SNS - Biology - Digestion Flashcards Preview

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Flashcards in SNS - Biology - Digestion Deck (16):
1

Unicellular Organisms

Amoeba

  • Phagocytosis to form food vaculoes.
  • Lysosomes fuse with these, releasing digestive enzymes
  • Simpler molecules formed diffuse into the cytoplasm and unusable end products are subsequently eliminated from the vacuole

2

Unicellular Organisms

Paramecium

  • Cila sweep food into the oral groove and cytopharynx
  • Food vacuole forms at lower end of cytophaynx
  • Eventually breaks of into the cytoplasm and progresses towards the anterior end of the cell
  • Enzymes are secreted into the vacuole and the products diffuse into the cytoplasm
  • Solid wastes are expelled at the anal pore

3


Invertebrates

Cnidarians

  • Hydra use intracellular and extracellular digestion
  • Tenticles bring food to the mouth (ingestion) and release the particles into cup-like sac.
  • Endodermal cells lining this gastrovascular cavity secrete enzymes into it
  • Thus digestion is principally extracellular, however once food is reduced to small fragments, are engulfed by gastrodermal cells and digestion completed intracellularly
  • Undigested food expelled via the mouth

4


Invertebrates

Annelids

  • One-way digestive tract with mouth and anus
  • Different parts specialised for different functions
  • Soluble nutrients diffuse via walls of small intestine into the blood

5


Invertebrates

Arthropods

Insects have digesitve systems similar to those of the earthworm

They also have a jaw for chewing and salivary glands which aid digestion

6


Invertebrates

1. Crop

2. Gizzard

3. Typholosole

  1. Stores food
  2. Grinds food
  3. Large dorsal fold of intestine to increase surface area for digestion and absorption

7


Humans

Mouth

  1. Mechnical digestion
  2. Chemical digestion - amylase - converts starch to maltose

8


Humans

Stomach

  1. Mucous - protects stomach lining
  2. Pepsin - hydorlysis proteins
  3. HCl - breakdown of food, activates enzymes such as pepsin

Chyme produced passes into duodenum of small intestine via pyloric sphincter

9


Humans

Small Intestine

Villi

  • Contain capillaries and lacteals (vessels of lymphatic system)
  • AAs and monosaccharides pass via villi walls into capillary system
  • Large FAs and glycerol pass into lacteals and are then reconverted into fats
  • Some nutrients actively absorbed (eg glucose, AAs) others passively absorbed

10

Humans

Small Intestine

 

  1. Duodenum - site of most dgestion in small intestine
  2. Jejunum
  3. Ileum

11

Humans

Small Intestine

Enzymes

 

  1. Lipases - fats
  2. Aminopeptidases - polypeptides
  3. Disaccharidases - maltose, lactose, sucrose

12

Humans

Liver

  • Produces bile which is stored in gallbladder
  • Emulsifies fats, breaking down larger globules into small droplets increasing surface area for action of pancreatic lipase

13

Humans

Pancreas

  • Has exocrine function which produces enzymes such as amylase (carbs), trypsin (proteins) and lipase
  • Secretes bicarbonate-rich juice which neutralises acidic chyme - pancreatic enzymes act optimally at this higher pH

14


Humans

Large Intestine

  • Absorption salts and water not already absorbed by small intestine
  • Rectum provides transient storage of faeces

15

Plants and Fungi

Intracellular Digestion

  • Plants store insoluble polymers, lipids, starches and proteins in cells
  • Broken down when required by enzyme hydrolysis
  • Products can be used in storage cell itself or diffuse to others

16

Plants and Fungi

Extracellular Digestion

  • Some heterotrophic organisms (eg fungi) must obtain preformed organic molecules from the environment
  • Enzymes secreted, hydrolysing complex nutrients into simpler molecules for absorption for energy or synthesis of larger molecules
  • For example, rhizoids

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