Human biology short notes

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Protein Synthesis

  • Proteins are produced at ribosomes in the cell
  • Nucleus determines the protein to be made
  • RNA produced by the nucleus acts as a messenger carrying the code to the ribosomes
  • RNA is released to the cytoplasmic fluid
  • And joins with ribosomes
  • Endoplasmic reticulum allows movement of amino acids in the cell
  • Ribosomes assemble the amino acids forming peptide bonds to make proteins

Movement of Substances

  • Passive Transport - Diffusion

                                    Osmosis – Hypotonic

                                          Isotonic

                                          Hypertonic

  • Active Transport

Passive Transport

Diffusion

  • Movement of molecules from a greater concentration to a lower concentration
  • Down the concentration gradient
  • Diffusion stops when the concentration gradient is zero (uniform distribution of molecules)

*Concentration gradient-Difference in concentration between the two regions

Osmosis

  • Is the movement of water molecules from a dilute region (high water potential) to a concentrated region (high water potential)
  • Through a partially permeable membrane  

a) Hypotonic- When the solution is more dilute (higher water potential) than inside of the cell

  • Water flows into the cell
  • Cytoplasm contain excess water
  • Cell burst

b) Isotonic – When the solution is the same concentration (zero water potential) than inside the cell

  • Cell stays the same

c) Hypertonic- When the concentration of the solution is greater (lower water potential) than inside the cell

  • Water diffuses out of the cell into the solution
  • Less water in the cytoplasm
  • Cell shrinks

Active Transport

  • Is the movement of molecules from a lower concentration to a greater concentration
  • Against the concentration gradient
  • Active transport uses a source of energy from respiration (ATP is broken down to ADP)
  • Lack of respiration is likely to stop active transport

Factors Affecting the Rate of Diffusion

Enzymes

Characteristics of Enzymes

  • Protein in nature
  • Affected by high temperatures and pH
  • Bio catalyst, they speed up a chemical reaction without getting used up during a chemical reaction
  • Specific  
  • Produced in living cells
  • Extra-cellular enzymes- carry out their function outside the protoplasm
  • Intra-cellular enzymes – carry out their function inside the protoplasm
  • Remain unchanged-does not alter there end products

Temperature and pH

  • Since enzymes are proteins they are affected by high temperatures and pH
  • Temperatures above 45C denature the enzyme
  • High temperatures and pH destroy the active site and enzymes can no longer combine with substrate to form a complex

*The maximum temperature/ pH, at which the chemical reaction is accelerated is called the optimum temperature/pH

                                       

Importance of enzymes

  • Many vital chemical reactions takes place inside the body
  • Enzymes are needed to speed up the rate at which the chemical reactions occur
  • If enzymes are not present or denatured, chemical reactions will occur slowly
  • For chemical reactions to take place without enzymes high temperatures are needed
  • Synthesis of materials will not be sufficient enough to support life
  • As a result organism will die

Respiration

Respiration is the process by which energy is made available by breaking down

Respiration-          Aerobic

                          Anaerobic

Aerobic Respiration

  • “Aerobic” means it uses oxygen
  •  Process-
  • Food molecule is oxidized by combining with oxygen
  • During oxidation the carbon in food molecules are converted to carbon dioxide and hydrogen to water
  • When bonds of the food molecules are broken energy with was present in the bonds is released
  • This process takes place inside the mitochondria
  • ATP is a short  term source of energy released by the mitochondria for cellular activities
  • The process of oxidizing food to release energy takes place in small step each step requiring it own enzymes

Anaerobic Respiration

  • “Anaerobic” means does not use oxygen
  • Food is not completely oxidized to carbon dioxide and water
  • Less energy is released

   

         a) Fermentation

  • Yeast cells respire anaerobically
  • Food is not completely oxidized instead Carbon dioxide and Alcohol is produced
  • Lots of energy is still present in the alcohol which the yeast cells are unable to use

        b) Anaerobic Respiration in Animals 

  • First stages of respiration in muscles cells is anaerobic
  • Pyurvic acid is formed
  • Only later is pyurvic acid completely oxidized to carbon dioxide and water
  • During vigorous exercise pyurvic acid may build up faster than it is oxidized
  • So it is converted to lactic acid and removed in the blood stream
  • Breathing rate increases to meet the oxygen debt
  • Lactic acid is completely oxidized
  • Accumulation of lactic acid leads to muscle cramps/ stop muscles from contracting/ muscular fatigue/pain and difficulty in movement

                                                                                         

                                                                                                                                     Oxygen

       Glucose             Pyurvic acid                Lactic acid          Carbon dioxide +  Water

Difference between Aerobic and Anaerobic Respiration

Teeth

Function

 They bring about mechanical digestion of food

Structure

Tooth Decay (Carries)

  • Bacteria present in the saliva
  • Act on the remains of sugar ( carbohydrates)
  • To produce an acid
  • The acid produced dissolves the enamel
  • Eventually if not treated the acid produced by the bacteria will dissolve the dentine and on reaching the plup cavity a sensation of pain will be produced
  • When the tooth decays remains of the tooth decayed and bacteria present accumulate on the surface of the tooth forming a hard substance called plaque

Act of brushing

  • Removes plaque formed
  • Gets rid of food remains left in the mouth preventing cavities  
  • Tooth paste containing fluoride covers the surface of the tooth allowing the enamel to absorb to fluoride

Diet for Healthy Teeth

Digestion

  • Digestion is the process in which large insoluble molecules are broken down into small soluble products
  • Digestion occurs in the alimentary canal
  • The alimentary canal is a muscular tube with a mucosa membrane
  • The lining secretes enzymes which are responsible for digestion
  • Secretes mucus which lubricates the lining of the gut

Peristalsis

  • Is the wave like movement of food along
  • Is the contraction and relaxation of circular muscles
  • Muscles behind the bolus contract
  • Muscles in front of the bolus relax
  • Pushes the bolus forward
  • Along the whole length of the alimentary canal

Digestion in the Mouth

*Mechanical Digestion 

  • Food is broken down up by the help of the teeth
  • Chopping is carried out by incisors and canines
  • Grinding is carried out by pre-molars and molars
  • Action of teeth increases the surface area for the action of enzymes

*Chemical Digestion

  • Saliva is secreted by three pairs of glands
  • Saliva is mixed by the help of the tongue
  • Saliva contains amylase
  • Amylase breaks down starch to maltose

Digestion in the Stomach

  • Food reaching the stomach is churned by muscles
  • Pepsinogen is secreted inactive form to prevent self-digestion
  • Pepsinogen is activated by HCl
  • Enzyme pepsin acts on proteins
  • Peptide bonds of proteins are broken down to peptides

(Enzyme rennin digests proteins in babies)

  • HCl provides an acidic medium (pH 1-3) for the optimum action of enzyme pepsin  
  • HCl also destroys any microorganisms in the stomach

Digestion in the Duodenum  

  • Pyloric Sphincter releases food from the stomach to the duodenum
  • Bile is secreted from the gall bladder
  • Bile emulsifies fats to fat droplets to increase the surface area for enzyme action
  • Neutralizes the acid medium from the stomach ( pH 8)
  • Pancreatic juices are secreted from the pancreas
  • Pancreatic juices contain
  • Amylase - Digest remaining starch to maltose
  • Trypsin (protease) - Trypsinogen (inactive form) is activated by Enterokinase

                                     Trypsin breaks down peptides to amino acids

  • Lipase - Act on emulsified fat droplets and break them down to fatty acids and glycerol

                         

Digestion in the Ileum

Digestion        

Enzyme        

  • Moltase- Acts on maltose and converts it to glucose
  • Trypsin- Form active enzymes from the duodenum convert peptides

   to amino acids

Absorption

  • Villi are present in the ileum
  • They absorb soluble products of digestion into the blood

Adaptation

  • Ileum is long structure (folded internally)
  • Presence of thousands of villi- provides a large surface area
  • Surrounded by a dense network of capillaries (Absorb Proteins and Glucose)    
  • Thin (single cell) epithelium(Diffuse across a short distance)
  • Villi have a lacteal to absorb fats

Large Intestine (Colon and Rectum)

  • Water is absorbed by the colon
  • Indigestable food is compacted into feces
  • Stored in the rectum
  • Egested via anus  

End products

Glucose

  • Absorbed into the blood by the villi
  • Used for immediate source energy
  • If not extra glucose is carried by the hepatic portal vein to the liver
  • In the liver glucose is converted to insoluble glycogen and stored

Proteins

  • Absorbed into the blood by villi
  • Used for blood plasma proteins and formation of cellular structures  
  • Extra proteins cannot be stored
  • So they are carried to the liver by the hepatic portal vein
  • In the liver extra amino acids are deaminated

Fatty Acids and Glycerol

  • Absorbed by the villi
  • Again joined to make fat molecules
  • Passed into the lacteal
  • Utilized for cell formation, energy
  • Excess is stored as insulation

Diet

  • Balanced Diet is a diet which contains all nutrients required by the body in correct portions
  • A balanced diet contains :- Carbohydrates, Fats, Proteins, Minerals, Vitamins, Water, Fibre

Carbohydrates

  • Monosaccharide simple soluble unit
  • Disaccharide- Two monosaccharide chemically combined
  • Polysaccharides- Many monosaccharide joined to form an insoluble complex structure

Fats

Fatty acids and glycerol (repeating units) are joined to form fats

Protein

  • Is formed when many amino acid units are joined with a peptide bond (polypeptide)

Water

  • Acts a solvent
  • Absorbs heat (temperature regulation)
  • Provides a medium for chemical reactions

Salt

  • Maintains the osmotic balance in the body

Change in Diet

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Rehydration

  • Is the process of restoring body fluids which was lost by excessive vomiting and diarrhea
  • Losses water and salts from the body
  • Body fluids become more concentrated than normal  

Two Methods of Rehydratrion

  1. Intravenous (IV)
  • Is for patients that are unable to keep down oral drink (due to excessive vomiting and age)
  • IV solutions contain sterile water with small amounts of salt
  1. Oral Rehydratrion Method  (ORL)
  • Is a drink which is taken in orally
  • Contains water with a balance of water, ...

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