life and cells 1

What characteristics do all living things possess?

Order; energy processing; response to the environment; homeostasis; growth and reproduction; genetic information; and being

made of one or more cells.

What does it mean that living things possess order?

Living things have organised structures and levels of organisation.

What does it mean that living things process energy?

Living things obtain and use energy to carry out life processes.

What does it mean that living things respond to their environment?

Living things detect and respond to changes in their surroundings.

What is homeostasis?

The maintenance of stable internal conditions.

What is required for an organism to be considered cellular?

It must be made of one or more cells.

Are viruses considered living organisms?

No. They depend on host cells for reproduction and are not made of cells.

Why are viruses not considered cells?

They are not made of cells and must infect a host cell to replicate

What are the levels of biological organisation from largest to smallest?

Biosphere → ecosystems → communities → populations → organisms → organs/systems → tissues → cells → organelles →molecules → atoms.

What is the largest level of biological organisation?

Biosphere

What is the smallest level of biological organisation?

Atoms

What are the two basic types of cells?

Prokaryotic and eukaryotic.

What is the approximate size range of prokaryotic cells?

0.5–5 µm.

What is the approximate size range of eukaryotic cells?

5–100 µm.

What are the key characteristics of prokaryotic cells?

No nucleus; no membrane-bound organelles; smaller; circular DNA; unicellular only.

What are examples of prokaryotes?

Bacteria and Archaea.

What are the key characteristics of eukaryotic cells?

A true nucleus; membrane-bound organelles; larger; linear DNA with histones; can be unicellular or multicellular

What organisms have eukaryotic cells?

Animals, plants, fungi and protists.

How does prokaryotic DNA differ from eukaryotic DNA?

Prokaryotic DNA is circular, whereas eukaryotic DNA is linear and associated with histones.

What is the main difference between prokaryotic and eukaryotic cells regarding the nucleus?

Prokaryotic cells have no nucleus; eukaryotic cells have a true nucleus.

What is the main difference between prokaryotic and eukaryotic cells regarding organelles?

Prokaryotes have no membrane-bound organelles; eukaryotes have membrane-bound organelle

Are prokaryotes unicellular or multicellular?

prokaryotes are always unicellular.

Can eukaryotes be unicellular?

Yes. Eukaryotes can be unicellular or multicellular.

What is the cell membrane?

A semi-permeable structure that controls what enters and leaves the cell.

What is the cell membrane made of?

A phospholipid bilayer with embedded proteins.

What are membrane proteins involved in?

Transport and receptors.

What does semi-permeable mean in relation to the cell membrane?

The membrane controls which substances can enter and leave the cell

What is the function of the nucleus?

It acts as a control centre, contains DNA, and is the site of DNA replication and transcription.

What does the nucleus contain besides DNA?

The nucleolus.

What is the function of the nucleolus?

It makes ribosomes.

What are the main characteristics of mitochondria?

They have two membranes, are the site of cellular respiration, produce ATP, and have their own DNA.

How many membranes surround a mitochondrion?

Two membranes.

What is the main function of mitochondria?

They are the site of cellular respiration and produce ATP.

Do mitochondria contain their own DNA?

Yes

What is the function of rough endoplasmic reticulum?

Protein synthesis; it has ribosomes.

Why is rough ER described as “rough”?

It has ribosomes associated with it.

What is the function of smooth endoplasmic reticulum?

Lipid synthesis and processing.

What is the key difference between rough ER and smooth ER?

Rough ER is involved in protein synthesis and has ribosomes; smooth ER is involved in lipid synthesis and processing.

What is the function of the Golgi apparatus?

it modifies, sorts and packages proteins and lipids for secretion or delivery.

What does the Golgi apparatus do to proteins and lipids?

It modifies, sorts and packages them.

What are lysosomes?

Structures containing digestive enzymes.

What do lysosomes contain?

Digestive enzymes.

What do lysosomes break down?

Waste, worn-out organelles and foreign particles.

What three features do plant cells have that animal cells do not?

A cellulose cell wall, chloroplasts and a central vacuole.

What is the plant cell wall made of?

Cellulose

What is the function of the plant cell wall?

It is a structural feature unique to plant cells in the comparison given

What are chloroplasts?

Organelles that are the site of photosynthesis.

Where are chloroplasts found?

In plant cells.

What do chloroplasts contain?

Their own DNA and a double membrane.

What is the main function of chloroplasts?

Photosynthesis.

How many membranes do chloroplasts have?

A double membrane.

Do chloroplasts contain their own DNA?

Yes.

What are the main features of a prokaryotic cell?

Cell membrane; cell wall made of peptidoglycan; single circular chromosome in the nucleoid; plasmids; small ribosomes; and no nucleus or membrane-bound organelles.

What is the prokaryotic cell wall made of?

Peptidoglycan.

Where is the main chromosome of a prokaryote located?

In the nucleoid.

What shape is the main prokaryotic chromosome ?

Circular

What are plasmids?

Additional DNA structures found in prokaryotic cells.

What type of ribosomes do prokaryotes have?

Small ribosomes.

Do prokaryotes have a nucleus?

No.

Do prokaryotes have membrane-bound organelles?

No

What organisms are prokaryotic?

Bacteria and Archaea.

Are bacteria and Archaea unicellular or multicellular?

Always unicellular.

What is a unicellular organism?

An organism consisting of a single cell.

What examples of unicellular organisms?

Bacteria, Archaea, protists and yeast.

What is a multicellular organism?

An organism consisting of multiple cells

What examples of multicellular organisms?

Plants, animals and most fungi.

What are the advantages of multicellularity?

Cell specialisation; not being dependent on one cell’s survival; and the possibility of larger size.

Why is cell specialisation an advantage of multicellularity?

Different cells can specialise in particular functions.

Why does multicellularity reduce dependence on one cell’s survival?

The organism is not dependent on a single cell for survival.

What is an advantage of being larger through multicellularity?

A larger overall size is possible.

What is the basic structure of a virus?

Nucleic acid (RNA or DNA) + protein coat (capsid) ± envelope.

What type of genetic material can a virus contain?

RNA or DNA.

What is a capsid?

The protein coat surrounding viral nucleic acid.

Do all viruses have an envelope?

No. An envelope is optional (± envelope).

Is a virus a cell?

No

Can viruses reproduce on their own?

No

Why can viruses not reproduce on their own?

They are metabolically inert and must infect a host cell to replicate.

What does “metabolically inert” mean for viruses?

They do not carry out the necessary metabolic processes independently and require a host cell to replicate.

What does a virus need in order to replicate?

A host cell

What is the key difference between viruses and living cells?

Viruses are not cells, lack independent reproduction, and require a host cell to replicate.

What are the key characteristics of prokaryotes in summary?

No nucleus, small, simple and unicellular.

What are the key characteristics of eukaryotes in summary?

A nucleus, organelles, larger, and can be unicellular or multicellular.

What are the key characteristics of viruses in summary?

Not considered alive in the notes, require a host, and consist of nucleic acid plus a capsid.

How do prokaryotes, eukaryotes and viruses differ in cellular organisation?

Prokaryotes are simple unicellular cells without a nucleus; eukaryotes have a nucleus and organelles and may be uni- or multicellular; viruses are not cells

How do prokaryotes, eukaryotes and viruses differ in reproduction?

Prokaryotes and eukaryotic cells are cellular organisms, whereas viruses cannot reproduce independently and must use a host Cell

What is the key feature of the virus life cycle?

A virus depends on a host cell for replication.

Why does a virus need a host cell during its life cycle?

Viruses cannot replicate independently and use the host cell’s machinery to produce new virus particles.

What happens during a basic virus life cycle?

The virus enters a host cell, uses it to produce viral components, assembles new particles, and releases them.

What does the virus life cycle demonstrate?

The dependence of viruses on host cells for replication.

What is an RNA virus life cycle?

A replication cycle in which the virus uses its RNA genetic information and the host cell to produce new viral components and

particles.

What is important to remember about an RNA virus life cycle?

It depends on the host cell for replication.

What is a retrovirus?

A type of RNA virus with a distinctive replication cycle.

What is distinctive about the retrovirus life cycle?

It involves a different replication pathway from the basic virus/RNA-virus cycles shown in the lecture.

What should you remember about the different virus life cycle?

Viruses have different replication cycles, but all depend on host cells; the lecture distinguishes basic, RNA-virus and retrovirus cycles.

Why are there different virus life cycles?

Viruses differ in their genetic material and replication mechanisms, producing variation in how their cycles occur.

What does the lecture say about virus life-cycle variation?

The virus life cycle can vary between different types of viruses.

What are the key virus points to remember?

Basic life cycle and variation; viruses are not cells but depend on cells; nucleic acid + capsid ± envelope; highly diverse and rapidly evolve

What is resolution in microscopy?

The minimum distance between two points that can still be distinguished as separate.

What is the approximate resolution of a light microscope?

About 0.2 µm.

What is the approximate resolution of an electron microscope?

About 0.1 nm.