BIO152

What is a cell?

The basic unit of life.

What are the two ways organisms can be organised?

Single-celled (unicellular) or multicellular.

What does cell theory explain?

The relationship between life and the properties of the cell.

State the three parts of cell theory.

(1) All organisms consist of one or more cells. (2) The cell is the basic unit of all organisms. (3) All cells come from pre-existing, living cells.

Name the four structures common to (almost) all cells.

Cell membrane, cytoplasm, DNA, ribosomes.

What is another name for the cell membrane?

Plasma membrane.

What is the function of the cell membrane?

Outer covering that separates the cell's interior from the environment.

What does cytoplasm consist of?

Cytosol + organelles - the materials within the cell along with other cellular components.

What is the function of DNA in a cell?

It is the genetic material of the cell.

What is the function of ribosomes?

Structures that make proteins.

List the four common functions of cells.

Duplicate DNA; use DNA and RNA to make proteins; handle energy transfer; regulate exchange of materials.

What three factors restrict the size a cell can be?

Diffusion rates of molecules; maintaining concentrations of substances in the cell; surface area-to-volume (SA/V) ratio.

How does cell size affect diffusion rate?

Molecules move (diffuse) faster in smaller cells.

How does concentration of substances relate to reaction rate in a cell?

Higher concentration leads to increased collision rate, leading to more reactions happening.

What does a higher SA/V ratio mean for a cell?

More efficient exchange of materials with the environment.

Why can't cells grow indefinitely large?

As a cell grows, volume increases faster than surface area, lowering the SA/V ratio and reducing exchange efficiency; diffusion also becomes too slow to service the increased volume.

What term describes unicellular organisms, and what term describes multicellular organisms?

Unicellular = prokaryotes; multicellular = eukaryotes.

Give examples of prokaryotes.

Bacteria and archaea - unicellular, cells small and efficient.

Give examples of eukaryotes.

Plants and animals - large, multicellular, complex overall, though individual cells remain small and efficient.

Compare prokaryote vs eukaryote cell size.

Prokaryotes are smaller; eukaryotes are larger.

Do prokaryotes have membrane-bound organelles?

No. Eukaryotes contain membrane-bound organelles.

Do prokaryotes have a nucleus?

No. Eukaryotes contain a nucleus.

Where is genetic information stored in a prokaryote vs a eukaryote?

Prokaryote: in the nucleoid (no membrane). Eukaryote: in a membrane-bound nucleus.

What shape is the chromosome (DNA) usually in prokaryotes vs eukaryotes?

Prokaryotes: usually circular. Eukaryotes: usually linear.

How do prokaryotic cells divide? How do eukaryotic cells divide?

Prokaryotes: binary fission. Eukaryotes: mitosis and meiosis.

Where does DNA replication occur in prokaryotes vs eukaryotes?

Prokaryotes: in the cytoplasm. Eukaryotes: in the nucleus.

Describe the key features of bacteria.

Prokaryotic; genetic material folded and packed tightly in a region called the nucleoid; divide by binary fission.

Describe the key features of archaea.

Prokaryotic; many species live in extreme environments (e.g. acidic hot springs, pH 2, temperature >100 degrees C); divide by binary fission.

What key structural difference exists between a bacterium and an animal cell in terms of organelles?

Animal cells (eukaryotic) contain membrane-bound organelles (e.g. nucleus, mitochondria) that require membrane fusion events to exchange materials; bacteria (prokaryotic) lack these.

How do animal cells divide?

Mitosis/meiosis + cytokinesis.

What distinguishes plant cells structurally, mentioned alongside division?

Plant cells have walls containing cellulose and large vacuoles; they also divide by mitosis/meiosis + cytokinesis.

What is the basic structure of the cell membrane?

A lipid bilayer with embedded proteins.

What are the two regions of a phospholipid, and what is each region's water relationship?

Polar (hydrophilic) heads and non-polar (hydrophobic) tails.

Define hydrophilic.

Attracted to water.

Define hydrophobic.

Repels water.

List the five functions of the cell membrane.

(1) Define boundaries of the cell and internal compartments (e.g. mitochondria). (2) Serve as sites for biochemical functions (e.g. electron transport in mitochondria). (3) Transport solutes in and out of the cell (selective permeability). (4) Detect and transmit electrical and chemical signals. (5) Provide mechanisms for cell-to-cell contact, adhesion and communication.

What is cytosol?

The semi-fluid part of the cell; the site where many chemical reactions take place (e.g. glycolysis).

What is cytoplasm?

The majority of the internal volume of the cell; comprises cytosol, organelles and cytoskeletal fibres.

Are ribosomes membrane-bound?

No, ribosomes are not membrane-bound.

What are ribosomes made up of?

RNAs and proteins.

How many subunits do ribosomes consist of, and name them.

Two - a large subunit and a small subunit.

In what two forms/locations can ribosomes exist?

Free (individual) in the cytosol, or grouped as part of the rough endoplasmic reticulum (ER).

What is the function of ribosomes?

Protein synthesis.

List the components found in an animal cell.

Cell membrane, cytosol, organelles, nucleus, cytoskeleton, mitochondria, endoplasmic reticulum (ER), Golgi complex, lysosome, peroxisome, ribosome.

What covers the nucleus, and how many membranes does this structure have?

The nuclear envelope; it is a double membrane.

What does the nucleus contain, and what is its role?

Chromatin (DNA and proteins) - the nucleus is the information centre of the cell.

What passes through the nuclear envelope, and via what structure?

Pores forming channels transport molecules such as RNAs, proteins and ions - but NOT chromosomes.

What is the nucleolus, and what is its function?

A structure within the nucleus; it is the site of ribosome component synthesis.

Differentiate chromatin from a chromosome.

Chromatin is the loose, thread-like form of DNA used for daily cell work; a chromosome is a tightly coiled, dense package of DNA used when a cell divides.

What is the cytoskeleton?

A 3D array of interlaced proteinaceous structures.

List the four functions of the cytoskeleton.

Internal framework for the shape of the cell; organelle/cell movement and contractility; permits cell division; influences water distribution.

Name the three types of cytoskeletal filament shown in fluorescence images.

Microtubules, microfilaments, intermediate filaments.

How many membranes does a mitochondrion have?

Double membrane (outer membrane and inner membrane).

What are the folds of the inner mitochondrial membrane called, and what do they enclose?

Cristae; they enclose the matrix (semifluid).

What is the function of mitochondria?

Generation of energy (ATP) via aerobic respiration.

What does the term "endoplasmic reticulum" mean, based on its word origin?

Endo = within the plasm; reticulum = network.

How many membranes does the ER have, and what does it contain internally?

A single membrane with a lumen inside; usually attached to the nuclear envelope.

Name the two types of ER.

Smooth ER and rough ER.

What distinguishes rough ER from smooth ER in appearance?

Rough ER has ribosomes dotted on its surface; smooth ER does not.

List the functions of smooth ER.

Lipid/steroid synthesis; carbohydrate metabolism; inactivating and detoxifying drugs; storing and releasing Ca2+ ions.

What is the function of rough ER?

Protein synthesis and processing.

What is the Golgi apparatus often called, and why?

The "processing centre" of the cell.

Describe the structure of the Golgi apparatus.

Single membrane-bound sacs called cisternae.

List the two functions of the Golgi apparatus.

Forms vesicles (packages of secretory proteins and lipids); synthesis of complex polysaccharides.

What produces lysosomes, and what is their structure?

A single membrane-bound vesicle produced from the Golgi complex.

List the three functions of lysosomes.

Stores enzymes (e.g. lysozyme, hydrolase); destroys/lyses material in vesicles; breaks down macromolecules (e.g. proteins) and recycles cell contents (e.g. ageing organelles).

What is the structure of a peroxisome?

A single membrane-bound vesicle with a crystalline core.

List the functions of a peroxisome.

Packages and destroys hydrogen peroxide safely using catalase; protects the cell from damaging reactive oxygen species (ROS).

What is a specialised peroxisome called, and what is its role?

A glyoxysome - has a crystalline core containing the enzyme catalase; involved in converting fat into carbohydrates during germination, and in photorespiration.

What is a centrosome, and what does it consist of?

A microtubule-organising centre; consists of two centrioles.

What is the function of a vacuole (in this context)?

Temporary storage or transport.

What is a cilium?

An appendage on the cell surface, made of microtubules.

List the components found in a plant cell.

Cell wall, cell membrane, cytosol, nucleus, organelles, plastids (e.g. chloroplast), vacuole, cytoskeleton, mitochondria, endoplasmic reticulum (ER), Golgi complex, peroxisome, ribosome.

What is the cell wall made of, and what property does this give it?

Cellulose microfibrils in a matrix of polysaccharides and proteins; this makes it flexible and extensible.

What is the function of the cell wall?

Provides structural support.

How are adjacent plant cell walls connected, and what do these connections allow?

Connected by plasmodesmata (openings); these are membrane-lined and allow water and small solutes to pass between cells.

How many membrane systems does a chloroplast have?

Three - inner membrane, outer membrane, and a third (thylakoid) membrane system.

What is a granum, and what does it consist of?

A stack of flattened sacs called thylakoids.

What are stroma thylakoids, and what is their function?

Tubular membranes that connect the grana (stacks) together.

What is the function of the chloroplast?

Site of photosynthesis (occurring in the stroma); a light-driven process using solar energy and CO2 to produce sugars and organic compounds.

How many membranes bound a plant vacuole?

Single membrane bound.

List the functions of the plant vacuole.

Temporary storage and transport; phagocytosis; storage and intracellular digestion; maintaining turgor pressure.

Name three features present in plant cells but absent in animal cells.

Cell wall (cellulose), chloroplasts/plastids, large central vacuole.

Do both plant and animal cells have mitochondria?

Yes, both have mitochondria.

Do both plant and animal cells divide by mitosis/meiosis?

Yes - both divide by mitosis/meiosis + cytokinesis.