chapter 2.1 the cell theory

Question 1

What makes something alive?

Answer 1

Living things have a variety of characteristics:

• they can move
• they can respire
• they can respond to stimuli (sensitive)
• they grow
• they reproduce
• they excrete
• they take in surrounding materials for energy or to grow (nutrition)

Question 2

How has technology contributed to our understanding of cells and cell theory?

Answer 2

There are many different types of microscopes available today:

• light microscopes can magnify images up to 1000x times
• recent technological advancements have led to transmission electron microscopes (TEMS), enabling cell structures to be magnified to greater than 100000x times
• Scanning electron microscopes (SEMS) have also been developed allowing objects to be scanned in three dimension.

All allowing our understanding of cells and cell theory to grow and develop.

Question 3

What is cell theory?

Answer 3

The cell theory states 5 things:

• Cells are the units of structure and function in all organisms.
• New cells arise from pre-existing cells.
• Cells require and use energy.
• Cells contain DNA which is passed on to daughter cells; it is the genetic information.
• Some organisms are unicellular i.e. they are made up of one cell, while others are multicellular and consist of a large number of cells of different types that have a hierarchical organisational structure.

Question 4

What is the cell membrane?

Answer 4

The cell membrane separates the cell from its surroundings and is found in all living cells. The cell membrane controls the exchange of materials (nutrients, waste etc.) between the cell and its environment and is selectively permeable.

Question 5

The cell membrane is said to be selectively or ‘semi permeable’ relate the structure to the structure of the cell membrane.

Answer 5

Meaning it allows some molecules to pass through and does so through structural characteristics e.g. phospholipid chemical nature, channel and carrier proteins and flexible nature allowing to enclose molecules in vesicles.

Question 6

What is the fluid mosaic model?

Answer 6

The fluid mosaic model is a model used to describe the cell membrane allowing better understanding by scientists. ‘Fluid’ because the lipids and proteins are able to move sideways. Mosaic because there are various proteins embedded or attached throughout the model

Question 7

What are phospholipids?

Answer 7

The cell membrane is comprised of a phospholipid bilayer, consisting of two layers of lipids(acting as a barrier. A lipid is made of a polar phosphate group (hydrophilic[likes water] head) and a non-polar tail (hydrophobic[does not like water]).

Question 8

Describe the proteins in the cell membrane and some of their functions

Answer 8

Cell membrane consists of two types of proteins:
- integral proteins (permanently in the bilayer)
- peripheral proteins (tend to move temporarily and are not permeant to the membrane.

Membrane proteins carry out a range of functions in: Hormone binding sites(protein receptors), Cell communication, Cell adhesion(cytoskeleton) and as Channel proteins(aquaporin) and pump proteins.

Question 9

What are some other components of the cell membrane?

Answer 9

Some other components include:
- cholesterol which is usually positioned between the phospholipids (in animal cells only)
- glycoproteins which are membrane proteins with carbohydrate chains attached
- glycolipids which are phospholipids with carbohydrate chains attached