Biology — Cells & Cell Theory

What is biology?

the study of life

Name some properties shared by all living things?

they reproduce grow respond to their environment and are made of cells

What do organisms do with matter and energy?

they obtain and use them for life's functions

What does it mean that an organism maintains a stable internal environment?

it keeps its internal conditions steady

What genetic feature do all organisms share?

a universal genetic code

At what level do organisms undergo evolution?

at the population level

What is a cell?

a small living membrane-enclosed structure that is the basis of life

What is the smallest unit of life?

the cell

Why is the cell called the smallest unit of life?

it is the smallest thing that can carry out all the activities needed for life

What is a unicellular organism?

an organism made of a single cell

What is a multicellular organism?

an organism made of many cells often specialised for different functions

What is the difference between unicellular and multicellular organisms?

unicellular is made of one cell and multicellular is made of many

Give an example of a unicellular organism?

an amoeba

Give examples of multicellular organisms?

a butterfly and a flowering plant

What is a colonial organism?

unicellular organisms that cluster together with some cells taking on special roles (like Volvox algae)

How are new cells produced?

from existing cells by cell division

What happens during cell division?

a cell grows copies its parts and splits into two cells with the same genetic material

What are the two categories of all cells?

prokaryotic and eukaryotic

What features do all cells share?

a plasma membrane cytoplasm DNA and ribosomes

What is the plasma membrane?

the outer layer that separates a cell's interior from its surroundings

What is cytoplasm?

the jelly-like cytosol plus all the structures suspended in it

What are ribosomes?

structures that build the cell's proteins

What defines a eukaryotic cell?

it has membrane-bound organelles including a nucleus

What is an organelle?

a membrane-bound structure that carries out a function inside a cell

Where is a eukaryotic cell's DNA kept?

inside a membrane-bound nucleus

How is a eukaryotic cell's DNA shaped?

as multiple linear chromosomes

How big are eukaryotic cells?

relatively large about 10 to 100 micrometres

Can eukaryotes be unicellular multicellular or both?

both

Give examples of eukaryotes?

protists fungi plants and animals

What defines a prokaryotic cell?

it has no membrane-bound organelles and no true nucleus

What is the nucleoid?

the region of a prokaryotic cell where the DNA sits without a membrane

How is a prokaryotic cell's DNA shaped?

as a single circular chromosome

How big are prokaryotic cells?

relatively small about 1 to 10 micrometres

Are prokaryotes usually unicellular or multicellular?

usually unicellular

Give examples of prokaryotes?

bacteria and archaea

Where are archaea often found?

in extreme environments like hot springs

Which cells are simpler and more ancient?

prokaryotic cells

What is the difference between a nucleus and a nucleoid?

a nucleus is membrane-bound while a nucleoid is just a region with no membrane

How does DNA shape differ between the two cell types?

eukaryotic DNA is linear and prokaryotic DNA is circular

Which cell type has membrane-bound organelles?

only eukaryotic cells

Which cell type is larger?

eukaryotic cells

What are the three tenets of cell theory?

all living things are made of cells the cell is the basic unit of life and all cells come from other cells

What is the first tenet of cell theory?

all living organisms are made of one or more cells

What is the second tenet of cell theory?

the cell is the basic unit of structure and function in living things

What is the third tenet of cell theory?

all cells come from other cells

Who first observed and named cells?

Robert Hooke

What did Robert Hooke publish in 1665?

Micrographia

What was Hooke looking at when he named cells?

cork

Why did Hooke call them cells?

the little boxes reminded him of the small rooms that monks lived in

What did Hooke actually see in the cork?

dead cell wall remnants rather than living cells

Who first observed living cells?

Antonie van Leeuwenhoek

What was Leeuwenhoek's trade?

he was a Dutch lens crafter

What did Leeuwenhoek call the living microbes he saw?

animalcules

Which scientist saw dead cells and which saw living cells?

Hooke saw dead cell walls and Leeuwenhoek saw living cells

Who proposed the first two tenets of cell theory?

Schleiden and Schwann in the 1830s

Who established that all cells come from other cells?

Robert Remak

Who is often wrongly credited for the third tenet?

Rudolf Virchow who plagiarised Remak's work

When did the first cells likely emerge on Earth?

about 3.5 billion years ago

What may have helped the first cell membranes form?

phospholipids which naturally form bilayer spheres