Topic 3 - Nutrition & Digestion Flashcards
What proportion of society is considered overweight?
Over 1/3 of adults and nearly 1/3 of children
Simplified, what causes obesity?
Too much energy-rich food and too sedentary a lifestyle
What are the possible neurological effects of excessive fat storage?
- Headache
- Stroke
- Dementia, inc. Alzheimer’s
- Vision loss from diabetic complications
- False brain tumour (pseudo tumour cerebri)
- Diabetic neuropathy (weak/numbness)
What are the possible respiratory effects of excessive fat storage?
- Asthma
- Sleep apnoea
- Pulmonary embolism (blockage of the main artery of the lung)
- Pulmonary hypertension (increased blood pressure in the arteries of the lungs)
What are the possible urological effects of excessive fat storage?
- Diabetes
* Kidney cancer
What are the possible circulatory effects of excessive fat storage?
- High blood pressure
- High cholesterol
- Atherosclerosis (fatty deposits in the arteries)
- Irregular heartbeat
- Heart attack/failure
- Poor circulation
- Leg/ankle swelling
- Peripheral artery disease (buildup of plaque in arteries)
- Certain lymphomas
What are the possible psychological effects of excessive fat storage?
- Depression
- Anxiety
- Eating disorders
What are the possible gastrointestinal effects of excessive fat storage?
- GERD
- Oesophageal cancer
- Colon polyps
- Fatty liver disease
- Cirrhosis (disease of the liver)
- Liver cancer
- Gallstones
- Gallbladder cancer
What are the possible pancreatic effects of excessive fat storage?
- Type 2 diabetes
- Pancreatitis
- Pancreatic cancer
What are the possible nutritional effects of excessive fat storage?
- Vitamin D deficiency
* Other vitamin/mineral deficiencies
What are the possible female reproductive effects of excessive fat storage?
- Irregular periods
- Infertility
- PCOS
- Ovarian/Endometrial/Cervical/Breast cancer
What are the possible male reproductive effects of excessive fat storage?
- Prostate cancer
- Infertility
- Erectile dysfunction
What is adipose tissue?
Body fat - specialised connective tissue made of lipid-rich cells called adipocytes
What does the term ‘lean body mass’ refer to?
All body organs (eg bone, muscle, lungs) which do not store fat
What are the two types of adipose tissue?
- White adipose tissue
* Brown adipose tissue
What is white adipose (WAT) tissue?
- The most common type of adipose tissue found in the body
* Stores energy as fat
What is brown adipose (BAT) tissue?
Tissue whose primary function is thermoregulation
What is the function of brown adipose tissue?
To produce body heat from the energy which comes from the food we consume
What is the function of white adipose tissue?
Its main function is insulation and energy storage
Where is brown adipose tissue typically stored?
- The neck
* Around the large blood vessels of the thorax
What are adipocytes?
Cells which are specialised in the synthesis and storage of fat
We need some white adipose tissue (WAT), but what for?
Cushioning, insulating and protecting organs and bones in the body
What are the factors which likely affect a person’s volume of adipose tissue (adiposity)?
- Genetics
- Age
- Sex
- Physical activity
- Diet
Where do men tend to carry their excess fat?
Abdomen
Where do women tend to carry their excess fat?
- Thighs
* Hips
After what age do people tend to lose fat and lean body mass?
70
How does the WHO recommend assessing an individual’s adiposity?
By using their waist-to-hip ratio in combination with their BMI
What are the two factors that make up an individual’s TEE (total energy expenditure)?
- The total energy required to carry out basic processes of life (eg heartbeat, breathing)
- The total energy required for other tasks such as brain activity
What is the definition of BMR?
The number of calories your body uses to maintain vital functions, such as breathing, heart rate, and brain function
How would you be in a state of energy balance?
If your total energy intake (TEI) exactly matches your total energy expenditure (TEE)
How would you be in a state of positive energy balance?
If your total energy intake (TEI) is greater than your total energy expenditure (TEE)
How would you be in a state of negative energy balance?
If total energy intake (TEI) is less than total energy expenditure (TEE)
Is obesity caused by a positive or negative energy balance?
A positive energy balance
What is catabolism?
The breaking down of complex substances in to simpler ones, with the release of energy
Are catabolic reactions exergonic or endergonic?
Exergonic
Define exergonic
A reaction which relases or generates more energy than it uses
Define endergonic
Reactions which use more energy than they release
What is anabolism?
The process by which the body utilizes the energy released by catabolism to synthesize complex molecules
In which part of the cell is ATP made?
The cytosol
What is glycolisis?
The process that combines sugars and glycerol to produce ATP
What is the TCA (tricarboxylic acid) cycle?
A series of metabolic reactons that occur in the mitochrondria producing ATP
By what other term is the TCA cycle known?
Aerobic respiration
What are the waste products of the TCA cycle?
- Water
* Carbon dixoide
Which is more efficient: anaerobic or aerobic respiration?
Aerobic
How many more times more ATP than anaerobic respiration does aerobic respiration produce?
15 times
During periods of heavy exercise, what is the main source of ATP, glycolysis or aerobic respiration?
Glycolysis
What is de novo lipogenisis?
The process which converts glucose and some amino acids in to fat
What are the six key nutrient groups?
- Carbohydrates
- Fats
- Proteins
- Minerals
- Vitamins
- Water
Which nutritional group is important to assist with the maintenance of ionic gradients?
Minerals
What is the definition of the term macronutrients?
The nutrients required in large amounts in the diet, i.e. carbohydrates, fats and protein
What is the definition of the term micronutrients?
Nutrients that are needed in only very small quantities by the body
What is the definition of the term antioxidants?
Molecules, including certain vitamins, that can inactivate harmful free radicals
What proportion of your energy intake does the WHO recommend to come from carbohydrates?
55-75%
What proportion of your energy intake does the WHO recommend to come from fats?
Less than 30%
What proportion of your energy intake does the WHO recommend to come from proteins?
10-15%
What are some of the main roles of iron within the body?
What can arise from deficiency in this?
- Transport of oxygen in the blood
* Anaemia, the reduction of the capacity to transport oxygen
What are some of the main roles of zinc within the body?
What can arise from deficiency in this?
- Regulation of several biochemical pathways
- Stunt growth in children
- Reduce effectiveness of immune system
What are some of the main roles of folate within the body?
What can arise from deficiency in this?
Fetal development
Neural tube defects
What are some of the main roles of vitamin A within the body?
What can arise from deficiency in this?
- Development and maintenance of immune and visual systems
- Blindness
- Susceptibility to infection
What are some of the main roles of vitamin C within the body?
What can arise from deficiency in this?
- Facilitates absorption of iron in the gut
- Involved in several enzymatic pathways, inc. collagen synthesis
- Scurvy due to breakdown and poor maintenance of connective tissues containing collagen
Which of the following types of carbohydrate has the simplest structure?
Polysaccharaide
Monosaccharide
Disaccharadie
Monosaccharide
What do polysaccharaides consist of?
Linear or branched chains of sugars joined together
Which sugars are polysaccharides?
- Starch
- Cellulose
- Glycogen
Name the two monosaccharides
- Glucose
* Fructose
Which sugar is a disaccharide?
Sucrose
What percentage of body mass do lipids account for?
Roughly 18-25%
What functions can lipids perform?
- Structural components of cell membranes
- Signalling molecules
- Long-term energy storage
Which of the following is the simplest form of lipid?
Fatty acids
Triglycerides
Phosopholipids
Steroids
Fatty acids
What is the typical cellular structure of steroids?
Multiple carbon rings
Is a fatty acid with one or more carbon-to-carbon covalent bonds in its tail a saturated or unsaturated fatty acid?
Unsaturated
What are the functions of lipids?
- Protection
- Insulation & thermoregulation
- Formation of the plasma membrane
- ATP synthesis
What are the components of a the basic structure of an amino acid?
- Hydrogen group
- Amine group
- Carboxyl group
- R group
What do all amino acids have in their structure?
A central carbon atom with four entities bonded to it
What is the term used to describe cells which are exposed to the external environment?
Epithelial cells
In the process of digestion, where does absorption start?
The small intestine
What is the enzyme produced in the mouth which helps begin to break down food?
Salivary amylase
What is the name for chewed and partially digested food?
The bolus
What is receptive relaxation (in terms of digestion)?
Which are the muscles that relax as part of this?
- The relaxation of the stomach in response to swallowing
* The sphincter and upper stomach muscles
What are the minimum and maximum volumes of the stomach?
- 50ml
* 1500ml
Up to how many times in size can the stomach increase?
30
What is the gastric mucosa?
The mucus membrane lining of the stomach
In which region of the stomach does gastric empyting occur?
The pyloric region
How much chyme does the stomach release with each of its contractions?
3ml
What is the hormone produced in the gastric mucosa?
Gastrin
With regards to the stomach and digestion, what are neck cells?
Mucus-producing cells which cover the inside of the stomach, protecting it from the corrosive nature of gastric acid.
With regards to the stomach and digestion, what are chief cells?
Epithelial cell that are found mainly in the mucosal layer of the stomach lining and which secrete pepsinogen and gastric lipase, as well as chymosin
With regards to the stomach and digestion, what are parietal cells?
Epithelial cells in the stomach that secrete hydrochloric acid (HCl) and intrinsic factor
Which type of gastric cell is responsible for secreting hydrochloric acid and intrinsic factor?
Parietal cells
Which type of gastric cell is responsible for secreting pepsinogen, gastric lipase and rennin?
Chief cells
Which type of gastric cell is responsible for secreting (stomach) mucus?
Neck cells
In the mouth, carbohydrates such as starch are digested into which smaller molecules?
Maltose and short-chain polysaccharides
Which enzyme is present in saliva?
Salivary amylase
In the stomach, what is food broken further down into?
- Amino acids
* Peptides
In the stomach, which enzyme and which secreted substance denature and partially break down food?
- Pepsin
* Hydrochloric acid
In the stomach, what are the two things lipids are broken down into?
- Mologlycerides
* Fatty acids
What is the name for the finger-like projections in the small intestine?
Villi
In the small intestine, how many villi are there (roughly) per square centimetre?
20 to 40
Approximately how long is the small intestine?
5m
What is the purpose of the villi in the small intestine?
To increase surface area, which aids in absorption
By how much do the villi in the small intestine increase its surface area?
Around 600-fold
What are the secretions which enter the GI tract?
- Saliva
- Gastric digestive secretions
- Gastric mucus secretions
- Bile from the liver
- Pancreatic secretions
What are the three parts of the small intestine?
- Duodenum
- Jejunum
- Ileum
What is the luminal surface (in the small intestine)?
The surface facing the lumen of the GI tract
In biology, what is a lumen?
The inside space of a tubular structure, such as an artery or intestine
In the small intestine, what is the surface of each villus folded in to?
Small, finger-like projections calls microvilli
What is the name for the microvilli layer (within the small intestine)?
The brush border
Roughly what is the size of the surface area of the human small intestine?
Approximately 300 sq m
What is the sphincter of Oddi?
A muscle that opens and closes to allow bile and pancreatic juice to flow between the pancreas and the small intestine
What are the names for the cells which the pancreas produces?
- Exocrine cells
* Endocrine cells
What is the distinguishing feature of all exocrine cells?
They release their fluids via ducts, onto an epithelial surface
What is an example of an exocrine secretion?
Sweat
Where do the secretions from endocrine cells go?
Directly into the bloodstream
What is pepsinogen?
A protein digesting enzyme (proteolytic)
What is the active form of pepsinogen?
Pepsin
What type of ions are produced by the exocrine cells of the pancreas?
For what purpose?
- Bicarbonate ions
* They neutralise the hydrogen ions in the chyme and neutralise the acidity of the contents of the duodenum
Is pepsin released as an active or inactive precursor?
Inactive
What is the name of the enzyme which activates the digestive enzymes in the duodenum?
Enterokinase
Where is enterokinase located?
The brush border of the intestinal mucosa
What is the pancreatic enzyme which is activated by enterokinase?
Trypsinogen
What is the active form of trypsinogen?
Trypsin
What is unusual about enterokinase?
It is not free in the lumen, but is restricted to the brush border
What are the main pancreatic enzymes?
- Trypsin
- Chymotrypsin
- Elastase
- Carboxypeptidase
- Pancreatic amylase
- Pancreatic lipase
- DNA/RNA
What is the function of trypsin, chymotrypsin and elastase?
To break peptide bonds in proteins in order to form peptide fragments
What is the function of carboxypeptidase?
To remove terminal amino acids from the carboxyl end of the chain
What is the function of pancreatic amylase?
To split polysaccharides into disaccharides and short chains of glucose units (dextrins)
What is the function of pancreatic lipase?
To split two fatty acids from each tryglyceride molecule in order to form free fatty acids and monoglyceride
What is the largest gland in the body?
The liver
What does the liver produce and secrete?
Where does this secretion go?
- Bile
* The duodenum
What is bile?
An aqueous mixture of:
- Bicarbonate ions
- Phospholipids
- Cholesterol/cholesterol-derived products (bile salts)
- Waste products such as bilirubin
What is bilirubin?
A yellow/brown molecule which is derived from the catabolism of aged red blood cells which have reached the end of their useful life
Where in the body is bile stored in between meals?
The gall bladder
What are bile salts involved in the digestion of?
Lipids
Fats
How do bile salts break up the globules of lipids?
Emulsification
How would you describe the enzymatic action of lipases?
They act on triglycerides by splitting it into monoglyceride and two fatty acids
What are micelles?
Lipid molecules that arrange themselves in a spherical form in aqueous solutions
What is the shortest section of the small intestine?
What is the longest?
How long are they?
- Duodenum - 25cm
* Ileum - 3 metres
In which part of the intestine does most of digestion occur?
The small intestine
The formation of a peptide bond liberates a molecule of what, an is an example of what type of reaction?
- Water
* Condensation reaction
The cleavage of a peptide bond consumes a molecule of what?
Water
What does carboxypeptidase release from peptide chains?
- Amino acids from one end
* Aminopeptidase from the other end
Are amino acids able to diffuse across the cell membrane?
If not, how do they cross it?
- No, they are hydrophilic
* They are transported by carrier proteins
How is the hydrogen ion gradient maintained in the absorptive cells of the gut epithelium?
Because hydrogen ions are transported out of the cells into the gut lumen by antiporter proteins
How is the hydrogen ion gradient (of the gut) maintained?
By secondary active transport
What are the end products of protein digestion?
Free amino acids
If food is chewed thoroughly, how much of ingested protein can be broken down into amino acids and absorbed?
Roughly 98%
What does the enzyme maltase break down into glucose?
- Maltose (disaccharide)
* Maltotriose (trisaccharide)
What are dextrins broken down by?
Dextrinase
What maintains the sodium ion gradient for the transport of glucose or galactose into the absorptive cells of the gut epithelium?
The action of the sodium-potassium pumps on the basal membrane
How do monoglycerides and fatty acids cross the cell membrane?
They diffuse across it
What does the smooth endoplasmic reticulum convert fatty acids and monoglycerides in to?
Triglycerides
What is a chylomicron?
A lipoprotein rich in triglyceride and common in the blood during fat digestion and assimilation
What is pinocytosis?
The process by which extracellular fluids are taken into a cell by the invagination of the cell membrane to form small vesicles
Which vitamin must be present to enhance the absorption of calcium?
Vitamin D
In the human body, iron comes in two forms; what are they?
- Haem
* Iron salts
Roughly how much (percentage) of ingested iron salts actually enter the bloodstream?
10-15%
Which vitamin enhances the absorption of iron?
Vitamin C
In the body, iron exists in two positively charged forms (ferric and ferrous).
What are their charges?
- Ferric FE3+
* Ferrous FE2+
Of the two types of iron in the body (ferric/ferrous), which is the form that is absorbed by the gut epithelium?
Ferrous iron
What is haem iron?
Iron which is derived from meat and fish and is mainly bound to proteins
What is ferric iron also known as?
Non-haem iron
How is ferric iron absorbed by the body?
An enzyme called ferrireductase converts it to FE2+ (ferrous iron)
What is the protein which ferric iron is bound to so that it can be transported in the bloodstream, or stored in tissues?
Transferrin
How are fat soluble vitamins absorbed?
Fat-soluble vitamins such as vitamin D are transported by micelles, together with digested lipids, to the brush border where they then diffuse into the intestinal cell
What must vitamin B12 bind to in order to be taken up by the epithelial cells of the ileum?
Intrinsic factor
What is the purpose of vitamin B12?
It promotes enzymatic activity in many biochemical reactions
Where is most of the water in the GI tract absorbed?
The small intestine
What is the paracellular route?
A route between cells via very small pores located at the junctions between them
What does the large intestine mainly absorb?
Water and salts
Does the large intestinal mucosa have villi?
No
What is the gut microbiome?
The totality of microorganisms, bacteria, viruses, protozoa, and fungi, and their collective genetic material present in the gastrointestinal tract
What conditions can be associated with a disturbed gut flora?
- Diarrhea
- Diabetes
- Obesity
- Atherosclerosis
- Colitis
- Crohn’s disease
- Autism
What types of flora exist in the body?
- Gastrointestinal tract
- Genitourinary tract
- Skin
- Conjunctiva
- Nose/nasopharynx
- Upper respiratory tract
Aside from causing disease, what other effects can a disturbed gut flora cause?
- It influences brain development
* Anxiety behaviour
What does the term ‘hunger’ refer to?
The processes which make eating more likely
What does the term ‘satiety’ refer to?
The processes which make eating more likely to stop once it has started (to feel full)
Which part of the brain regulates many of the homeostatic functions?
The hypothalamus
What is leptin?
What is its purpose?
- A protein hormon released mainly by adipocytes
- It acts on the brain to stimulate the satiety centre and inhibit the hunger centre, reduces the desire to eat, promotes a sense of being full
What is ghrelin?
What is its purpose?
- A hormone which is released by endocrine cells in the gastric mucosa
- It promotes feelings of hunger, inhibits feelings of satiety
Which part of the brain can be stimulated by food?
What effects can occur?
- The ventral striatum
* Feelings of reward and pleasure
Which neurotransmitters are released due to stimulation of the ventral striatum as a result of ingesting food?
Dopamine
What happens to the amount of dopamine receptors in an obese person?
They decrease