Nutrition in Humans

Question 1

what is nutrition

Answer 1

intake of food and processes that convert food substances into living matter

Question 2

describe the 5 processes in human nutrition

Answer 2

• ingestion: intake of food into body
• digestion: breaking down of large food molecules into smaller soluble and diffusible molecules that can be absorbed into body cells
• absorption: taking up of small molecules (e.g. simple sugars/amino acids) by body cells from digestive tract
• assimilation: conversion of absorbed food molecules to new protoplasm/used to provide energy
• egestion: undigested food removed from body

Question 3

describe chewing in the mouth (3 points)

Answer 3

• teeth cut and grind to break up food for easier swallowing and increasing surface-area-to-volume ratio for digestive juices containing enzymes to act efficiently
• presence of food in mouth triggers a reflex, causing salivary glands to secrete saliva
• tongue tastes food and manipulates it during chewing, shapes food into a ball (bolus), during swallowing, tongue pushes bolus back into pharynx

Question 4

what does saliva contain (4 points)

Answer 4

• salivary amylase: starch > maltose (optimum pH 7)
• mucin: protects soft lining of mouth from abrasions, lubricates food for easier swallowing
• buffers: prevent tooth decay by neutralising acid in mouth
• antibacterial agents: kill bacteria that enter mouth with food

Question 5

what is peristalsis

Answer 5

rhythmic, wave-like contractions by smooth muscles in wall of alimentary canal

Question 6

what is the function of the oesophagus

Answer 6

conducts food form pharynx down to stomach by peristalsis

Question 7

describe the antagonistic relationship between the walls of the oesophagus (2 points)

Answer 7

• circular contracts, longitudinal relaxes — wall contricts, becomes narrower and longer
• longitudinal contracts, circular relaxes — wall dilates, becomes wider and shorter

Question 8

what does gastric juice contain (2 points, 4/2 subpoints)

Answer 8

• dilute solution of HCl
  
  • stops action of salivary amylase by denaturation
  • kills most bacteria swallowed with food
  • provides acidic environment for gastric enzymes to work
  • converts inactive forms of enzymes into active forms (pepsinogen to pepsin, prorennin into rennin)
• pepsin (optimum pH 2)
  
  • protease that breaks down protein into polypeptides
  • released into lumen as pepsinogen

Question 9

briefly describe digestion in the stomach

Answer 9

churning action (peristalsis) by smooth muscles of stomach wall mixes food with gastric juice into chyme

Question 10

what does pancreatic juice contain (3 points)

Answer 10

• pancreatic amylase (starch > maltose)
• pancreatic lipase (fats > fatty acids + glycerol)
• pancreatic protease (trypsin) (protein > polypeptides)

Question 11

what is secreted OR released into the duodenum (4 points)

Answer 11

• intestinal juice
• pancreatic juice
• bile
• chyme

Question 12

what does intestinal juice contain (3 points)

Answer 12

• intestinal carbohydrase (maltase) (maltose > glucose)
• intestinal protease (polypeptides > amino acids)
• intestinal lipase (fats > fatty acids + glycerol)

Question 13

what does bile contain (2 points)

Answer 13

• bile salts: emulsifies and break up big fat globules into tiny fat droplets that form stable emulsion in water (emulsification)

*emulsification greatly increases surface-area-to-volume ratio of fats for digestion by pancreatic and intestinal lipase

• bile pigments: by-product of red blood cell destruction in liver, removed with faeces

Question 14

what are 6 adaptations of the small intestine

Answer 14

1) inner surface has numerous finger-like projections (villi)
- increases surface area for absorption

2) epithelium of villus is one-cell thick
- provides short diffusion distance for nutrients to pass through

3) cells of epithelium has many microvilli
- further increases surface area for absorption

4) each villus has many blood capillaries
- capillaries allow blood to transport absorbed glucose & amino acids away to maintain diffusion gradient

5) each villus contains a lacteal
- allows transport of absorbed fats away to maintain steep diffusion gradient

6) epithelial cells contain many mitochondria
- mitochondria provide energy for active transport of nutrients into villi

Question 15

how are digested food absorbed (2 points)

Answer 15

• glucose & amino acids — diffusion + active transport into blood capillaries of villi
• glycerol & fatty acids — diffuse into epithelium, combines to form minute fat globules that enter lacteals

Question 16

how is glucose assimilated (3 points)

Answer 16

• most are converted into glycogen and stored in the liver
• some transported by blood leaving liver, distributed around body to be used for energy during cell respiration
• excess glucose then transported back to liver and stored as glycogen for future use

Question 17

how are amino acids assimilated (3 points)

Answer 17

• those that enter cells are converted into new cytoplasm used for growth and repair of worn-out parts of the body
• used to form enzymes and hormones
• excess AAs’ amino groups are removed and converted into urea in liver (deamination)

*urea removed from body in urine
*remains of deaminated AAs converted into glucose in liver

Question 18

how are fats assimilated (5 points)

Answer 18

• absorbed into lymphatic capillaries (lacteal) which join to form larger lymphatic vessels, which discharge fats into bloodstream
• blood carries fats to all parts of body, especially liver
• enough glucose: fats not broken down and used to build protoplasm like cell membranes
• not enough glucose: fats broken down to provide energy for vital activities in body
• excess stored in adipose tissues (protects body as shock absorbers) beneath skin and around heart and kidneys

Question 19

what are functions of the liver

Answer 19

• produces bile (fat digestion)
• deamination of amino acids
• regulates blood glucose concentration (insulin + glucagon)
• breakdown of hormones (after they serve their purpose)
• detoxification (e.g. alcohol, food preservatives)

Question 20

what is a hormone

Answer 20

chemical substance produced in very small quantities by an endocrine gland

Question 21

how is blood glucose concentration regulated (2 points, 4/3 subpoints)

Answer 21

high conc.:
- pancreas detects this and produces insulin
- transported in blood to liver and muscle cells
- makes cell membranes more permeable to glucose for more diffusion
- stimulates liver/muscle cells to convert excess glucose into glycogen for more respiration

low conc.:
- pancreas detects this and produces glucagon
- transported in blood to liver
- stimulates conversion of glycogen into glucose

Question 22

how does alcohol affect the digestive system (2 points)

Answer 22

• alcohol stimulates acid secretion in stomach, excess increases risk of gastric ulcers
• cirrhosis, where liver cells are destroyed and replaced with fibrous tissue, makes liver less able to function and may lead to haemorrhage in liver, liver failure, and death

Question 23

what are the impacts of alcohol on the nervous system (3 points)

Answer 23

• depressant (slows down brain functions, effects vary from person to person)
• reduced self-control
• slower/increased reaction time, slurred speech, blurred vision, poor muscular coordination

Question 24

what are 2 long-term impacts of alcohol on the brain

Answer 24

1) wet brain
- type of dementia caused by brain damage

2) shrinkage of brain volume
- brain shrinks smaller than normal, especially region associated with memory and reasoning

*overconsumption can also affect foetus’ brain development

Question 25

what are some social implications of alcohol overconsumption

Answer 25

• neglect their work and families
• exhibit violent behaviour, especially towards family members
• higher risk of committing crimes

*may lead to addiction as well