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36 Cards in this Set

  • Front
  • Back
What is heterotrophic?
Unable to synthesize own nutrients
What is intracellular digestion?
Occurs within cell, membrane-bound vesicles
What is extracellular digestion?
Digestion that occurs outside of cell, in lumen or tract
In unicellular organisms, how is food captured?
Primarily by phagocytosis
How does digestion occur in simple unicellular organisms?
Food vacules that have been phagocytosed are approached by lysosomes that contain digestive enzymes

Digestive enzymes released into cell

Simpler molecules are then released into cytoplasm

Unusable products are eliminated from vacuole
In paramecium, how does ingestion and digestion occur?
Cilia sweep food into oral groove and cytopharynx

Food vacuole forms

Enzymes secreted into cell
What does chewing do?
Increases surface area for enzymes to act upon
How does chemical breakdown of molecules occur?
Enzymatic hydrolysis
How do cnidarians digest food?
Hydra use intracellular and extracellular digestion

Tentacles bring food to mouth and release food into cup-like sac

Endodermal cells lining gastrovascular cavity release digestive enzymes into cavity

Digestion occurs primarily outside of cell

Undigested food is expelled through mouth
How do annelids digest food?
Earthworms have one-way digestive tract with mouth and anus, allowing for specialization

Specialized parts: mouth, pharynx, esophagus, crop (store food), gizzard (grind food), intestine (absorb nutrients), anus
How do arthropods digest food?
Insects have similar digestion system to earthworms

In addition, have jaws for chewing and salivary glands
What is the digestive tract in humans?
Oral cavity -> pharynx -> esophagus -> stomach -> small intestine -> large intestine -> anus
What are the accessory organs for human digestion?
salivary glands, pancreas, liver, gall bladder
What enzyme does saliva have and what does it do?
Saliva contains enzyme "Salivary Amylase" which hydrolyzes starch to maltose
What is peristalsis?
Rythmic involuntary contractions that move food down esophagus
What does the stomach do?
Stores and partially digests food

Walls lined with thick mucosa and contains the glands that secrete mucus that protects stomach from acid

Secretes pepsin and HCl
What does pepsin do?
Protein-hydrolyzing enzyme
What does HCl do?
kills bacteria, dissolves intercellular "glue" holding food tissues together, activates certain proteins
What is chyme?
Acidic, semi-fluid, mixture of partially digested food
Where does food go after stomach?
Passes through pyloric sphincter to the duodenum of the small intestine
Where does chemical digestion finish?
Small intestine
What are the parts of the small intestine?
What is the purpose of the small intestine?
Highly adapted for absorption
Why is small intestine so long?
Increase surface area for absorption
What is the purpose of villi in small intestine?
Small finger-like projections in small intestine

Villi contain blood vessels and lymphatic vessels that help absorption of blood
Where does most of the digestion occur in the small intestine?
Duodenum where secretions of intestinal glands, pancreas, liver and gall bladder mix with acidic chyme
What does the intestinal mucosa secrete?
Lipases (fat digestion)
Aminopeptidases (polypeptide digestion)
Disaccharidases - digestion of maltose, sucrose, lactose)
What does the liver do?
Produce bile which is stored in gall bladder prior to release in small intestine
What does bile do?
contains no enzymes, emulsifies fat, breaking large globules into smaller droplets
What does the pancreas do?
Produces enzymes such as amylase (carbohydrate digestion), trypsin (proteins), lipase (fats)

Secretes bicarbonate rich juice that neutralizes acid chyme arriving from the stomach

Pancreatic enzymes operate optimally at this higher pH
What is the purpose of the large intestine?
Absorption of salts and water
What is purpose of rectum?
Transient storage of feces
Do plants have a digestive system?
No, but they do have similar digestive processes coordinating utilization of nutrients with their production
Describe intracellular digestion in plants
Store insoluble polymers, starches, lipid and proteins in cells

Principle storage food is starch

When nutrients needed, starch broken down by hydrolysis and used by cell or transported by diffusion to other cells
Why does the venus fly trap eat flys?
To obtain nitrogen in nitrogen poor soils, NOT for food, they are still autotrophs
Describe extracellular digestion in plants:
Enzymes are excreted, more simpler substances are absorbed