Digestion, Absorption, Assimilation (Simple explanation)





Human Digestion

Mouth

Salivary glands produce saliva which contains salivary amylase. Starch is hydrolysed into maltose.

Stomach

Gastric glands produce gastric juice which contains enzyme pepsin and rennin. Proteins are hydrolysed into polypeptide. Caseinogens is converted into casein.

Duodenum

Liver produces bile. Bile emulsifies lipid. Pancreas produces pancreatic amylase, trypsin & lipase. Starch is hydrolysed into maltose. Polypeptide is hydrolysed into peptide. Lipid is hydrolysed into fatty acids & glycerol.

Ileum

Intestinal gland secretes intestinal juice which contains enzyme maltase, lactase, sucrase and erepsin. Maltase hydrolyses maltose into glucose & glucose. Lactase hydrolyses lactose into glucose and galactose. Sucrase hydrolyses sucrose into glucose & fructose. Erepsin hydrolyses peptide into amino acids

Absorption

Glucose, amino acids, Vitamins B & C are absorbed through facilitated diffusion into blood capillaries in the villi then into hepatic portal vein that leads to liver.

Fatty acids, glycerols, Vitamin ADEK are absorbed into lacteals (FA & G in the form of lipid droplets). Then lacteal converge into lymphatic system. Flows into right lymphatic duct & thoracic duct, finally enters subclavian veins into bloodstream.

Assimilation

In the liver

Liver synthesises plasma proteins from amino acids. Short supply of glucose – liver converts amino acids into glucose. Excess amino acids are broken down – deamination. Urea is produced & transported to kidney to be excreted.

Glucose is converted & stored in the liver. Blood sugar level falls, glycogen is converted back into glucose. Liver full of glucose – converted into lipids.

Lipids enter the heart through subclavian vein transported in the bloodstream to body cells.

In the cells

Amino acids – used for synthesising new protoplasm & repair damaged tissues. Build enzymes & hormones. Synthesise plasma membrane.

Glucose – oxidised to release energy (cellular respiration). Used for muscle contraction, synthesis of proteins. Excess glucose is stored in muscles (glycogen).

Lipids – phospholipids & cholesterol : components of plasma membrane

Fats are stored around organs act as cushions that protect organs from injuries. Excess fats are stored in adipose tissue as reserve energy. When body lacks glucose, fats are oxidised to release energy.

Last-Minute Study

Exams are just around the corner. Being prepared reduces stress so take time to set your priorities in the days ahead. 

Keep friends and family updated about your plans and ask them to cheer you along to the finish line.
Think about what you’ve already covered and review your study schedule. 

Set 15 minute study goals and take a 10 minute break every 50 minutes or after two hours. 

Repetition improves memory. Continue being an active learner- eg. use highlighters, make summaries or mind maps. 

You might like to revise past papers, practice writing timed essays or study with a friend. Give yourself regular rewards.
If you become distracted while studying, just notice and refocus on the task at hand. Break tasks down into smaller chunks and tackle them one at a time. 

Remind yourself “I can do this” “I enjoy learning.” Expect to succeed.
Minimise interruptions eg. turn your mobile on silent. 

If you find your self procrastinating, weigh up the pros and cons. 

Stay motivated by imagining a well earned break or seeing yourself on graduation day. 

Maintain some balance. A brisk walk will clear your mind.
Try not to live on caffeine.
If you like, you can practice slow abdominal breathing whenever you sit down to study.
Inhale in a way that allows your stomach to expand. As you exhale, your stomach should move inward. If you practice this for a minute your body and mind will naturally begin to relax.
You can use this technique in your exams to improve your concentration or calm yourself.
Each day imagine yourself in the exam room, knowing how to answer the questions well.
Make sure you check the date and location of your exams.

On the day of the exam:
Eat well. Have a good breakfast the morning of your exam.
Wear a watch, check your pens etc. and give your self extra time to travel.
Sit apart from the anxious crowd just prior to your exam.
Use self talk to stay focussed. Tell yourself “I’m calm and thinking clearly.”
In the exam room, scan your entire paper, read questions carefully and allocate your time according to marks.
Some anxiety is a cue to cope. If you feel too anxious or blank out for a moment, just take a few slow, deep breaths and remind yourself “Relax. Concentrate. I can easily do this, just one step at a time.”
You can also describe your surroundings for a moment, have a drink of water.
You can take a mental break and then begin again. 

Don’t give up.
Dangle your arms by your sides to promote circulation when resting briefly from writing.
 

Good luck and enjoy.