Nutrition

Define Autotrophic organisms and the 2 types

Autotrophic - organisms that make their own food from simple inorganic molecules

Photoautotrophic - use light energy to make food via photosynthesis

Chemoautotrophic - use energy from chemical reactions

Define Heterotrophic organisms

organisms that consume complex organic molecules for nutrition

Define Saprotrophic , Parasitic and Holozoic Nutrition carried out by Heterotrophic organisms

Saprotrophic - used by fungi to feed on dead/decaying matter

Parasitic - obtain food from another living organism the host (Endoparasites - live in body of host, Ectoparasites - live on surface)

Holozoic - food is ingested, digested, absorption of nutrients, assimilation and egestion using a specialised disgestive system

Describe nutrition in unicellular organism Ameoba

-Holozoic Nutrition

-food taken in my endocytosis + digested by lysosomal enzymes

-products absorbed into cytoplasm

-remains egested by exocytosis

Describe nutrition in multicellular organism Hydra

-Hydra lives in freshwater

-simple undifferentiated tube like gut with single opening

Describe structure + function of Gut wall (in order)

-lumen surrounded by epithelium

-mucosa -> innermost layer of wall where epithelium secrets mucus to lubricate + protect mucosa

-submucosa -> made up of connective tissue containing, blood vessels, nerves and lymph vessels which remove absorbed digestion products

-muscle of mucosa

-circular + longitudinal muscle -> help carry out peristalsis

-serosa -> tough connective tissue which protects gut wall by reducing friction with other organs when gut moves whilst processing food

Explain role of Buccal Cavity

-mechanical digestion of food to increase surface area

-so saliva can mix with food which has amylase to break down starch + glycogen into maltose

-lubricates food for passage down oesophagus

Explain role of Stomach

-food mixes with gastric juice as wall contracts rhythmically to mix it

What is gastric juice made from and where is it secreted from?

-secreted from gastric pits

-contains peptidases, HCL (to lower stomach pH), mucus (lubricates food + protects stomach wall)

Explain role of Duodenum

-first part of small intestine where lipids + proteins are digested

-bile made in liver + stored in gall bladder passes into duodenum to emulsify lipids by breaking down large globules into smaller ones to increase SA

Explain role of Ileum

-lining of epithelium cells with villi for digestive enzyme synthesis

-carbohydrase to digest disaccharides into monosaccharides

-endopeptidases + exopeptidases to digest dipeptides into amino acids

Explain role of Large Intestine

-undigested food + bacteria + dead cells passes through colon where water in absorbed from them to result in semi-solid faeces stored in the rectum

-colon has less villi then ileum

Explain adaptation of Villi

-microvilli increases SA

-good blood supply to maintain conc gradient

-thin diffusion pathway

-permeable

Role of Saliva

-lubricates food

-contains amylase which starts chemical digestion of starch + glycogen into maltose (hydrolysed further by maltase into alpha-glucose)

Role of Pepsin + Trypsin

Pepsin - type of endopeptidase produced in gastric glands as inactive pepsinogen

-endopeptidases hydrolyse peptide bonds in molecules

-exopeptidases hydrolyse terminal peptide bonds

Trypsin - type of endopeptidase produced in pancreas as inactive trypsinogen activated by enterokinase

-digests proteins in duodenum

Role of Bile salt and Lipase

Bile salt - emulsifies lipids

Lipase - breaks down triglycerides into mono + fatty acids

How and where are fatty acids monoglycerides and fat-soluble vitamins absorbed?

by diffusion from lumen -> epithelial cell -> lacteal

(fatty acids have same process instead they are rearranged into triglycerides before passing into lacteal)

How and where are amino acids and disaccharides absorbed?

Amino acids - by active transport from lumen -> epithelial cell

-> by FC diffusion into capillaries

Disaccharides - active transport from lumen -> epithelial cell -> FC diffusion into capillaries

How and where is glucose and minerals absorbed?

Glucose - by co-transport into lumen -> epithelial cell -> FC diffusion into capillaries

Minerals - by FC diffusion into lumen -> epithelial cell -> capillaries

How and where is water and water-soluble vitamins absorbed?

Water - by osmosis into lumen -> epithelial cell -> capillaries

Water-soluble vitamins - by active transport into lumen -> epithelial cell -> FC diffusion into capillaries

How are amino acids + glucose transported to liver?

via hepatic portal vein