Multicellular Organisms

What is cell differentiation?

The process by which cells develop specialized structures to perform specific functions.

How many different cell types are approximately found in the human body?

Approximately 230 different cell types.

Do all cells in the body have the same DNA?

Yes, all cells have the same DNA.

What does DNA carry?

Genetic information and codes for proteins.

What are the bases that make up DNA?

Adenine (A), Thymine (T), Cytosine (C), and Guanine (G).

What is the first step of protein synthesis?

Transcription, where DNA unwinds to expose a gene and RNA polymerase binds to the gene site to make a complementary strand of mRNA.

What replaces thymine in the mRNA strand during transcription?

Uracil (U) replaces thymine (T).

What happens during translation in protein synthesis?

mRNA is taken to the ribosome, where codons match with mRNA to bring amino acids that join to form a polypeptide chain.

What is gene expression?

The process by which genes can be switched on and off.

What role do activators play in gene expression?

Activators bind near the gene promoter to open up a section of DNA, making it easier for RNA polymerase to bind.

What is the function of repressors in gene expression?

Repressors bind near the gene promoter to close off a section of DNA, preventing RNA polymerase from binding.

How do stem cells become specialized cells?

By having specific genes switched on and off.

What is the hierarchy of biological organization?

Cells → tissues → organs → organ systems.

What are the four types of tissues?

Connective, muscle, epithelial, and nervous tissue.

What are the characteristics of exchange surfaces?

They are thin (one cell thick), moist, have a large surface area, and are close to a blood supply.

What is simple diffusion?

A passive transport process where substances move across the cell membrane with the concentration gradient.

What is facilitated diffusion?

A passive transport process that uses channel proteins to assist the movement of substances with the concentration gradient.

What is active transport?

An active process that requires energy (ATP) and a transport protein to move substances against their concentration gradient.

What are the main components of blood?

Red blood cells, white blood cells, plasma, and platelets.

What is the function of capillaries in the circulatory system?

Capillaries are the sites of exchange between blood and different areas of the body.

What is the difference between physical and chemical digestion?

Physical digestion involves the mechanical breakdown of food, while chemical digestion involves enzymatic breakdown.

What factors can affect enzyme activity?

Temperature, pH, concentration of substrate, and concentration of enzyme.

Where does nutrient exchange occur in the digestive system?

In the villi.