Digestion Flashcards
1
Q
What are nutrients?
A
- chemical substances found in foods that are used in human body
2
Q
Why are some nutrients essential?
A
- essential nutrient = ones that cannot be synthesised
- obtained from food only
- water (is synthesised however, not sufficient amount)
3
Q
What are two groups of vitamins?
A
- water-soluble and lipid-soluble
- water-soluble are easily excreted
- lipid-soluble = A D E K (rest is water-sol.)
- vitamins do not have a common structure
4
Q
What is malnutrition?
A
- imbalance of nutrients that causes health problems
- deficiency, imbalance or excess
5
Q
What are minerals?
A
- essential chemical elements found in food (ions)
6
Q
What are different minerals and their function?
A
- Ca2+ — secondary messenger in signalling (muscle contraction. synapse); component of bones
- Fe2+ — part of heme
- Zn2+ — zinc fingers (found in proteins, enzymes)
- Na+, K+ — membrane potential; signalling
- I- — thyroid hormones (growth); nervous system development; metabolic processes
7
Q
Are vitamins universal for all organisms?
A
- no
- some substances which are synthesized by human body may be vitamins for other animals
8
Q
What is the role of vitamin C?
A
- antioxidant
- reduces molecules (electron donor)
- during immunological response
- synthesis of collagen
- deficiency = scurvy
- leads to bleeding gums and under skin
- found in: veggies and fruits
- unstable – amount lowers with time, temp increase, exposure to metals (iron and copper)
9
Q
Do rats synthesise vitamin C?
A
- yes
- experiments with vitamin C deficiency could not be performed on rats
- rats produce their own ascorbic acid (not a vitamin for them)
10
Q
What are the consequences of scurvy?
A
- pain in joints (lack of collagen)
- haemorrhages (bleeding) from gums, under skin, disintegration of blood vessel walls
- teeth loss
- even death
- anaemia
- osteoporosis
11
Q
What is the role of vitamin D?
A
- produced in skin irradiated with UV
- risk of skin cancer
- instead of vitamin it should be prohormone
- turned into calcitriol
- transcription regulator for genes connected to calcium
- Ca homeostasis
- bone mineralisation, muscle contraction, nervous and cellular signalling,
- immune response
12
Q
What are the consequences of overdosage of vitamin D?
A
- toxicity symptoms and hypercalemia
13
Q
What is RDA (recommended daily amount) of vitamin D?
A
- 30 min exposure to sunlight UV (or more)
- depends on latitude, ageing, season, skin pigmentation, clothing
- dietary supplementing needed
- 5 μg/day
14
Q
What are the consequences of vitamin D deficiency?
A
- rickets
- impeded growth, long bones deformation
- osteomalacia
- impaired calcium deposition in bones
- lower mineral density
- posture abnormalities
15
Q
What are essential fatty acids?
A
- omega 3 and 6
- unsaturated
16
Q
What are essential amino acids?
A
- Phenylalanine
- Threonine (if no Phe)
- Valine
- Tryptophan
- Methionine
- Leucine
- Isoleucine
- Lysine
- Histidine
- Arginine (in infants)
17
Q
What are the consequences of starvation?
A
- scarcity of food leading to deficiencies
- lack of protein
- breakdown of muscle tissue and other
- instead essential amino acid are produced
- cardiac muscle can be destroyed
- anorexia = reduced appetite
- anorexia nervous = psychiatric illness, voluntary starvation
- weight, hair loss
- loss of energy
- skin bruises
- suspension of menstrual cycle and ovulation
- reduced blood pressure, slower heart rate
- anorexia nervous = psychiatric illness, voluntary starvation
18
Q
What are the consequences of plasma protein deficiency?
A
- lack of amino acids —> lack of important blood plasma proteins (albumins)
- maintain colloid osmotic pressure
- tissue fluid doesn’t come back to circulatory system
- retended in tissues
- tissue swelling (in abdomen) = edema
19
Q
What is phenylketonuria?
A
- autosomal recessive genetic disorder
- diagnosed in infants
20
Q
What are the causes and consequences of phenylketonuria (PKU)?
A
- caused by lack of enzyme converting phenylalanine —> tyrosine
- phenylalanine converted into phenylpyruvate
- later in urine
- impairment of brain development
- mental retardation
- brain damage
- seizures
21
Q
What is PKU treatment?
A
- incurable
- low-phenylalanine diet
- meat, nuts, cheese, dairy, legumes —> a lot
- controlled amounts: bread, pasta, corn, potatoes
- diet not enough
- medication (BH4)
- removal of phenylalanine
- supplementing of tyrosine
- medication (BH4)
22
Q
How is appetite controlled?
A
- Appetite Control Centre (ACC) in brain (hypothalamus)
- sugar levels
- insulin
- adipose tissue
- leptin
- stomach filling state
- ghrelin
- smell (tasty or disgusting)
23
Q
What are the risks of obesity?
A
- diabetes II
- high blood pressure
- arteriosclerosis (atherosclerosis)
- joint damage
- impotence
- self-esteem issues
- thyroid dysfunctions
- cancer
24
Q
What are exocrine glands?
A
- substances sent out of body
- release them to ducts
- not to blood stream (like endocrine glands)
- examples: sweat, moll, mammary, sebaceous
25
What are parts of alimentary canal?
- mouth, large intestine, small intestine, oesophagus, stomach, duodenum, rectum
26
What are digestive glands?
- salivary glands
- pyloric glands
- stomach
- pancreatic exocrine and endocrine glands
- goblet cells
- small intestine
27
What are accessory organs?
- teeth, liver, gall bladder, bile duct, salivary glands, tongue, pancreas
28
What is digestion?
- enzymatic breakdown into monomers
29
Which molecules are digested?
- lipids —> fatty acids and glycerol
- lipase + bile
- proteins —> amino acids
- pepsin
- polysaccharides —> monosaccharides
- amylase
- beta-D-glycosidic bond no digested (cellulose)
- nucleic acids —> nucleotides
30
What is the role of mouth in digestion?
- teeth: chewing
- tongue: mixing food with saliva + pushing bolus to oesophagus
- saliva
- antimicrobial gents (lysosomes)
- digestion of starch by amylase
- moistens bolus
31
What is the role of stomach in digestion?
- churning and mixing bolus with water and acid
- muscle tissue
- HCl
- kills microorganisms
- protein denaturation
- protein digestion (pepsin)
- bolus —> chyme
32
What happens during the first phase of gastric secretion?
- cephalic phase
- signal is sent to the brain (senses)
33
How is acid maintained in the stomach?
- gastric acid in lumen
- protection: mucus + dead cells
- acid could damage stomach
- proton pump (H+/K+ ATPase)
- lower pH by exchanging H+ and K+
- acid overproduction = inhibitors of the pump (medication)
- not permanent —> pumps are recycled
34
What is stomach ulcers?
- gastric ulcers
- lesion in stomach wall
- lining exposed to juice
- bleeding and pain
- stress may contribute
35
What is Helicobacter pylori?
- bacterium
- gastric mucous membrane destroyed
- stomach ulcers
- inflammation, toxins, exposure to acid, production of urease (toxic ammonia), more acid production
- peptic ulcers can lead to cancer
- H. pylori infections correlate
36
What is the role of pancreas in digestion?
- in duodenum (pancreatic juice)
- endopeptidases (proteases) activates pepsin in stomach
- lipase
- amylase
- HCO3- ions neutralise acid
- nuclease
37
What is the protein regulating pH in stomach?
- proton pump
- H+/ K+ ATPase
38
What is the role of bile?
- emulsifies lipids
- lipase water soluble
- lipids aren’t
- dispersion of lipids = larger surface area
- not an enzyme
39
How are sugars digested?
- starch (other polymers of glucose) —> maltose (by amylase)
- at the surface of small intestine
- maltose —> glucose (by maltase)
- easy absorption
40
What is the function of endopeptidases?
- cut polypeptide chains in the middle
- recognises bonds
- producing shorter and shorter chains
- individual amino acids
41
What happens in small intestine?
- digestion (beginning) and absorption (later)
- neutralising stomach acid
42
What allows for the movement of chyme?
- peristalsis
- smooth muscles
- away from mouth
- circular muscles – no movement backwards
- longitudinal muscles – movement along gut
- vomiting = contraction of abdominal muscles
- slow = time for digestion
- another function of peristalsis: segmentation
43
How is role of villus?
- increases surface area for absorption
- microvilli (increase even further)
- blood vessel + lacteal (part of lymphatic system, lipid absorption)
44
What are the layers of small intestine?
- mucosa (closest to lumen)
- folded inner layer (villi)
- sub-mucosa
- connective tissue
- separation: mucosa - muscles
- muscle layer
- out: longitudinal
- in: circular
- serosa
- most outer protective layer
- fibrous connective tissue
45
Why do tight junctions exist?
- no substances can go between villi (absorption)
46
What are the adaptations for absorption?
- large surface area
- villi & microvilli
- short distance
- single epithelial
- concentration gradient
- dense capillary network (blood flow)
- lacteal for lipids
- control of transport
- tight junctions between cells
47
What is the structure of brush border cells?
- effective absorption
- polarity
- absorption surface and capillary facing surface
- microvilli
- mitochondria
- protein transporters, pumps and channels
- nutrients into bloodstream
48
What is the type of transport used to move sugars?
- glucose / galactose
- co-transport (Na+) —> epithelial cells of villi
- monosaccharides
- facilitated diffusion —> capillaries
- other sugars
- facilitated diffusion —> epithelial cells of villi
- monosaccharides (the same)
49
What is co-transport?
- protein that can bind 2 molecules
- Na+ binds (moves down the gradient)
- another molecule binds and is moved with the energy of Na+ (or other molecule)
- against the gradient (active transport)
50
What is the type of transport used to transport proteins?
- amino acids
- co-transport (Na+) —> epithelial cells (villi)
- amino acids
- simple diffusion —> capillaries
- peptides (<5 a. a.)
- co-transport (H+) —> villi
- amino acids
51
What is the type of transport used to move lipids?
- triglycerides —> fatty acids + monoglycerides
- simple diffusion —> epithelial cells of villi
- fatty acids
- facilitated diffusion (fatty acid transporters in microvilli)
- inside epithelium cells —> recombines to triglycerides
- cannot diffuse back
- triglycerides with cholesterol —> form LDL
- exocytosis —> villi
- enter lacteal
- lymph or bloodstream
52
What happens in large intestine?
- re-absporption of water
- digestion of carbohydrates (symbiotic bacteria)
- some of the products that are not digested in small intestine
- formation of faeces
53
What is the pathway of starch to glucose?
- starch —> dextrins + maltose
- amylase
- intestinal lumen
- dextrins + maltose —> glucose
- enzymes + cells of brush border
- glucose absorbed
- facilitated and active transport
- glucose to liver (in blood), absorbed in liver
- triggered by glucagon
- facilitated diffusion
- glucose —> glycogen
54
Why is fibre important in egestion?
- movement of chyme and faeces
- easy defecation
- cellulose, waxes, lignin
- absorbs water
55
What happens to water in large intestine?
- absorbed
- contains many secretions (dilutes them)
- easy absorption
- speed of peristalsis
- low speed —> constipation
- high speed —> diarrhoea
56
What is cholera and its mechanism?
- cholera toxin produced by Vibrio cholerae
- binds to epithelium in intestines
- cascade: Cl-, Na+, HCO3- to gut lumen
- water flows by osmosis —> extreme diarrhoea
- dehydration
57
What are the functions of the liver?
- storage
- glucose
- lipids
- detoxification
- NH3
- bile production
- metabolism
58
What are the 3 blood vessels involved in liver circulation and their function?
- hepatic artery (incoming)
- oxygen-rich blood
- arterioles join sinusoids
- hepatic portal vein (incoming)
- blood from stomach and intestines (rich in nutrients), low oxygen
- hepatic vein (coming out)
- venues merge with sinusoids
- blood to vena cava
59
What is the structure of the liver?
- built out of lobules
- branches of portal veins and hepatic artery (to the central vein)
- sinusoids — blood leaks from veins to structures
- hepatocytes — washed by blood in sinusoids
- direct uptake
60
What is the structure of a sinusoid?
- wide blood vessels (wider than capillaries)
- fenestration — pores between endothelial cells
- blood in direct contact with hepatocytes
- Kupffer cells — macrophages (destroy erythrocytes)
- no basal lamina (net of proteins)
- no barrier
- no tight junctions
61
How are nutrients stored in the liver?
- glucose
- condensed to glycogen
- released by glucagon
- excess glucose = no osmotic balance
- amino acids
- excess toxic
- vitamins A, D, B12, K
- excess toxic
- iron
- toxic in the form of ions
- stored with proteins (transferrin)
- Kupfer cells kill erythrocytes
- iron is uptaken (not wasted)
- copper (used as coenzyme)
62
Where are plasma proteins produced?
- in endoplasmic reticulum and Golgi apparatus in hepatocytes (liver)
- a lot with secretory granules
- produced: albumins, fibrinogen
- hepatocytes
63
What is the pathway of cholesterol?
| How is it absorbed
1. cholesterol and triglycerides absorbed
- incorporated into chylomicrons (large lipoproteins)
2. secreted into lymph and later in liver
3. fat to adipose tissue
- taken up as fatty acids
4. small chylomicrons remnant removed from plasma by liver
- as HDL
5. converted into bile
64
What is the pathway of triglycerides?
- fatty acids + triglyceride (with cholesterol) —> (very)LDL
- between meals
- fat to adipose and muscle tissues (chylomicron)
- energy use or storage
65
What are functions of cholesterol?
- synthesis
- vitamin D, steroid hormones, bile
- membrane components
66
How does liver detoxify substances?
- toxic substances from blood
- oxidised
- processed by enzymes
- alcohol dehydrogenase
- production of urea
- hydrophobic compounds —> transferred into hydrophilic
- liver has regenerative potential
67
How does liver recycle erythrocytes?
- lifespan: 120 days
- Kupffer cells
- ingestion by phagocytosis
- recycling
- heme
- iron —> production of new cells
- bilirubin —> bile
- globin (amino acids) —> return to bloodstream
68
Where is bile formed and what are its components?
- produced by liver, stored in gall bladder
- released via bile duct (duodenum)
- components: hydrogen carbonate ions, bile salts and pigments, cholesterol
69
What is jaundice?
- yellow skin, conjunctives and mucous membranes
- high concentration of bilirubin (bile pigment)
- liver disjunction
- hepatitis
- liver cancer
- obstruction of bile duct
- newborn jaundice: immature processes of bilirubin excretion
70
What are the consequences of jaundice?
- no need for treatment (as it is a symptom)
- bilirubin accumulation in nervous tissue
- neurological damage (brain)
- infants and elderly
71
What are conditionally essential vitamins?
- conditionally essential: vitamin D&K
- needed only in some circumstances
(ex. vit K is needed for infant’s microbe which is underdeveloped)
72
What is the structure of exocrine glands?
- secretory cells in groups = acinus
- around duct branch (not to bloodstream)
- lots of endoplasmic reticulum and mitochondria
- secretory vesicles
- exocytosis to the ducts
73
How is iron reused in synthesis of red blood cells?
- red blood cells have transferrin receptors
- synthesised in bone marrow by stem cells
- receptor-iron complex enters cells
- iron incorporated to heme
74
How are gastric juices regulated?
- nerves and hormones regulate digestive juices
- sight / smell of food —> nerve impulses from brain via vagus nerve
- from medulla
- gland cells in stomach —> secrete components of gastric juice
- chemoreceptors in stomach wall detect peptides
- or stretch receptors detect distension of stomach
- impulses to brain
- brain —> vagus nerve
- to endocrine cells (duodenum) —> gastric secretion
- gastric —> secretion of acid and pepsinogen (exocrine gland cells in stomach wall)
- secretin and somatostatin inhibit gastric secretion —> pH too low
