chapter 4: nutrients Flashcards
why do we need food? and what are some examples?
- provides energy for vital activities
-during photosynthesis, green plants use light energy from sun to convert raw materials from their surroundings into food such as carbs
- food contains stored energy called chemical energy - food helps organisms to stay healthy
- eg. vitamin c found in limes prevent gums from bleeding and teeth from falling out
- eg. calcium, found in milk, needed to keep bones and teeth strong - provides raw materials to make new protoplasm
-body of living organism undergoes wear and tear
> and is able to grow, reproduce and repair worn out parts
>to do this, organisms must make new protoplasm from certain substances in food
what are the functions of water?
- a solvent for chemical reactions
- chemical reaction taking place in living things
- plants need water for photosynthesis - a key component of tissues
- key component for cells tissue fluid, digestive juices and blood - controlling body temperature
- a component of sweat
-when sweat evaporates from skin surface, latent heat is removed
> body cooled down - transporting dissolved substances
how is water needed for transporting dissolved substances in animal cells and how is water used for plant cells?
in animal cells,
- transport digested products from the small intestines to all the other parts of the body
- transports waste products from cells for removal from the body
in plants, water is needed:
- for photosynthesis
- to keep the cells turgid or firm
- needed to transport mineral salts up the plant through the xylem
- to transport food substances made in the leaves to all the other parts of the plant
how is water lost and how much water does a normal, healthy adult need?
- water is lost from the body in exhaled air, sweating, in the urine and in faeces
- a normal healthy adult requires 3 litres of water
what are carbohydrates?
carbohydrates are organic molecules made of the elements: carbon, hydrogen and oxygen
- hydrogen and oxygen are present in the ratio of 2:1
what are monosaccharides and what are some examples of it?
- they cannot be digested into smaller molecules
- can pass through cell membrane and be absorbed by the cells
- glucose, fructose, galactose
- all have the same chemical formula: C6 H12 O6
> atoms arranged differently within the molecules
> different arrangements give the sugars different chemical and biological properties
where are the three monosaccharides found?
- glucose: found in plants and animals
- fructose: common in plants, rare in animals
- galactose: present in milk sugar in mammals
what are some examples of disaccharides?
maltose, sucrose and lactose
what is condensation and what are some examples?
- the formation of disaccharides from monosaccharides
eg: glucose x2 > maltose
glucose + fructose > sucrose
glucose + galactose > lactose
what is hydrolysis?
A chemical reaction in which water is used to break down a compound
what are some examples of polysaccharides and why is it stored the way it is?
- starch, glycogen and cellulose
- glycogen and starch are stored of glucose
are stored like this because:
> insoluble in water and will not affect water [potential of the cell
> large molecules which cannot diffuse through the cell membranes so they will not be lost from the cell
> can be easily hydrolysed to glucose when needed
eg. tissue respiration
> have compact shapes so occupies less space than individual glucose molecules
what are the reducing sugars?
- all monosaccharides and disaccharides except for sucrose
- glucose, fructose, galactose, maltose, lactose
what is the test for reducing sugars? describe the test and possible results
benedicts test:
1. place 2cm3 of food sample in the test tube
2. add 2cm3 of benedicts solution to the food sample
3. shake the mixture and place it in a boiling water bath for 2-3 minutes
results:
- solution remained blue: no reducing sugar
- blue to green precipitate: traces of reducing sugar
- blue to yellow or orange precipitate: moderate amount of reducing sugars
- blue to brick red: large amount of reducing sugar
what are complex carbohydrates?
- polysaccharide consists of many monosaccharide molecules joined together.
- produced by the condensation of many similar molecules to form a long molecule
- starch, cellulose and glycogen are complex carbohydrates made of numerous glucose molecules
- glucose molecules link in different ways
> giving rise to different structures
what is the structure, role and occurrence of starch?
structure: starch molecule made of several thousands of glucose molecules joined together
role: storage form of carbohydrates in plants
- when needed, it can be digested to form glucose to provide energy for cell activities
occurrence: in storage organs of plants
eg: potato tubers and tapioca
what is the structure, role and occurrence of cellulose?
structure: a starch molecule is made of several thousand glucose molecules joined together
- bonds between the glucose units are different from that in starch
role: - cellulose cell wall protects plant cells from bursting or damage
- cannot be digested in our intestines
- serve as dietary fibres that prevent constipation
occurrence: present in the cell walls of plants
what is the structure, role and occurrence of glycogen?
structure: it is a branched molecule
- made up of many glucose molecule joined together
role: it is a storage form of carbohydrates in mammals
- when needed, it is digested to glucose to provide energy for cell activities
occurrence: stored in the liver and muscles of mammals
describe the hydrolysis of starch.
-starch in the food we eat may be hydrolysed or digested in our alimentary canal
- when starch hydrolysed > bonds within the polysaccharide are broken and the glucose molecules are released
- enzyme amylase digests starch to form maltose
- maltose hydrolysed by the enzyme maltase to form glucose
what are the functions of carbohydrates?
- needed as a substrate for respiration
> to provide energy for cell activities - to form supporting structures
> eg, cell walls in plants
3.to be converted into other organic compounds such as amino acids and fats - for the formation of nuclei acids
> like DNA - To synthesis lubricants
>eg. Mucus which consists of a carbohydrate and protein - Synthesis the nectar in some flowers
> nectar: a sweet liquid that plants produce to attract insects
What are fats?
- fats are like carbohydrates
> are organic molecules made up of the elements carbon, hydrogen and oxygen
> BUT unlike cards, fats contain much less oxygen in proportion o hydrogen
Eg. Tristearin ( beef fat)
C57 H110 O6
- the proportions of th elements that make up fats are not fixed
> no general formula for fats
How and what is fats broken down into?
-broken down into similar compounds by hydrolysis
- hydrolysis to fatty acids and glycerol
Fat molecule + 3H2O >glycerol + 3 fatty acid molecules
What are the sources of fats?
- foods that are rich in fat
> butter, cheese, fatty meat, olives, many nuts, peas, beans, seeds of caster oil and palm oil - the meat of most fishes and ‘ white meat’ have relatively less fats
> some fishes such as herring and salmon have a lot of fats
What is the test for fats? Describe the test and possible results
- ethanol ( alcohol) emulsion test
ON LIQUID FOOD:
1. Add 2cm3 of ethanol to a drop of coconut oil in a dry test tube and shake the mixture throughly
2. Add 2cm3 of water to the mixture and shake the mixture
ON SOLID FOOD:
1. Crush the peanut into small pieces and place the pieces in a dry test tube. Add 2cm3 of ethanol and shake throughly
2. Allow solid particles o settle.
Carefully decant the ethanol into another dry test tube containing 2cm3 of water
Results:
- if a cloudy white emulsion is formed, fat is present
- if the solution remains clear, no fat is present
What are the functions of fats?
- A source and store of energy
- An insulating material that prevents excessive heat loss
> eg. Animals like seals have a thick layer of fat ( blubber) beneath the skin which helps reduce the loss of body heat - A solvent for fat-soluble vitamins and many other vital substances such as hormones
- Essential part of protoplasm > esp in cell membrane
- Way to reduce water loss from skin surface
