Cells

Name the two main types of cells.

Prokaryotic and Eukaryotic

What type of cell are animal and plant cells?

Eukaryotic

What does a eukaryotic cell have that a prokaryotic cell doesn’t?

Membrane bound organelles

What is a cells ultrastructure?

The organelles that make up the cell

What are the main structures found in most eukaryotic cells?

Nucleus, Cell-surface membrane, mitochondria, Golgi apparatus, smooth endoplasmic reticulum, rough endoplasmic reticulum, ribosomes.

What is the function of the nucleus?

Retains genetic material of the cell in the form of DNA and chromosomes

What type of DNA is found in the nucleus?

Protein bound, linear DNA

What molecules are made inside the nucleus?

mRNA, tRNA, rRNA and ribosomal subunits

What is the structure and function of the nucleolus?

Dark, dense region of the nucleus, produces ribosomes

In a nucleus can there be more than one nucleolus?

Yes

What is this structure of the nuclear envelope?

A double membrane embedded with channel protein forming pores. Continuous with endoplasmic reticulum.

What is the function of the nuclear envelope?

Separates the nucleus from the rest of the cell. Pores allow ribosomes and mRNA to leave the nucleus.

What is the structure of the rough endoplasmic reticulum (RER)?

A system of fluid filled membranes studded with ribosomes. Continuous with the nuclear membrane. Large surface area formed by folding.

What is the function of the rough endoplasmic reticulum (RER)?

Synthesis and transport of proteins and glycoproteins.

What is the structure of the Golgi appartus?

A stack of flattened membrane bound sacs called cisternae.

What is the function of the Golgi apparatus?

Modifies and packages proteins and lipids.

What molecules are ribosomes made out of?

rRNA and proteins

What’s the structure of the ribosome?

2 subunits, large and small

What size of ribosome is found in eukaryotic cells?

80S

What is the function of ribosomes?

Protein synthesis

What is the name of the model which shows the structure of the cell membrane?

Fluid mosaic model

What molecules make up the fluid mosaic model of the cell membrane?

Phospholipid bilayer, cholesterol, proteins, glycoproteins, glycolipids

What is the role of the phospholipid bilayer in the plasma membrane?

It creates a waterproof barrier as water soluble material is unable to move in or out of the cell.

How are proteins embedded under the plasma membrane?

Either they occur on one surface only or completely span the bilayer from none side to the other.

What is the role of proteins which are embedded on the surface of a plasma membrane?

Mechanical support and/or receptors

What is the role of proteins which span the width of the plasma membrane?

Protein channels and carrier proteins.

How does cholesterol interact with water?

It is very hydrophobic

What is the role of cholesterol in the membrane?

Reduce membrane fluidity at high temperatures and prevent leakage of water and ions

What does cholesterol do to other molecules in the membrane?

They hold phospholipids tightly together.

Which structures are only found in plant cells?

Chloroplasts, cell wall, cell vacuole

What is the structure of chloroplasts?

Double membrane bound. Contains thylakoid disc which forms stacks called grand and stroma.

What is the function of chloroplasts?

Site of photosynthesis.

From what type of cell is a chloroplast descended?

Prokaryotic cell

What structure within the chloroplast show it is descended from a prokaryotic cell?

Contains circular DNA and 70S ribosomes

What is the structure of the vacuole?

Fluid filled membrane sac. In a plant the membrane is called the tonoplast.

What is the structure and function of the vacuole?

It contains salts, sugars, amino acids, waste and sometimes pigments.

What is the function of a plant's vacuole?

Provides structure to plants by making cells turgid. Temporary food store. Provides colour to plants attracting insects.

What cell structure is found in some prokaryotes, plants, fungi and algae?

Cell wall

What molecule makes up a plant cell wall?

Cellulose

What type of molecule is cellulose?

Polysaccharide

What molecule makes up the fungi cell wall?

Chitin

What type of molecule is chitin?

Polysaccharide

What is the function of the cell wall?

Provides support and strength, maintaining the cell's shape. prevents the cell from bursting when turgid. Permeable to allow solutions through.

What is a specialised cell?

A cell that is adapted to carry out a specific function.

In what basic way are specialised cells adapted to perform their role?

They have more or fewer of certain organelles and structures to suit it's role.

What is a somatic cell?

A cell that is not a sex cell.

What is a gamete?

A sex cell.

What is the name of the process in which cells become specialised?

Differentiation.

What kind of organisms have specialised cells?

Multicellular organisms

Why do multicellular organisms have specialised cells?

So that different cells can perform specific functions.

What is a tissue?

A group of similar cells working together to perform a specific function.

What is an organ?

A collection of tissues, coordinated to perform specific functions

What is an organ system?

A group of organs working together as a single unit.

What is the hierarchy of organisation in terms of cells in an organism?

Cells -> tissues - organs -> organs systems - organism.

What is the difference between prokaryotic and eukaryotic cells?

Prokaryotic cells are smaller and have no nucleus or membrane bound organelles.

What is the role of circular DNA in bacteria?

it contains the genetic information for replication of bacteria.

How is the structure of DNA different from prokaryotes to eukaryotes?

Prokaryotes have a single, circular DNA molecule that is free in the cytoplasm and not associated with proteins.

Prokaryotic cells can store DNA outside of the single circular chromosome using another structure. What is this structure?

Rings of DNA called plasmids

What are the roles of plasmids in bacteria?

Posses genes that may aid survival

What size of ribosome is found in prokaryotic cells?

70S

What molecule makes up prokaryotic cell walls?

Murein

What type of molecule is murein?

Glycoprotein

What are the main structures of bacterial cells?

Cell surface membrane, 70S ribosomes and circular DNA

What are the role of the cell wall in bacteria?

Physical barrier to some substances, protects against mechanical damage and osmotic lysis

What is the role of the capsule in bacteria?

Made of mucilaginous slime, it protects against other cells and allows bacteria to stick together for protection

What is the role of the cell surface membrane in bacteria?

Differentially permeable, controls try and exit of chemicals

How are viruses described?

A-cellular non-living particles

What range of sizes are viruses?

Generally between 20-300nm

What is the basic structure of a virus?

Nucleic acids contained within a protein coat called a capsid and surrounded by a lipid envelope. Attachment proteins are found on the surface.

Where do viruses reproduce?

Within host cells.

What do attachment protein allow the virus to do?

Allows the virus to identify itself and attach to a host cell

What is magnification?

A measure of how much larger the image of a specimen looks under the microscope

What is resolution?

The ability to distinguish between two adjacent individual points and separate

What is a specimen?

The item you are studying under the microscope

Name the type of microscope which uses lights to visualise specimens.

A light microscope

What is a light microscope used for?

Observing living and dead specimens

What resolution are light microscopes limited to?

0.2 micrometres

What are the pros of a light microscope?

Can observe living specimens, can see in colour, easier to prepare specimen, no artefacts

What are the cons of using a light microscope?

Limited magnification, poor resolution

Name the type of microscope which uses electrons to visualise specimens.

Electron microscope

What type of electron microscope uses an electron gun to produce an electron beam which is focussed onto the specimen by a condensor electromagent?

Transmission electron microscope

In which type of electron microscope, do electrons not penetrate the specimen?

Scanning electron microscope

What is transmission electron microscope used for?

Observing the internal ultrastructure of cells under high magnification and resolution

What is a scanning electron microscope used for?

Viewing the surface of objects under high magnification and resolution

What are transmission electron microscope artefacts?

Substances that are created during sample preparation and can be seen in a TEM image

What can transmission electron microscope artefacts e mistaken for?

Cellular components

What is the resolving power of a transmission electron microscope compared to a scanning electron microscope?

TEM= 0.1nm, SEM= 20nm

What the of image is produced by a. transmission electron microscope?

2D image of the contents of the cell

What type of image is produced by a scanning electron microscope?

3D image of the surface of an object

Why do electron microscopes give a clearer image than light microscopes?

The wavelength of electrons allows a resolution of 0.1 nanometres which is much shorter than the wavelength of light

What is the formula to calculate magnification?

Magnification = Image size / Actual size

How do we work out image size?

Use a ruler and measure the image

What units do you always use when measuring image size?

Millimetres

What is an eye piece graticule?

A small ruler fitted to a light microscopes eye piece

What is a stage micrometre?

A millimeter long ruler etched onto a slide. It has 100 divisions, each of 0.01mm or 10 micrometers. It is used to calibrate an eyepiece graticule.

By which process are large quantities of cell organelles collected?

Cell fractionation

What is cell fractionation?

The process of breaking up cells to separate out the organelles.

What are the two stages of cell fractionation?

Homogenisation and ultracentrifugation

What is homogenisation?

Breaking up of cells in a blender. This releases organelles into the homogenate.

What is homogenate?

Fluid containing cell organelles, prior to ultracentrifugation.