Nutrition

eduqas biology alevel

What is nutrition

the process by which organisms obtain energy to maintain life functions and obtain matter to ceate and maintain structure

autotrophic meaning

use simple inorganic molecules to synthesis complex organic compounds

phototropic

energy for food synthesis comes from sunlight

chemoautotrophic

energy for food synthesis comes from special chemical processes

heteotrophic

organisms obtain food synthesized by other organisms

parasitic

feeding on living animals and plants

Saprotrophs

-feedings on dead and decaying organic material

-secrete enzymes which break down food into simple molecules that can be diffused > extracellular digestion

fungi

-mycelium secretes enzymes onto the food

-enzymes hydrolyse large organic molecules into their monomers

-soluble molecules can then be absorbed through diffusion

holozoic

eating other organisms

-take food into bodies and break it down by digestion

-for multicellular > digestive system

-digested material used by cells

Amoeba

-live on solid surfaces near water and feed on prokaryotes and protoctists. It is motile and phagocytic

how do amoeba eat

1- amoeba sences food 2- pseudopodia surrounds food 3- food is enclosed in a food vacuole 4-enzymes from lysosomes are secreted into food vacuole 5- food is digested and soluble materials are absorbed and assimilated 6-undigested waste is expelled» intracellular digestion

How do hydra eat

multicellular simple organism, live in water and have gut cavity with single opening. food goes in and out through same opening

ingestion

nutrients taken into body

digestion

organic molecules borken down

absorption

soluble products enter the blood

egestion

discharge or explusion of undigested material

assimilation

food used in respiration

layers of the gut

a hollow muscular tube made of four layers (serosa, muscle layers, sub-mucose, mucosa). The layers remain the same throughout the gut but they are specialised in different regions depending on the function

serosa

tough outer-most protective layer

muscle layers

these act together to bring about peristalsis

sub-mucosa

a layer of connective tissue, nerves, blood vessel, muscles, lymph vessels and glands

mucosa

inner-most layer that produces protective and lubricating mucus from special glands. Some areas are specialised for producing digestive enzymes or for abroption of food. May have villie to increase surface area

gut diagram

mechanical digestion in mouth-buccal cavity

food is chewed using teeth and tongue adn then formed into a bolus ready for swallowing

salivary glands

produce saliva which contains amylase, mucus and mineral ions to keep the pH

chemical digestion- amylase breaks down startch into maltose

stomach

food enters through thr cardiac sphincter. The circular and longitudianl muscles contract rhythmically to mix the food

glands in the stomach mucosa secrete gastric juices

gastric juice HCL

maintain low pH, kill bacterial, hydrolyses proteins and activated pepsin

gastric juice pepsin

pesinogen is secreted then, activiated by HCL into pepsin and secreted by parietal cells. its an endopeptidase that breaks up proteins into polypeptide

what does gastric juice mucus do

lubricates and protects the stomach wall from acid and enzymes

Zymogenic/ chief cells

secrete pepsinogen

oxyntic cells

secrete HCL which denatures proteins and softens connective tissue

goblet/ neck cells

secrete mucus which forms barrier between stomach lining and gastric juice

Duodenum- intestinal juice

the first 30cm of the small intestine. Secretes:

intestinal juice> glands in mucosa produce mucus and alkali (secreted from Brunner’s Glands) to neutralise stomach acid

Duodenum- pancreatic juice

Pancreatic juice> secreted from exocrine pancreas via pancreatic duct- contains endopeptidase, amylase, lipase

Duodenum- bile

Bile> produced by the liver and stored in the gall bladder which emulsifies fats.

What is before the liver, what happens in the Liver?

The hepatic portal vein carries the product of digestion to the liver where glycogen is produced and decimation takes place

Pancreas

seceretes hormones, enzymes, enzymes persecutors abd sodium hydrogen carbonate as part of pancreatic juice

label illeum

illeum adaptations (7)

-digestive tissues- bound to microvilli membranes

-large surface area- where enzymes come into contact and digest food

-muscle fibres- present in each villus allowing mixture of gut contents which increase contact with food

-many mitochondria-in columnar epithelial cells provide energy for active transport

-many capilleries- for transport to maintain concentration gradients for diffusion

-lacteal for removal of lipids

-thin epithilias layer- reduces diffusion distance

What are the sections of large intestine

caecum, appendix, colon, rectum

What happens in the large intestine?

water is absorbed with minerals, vitamins fom microorganisms and vitK

fibre allows for peristalsis.

undigested food is compacted into faeces and edpelled from body (defaecation)

What happens to maltose

hydrolysed by carbohydrase enzymes. Salivary amylase and pancreatic amylase in duodenum digest starch and glycogen to maltose. Maltose is further hydrolysed by maltase in small intestine

how is sucrose absorbed

sucrase enzymes are found embedded on the brush border of the small intestine . Secreted by the tips of the villi and break down sucrise. work best in ph 7-8

Exocrine cells

Goblet cells secrete mucus, tubular gastic glands secrete gastric juice and intestinal galds (brunners glands in crypts in Leiberkuhn) which secrete iintestinal juice with antibacterial enzymes

Mucus

lubricates oesophagus and protects stomach from acid. Brunner’s gland in submucosa of duodenum secrete alkaline mucus to protects against chime. Helps reduce inflammation in small intestine by decreasing bacterial interactions with epithelial cells.

Enzymes for digestion

animals with a varied diet need several enzymes for digestion. Most food substrates require more then one enzyme to be complete digestion. They are produced in various parts of the gut

Carbohydrates

hydrolysed by carbohydrase enzymes

process of digesting starch and glycogen

digested by salivary amylase and pancreatic amylase into maltose. This is then hydrolyzed by maltase into alpha glucose in the small intestine

where are sucrose enzymes found and secreted

found on brush border of small intestine and secreted by tips of villi

Endopeptidase

hydrolyse peptide bonds within protein chains to form shorter polypeptides

exopeptidase

hydrolyse the terminal peptide bonds to form amino acids

How are proteins digested in the stomache

The presence of food causing a change in the pH of the stomache stimulates the release of the hormone GASTRIN, which stimulates the production of gastric juices by the gastric glands.

Pepsin (an endopepsinase) is secreted as inactive pepsinogen which is activated by gastric juices (HCL) secerted by PARIETAL CELLS in gastric glands

Why are protease enzymes secreted in an inactive form? At what pH do they work

so they dont digest proteins from the alimentary canal. Pepsin works at pH 2

Protein digestion in duodenum- trypsin

Trypsin is an endopeptidase secreted by the pancrease as inactive trypsinogen. This is activate by enterokinase/ enteropepsinase from intestinal glands in duodenum after ingested food from stomache passes in

Bile

thick yellow/brown or olive green fluid that contains: bile salts, mucus, pigments and cholesterol. It emulsifies fats, increasing their surface area to lipase to work on and neutralize stomach acid.

Bile salts

emulsify fats to form oil droplets called micelles which have a large surface area

what does Pancreatic lipase do and where does it work

what is ezyme that digests triglycerides to fatty acids and glycerol in duodenum whcih are lipid soluble and diffuse across the membrane into epithilial cells of the villi in illeum

How is glucose absorbed into blood

sodium/potassium pump. Cotransport/ secondary active transport then facillitated iffusion into blood. Diffusion would be to slow and may result in glucose moving into the gut form blood

How are Amino acids absorbed

proteins are digesteted to peptides and amino acids by pancreatic proteases and bush border enzymes.

Amino acids are absorbed by active transport into epithelial cells of villus and peptides go through intracellular digestion

How are glucose and amino acids transported and to where?

from capillaries via the heptic portal vein to the liver

How are triglycerides transported

from lacteals via the lymphatic system to the blood

How are fats absorbed

fatty acids and glycerol diffuse into the epithelial cells where they are reassembled into the triglycerides which are packages in lipoproteins called chylomicrons and pass into the lacteal of the villus

how are water and water soluble vitamins absorbed?

diffusion

What are teeth used for?

mechanical digestion to increase surface area for enzyme action and make it easier to swallow

Human teeth

-8 CHISEL shaped incisors at front for biting and cutting

-4 pointed canines with same function

-20 large flat premolars and molars at the back and side of chewing

carnivore teeth

-sharp incisors to grip and tare flesh from bone

-enlarged, curved, pointed canines for tearing flesh and for catching and killing prey

-premolars and molars for crushing and cutting

-jaw moves up and down, powerful jaw muscles- catching and killing

-specialised cheek teeth called carnassials which slide past eachother for slicing

Herbivore teeth

jaws move vertically in circular motion

-grooved teeth for grinding (tough cellulose)

-incisors on lower jaw only and cuts against a horny pad on upper jaw

-canine teeth indistinguishable from incisors

-gap called diatema with tongue to move freshly cut grass to grinding area

-cheek teeth interlock

-grinding surfaces wear down exposing enamel ridges to help grind

Ruminants stomache

have four chambers- three derived from oesophagus and one is the “true” stomach

rumen, reticulum, amasum and abomasum

The rumen.

mutualistic bacteria live here and allow for a complete breakdown of cellulose into glucose as it mixes with cud (grass and saliva). They must be kept seperate so

1. food can be kept long enough for bacteria to digest cellulose

2. bacteria is isolated from own digestive juices for to be kept optimum pH with no extremes and enzymes dont denature

Glucose is fermented into organic acids that are absorbed into blood for energy. Waste as CO2 and methane

reticulum

cud passes into here before being regurgitated into mouth and chewed again

amasum

cud passes into here where water is reabsorbed

abomassum

functions like a normal stomach. protoctists ingest protein made by bacteria and are digested to porive amino acids. this is their main from of protein

mutulism (symbiosis)

a close association between members of two different species- both benefit

endoparasite

IN the host

ectoparasite

ON the host

Tapeworm

-pig becomes infected if it feeds from drainage channels contaminated by human feaces. Humans are infected if they eat the raw pig that is infected

Adaptations of tapeworm

-suckers and hooks on scolex to attach and remain attached to gut (peristalsis)

-thin and long for large SA:V for nutrient absorption

-body covering protecting from hosts immune system responses

thick cuticle and production of inhibitory substances on the surface of the segments ot prevent digestion by the hosts enzymes

-produce large number of eggs that pass out with hosrs faeces to increase chance of infecting secondaary host

-dont move and dont have a sensory system, unecessary organs are degenarated

-simple excretory and nervous system

-resistent shell on eggs (40,000!) enable them to survive outside of hosts body. embryos remain dormant as cysts until consumed

Headlice

-found on scalp of humans and fed by piercing the skin and sucking blood

-mouth parts for biting through epidermis

-claws to hold ontp hair

lay eggs which are glued to base of hairs

-transfer bnetween hosts by direct contect