Notesale: Turn your study into money

Document Preview

Extracts from the notes are below, to see the PDF you'll receive please use the links above

---

Nutrition, digestion and excretion
COMPOUNDS IN LIVING ORGANISMS
A nutrient is a substance which is needed for growth, repair and metabolism
...
This means that they all contain carbon atoms, covalently
bonded to the atoms of other elements
...
These are also called
monosaccharides; Glucose and fructose have the same molecular formula, C6H12O6
...

Disaccharides; Sucrose is a disaccharide
...

Polysaccharides; Starch (found in plants) and glycogen (found in animals) are polysaccharides
...
They give immediate energy and also store it
Lipids
Lipids are fats and oils
...
Also store
energy
Proteins
Proteins are large molecules made from smaller units of amino acids
...

However, each protein molecule has hundreds, or even thousands, of
them joined together in a unique sequence and folded into the correct
shape
...

Enzymes; an enzyme is a protein that functions as a biological catalyst – a
substance that speeds up a chemical reaction without being changed by
the reaction
...
The place where these molecules fit is called
the active site
...
However, at high temperatures the rate decreases again because
the enzyme becomes denatured and can no longer function as a biological catalyst
...
Different enzymes work best at
different pH values
...
For example,
intestinal enzymes have an optimum pH of about 7
...
A lack of vitamins in the diet leads to
deficiency symptoms
...
Good sources of vitamin C include:
 citrus fruits (such as oranges, lemons and limes)
 leafy green vegetables (such as sprouts and broccoli)
Vitamin C deficiency leads to scurvy
...

Vitamin D; the human body can make vitamin D when our skin is exposed to sunlight
...
Vitamin D deficiency leads to rickets and bone pain
...
Good
sources of vitamin A include:
 milk, and dairy products (such as cheese and yoghurt)
 mackerel and other oily fish
Vitamin A deficiency leads to night blindness, which is when a person finds it difficult to see well in dim light
...


MINERAL IONS
Like vitamins, mineral ions are only needed in small amounts to maintain a healthy body
...

Calcium; Calcium is needed to maintain healthy bones and teeth, for normal blood clotting and to control muscle
contractions
...

Iron; Iron is needed to produce haemoglobin, found in red blood cells
...
People with anaemia become tired and weak because their blood does not transport
enough oxygen
...


STRUCTURE
Mouth
Salivary Glands
Esophagus
Stomach
Pancreas
Liver
Gall Bladder
Small intestine-duodenum
Small intestine-ileum
Large intestine- colon
Large intestine- rectum
Large intestine- anus

FUNCTION
Where food enters the alimentary canal and digestion begins
Produce saliva containing salivary amylase
Muscular tube which moves ingested food to the stomach
Muscular organ where digestion continues
Produce digestive enzymes
Produce bile
Stores bile before releasing it into the duodenum
Where food is mixed with digestive enzymes and bile
Where digested food is absorbed into the blood and lymph
Where water is reabsorbed
Where faeces are stored
Where faeces leave the alimentary canal

TEETH
Food is broken down into smaller pieces in the mouth by chewing
...
The
teeth cut and crush food, and the pieces are mixed with saliva to form a ball of food called a bolus
...
This can happen when
bacteria in the mouth convert sugars into acids that react with the enamel
...
It can be prevented by consuming fluoride, avoiding high sugars, brushing your teeth regurlarly

INGESTION
Food enters the digestive system through the mouth
...
Once in the mouth, the food is
chewed to form a ball of food called a bolus
...
Food is moved
through the digestive system by a process called peristalsis
...
These have a ‘squeezing action’ that pushes the bolus
through the gut
...
Mechanical digestion includes:
 chewing in the mouth
 churning in the stomach
Chemical digestion involves enzymes
...
Enzymes can break
down nutrients into small, soluble molecules that can be absorbed
...
Where enzymes are produced
ENZYME
Salivary Amylase
Protease
Lipase
Pancreatic Amylase
Maltase

SUBSTRATE
Starch
Protein
Lipids (fats and oils)
Starch
Maltose

END-PRODUCTS
Maltose
Amino acids
Fatty acids and Glycerol
Maltose
Glucose

WHERE PRODUCED
Salivary Glands
Stomach, Pancreas
Pancreas
Pancreas
Small intestine

ABSORPTION
Absorption is the movement of digested food molecules through the wall of the
intestine into the blood or lymph
...
Most absorption happens in the ileum
...
The small
intestine has a large internal surface area for absorption to happen quickly and
efficiently
...
They have several important features:
 wall just one cell thick - ensures that there is only a short distance for
absorption to happen by diffusion and active transport
 network of blood capillaries - transports glucose and amino acids away
from the small intestine in the blood
 internal structure called a lacteal - transports fatty acids and glycerol away from the small intestine in the
lymph

In Plants
PHOTOSYNTHESIS
Photosynthesis is the process by which plants make carbohydrates from raw materials, using energy from light
...
The stored starch can
later be turned back into glucose and used in respiration
...

A leaf needs:
 a way to transport water to the leaf, and glucose to other parts of the plant
 a way to exchange carbon dioxide and oxygen
 the ability to absorb light energy efficiently
Transport; Xylem tissue delivers water from the roots to the leaf, and phloem
tissue transports glucose away from the leaf
...

Gas exchange; Gas exchange happens in the spongy mesophyll tissue of the leaf
...

When the plant is photosynthesising during the day, these features allow carbon dioxide to diffuse into the spongy
mesophyll cells, and oxygen to diffuse out of it
...
They also
open or close to control the loss of water from leaf by the process of transpiration
...
Palisade cells are
column shaped and packed with many chloroplasts
...

Features and it’s functions;
Feature
Large surface area
Thin
Thin waxy cuticle
Thin transparent epidermis

Function
Maximise light absorption
Short distance for carbon dioxide to diffuse into leaf cells
This protects the leaves without blocking out light
Allows light to reach the palisade cells

Temperature- Light
intensity and carbon
dioxide concentration
affect the rate of
photosynthesis

PLANTS AND MINERAL IONS
Plants need minerals for healthy growth
...

Magnesium and nitrate; Magnesium ions and nitrate ions are
needed by plants
...
(mag= leaves turn yellow/ nit= stunted growth)
Nitrogen fertilizers; Fertilizers are used to replace minerals used
by plants
...

They allow farmers to increase the yield and quality of their
crops
...
Eutrophication happens
when excess nitrate (or phosphate) enters rivers or lakes from
fields
...


Excretion in plants and animals
EXCRETION
Excretion is the removal of the following substances:
 toxic materials
 waste products of metabolism
 excess substances from organisms
Excretion is not the same as egestion - which is the passing out of undigested food through the anus as faeces
...
Carbon dioxide is a waste product of aerobic
respiration in plant cells
...
Excess carbon dioxide and oxygen are
excreted from the plant through the stomata in the leaves
...
The water in sweat helps to keep the body cool in hot conditions, and
it contains salts and urea
...

Kidneys: The kidneys are organs of the urinary system - which removes excess water, salts and urea
...
The kidneys filter the blood and then
reabsorb useful materials such as glucose
...

Urine is taken from the kidneys to the bladder
by the ureters
...

Note that ‘ureter’ differs from the word
‘urethra’
...

Urine->Urine contains water, urea and salts
...
It is the main waste product removed in the urine
...
A renal artery carries blood to the
kidney and a renal vein carries it away
...

Blood is filtered at high pressure to remove glucose, water, salts and urea
...
Note that urea is not reabsorbed
...
Each kidney contains around a million
nephrons

---