Cells

Cell history

Spontaneus?

Louis Pasteur

How?

Recreating early earth

Miller and Urey

Conditions.

1. Simple organic molecules, such as amino acids, fatty acids and carbohydrates, must be formed

2. Larger organic molecules, such as phospholipids, RNA and DNA, must be assembled from simpler molecules.

3. Organisms reproduce, so replication of nucleic acids must be possible

4. Biochemical reactions require set conditions, such as pH. Therefore, self-contained structures, such as membranes, are necessary

The endosymbiotic theory

Have double membranes, as expected for cells taken in by endocytosis.

Have singular naked DNA, as in prokaryotes.

Have 70S ribosomes, as in prokaryotes.

Divide by binary fission like prokaryotic cells.

Are susceptible to some antibiotics.

Cell theory

Development of cell theory was made possible thanks to advances in microscopy.

Living organisms are composed of cells (one or more) – that is, cells are the building blocks of organisms.

Cells are the smallest units of life – that is, a cell is the basic unit capable of carrying out all the functions of a living organism.

Cells come from pre-existing cells (omni cellulae e cellula) – that is, cells do not show spontaneous generation

1.1.U1 ​According to the cell theory, living organisms are composed of cells.

Cell types

​1.1.A1 ​Questioning the cell theory using atypical examples, including striated muscle, giant algae and aseptate fungal hyphae.

Atypical cells

In living systems there are trends but there are exceptions.

(Sarcomeres)

Acetabularia

0,5 - 10 cm

Complex

Multinuclei with no walls between

Functions of life

• Metabolism – The regular set of life-supporting chemical reactions that takes place within the cells of living organisms.

• Growth – An increase in size or shape that occurs over a period of time.

• Response (to a stimulus) - A reaction by the living organism to changes in the external environment.

• Homeostasis – The maintenance of a constant internal environment by regulating internal cell conditions.

• Nutrition – The intake of nutrients, which may take different forms in different organisms. Nutrition in plants involves making organic molecules (during photosynthesis), while nutrition in animals and fungi involves the absorption of organic matter.

• Excretion – The removal of waste products of metabolism and other unimportant materials from an organism.

• Reproduction – The production of offspring, either sexually or asexually, to pass on genetic information to the next generation.

​​1.1.A2 ​Investigation of functions of life in Paramecium and one named photosynthetic unicellular organism.

Unicellular organisms

Chlamydomonas

Algae

10 - 30 µm

Autothroph

Produces its own food from inorganic sources.

Paramecium

Protozoa

< 25 µm

Heterotroph

Feeds by taking in organic substances

Surface area to volume ratio

SA:V

As a cell grows, its volume increases by the power of 3 (cubed), whereas the surface area increases by the power of 2 (squared). Therefore, its surface area to volume ratio decreases.

1.1.U3 ​Cell Surface to volume is an important limitation to cell size.

Surface area to volume ratio

A cell needs a large surface area to volume ratio to be able to get enough necessary molecules in and enough waste out.

Folding

Multicellular organisms

How??

• Organisms grew larger because they were no longer limited by the size of one cell.

• Cells in such an organism were able to specialise through differentiation. Differentiation is a process in which unspecialised cells develop into cells with a more distinct structure and function

• Multicellular organisms displayed emergent properties. This means that the whole organism can do more things than individual cells are capable of, because of the interaction between the different parts

1.1.U4 ​Multicellular organisms have properties that emerge due to the interaction of their cellular components

1.1.U5 ​Specialized tissues can develop by cell differentiation in multicellular organisms.

Genome

The genome refers to the complete set of genes, chromosomes or genetic material present in a cell or organism.

21 000

Active

or

not?

1.1.U6 ​Differentiation involves the expressions of some genes and not others in a cell’s genome.

Cellular differentiation

When an unspecialised stem cell changes and carries out a specific function in the body, the process is called cellular differentiation. Cells differentiate to form different cell types due to the expression of different genes.

Stem cells

"A stem cell is an undifferentiated cell of a multicellular organism that can form more cells of the same type indefinitely, and from which certain other kinds of cell arise by differentiation"

1.1.U7 ​The capacity of stem cells to divide and differentiate along different pathways is necessary in embryonic development and also makes stem cells suitable for therapeutic uses.

Stem cells

Stem cells

1.1.A3 ​Use of stem cells to treat Stargardt’s disease and one other named condition.

Stem cells in treatment

Stargard`s disease

Leukemia

Ethics

1.1.A4 ​Ethics of the therapeutic use of stem cells from specially created embryos, from the umbilical cord blood of a new-born baby and from an adult’s own tissues.

DISCUSS!!!!

Command term