IB bio 1.1 Introduction to cells

Which of these are part of cell theory? (check all that apply)

• All living things are made of cells

• Cells carry out all of the functions of life

• Cells only have one nucleus

• The cell is the smallest unit of life

• Cells come from pre-existing cells

The giant alga Acetabularia has a feature that suggests it is an exception to cell theory. What feature is this?

• It lacks a nucleus

• It lacks a cell wall

• it has only one mitochondrion

• It lacks subdivision into separate cells

Answer explanation

Acetabularia is a large (7 cm) single-celled organism thus challenges the idea that cells are small and that larger organisms must be made of many smaller cells.

When compared to other body cells, which characteristic of stem cells is the most important for therapeutic uses?

• Less differentiated

• Less excretion

• Lower rate of reproduction

• Lower rate of metabolism

What is likely to be the function of this adaptation of the plasma membrane?

• Increases absorption by increasing the diffusion distance

• Increases absorption by making surface area:volume ratio bigger

• Increases absorption by making surface area:volume ratio smaller

• Increases absorption by increasing the concentration gradient

If cells of all multicellular organism have the same genes, how can there be many different cell types in a body?

• Some genes, but not others, are expressed in each cell type

• Cells lose some genes as development occurs

• Genes do not determine the structure of a cell

• Cells must practice division of labour in order to survive

Multicellular organisms show emergent properties. What does this mean?

• The whole is greater than the sum of its parts.

• Cells of the same shape and function unite to form a tissue.

• Multicellular organisms are made up of billions of cells.

• The older a cell is the more different things it can do

What do we call the process where cells change to become specialised and carry out a specific function?

Which type of stem cell can differentiate into all body cell types, but cannot give rise to a whole organism?

• Unipotent stem cells

• Multipotent stem cells

• Totipotent stem cells

• Pluripotent stem cells

Stem cells retain the ability to do two things that most body cells can not. What are they?

Which graph represents the change in surface area to volume ratio with increasing cell diameter?

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Answer explanation

As cell diameter increases the volume increases more than the surface area (it's a cubed number, not a squared number!) so the SA:Vol ratio gets smaller.