity odor
  • Common with
  • No carbohydrate diets Atkins diet
  • Uncontrolled diabetes mellitus
  • Starvation

18
ATP Formation
Figure 14.21d
19
Protein Metabolism
  • Proteins are conserved by body cells because they
    are used for most cellular structures
  • Ingested proteins are broken down to amino acids
  • Cells remove amino acids to build proteins
  • Need 20 amino acids 9 are essential (cannot be
    made by body)
  • Synthesized proteins are actively transported
    across cell membranes
  • Amino acids are used to make ATP only when
    proteins are overabundant or there is a shortage
    of other sources

20
Production of ATP from Protein
  • Amine groups are removed from proteins as ammonia
  • The rest of the protein molecule enters the Krebs
    cycle in mitochondria
  • The liver converts harmful ammonia to urea which
    can be eliminated in urine

21
Protein Metabolism
Figure 14.21c
22
Role of the Liver in Metabolism
  • Several roles in digestion
  • Manufacturers bile
  • Detoxifies drugs and alcohol
  • Degrades hormones
  • Produce cholesterol, blood proteins (albumin and
    clotting proteins), lipoproteins
  • Albumin maintains osmotic pressure of blood
    keeps fluids in the blood
  • Plays a central role in metabolism
  • Process all nutrients
  • Removes amino acids, fatty acids glucose for
    later use
  • Removes bacteria
  • A person will die within 24 hours of liver loss!!

23
Role of the Liver in Metabolism
  • Humans have excess liver tissue it also
    regenerates if part of it is damaged or removed
  • Hepatic portal circulation-
  • Brings nutrient-rich blood from digestive system
    to liver so liver can process it

24
Metabolic Functions of the Liver
  • Glycogenesis glycogen formation
  • Glucose molecules are converted to glycogen
  • Glycogen molecules are stored in the liver
  • Glycogenolysis glucose splitting
  • Glucose is released from the liver after
    conversion from glycogen
  • Gluconeogenesis formation of new sugar
  • Glucose is produced from fats and proteins

25
Metabolic Functions of the Liver
Figure 14.22
26
Metabolic Functions of the Liver
  • Fats and fatty acids are picked up by the liver
  • Some are oxidized to provide energy for liver
    cells
  • The rest are broken down into simpler compounds
    and released into the blood
  • Acetic acid acetoacetic acid
  • Makes cholesterol, which is used to strengthen
    cell membranes

27
Cholesterol Metabolism
  • Cholesterol is not used to make ATP (not used for
    energy)
  • Functions of cholesterol
  • Serves as a structural basis of steroid hormones
    and vitamin D
  • Is a major building block of plasma membranes
  • In bile salts
  • Most cholesterol is produced in the liver (85)
    and is not from diet (15)

28
Cholesterol Transport
  • Cholesterol and fatty acids cannot freely
    circulate in the bloodstream
  • Not water soluble
  • They are transported by lipoproteins (made in
    liver) (lipid-protein complexes)
  • Low-density lipoproteins (LDLs) transport to body
    cells
  • Bad cholesterol since they can lead to
    artherosclerosis
  • High-density lipoproteins (HDLs) transport from
    body cells to the liver
  • good cholesterol

29
Body Energy Balance
  • Energy intake total energy output
  • (heat work energy storage)
  • Energy intake is liberated during food oxidation
  • Glycolysis, Krebs cycle, electron transport
  • Energy output
  • Heat is usually about 60 of total
  • Storage energy is in the form of fat or glycogen

30
Regulation of Food Intake
  • Body weight is usually relatively stable
  • Energy intake and output remain about equal
  • Mechanisms that may regulate food intake
  • Levels of nutrients in the blood
  • Glucose, amino acids
  • Hormones
  • Insulin, glucagon, leptin
  • Body temperature
  • Psychological factors

31
Metabolic Rate and Body Heat Production
  • Basic metabolic rate (BMR) amount of heat
    produced by the body per unit of time at rest
  • energy needed for essential life activities
  • Average BMR is about 60 72 kcal/hour
  • Kilocalorie (kcal) is the unit of measure for the
    energy value of foods and the amount of energy
    used by the body

32
Metabolic Rate and Body Heat Production
  • Factors that influence BMR
  • Surface area small body usually has higher BMR
  • Gender males tend to have higher BMR
  • 70kg adult has BMR of 60-72 kcal/hr
  • Age children and adolescents have a higher BMR
  • The amount of thyroxin (from thyroid) produced is
    the most important control factor
  • More thyroxin means higher metabolic rate
  • Hyperthyroidism- lose weight
  • Hypothyroidism- gain weight

33
Factors Determining BMR
Table 14.3
34
Total Metabolic Rate (TMR)
  • Total amount of kilocalories the body must
    consume to fuel ongoing activities
  • TMR increases with an increase in body activity
  • TMR must equal calories consumed to maintain
    homeostasis and maintain a constant weight
  • ? TMR leads to ? weight gain

35
Body Temperature Regulation
  • Most energy is released as foods are oxidized
  • Most energy escapes as heat
  • Less than 40 of food energy forms ATP

36
Body Temperature Regulation
  • The body has a narrow range of homeostatic
    temperature
  • Must remain between 35.6 to 37.8C (96 to 100
    F)
  • The bodys thermostat is in the hypothalamus
  • Initiates heat-loss or heat-promoting mechanisms

37
Heat Promoting Mechanisms
  • When cold
  • Vasoconstriction of blood vessels
  • Blood is rerouted to deeper, more vital body
    organs
  • Skin becomes cold
  • Shivering contraction of muscles produces heat
  • Hypothermia
  • ? respiration rate, BP, heart rate, metabolism
    comes to a halt

38
Mechanisms of Body Temperature Regulation
Figure 14.23
39
Mechanisms of Body Temperature Regulation
Figure 14.23, step 3
40
Mechanisms of Body Temperature Regulation
Figure 14.23, step 4
41
Mechanisms of Body Temperature Regulation
Figure 14.23, step 6
42
Heat Loss Mechanisms
  • When hot
  • Heat loss from the skin via radiation and
    evaporation
  • Skin blood vessels and capillaries are flushed
    with warm blood
  • Evaporation of perspiration cools the skin
  • Less evaporation if humidity is high

43
Mechanisms of Body Temperature Regulation
Figure 14.23, step 7
44
Mechanisms of Body Temperature Regulation
Figure 14.23, step 12
45
Mechanisms of Body Temperature Regulation
Figure 14.23, step 13
46
  • Hyperthermia
  • ? T depresses hypothalamus ? positive feedback
    causing ? metabolism ? ? T ? brain damage
  • heat stroke heat loss mechanism NOT working
  • Heat exhaustion
  • From dehydration ? BP, ? heart rate cool,
    clammy skin, heat loss mechanisms still work

47
Body Temperature Regulation
  • Fever controlled hyperthermia
  • Results from infection, cancer, allergic
    reactions, CNS injuries
  • Body T reset high heat promoting mechanisms
    vasoconstriction, shivering (the chills), ?
    metabolic rate inhibits bacterial growth
  • Too high a fever can lead to body proteins being
    denatured and permanent brain damage

48
Developmental Aspects of the Digestive System
  • The alimentary canal is a continuous tube by the
    fifth week of development
  • Digestive glands bud from the mucosa of the
    alimentary tube
  • The developing fetus receives all nutrients
    through the placenta
  • In newborns, feeding must be frequent (small
    stomach), peristalsis is inefficient, and
    vomiting is common

49
Developmental Aspects of the Digestive System
  • Newborn reflexes
  • Rooting reflex help the infant find the nipple
  • Sucking reflex helps the infant hold on to the
    nipple and swallow
  • Teething begins around age six months

50
  • Congenital defects
  • Cleft lip/palate
  • Tracheoesophageal fistula
  • Inborn errors of metabolism
  • Cystic fibrosis pancreatic duct blocked
  • No fat digestion
  • PKU brain damage

51
Cleft lip
52
Cleft lip
53
Cleft lip palate
54
Tracheoesophageal fistula
55
Developmental Aspects of the Digestive System
  • Problems of the digestive system
  • Gastroenteritis inflammation of the
    gastrointestinal tract
  • Appendicitis inflammation of the appendix
  • Metabolism decreases with old age
  • Metabolic rate ? by 5-8/10 years
  • Middle age digestive problems
  • Ulcers
  • Gall bladder problems

56
Developmental Aspects of the Digestive System
  • Activity of digestive tract in old age
  • Fewer digestive juices
  • GI activity slows
  • Peristalsis slows
  • Diverticulosis and cancer (stomach colon) are
    more common
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