Summarised Flash Cards

Nutrition Information and Healthy Diet

• Nutrition information labels provide details about the contents of food, including the amount of chemical energy stored, measured in kilojoules (kJ).
• A healthy diet involves a balanced intake of different foods and the right amount of energy, providing essential nutrient groups.
  • Carbohydrates: For energy and cell structure.
  • Fats: For energy, insulation, and cell structure.
  • Proteins: To control cell reactions (enzymes) and build cell structures.
  • Vitamins and Minerals: To aid body functions.

Nutrients, Examples, and Sources

• Carbohydrates
  • Examples: Starch, sugars
  • Why it’s needed: For respiration to release energy
  • Good sources: Pasta, bread
• Protein
  • Examples: Growth and repair
  • Why it’s needed: Meat, beans
  • Good sources: health
• Vitamins
  • Examples: Vitamin C
  • Why it’s needed: Fruits and vegetables (oranges contain a lot of vitamin C)
  • Good sources: health
• Minerals
  • Examples: Calcium
  • Why it’s needed: Fruits, vegetables, and dairy products (milk contains a lot of calcium)
  • Good sources: health
• Fibre
  • Examples: Wholemeal bread
  • Why it’s needed: For health; helps to keep our intestines clean and stops them from getting blocked up (constipation)
  • Good sources: health
• Water
  • Examples: For health; water is an important solvent in the body
  • Why it’s needed:
  • Good sources:

Malnourishment

• Malnourishment occurs when a diet is not balanced, leading to being overweight or underweight.
• An unbalanced diet can cause diseases, and a lack of essential nutrients can result in deficiency diseases.

Exercise

• Exercise increases the energy expended by the body.
• Regular exercise promotes better health compared to a sedentary lifestyle.
• People who exercise regularly expend more energy and have more efficient circulatory systems.

Metabolic Rate

• Metabolic rate is the rate at which all chemical reactions in the cells of the body are carried out.
• Respiration is a major set of metabolic reactions.
• The rate of these reactions varies with activity level; more activity requires more energy.
• Metabolic rate also varies with the proportion of muscle to fat in the body; a higher proportion of muscle results in a higher metabolic rate.

Stomach Structure

• The stomach contains:
  • Muscular tissue: to churn the contents.
  • Glandular tissue: to produce digestive juices.
  • Epithelial tissue: to cover the outside and inside of the stomach.

Digestive System

• The digestive system facilitates the exchange of substances with the environment and includes:
  • Glands (e.g., pancreas, salivary glands): produce digestive juices.
  • Stomach and small intestine: digestion occurs.
  • Liver: produces bile.
  • Small intestine: absorption of soluble food.
  • Large intestine: absorption of water from undigested food, producing faeces.

Proteins Summary

Proteins have many functions, both inside and outside the cells of living organisms.

Enzymes as Proteins

• Proteins act as biological catalysts called enzymes.

Protein Structure

• Protein molecules are made up of long chains of amino acids.

Enzymes Structure and Function

• Enzymes are biological catalysts that increase the rate of chemical reactions.
• Enzymes are protein molecules made up of long chains of amino acids.

Nutrient Food Tests

• Protein: Add 5–10 drops of Biuret solution to a test tube containing food mixed with 0.5 cm depth water, then add 5–10 drops of Biuret B solution. A color change from light blue to lilac indicates the presence of protein.
• Fat: Rub or add some of the food to a piece of paper. Hold the paper to the light. The paper appearing translucent when held up to the light indicates the presence of fat.
• Glucose: Add 5–10 drops of Benedict’s solution to a test tube containing food shaken with 0.5 cm depth of water. Put the test tube into a hot water bath. A color change from blue to either green, yellow, orange, or brick-red indicates the presence of a sugar such as glucose.
• Starch: Add 2–5 drops of iodine solution to your food or to a test tube containing your food mixed with 0.5 cm depth water. A color change from orange to blue-black indicates the presence of starch.

Enzyme Structure

• Long chains of amino acids are folded to produce a special shape, enabling other molecules to fit into the enzyme.
• This shape is vital for the enzyme's function.
• Normally, only one type of molecule (the substrate) will fit into the enzyme.
• The active site is the part of the enzyme into which the substrate fits.

Effect of Temperature on Enzymes

• Like most chemical reactions, the rate of enzyme-controlled reactions increases as the temperature increases.
• The enzyme and substrates move around faster, so they collide more often.
• The temperature when the enzyme works fastest is called the optimum.
• This is true up to approximately 40°C; higher than this, the structure of the enzyme changes.
• As a result, the active site becomes a different shape, and the substrate no longer fits.
• It is then described as denatured.
• Digestive enzymes work best at 37°C because this is body temperature.

The effect of pH on enzymes

• pH can also affect the shape of the active site.
• It does this by affecting the forces that hold the enzyme molecule together.
• A change in pH can denature the enzyme.
• Different enzymes work best at different pH values.
• Eg. Stomach enzymes (pepsin) work best in acidic conditions.
• Mouth enzymes (salivary amylase) work best in neutral conditions.

Digestion

• Some enzymes work outside the body cells.
• These are called extracellular enzymes.
• The digestive enzymes are produced by specialised cells in glands and in the lining of the gut.
• The enzymes then pass out of the cells into the gut where they come into contact with food molecules.
• They catalyse the breakdown of large molecules into smaller molecules.
• Digestion is the process where food is broken down into substances the body can absorb.
• Nutrition is the process of taking in and using food.

Digestion in the Mouth

• Food is chewed to create a larger surface area for enzyme action.
• Saliva is released, containing amylase.
• Amylase digests starch into smaller sugars (maltose).
• Further chewing enables swallowing.
• The food enters the oesophagus.

Digestion in the Stomach

• Food enters the stomach from the oesophagus.
• The walls of our stomach produce juice.
• This juice contains:
  • A protease enzyme (called pepsin).
    • This digests proteins into amino acids.
  • Hydrochloric acid – this kills bacteria in our food. It creates pH3.
  • Mucus – this protects the wall of our stomach from acid and pepsin.
• The wall of our stomach is muscular and churns our food.
• The food remains in our stomach for a few hours. The proteins are digested.
• Food leaves our stomach in small squirts into the small intestine.

Digestion and Absorption in the Small Intestine

The small intestine has 2 main jobs:

• To complete the digestion of the food
• To absorb the soluble products of digestion into the blood.

Digestion in the Small Intestine

3 juices are released:

1. Bile
   • Produced by the liver.
   • Stored in the gall bladder.
   • Released into the small intestine.
   • 2 main things in bile:
     • Alkali to neutralise the stomach acid
     • Bile salts which convert large fat droplets to small fat droplets – for a large surface area for the enzymes to act on. (Emulsifies the fat)
   • There are no enzymes in bile.
2. Pancreatic juice and
3. Intestinal juice
   • Both are released into the small intestine.
   • Both contain 3 main enzymes:
     • Amylase to complete the digestion of starch into sugars.
     • Protease to complete the digestion of proteins into amino acids.
     • Lipase to break down fats into fatty acids and glycerol.

Respiration

Respiration in cells can take place aerobically or anaerobically. The energy released is used in a variety of ways. The human body needs to react to the increased demand for energy during exercise.

Respiration

• Definition: The process of transferring energy from food molecules in every living cell.
• Aerobic respiration - uses oxygen
• Anaerobic respiration - uses no oxygen
• All chemical reactions inside cells are controlled by enzymes, including respiration

Aerobic Respiration

• Glucose reacts with oxygen, producing carbon dioxide and water as waste products.
• This takes place continuously in animals and plants.
• Word equation: Glucose + Oxygen → Carbon dioxide + Water + Energy
• Respiration actually involves a series of many small reactions.
• Each reaction is controlled by an enzyme.

Mitochondria

• Most of the reactions in respiration happen in the mitochondria.
• The inner surface of the mitochondria is highly folded to increase the surface area for enzymes.

Energy Use

The energy that is released during respiration is used:

• To build up larger molecules using smaller ones.
• In animals, to enable muscles to contract.
• In mammals and birds, to maintain a steady body temperature in colder surroundings.
• In plants, to build up sugars, nitrates and other nutrients into amino acids which are then built up into proteins.

The Role of Respiration During Exercise

• Muscles contract to move the bones in our bodies.
• Respiration releases energy, which is used to contract the muscles:
• When we exercise, our muscles contract more quickly and with more force.
• This requires more energy.
• This requires more glucose and oxygen.
• Also, more carbon dioxide is created which needs to be removed.
• The human body needs to react to the increased demand for energy during exercise.

Changes During Exercise

• During exercise a number of changes take place:
  • The rate and depth of breathing increases.
    • This increases the rate of gaseous exchange.
    • More oxygen is taken into the blood.
    • More carbon dioxide is removed from the blood.
  • The heart rate increases.
    • This increases rate of blood flow to the muscles
• All of these changes increase the blood flow to the muscles and so increase the supply of sugar and oxygen and increase the rate of removal of carbon dioxide.

Anaerobic Respiration

• During exercise, if insufficient oxygen is reaching the muscles they use anaerobic respiration to obtain energy.
• Anaerobic respiration is the incomplete breakdown of glucose and produces lactic acid.
• As the breakdown of glucose is incomplete, much less energy is released than during aerobic respiration.
• glucose → lactic acid + small amount of energy released
• However, lactic acid is poisonous. We can only tolerate small amounts in our body.
• If muscles are subjected to long periods of vigorous activity they become fatigued, ie they stop contracting efficiently.
• One cause of muscle fatigue is the build up of lactic acid in the muscles.
• Blood flowing through the muscles removes the lactic acid.
• During and after exercise, we breathe heavily to take in extra oxygen to oxidise the lactic acid:
• lactic acid + oxygen → carbon dioxide + water
• The products of anaerobic respiration in yeast can be used to make bread rise and alcoholic drinks.
• glucose → ethanol and carbon dioxide

The Lungs

Gaseous Exchange

• The lungs are in the upper part of the body (thorax).
• They are protected by the ribcage.
• They are separated from the lower part of the body (abdomen) by the diaphragm.
• The breathing system takes air into and out of the body.
• Oxygen from the air diffuses into the bloodstream.
• Carbon dioxide can diffuse out of the bloodstream into the air.
• The alveoli provide a very large, moist surface, richly supplied with blood capillaries so that gases can readily diffuse into and out of the blood.
• Many small spherical alveoli provide a large surface area.
• The moist surface helps oxygen to dissolve so that it can diffuse into the cells.
• The capillaries are very close to the alveoli so that the gases have a short distance to diffuse.
• Concentration gradients are maintained by:
  • The blood removing oxygen from and bringing carbon dioxide to the lungs.
  • Breathing, which replenishes oxygen and removes carbon dioxide.

Ventilation (Breathing)

• The movement of air into and out of the lungs is known as ventilation.
• Breathing in (inhalation):
  • The ribcage moves out and up.
  • The diaphragm becomes flatter.
  • This increases the volume inside the thorax.
  • This reduces the pressure inside the thorax.
  • Air enters the lungs.
• Breathing out (exhalation):
  • The ribcage moves down and in.
  • The diaphragm moves upwards into a domed shape.
  • This reduces the volume inside the thorax.
  • This increases the pressure inside the thorax.
  • Air leaves the lungs.

Transport Systems in Humans Summary

Substances are transported around the body by the circulatory system (the heart, the blood vessels and the blood). They are transported from where they are taken into the body to the cells, or from the cells to where they are removed from the body.

The Blood System

• The circulatory system transports substances around the body.
• The heart is an organ that pumps blood around the body.
• Much of the wall of the heart is made from muscle tissue.
• This muscle contracts to pump blood through the circulation systems.
• It is a double pump, because there are two separate circulation systems:
  • One to the lungs
  • One to all the other organs of the body.
• The blood passes through the heart twice in order to pass round both of these circulation systems.
• In one cardiac cycle:
  • Blood enters the atria of the heart.
  • The atria contract and force blood into the ventricles.
  • The ventricles contract and force blood out of the heart.
• Valves in the heart ensure that blood flows in the correct direction.
• Blood flows from the heart to the organs through arteries and returns through veins.
• Blood is pumped to the lungs from the right ventricle through the pulmonary artery.
• The blood returns from the lungs to the left atrium through the pulmonary vein.
• Blood is pumped to the organs of the body from the left ventricle through the aorta.
• Blood returns to the heart from the organs into the right atrium through the vena cava.

Blood Vessels

• Blood flows from the heart to the organs through arteries and returns through veins.
• Arteries have thick walls containing muscle and elastic fibres.
• Veins have thinner walls.
• Veins often have valves to prevent back-flow of blood.
• In the organs, blood flows through very narrow, thin-walled blood vessels called capillaries.
• Substances needed by the cells in body tissues pass out of the blood, and substances produced by the cells pass into the blood, through the walls of the capillaries.

Arteries vs Capillaries vs Veins

Blood

• Blood is a tissue.
• It consists of a fluid called plasma in which red blood cells, white blood cells, and platelets are suspended.

Plasma

• The liquid part of the blood.
• Blood plasma transports:
  • Carbon dioxide from the organs to the lungs
  • Soluble products of digestion from the small intestine to other organs:
    • Glucose
    • Amino acids
  • Urea from the liver to the kidneys.

Blood Cells

• Red blood cells transport oxygen from the lungs to the organs.
• Red blood cells have no nucleus.
• They are packed with a red pigment called haemoglobin.
• In the lungs:
  • Oxygen diffuses into the red blood cells.
  • Haemoglobin combines with oxygen to form oxyhaemoglobin.
• In the other organs:
  • Oxyhaemoglobin splits up into haemoglobin and oxygen.
  • Oxygen diffuses out of the red blood cell.
• They have a biconcave shape.
• This increases their surface area to increase rate of diffusion across the cell membrane.
• White blood cells have a nucleus.
• They form part of the body’s defence system against disease causing microorganisms (pathogens)
• Some produce antibodies which help to destroy pathogens.
• Some engulf and digest pathogens.
• Produce antitoxins to neutralise toxins produced by microbes

Movement of Molecules In and Out of Cells

• To get into or out of cells, dissolved substances have to cross the cell membranes.
• Solutes = particles in solution e.g., glucose, sodium ions, chloride ions.
• Solvent = liquid in which the particles are dissolved e.g., water.
• Solute and solvent molecules move around randomly.
• Solutes can move into and out of cells by diffusion.

Diffusion

• Diffusion is the spreading of the particles of a gas, or of any substance in solution, resulting in a net movement from a region where they are of a higher concentration.
• Oxygen required for respiration passes through cell membranes by diffusion.
• The greater the difference in concentration, the faster the rate of diffusion.
• Hydrochloric acid – this kills bacteria in our food. It creates pH3.
• Mucus – this protects the wall of our stomach from acid and pepsin, lubricates the food and makes food pass along the intestine easily
• The wall of our stomach is muscular, and churns our food.
• The food remains in our stomach for a few hours. The proteins are digested.
• Food leaves our stomach in small squirts into the small intestine.

Digestion and Absorption in the Small Intestine

The small intestine has 2 main jobs:

• To complete the digestion of the food
• To absorb the soluble products of digestion into the blood.

Movement of molecules in and out of cells

Dissolved Substances

• The cells, tissues and organs in plants and animals are adapted to take up and get rid of dissolved substances. Different conditions can affect the rate of transfer. Sometimes energy is needed for transfer to take place.
• Dissolved substances move by diffusion and by active transport.

Diffusion

• The movement of particles in a liquid or gas from an area where they are in higher concentration to an area where they are in lower concentration.
• The greater the difference in concentration, the faster the rate of diffusion.
• 2 examples of diffusion through the cell membrane:
  • Oxygen required for respiration diffuses into cells.
  • Carbon dioxide produced by respiration diffuses out of cells.

Osmosis

• Water often moves across boundaries by osmosis.
• Osmosis is the diffusion of water from a dilute to a more concentrated solution through a partially permeable membrane that allows the passage of water molecules.
• Differences in the concentrations of the solutions inside and outside a cell cause water to move into or out of the cell by osmosis.
• If there is a higher solute concentration on one side of a membrane, water will move in that direction.

Osmosis in Animal Cells

• If animal cells are placed in a solution that has a higher solute concentration than the cytoplasm, then water will leave the cell by osmosis until it shrinks and dies.
• If animal cells are placed in a solution that has a lower solute concentration than the cytoplasm, then water will enter the cell by osmosis until it bursts.
• This is why it is vital that we maintain the concentration of our body fluids at an equal solute concentration to our cells’ cytoplasm.

Specialised Exchange Surfaces

• Many organ systems are specialised for exchanging materials.
• The effectiveness of an exchange surface is increased by:
  • Having a large surface area
  • Being thin to provide a short diffusion path
  • Animals can also maintain high concentration gradients:
    • By having an efficient blood supply.
    • For gaseous exchange by being ventilated.
• Gas and solute exchange surfaces in humans and other organisms are adapted to maximise effectiveness.
• The size and complexity of an organism increases the difficulty of exchanging materials.
• Larger organisms have more cells, so have a greater requirement for exchange.
• However, the larger an organism, the smaller their surface area to volume ratio.
• Therefore, they require even more complex exchange surfaces to supply their requirements.

Exchange systems in humans

Absorption of Nutrients in the Small Intestine

• Food in the small intestine has been digested into:
  • Glucose
  • Amino acids
  • Fatty acids
  • Glycerol
• These nutrients need to be absorbed into the blood across the wall of the small intestine.
• They are absorbed by diffusion and active transport.
• The wall of the small intestine is covered with finger-like extensions called villi.
• Many villi provide a large surface area.
• The wall is only one cell thick so the diffusion pathway is short.
• Villi have an extensive network of capillaries to absorb the products of digestion.
• Concentration gradients are maintained because the blood removes the absorbed nutrients.