Human Biology

What is validity in a scientific investigation?

Whether the investigation tests what it is designed to test; control relevant variables so results can be linked to the independent variable.

What is accuracy?

How close a measurement is to the actual or true value.

What is reliability?

The consistency of results when an investigation or measurements are repeated.

Can results be reliable but inaccurate?

Yes. Measurements can be consistently different from the true value.

What is cell theory?

All living things consist of one or more cells; cells are life's basic unit; cells arise from pre-existing cells.

What is the difference between cytoplasm and cytosol?

Cytoplasm consists of cytosol, organelles and inclusions; cytosol is the liquid component.

What is the function of the cell membrane?

It forms the cell boundary and is selectively permeable, controlling movement of substances into and out of the cell.

What does selectively permeable mean?

The membrane allows some substances to cross more readily than others.

What are the three components of cytoplasm in this course's terminology?

Cytosol, organelles and inclusions.

What is the function of the nucleus?

It contains DNA; genes provide instructions that help control cell activities.

What does the nucleolus do?

It manufactures and stores ribosomal RNA and is involved in ribosome production.

What is the function of ribosomes?

They synthesise proteins by joining amino acids according to mRNA instructions.

What is the difference between rough ER and smooth ER?

Rough ER has ribosomes attached and helps process/transport proteins; smooth ER is involved in lipid manufacture.

What does the Golgi body do?

It modifies, sorts and packages proteins for secretion and processes lipids to form lysosomes.

What is the function of lysosomes?

Their digestive enzymes break down ingested foreign material and redundant cell structures.

What is the function of mitochondria?

They are the site of the aerobic phase of cellular respiration and are involved in ATP production.

What are the four basic tissue types?

Epithelial, connective, muscular and nervous tissue.

What is the order of biological organisation?

Cell → tissue → organ → organ system → organism.

What is the function of the cytoskeleton?

It helps maintain cell shape and supports cell movement and movement of materials within cells.

What do microtubules do in the teacher's cell presentation?

They help keep organelles in place or move them around the cell.

What do microfilaments do in the teacher's cell presentation?

They help move materials around the cytoplasm or move the whole cell.

What is the function of cilia?

Short, numerous projections that beat to move substances across a cell's surface, e.g. mucus in the trachea.

How does a flagellum differ from cilia?

A flagellum is a longer projection that can propel the cell itself, such as a sperm cell.

What is the fluid mosaic model?

The cell membrane is a fluid phospholipid bilayer containing different molecules, including proteins and cholesterol.

How are phospholipids arranged in a cell membrane?

Hydrophilic heads face watery environments; hydrophobic tails face inward toward each other.

What is the role of cholesterol in the cell membrane?

It helps regulate membrane fluidity and maintain membrane properties.

What do channel proteins do?

They provide pathways for particular substances to cross the cell membrane.

What do carrier proteins do?

They bind particular substances and change shape to transport them across the membrane.

What is simple diffusion?

Passive movement of particles down their concentration gradient without a transport protein.

What is facilitated diffusion?

Passive movement down a concentration gradient through a channel or carrier protein.

Why is facilitated diffusion passive?

The substance moves down its concentration gradient; the protein provides a pathway but no cellular energy is required.

What is active transport?

Transport using energy, commonly ATP, to move substances against their concentration gradient.

What is vesicular transport?

Movement of material into or out of a cell using membrane-bound vesicles.

What is endocytosis?

Vesicular transport that brings material into the cell.

What is exocytosis?

Vesicular transport that releases material out of the cell.

What is osmosis?

Passive diffusion of water through a differentially permeable membrane.

In osmosis, which way does water move if solute cannot cross the membrane?

From higher water concentration (lower solute concentration) toward lower water concentration (higher solute concentration).

Does osmosis require ATP?

No. Osmosis is passive transport.

Why does cell size affect exchange efficiency?

As a cell grows, volume increases faster than surface area, so its surface area-to-volume ratio decreases.

Why is a low surface area-to-volume ratio a problem?

There is less membrane surface available per unit of cell volume to exchange nutrients, gases and wastes.

How does simple diffusion differ from facilitated diffusion?

Simple diffusion crosses the membrane without a transport protein; facilitated diffusion uses a channel or carrier protein.

What is metabolism?

All chemical processes that take place in the body.

What is catabolism?

Breaking down large molecules into smaller ones, releasing energy.

What is anabolism?

Building larger molecules from smaller ones; requires energy.

What are the three carbohydrate forms? Give an example of each.

Monosaccharide: fructose; disaccharide: lactose; polysaccharide: starch.

What is an enzyme?

A biological catalyst that lowers activation energy and is not consumed.

What is activation energy?

The energy needed for a chemical reaction to begin.

What is the lock-and-key model?

The enzyme active site already has a complementary shape to the substrate.

What is the induced-fit model?

Substrate binding causes the enzyme's shape to change to fit it.

What is an enzyme–substrate complex?

The temporary complex formed when a substrate binds to an enzyme's active site.

What is the active site?

The part of an enzyme where the substrate binds.

Why can high temperatures reduce enzyme activity?

High temperature can denature the enzyme, changing its active site so the substrate no longer fits.

What is enzyme saturation?

All available active sites are occupied, so adding more substrate no longer increases reaction rate.

How can increasing enzyme concentration affect reaction rate?

It can increase reaction rate if enough substrate is available.

How can increasing substrate concentration affect reaction rate?

It can increase rate until the enzymes' active sites become saturated.

What is a cofactor?

A non-protein substance some enzymes need to function.

What is an inhibitor?

A substance that slows or stops enzyme activity.

What is cellular respiration?

A series of cellular reactions that break down food molecules and transfer energy to ATP.

What is ATP used for?

Transferring energy to cellular processes that require it, such as active transport.

Where does glycolysis occur?

In the cytosol.

Does glycolysis require oxygen?

No. Glycolysis does not require oxygen.

What are the net products of glycolysis per glucose?

Two pyruvate molecules and a net gain of two ATP.

What happens to pyruvate in the anaerobic pathway described in class?

It is converted to lactic acid; no additional ATP is produced beyond glycolysis.

Where does the anaerobic pathway described in class occur?

In the cytosol.

How much ATP is gained per glucose in the anaerobic pathway described in class?

A net gain of two ATP, from glycolysis.

What is fermentation's role in the anaerobic pathway?

It converts pyruvate to lactic acid and allows glycolysis to continue without oxygen.

What happens to pyruvate in aerobic respiration?

It enters the mitochondrion and is converted to acetyl CoA before the Krebs cycle.

What are the stages after glycolysis in aerobic respiration?

Acetyl CoA formation, Krebs (citric acid) cycle, then the electron transport system.

What is produced in the Krebs cycle, according to the lesson?

Carbon dioxide is released, and two ATP per glucose are produced in this cycle.

What is oxygen's role in the electron transport system?

Oxygen is the final electron acceptor and combines with electrons and hydrogen to form water.

Where is most ATP produced during aerobic respiration?

In the electron transport system.

What is the maximum ATP yield stated in the lesson slides?

Up to 38 ATP per glucose.

What is the difference between aerobic and anaerobic respiration?

Aerobic requires oxygen and produces much more ATP; the anaerobic pathway uses no oxygen and yields two ATP per glucose from glycolysis.

What is the correct pathway of air to the alveoli?

Nasal cavity → pharynx → larynx → trachea → bronchi → bronchioles → alveoli.

What does the epiglottis do during swallowing?

Folds over the laryngeal opening, helping prevent food and liquid entering the airway.

How does cartilage help the trachea?

C-shaped cartilage rings prevent the trachea from collapsing and keep the airway open.

What is the role of mucus in the trachea?

It traps dust and other contaminants.

What is the role of tracheal cilia?

They move mucus upwards towards the pharynx to be swallowed or expelled.

Why is mucus alone insufficient to clear the trachea?

Mucus traps particles, but cilia move the mucus towards the pharynx.

What happens to the diaphragm during inspiration?

It contracts, flattens and moves downwards.

What happens to thoracic volume during inspiration?

It increases.

How does lung pressure change during inspiration?

It falls below atmospheric pressure, so air flows into the lungs.

What happens to the diaphragm during normal expiration?

It relaxes and moves upwards into a dome shape.

How does the rib cage move during normal expiration?

It moves downwards and inwards as the external intercostal muscles relax.

How does lung pressure change during normal expiration?

It rises above atmospheric pressure, so air flows out.

Why is normal expiration mostly passive?

The diaphragm and external intercostal muscles relax; elastic recoil helps move air out.

Which muscles contract during forced expiration?

The internal intercostal and abdominal muscles.

How do those muscles help forced expiration?

They further decrease thoracic volume, raise lung pressure and drive air out.

How do thin alveolar and capillary walls aid gas exchange?

Both are one cell thick, creating a short diffusion distance.

How does the large alveolar surface area aid gas exchange?

Many alveoli provide a large area for oxygen and carbon dioxide diffusion.

Why must the alveolar lining be moist?

Oxygen and carbon dioxide dissolve in the moisture before diffusing across the surface.

How does a rich alveolar blood supply aid gas exchange?

Blood flow carries oxygen away and brings carbon dioxide to the alveoli, helping maintain gradients.

Why does the deep location of alveoli help gas exchange?

It reduces evaporation of the moist lining.

How does constant ventilation aid alveolar gas exchange?

It replenishes oxygen and removes carbon dioxide, maintaining concentration gradients.

What are the directions of oxygen and carbon dioxide diffusion at alveoli?

Oxygen diffuses from alveolar air into blood; carbon dioxide diffuses from blood into alveoli.

What is the key exam structure for an alveolar adaptation answer?

State the feature, explain its function, then link it to more efficient gas exchange.

What are the three main components of the circulatory system?

Heart, blood and blood vessels.

What is the main function of the heart?

Pumps blood to the lungs and around the body.

What does blood transport to body tissues?

Oxygen and nutrients; it also carries carbon dioxide and other wastes away.