Ch1 - 4 Flashcards
What is a catalyst?
A catalyst is a substance that can speed up a chemical reaction, without itself being chemically changed at the end of the reaction
can a catalyst be reused?
yes
what are enzymes?
Enzymes are proteins that function as biological catalysts. They speed up the rate of chemical reactions. They remain chemically unchanged at the end of the reaction.
Why can’t proteins break down themselves, if enzymes are proteins anyway?
not all enzymes are proteins, hence proteins cannot breakdown themselves
what is activation energy?
the energy needed to start a chemical reaction is called activation energy
How are large molecules breaking down into smaller molecules beneficial?
allows substances to be soluble in water and small enough to diffuse through the cell membrane
What are the enzymes that are involved in digestion called?
digestive enzymes
what are the 4 digestive enzymes to remember?
amylase - starch to maltose
maltase - maltose to glucose
protease - proteins to polypeptides, then to amino acids
lipase - fats to fatty acids & glycerol
2 ways enzyme-catalysed reactions can be classifies into
- reactions that build up complex substances - anabolic reactions
- reactions that breakdown complex substances - catabolic reactions
How do anabolic reactions occur?
cells build up or synthesise complex substances from simpler ones.
When are digestive enzymes produces?
only when there is food in the digestive tract
what are the substances which the enzymes act on?
substrates
What are active sites?
they are grooveson the surface of an enzyme molecule
How is the substrate a key?
a substrate molecule has the matching fit with its enzyme
When is an enzyme-substrate complex formed
it is when the substrate binds to the enzymes
What happens when the reaction takes place at the active site?
the substrate molecules are converted into product molecules. the product molecule then separates from the enzymes
definition of carbohydrates
Carbohydrates are organic molecules made up of the elements carbon, hydrogen and oxygen
what is the ratio of hydrogen to oxygen atoms in carbs?
2:1
What can carbohydrates be classified as?
Sugars and Complex carbohydrates
what can sugars be classified into?
-single sugars
-double sugars
What are the different types of complex carbohydrates?
- starch
-cellulose
-glycogen
What are the different types of sugars?
-glucose
-fructose
what are the different types of double sugars?
-maltose
-sucrose
What is the benefit of sugar?
sugars provide us with energy to do work and carry out activities
basic unit of carbohydrates
a single sugar is the basic unit of carbohydrates
do fructose and glucose have the same chemical formula?
yes
How are glucose and fructose different?
their atoms are arranged differently, affecting the sugars chemical and biological properties
Where can glucose be found
animals and plants
where can fructose be found?
plants
animals(rarely)
what is the structure of a glucose molecule?
a hexagon but flattened a bit –> 6 sides
what is the structure of a fructose molecule?
pentagon –> 5 sides
What is a double sugar?
It is when 2 single sugars are joined together
where can maltose be found?
in germinating grains
what is a maltose molecule made up of?
2 glucose
what is a sucrose made up of?
1 glucose + 1 fructose
What are the different types of reducing sugars?
glucose, fructose and maltose
How can we test for the presence of reducing sugars?
Benedict’s test
What is the procedure of a Benedict’s test?
- place the substance into a test-tube
- add benedict’s solution to the test tube and shake the mixture
- place in boiling water-bath for 2-3 mins
What can be observed if reducing sugar is present?
a red precipitate is formed
What are complex carbohydrates?
a complex carbohydrate is made up of many similar molecules of single sugar joined together to form a large molecule.
Which molecules are the complex carbohydrates made up of?
it is made up of numerous glucose molecules
What makes starch, glycogen and cellulose different?
The glucose molecules are linked up in different ways.
How are starch, glycogen and cellulose different?
They have different chemical and biological properties and have different roles to play.
What is the structure of a starch molecule?
a starch molecule is made up of several thousand glucose molecules joined together
What is the role of a starch molecule?
Starch is the storage form of carbohydrates in plants. When needed, it can be digested to glucose to provide energy for the cell
where is starch found?
in storage organs of plants
what is the structure of cellulose?
a starch molecule is made up of many glucose molecules joined together. The bonds between glucose units are different from that in starch.
What is the role of cellulose?
- the cellulose cell wall protects plant cells from bursting or damage
- cellulose serves as dietary fibre that prevents constipation
Where is cellulose found?
In cell walls of plants
What is the structure of a glycogen molecule?
Glycogen is a branched molecule. It is made of many glucose molecules joined together
what is the role of glycogen?
it is a storage form of carbohydrates in mammals. When needed, it is digested to glucose to provide energy for cell activities
Where can glycogen be found?
it is found in the liver and muscles of mammals
What happens to the starch when consumed?
the starch is digested into glucose, which is then stored in animals as glycogen.
What makes glycogen and starch suitable as storage materials in cells?
- insoluble in water, do not change water potential in the cells
- they are large molecules that cannot diffuse through cell membranes, not lost from cell
- easily broken down to glucose when needed
- their molecules have compact shapes, occupy less space
Where is the starch we eat digested?
alimentary canal
What is starch digested into?
Starch is digested to maltose by the enzyme amylase
What is maltose digested to?
Maltose is digested to glucose molecules by the enzyme maltase
What are the different functions of carbohydrates?
- needed as a substrate for respiration, to provide energy for cell activities
- needed to form supporting structures
- needed to be converted to other organic compounds such as amino acids and fats
- needed for the formation of nucleic acids like DNA
- needed to synthesise lubricants, like mucus, which consists of a carbohydrate and a protein
- to synthesize the nectar in some flowers
How to test for starch
Iodine test
procedure of the iodine test
add a few drops of iodine to the substance
what should be observed if starch is present?
The iodine turns from brown to blue-black upon contact with the food sample
definition of fats
fats are organic molecules made up of the elements carbon, hydrogen and oxygen.
Does fats contain more or less oxygen when compared to hydrogen?
less
are fats a lipid
yes
what are the 2 types of fats
animal fats, plant fats
What is the common function of fats?
Fats are used as a store of energy, especially in animals
what are fats broken into?
glycerol and fatty acids
what is the exact number of glycerol and fatty acids 1 fat molecule is broken into?
1 glycerol + 3 fatty acids
examples on sources of fats
butter, cheese, fatty meat, olives, many kinds of nuts, peas, beans, seeds of castor oil and palm oil, herring and salmon
what are the function of fats?
- source and long term storage of energy
- fats are an insulating material that prevents excessive heat loss
- fats are a solvent for fat-soluble vitamins and many other vital substances
- important part in cells, especially in cell membranes
- fats are a way to reduce water loss from the skin surface because of glands in the skin secreting an oily substance
why are fats suitable for storing energy?
fats have a higher energy value compared to carbohydrates
what is an example of how fats are insulating?
animals such as seals have a thick layer of fat beneath the skin, which helps to reduce loss of body heat
how does the glands in our skin secreting oil benefit?
an oily substance forms a thin layer on the skin, reducing the rate of evaporation of water. The oily substance also reduces the rate of heat loss from the skin
Test for presence of fats
ethanol emulsion test
procedure of the ethanol emulsion test on liquid samples
- add ethanol to a drop of liquid sample in a test tube and shake
- add water to the mixture and shake
procedure of the ethanol emulsion test on solid samples
- crush the sample using a mortar and a pestle
- place the pieces into a test tube
- add ethanol into the test tube and shake
- add water to another test tube
- after the solid particles settle, decant the ethanol into test tube with water and shake
What should be observed if there is a presence of fats?
A white emulsion is formed
Definition of proteins
Proteins are organic molecules made up of the elements carbon, hydrogen, oxygen and nitrogen. Sulfur may also be present.
Can proteins be found in all cells?
YES
‘Proteins’s molecules are the smallest of all the food substances’. This sentence is wrong. What is the correct version?
Proteins’s molecules are the largest and most complicated of all the food substances
What is the building blocks of proteins?
Amino acids
what are the 3 things an amino acid made up of?
an amino group, an acidic group, a side chain
What causes the different amino acids differ?
the different R groups
‘amino acids are combined in 2 ways to form 2 different protein molecules’. Is this statement true? if not, what is the correct statement?
amino acids are combined in various ways to form millions of different protein molecules
What is a polypeptide?
Many amino acid molecules are joined in a linear manner to form a polypeptide
can different polypeptides be linked up to form a longer chain?
YES
What does one or more ‘linked polypeptides’ chain folded together like a 3-D shape make up?
a protein molecule
sources of proteins?
milk, eggs, seafood, chicken, lean beef, soya beans, nuts, grains, vegetables like French beans
Functions of proteins?
Proteins are used in the:
- synthesis of new cytoplasm, for growth and repair of worn-out body cells
- synthesis of enzymes and some hormones
- formation of antibodies to combat diseases
how to test for proteins?
the biuret test
what colour is the biuret solution?
blue
What is the biuret solution made up of?
sodium hydroxide and copper(II) sulfate
procedure of biuret test?
- an equal volume of biuret solution and food sample to be shaken well
- let the mixture stand for 5 mins
what is the observation made if there is a presence of proteins?
the blue biuret solution turns violet
what is the observation if the test is negative?
the blue biuret solution turns clear
What are cells?
- Cells are the building blocks of life.
- The simplest structural and functional units of life
How do we study the parts of a cell?
We use light microscopes and electron microscopes.
How much does a light microscope magnify up to?
A light microscope can magnify up to 1000x.
How much does an electron microscope magnify up to?
An electron microscope can magnify more than 200,000x.
What are the pictures taken by microscopes called?
Micrographs
What are the 2 types of cross sections of a cell?
Longitudinal section and transverse section
How does cutting a cell 2 different ways help?
It helps to create a 3D picture of the cell
What is protoplasm?
A complex jelly-like substance, consisting of the cell membrane, cytoplasm, and the nucleus
Function of protoplasm?
Provides a site for many chemical activities that allow the cell to:
1. survive
2. grow
Description of cell membrane?
- Made up of lipids (fats) and proteins
- A partially permeable membrane
Function of cell membrane?
- Controls the movement of substances in and out of the cell, through its partially-permeable membrane
Description of cell wall?
- Encloses the entire plant cell, enclosing the cell membrane
- Made up of cellulose (a type of carb) and is fully permeable
Function of cell wall?
- Protects the cell from injury
- Gives the plant a fixed shape
Description of cytoplasm?
- A jelly-like substance that fills the inside of the cell
- Enclosed by the membrane
- Contains organelles
Function of cytoplasm?
Provides a site for cellular activities
What are the different organelles found in the cytoplasm?
Nucleus, Ribosomes, Smooth Endoplasmic Reticulum (SER), Rough Endoplasmic Reticulum (RER), Golgi body, mitochondria, chloroplasts, vacuoles
Description of the nucleus?
- Surrounded by a membrane called the nuclear membrane
- Contains genetic info. in the form of chromosomes
Description of chromatin?
- Long thread-like structure found within nucleus
- Made up of proteins and a compound called DNA
- The DNA carries instructions that a cell needs for carrying out its activities
- The chromatin condenses and shortens to become thick, rod-like structures during cell division
- A human contains 46 chromosomes –> 23 pairs, 23 (mom) & 23 (dad)
Description of nuclear membrane?
- Separates the contents of the nucleus from the rest of the cytoplasm
Description of RER?
- Consists of a network of flattened spaces lined with a membrane
- Appears rough on the outside due to ribosomes attached to its outer surface
- The outer surface of RER is continuous with the nuclear membrane
Is the RER connected to the nuclear membrane?
YES
Function of RER?
- RER provides a site for ribosomes to be attached to
- transports proteins made by ribosomes to the Golgi body for secretion out of the cell
Description of ribosomes?
- small round structures
- either attached to RER’s membrane or lie freely in the cytoplasm
Function of ribosomes?
- ribosomes attached to RER synthesise proteins that are transported out of the cell
- ribosomes lying freely in the cytoplasm synthesise proteins to be used within the cytoplasm of that cell
Description of SER?
- does not have ribosomes attached to its membrane
- smooth
- more tubular than RER
Function of SER?
synthesises substances such as fats and steroids
- converts harmful substances into harmless substances through detoxification
Description of Golgi body?
- shaped like a disc
- consists of flattened spaces surrounded by membranes
- vesicles can be seen fusing with one side of the Golgi body and pinching off from the opposite side
Function of Golgi body?
- chemically modifies substances made by the ER
- stores and packages these substances in vesicles for secretion out of the cell
Description of mitochondria?
small oval-shaped organelles
What is differentiation?
differentiation is the process by which a cell becomes specialised for a specific function
Adaptation of red blood cell?
contains haemoglobin which binds to oxygen
