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IB Biology > Unit 4: Enzymes and digestion > Flashcards

Unit 4: Enzymes and digestion Flashcards

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1
Q

What are the 2 key functions of metabolic reactions?

A

Provide source of energy for cellular processes (eg, growth, reproduction)

Enable synthesis and assimilation of new materials for use within a cell

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2
Q

What is the difference between a saturated and an unsaturated fatty acid?

A

Saturated:
- Possess no double bonds (have the maximum number
of H atoms)
- Linear in structure
- Originate from animal sources (for example fats)
- Usually solid at room temperature

Unsaturated: 
- Mono / Poly unsaturated
- Mono = 1 double bond 
- Poly = 2 or more double bonds (in the hydrocarbon 
  chain)
- Unsaturated fatty acids are either cis or trans
- Bent in structure
- Originate from plant sources
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3
Q

What are fatty acids?

A

long hydrocarbon chains found in certain types of lipids (triglycerides and phospholipids)

Differ in length of hydrocarbon chain (usually 4-24 carbons) + number of double bonds

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4
Q

What is a cis isomer in an unsaturated fatty acid?

A

both hydrogen atoms on one side of the carbon double bond

look at doc for image

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5
Q

What is a trans isomer in an unsaturated fatty acid?

A

hydrogen atoms on opposite side of the carbon double bond

look at doc for image

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6
Q

What are the differences between cis and trans isomers?

A

Cis:
- Commonly occur in nature
- 2 hydrogen atoms attached to same side of 2 carbon
atoms
- Lower melting points → liquid at room temperature
- Healthier

Trans:
- Produced artificially when lipids (formed by
polyunsaturated fatty acids) are chemically changed. – — This turns plant fatty acids more solid (like saturated
fats)
- Hydrogen atoms on opposite side of 2 carbon atoms
- Higher melting points → solid at room temperature
- Dangerous for cardiovascular system.

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7
Q

What are polysaccharides used for?

A

store energy + act as a structural component

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8
Q

Describe Starch

A

In plants:

  • Used to store energy
  • Starch is made up of 2 polysaccharides → amylose and amylopectin
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9
Q

What is glycogen used for?

A

The only carbohydrate in animals used to store energy

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10
Q

What is cellulose used for?

A

Cellulose in plant wall → gives wall strength + protects cell from over expanding and bursting

Also stores enough energy to be a source for biofuels

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11
Q

Describe the structure of starch.

A

Amylose:

  • linear arrangement of glucose
  • a glucose
  • compact / good storage
  • check google doc for spiral structure

Amylopectin:

  • branched arrangement of glucose
  • Amylopectin gives starch its stickiness (useful for food, paper, chemical industries as it can make glue or lubricant)
  • Amylopectin makes up 80% of starch content in potatoes
  • a glucose
  • energy is released fast as enzymes break branches

Starch molecule consists of both forms → unbranched amylose and branched amylopectin

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12
Q

Describe the structure of cellulose.

A
  • long / straight
  • B glucose
  • chains linked by hydrogen bonds
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13
Q

Describe the structure of glycogen.

A
  • a glucose
  • much more side branches than amylopectin
  • good for energy release, also good for storage
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14
Q

Why are trans fats and saturated fatty acids bad for the body?

A

a

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15
Q

Why are lipids more suitable for long-term energy storage in humans than carbohydrates?

A

a

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16
Q

Evaluation of evidence and the methods used to obtain the evidence for health claims made about lipids.

A

a

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17
Q

How is BMI (body mass index) calculated?

A

(weight in kg) divided by (height in meters squared)

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18
Q

What is denaturation?

A

process in which proteins lose their secondary + tertiary structures

  • Hydrogen bonds formed between R groups of amino
    acids + amino groups of different amino acids =
    disrupted
  • Active sites lose their shape
    In enzyme denaturation: the whole enzyme loses its enzymatic properties
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19
Q

Describe the 2 ways to denature proteins

A

Temperature
Proteins lose their conformation → interaction between certain amino acids is changed
Quaternary + tertiary + (maybe) secondary structures are irreversibly changed
Denatured proteins lose their form and function
Peptide bonds do NOT break during the denaturation process → aka primary structure is not disrupted

PH
PH of a solution → may affect functionality of a protein
Strong alkaline/acidic solutions break bonds between non adjacent amino acids / polypeptide chains of quaternary proteins
The protein denatures and loses functionality

20
Q

Describe the active site of an enzyme

A

Active site = region on an enzyme to which substrates bind + where reactions are catalysed

Special area on the enzyme molecule where the catalytic reaction takes place → the active site

Active site is the result of the folding of polypeptide chains

Only 1 type of substrate fits into the active site

21
Q

What is the induced fit model?

A

During the reaction stage of an enzymatic reaction the active site changes slightly to fit the structure of the substrate. This is conformational change. After the release of the substrate, the enzyme reverses back to its original state.

22
Q

Describe how enzyme catalysis involves molecular motion and the collision of substrates with the active sit

A

Enzyme + substrate → enzyme - substrate complex → transition state → enzyme - product complex → enzyme + product

Molecular motion allows the substrate to collide with the active site, where the reaction takes place.

23
Q

Which 3 factors affect enzyme activity?

A

Temperature, pH and substrate concentration

24
Q

Describe how temperature affects enzyme activity.

A

Low temperature = molecules move slowly
Chance of collision between substrate and enzyme molecules = low
rising temperature = more rapidly moving molecules + collisions increase
All enzymes have an optimum temperature (at which enzymatic reaction is highest)
Optimal temperature for human enzymes = 37 degrees
Temperature higher than optimum = enzyme denatures (rate of enzymatic reaction decrease rapidly)

Check google document for graph.

25
Q

Describe how pH affects enzyme activity.

A

Enzymes work in different environments
- In the stomach the pH is very low (2)
- Small intestine: pH is alkaline (7.5)
Change of pH from optimum affects enzymes and their activity
Extreme pH values → denature enzyme (alter 3d structure of active site)
pH values higher/lower than optimum: decreases ROR

Check google document for graph.

26
Q

Describe how substrate concentration affects enzyme activity.

A

Low concentration → more enzyme molecules available than substrate
- Rate of reaction = relatively low

Increasing concentration → more chance of collision between substrate + enzyme molecules
- Rate of enzymatic reaction rises gradually

Increase stops when all active sites are occupied by substrate molecules

  • After this adding substrate does not change ROR
  • It becomes saturated

Check google document for graph.

27
Q

Describe how enzymes can be denatured

A

Enzymes are proteins → can be denatured + lose catalytic properties

Denaturation occurs during extreme pH and heat values + presence of heavy metals

Denaturation → irreversible change to a protein (it can no longer function)

Hydrogen bonds formed between R groups of amino acids + amino groups of different amino acids = disrupted

28
Q

What are the methods of production of lactose-free milk and its advantages?

A

a

29
Q

Explain how immobilized enzymes are widely used in industry

A

a

30
Q

Draw an annotated diagram of the digestive system

A

check the google document.

31
Q

Describe the movement of muscles in the small intestine

A

The contraction of circular and longitudinal muscle of the small intestine mixes the food with enzymes and moves it along the gut

32
Q

Go through the step by step process of eating

A

check the google document.

33
Q

Describe how the pancreas secretes enzymes into the lumen of the small intestine

A

Digestive enzymes produced by acinar cells of the pancreas:
Amylase → breaks down starch into maltose
Endopeptidase (called trypsin) → breaks down protein into smaller polypeptides
Lipase and phospholipase → breaks own lipids and phospholipids into glycerol and fatty acids
With phospholipid phosphate is also produced
Pancreatic juice containing the enzymes is carried via the pancreatic duct to the duodenum → release into the lumen of the small intestine
After pancreatic enzymes help with digestive process: most molecules STILL too large to be taken up by villi

34
Q

How does the liver help with digestion?

A

a

35
Q

Describe the digestive enzymes produced by acinar cells of the pancreas

A

a

36
Q

Describe how enzymes digest most macromolecules in food into monomers in the small intestine

A

Enzymes break down macromolecules into monomers in the small intestine so they can be absorbed (come from small intestine wall or from pancreas - pancreatic juices carry them over)
Wall of small intestine contains some glands that produce enzymes (immobilised) in the intestinal epithelial cells

This is the second group of enzymes
- Nucleases (break down DNA and RNA)
- Maltase (breaks down maltose into glucose)
- Lactase (lactose into galactose and glucose)
- Exopeptidases (remove single amino acid form end of
polypeptides)
- Dipeptidases (break down dipeptides into 2 amino acids)

37
Q

Describe digestion in the small intestine

A

a

38
Q

Why is cellulose not digested?

A

Because humans don’t have the enzyme cellulase which breaks down cellulose.

39
Q

Describe the structure of villi

A

a

40
Q

Describe how Villi aid in digestion

A

1) Villi increase the surface area of epithelium over which absorption is carried out
2) Villi absorb monomers formed by digestion as well as mineral ions and vitamins

Absorption of food molecules occurs in the small intestine

Transport proteins needed for absorption → large surface area needed to ensure enough transport proteins to absorb all necessary nutrients

SA of intestine greatly increased due to VILLI

Villi are the location of absorption of all monomers produced by the digestive processes in the small intestine

Epithelial cells: where absorption occurs
Each epithelial cell of the villus has projections of its plasma membrane that protrude into the lumen of the small intestine
Goblet cells: produce mucus
Capillary network + lacteal carry absorbed nutrients away from the intestine
Lamina propria: connective tissue of the villus

Molecules directly absorbed by villi: 
Bases + phosphates from nucleic acids
Fatty acids and glycerol
Amino acids
Monomeric carbohydrates (fructose, glucose, galactose, ribose
41
Q

What are the different methods of membrane transport required to absorb different nutrients?

A

Simple diffusion
When molecules are small and hydrophobic (so they pass through phospholipid bilayers)
Occurs mostly with products of lipid digestion

Facilitated diffusion
Fructose, glucose + other hydrophilic monomers moved by protein channels
Still requires a concentration gradient

Active transport
Needed when concentrations are lower in the lumen of the small intestine
Movement goes against the concentration gradient
Glucose, amino acids, some mineral ions → transported this way (requires ATP)
Cells of epithelium have mitochondria that synthesize ATP for this

Pinocytosis
Draw in small droplets of liquid surrounded by small section of phospholipid membrane
Occurs with fat droplets in the lumen of the small intestine

42
Q

What are the 3 parts of the small intestine?

A

Duodenum
Jejunum
Ileum

43
Q

Describe the tissue layers in the small intestine

A

Serosa
Outermost layer → consists of connective tissue in contact with body cavities

Longitudinal muscles
Responsible for peristalsis

Circular muscles
Responsible for peristalsis and segmentation

Submucosa
Connective tissue Responsible for peristalsis
Supports the mucosa + contains large veins and arteries → give rise to capillary bed of the mucosa

Mucosa
Innermost layer forming soft lining of the tube comprised of epithelium connective tissue + smooth muscle
Villi form part of this layer

44
Q

What is an enzyme?

A

Enzymes are globular proteins that act as catalysts for a biochemical reaction

45
Q

What is enzyme - substrate specificity?

A

Enzyme - substrate specificity → one enzyme can only catalyse one type of reaction

IB Biology (3 decks)

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