Digestion

Autotrophs

Use simple organic materials to make complex compounds

Heterotrophs

Consume other organisms

Holozoic feeders

Intake food and break it down

Parasites

Organisms that feed off other alive organisms

Saprotrophs

Feed on dead and decaying matter

Extracellular digestion

Secrete enzymes outside body then absorb the products back across

What happens in the buccal cavity (humans)

Food is broken into smaller pieces

moistened by saliva

What happens in the oesophagus

Bolus moves through via peristalsis

Cardiac sphincter

relaxes at upper end to allow food entry of stomach

Pyloric sphincter

Relaxes at lower end of stomach to allow food to move into duodenum

Function of stomach

Mucosa secretes gastric juice containing pepsin

HCL kills pathogens + provide PH 2

Pepsin begins to break proteins

How is carb and protein digestion finished

maltase and dipeptidase fixed in the epithelial cells of mucosa

Bile - production and storage

Produced by liver and stored in gall bladder

Function of bile

Emulsifies lipids into small droplets

Function of pancreas (3)

Secrete pancreatic juice containing:

Endo + exopeptidase

Amylase

Lipase

Duodenum strcucture (2)

First 20cm of small intestine

Receives secretions from liver + pancreas

Ileum - structure + function

Large surface area due to villi and microvilli - contain epithelial cells for diffusion and active transport

How is glucose transported in the ileum

Na+ / K+ active transport pump creates low conc of Na+ inside epithelium

Co transport with Na+ into epithelium

Facilitated diffusion into capillaries

How are amino acids transported in the ileum

Absorbed into epithelium by active transport

Facilitated diffusion into capillaries

What is on the end of epithelial cells

Microvilli

How are lipids absorbed in the ileum (4)

Diffuse into epithelial cells

Recombine into triglyceride in the SER

Exocytosed into lacteal

Transported in lymphatic system

Lacteal + function

Lymph capillary at centre of villus

Transport into lymphatic system

How are vitamins absorbed in the ileum

Water soluble - through facilitated diffusion

Fat soluble - diffusion

2 reasons why herbivore guts are larger

Plant material needs more time / action to be broken down

More space to accommodate bulky plants

What are the 4 chambers of a ruminant stomach

Rumen

Reticulum

Omasum

Abomasum

What happens to the food in the rumen

Mutualistic bacteria causes fermentation and produces beta glucose + fatty acids to be sed as energy

What happens in the reticulum

Food is regurgitated to the buccal cavity where the cow chews the cud

What happens after the cud is chewed

Re-swallowed into the omasum

What happens in the Omasum

Food is churned - further fermentation

What happens in the abomasum (true stomach)

Acts like monogastric stomach (humans)

Hydrochloric acids + enzymes

What is the final stage of ruminant digestion

Food moves to intestines for absorption

How many stomachs does a cow have

One true stomach - 3 oesophagus chambers

4 types of teeth

Incisors

Canines

Carnassial

Molars + premolars

Incisors

Chisel shaped - strip flesh from bones

Canines

Sharp pointy - Kill + grip prey

Carnassial teeth

Scissors to snip meat + crush bones

Molars

Cut / gnaw meat

Limitations to a dogs jaw

Cannot chew as it only moves vertically

Causes things to be swallowed in whole

Incisors in sheep

Snip grass by biting against the horny pad

Diastema in sheep

Space behind the horny pad to hold grass

Molars in sheep

Hardened with concrete to prevent chipping

Grind plant material in circular motion

What is the purpose of sheep molar root cavities being open

Allows blood supply and growth throughout life

Parasite in stomach withstand: (3)

Lack of o2

Extreme PH conditions

Digestive juices / enzymes

Explain why a low protein diet causes a build up of fluid

Low protein reduces plasma proteins

this increases water potential in blood

meaning less is reabsorbed into blood

more remains in tissue fluid

Ingestion

Food taking in through the mouth to the body

Digestion

Break down of large molecules into soluble molecules

What produces mucus

Goblet cells

Layers of the gut - inside to out

Mucosa

Sub-mucosa

Circular muscles

Longitudinal muscles

Serosa

How do endo and exopeptidase work together

Endopeptidase break down protein to make smaller chains so that exopeptidase can break down more terminal ends

How is pepsin produced

Pepsinogen produced by chief cells

Activated by HCL

Why is pepsinogen released in its inactive form

To prevent autolysis (Digest cells making it)

Function of the diastema

Allow space for manipulating food

Goblet cells

Secrete mucus

Features of epithelium cells + functions

Mitochondria - provide ATP for active transport

Microvilli - Increased SA for diffusion/digestion

What does mucus do in digestion

Lubricates passage

Prevents autolysis of enzymes on gut wall