Topic 2- Cells

Define a eukaroytic cell

A cell containing a nucleus and other membrane-bound organelles

Define a prokaryotic cell

A cell that does not contain a membrane-bound nucleus or any membrane-bound organelles

Cell theory states...

All living organisms are composed of one or more cells,the cell is the basic unit of life, all cells arise from pre-existing cells

4 structural differences between eukaryotic and prokaryotic cells

Prokaryotes have no nucleus, no membrane-bound organelles, 70S ribosomes, naked DNA

Viruses are made up of...

Genetic material, capsid, attachment protein

Difference between light and electron microscopes

Electron microscope uses beam of electrons

3 advantages of the electron microscope

Higher magnification, higher resolution, useful for looking at 3D structures,

disadvantages of the electron microscope

Expensive, organism must be dead

Magnification =

Size of image/size of real object

What is the method of cell fractionation?

Tissue broken up in homogeniser, add pH buffer, solution filtered, centrifuged, pellet forms

Define magnification

The number of times bigger the image is than in real life

Define resolution

The ability to distinguish between two separate structures

Function of cell surface membrane

Controls passage of substances into and out of the cell

Function of nucleus

Contains the genetic material

Function of ribosomes

Site of protein synthesis

Function of mitochondria

Produces ATP in respiration

Function of rough endoplasmic reticulum

Synthesises and transports proteins around the cell

Function of smooth endoplasmic reticulum

Synthesises and transports lipids

Function of golgi body

Packages and processes molecules such as proteins and forms lysosomes

Function of vesicles

Transport substances around the cell

Function of lysosomes

Digests unwanted material in the cell using enzymes

Function of spindle fibres

Attach to chromosomes to divide genetic material

Function of chloroplasts

Site of photosynthesis

Function of vacuole

Contains cell sap to help support the cell

Function of cell wall

Adds strength to the cell

Function of plasmids

Small loops of DNA found in prokaryotes

Function of the capsule

Protective layer present in some bacteria

Function of the flagella

Helps the bacteria to swim

3 phases of the cell cycle are...

Interphase, Mitosis, Cytokinesis

3 stages within interphase are...

G1, S, G2

2 events during G1 phase

Cell growth, organelles replicate

1 event during S phase

DNA replication

2 events during G2 phase

Cell growth, organelles replicate

Behaviour of chromosomes during interphase

Replicate

Behaviour of chromosomes during prophase

Chromosomes coil, becoming shorter, fatter and visible

Behaviour of chromosomes during metaphase

Chromosomes line up on the equator of the cell

Behaviour of chromosomes during anaphase

Chromosomes separate and pulled to opposite poles of cell

Behaviour of chromosomes during telophase

Chromosomes become long, thin and not visible

Events during cytokinesis

Cytoplasm and cell membrane divides to give two new cells

How does cytokinesis in animal cells happen?

Cell membrane pulled inwards, pinching off the cytoplasm

How does cytokinesis in plant cells happen?

Vesicles fuse to create cell membrane and new cell walls develop

Purpose of mitosis

Produce genetically identical daughter cells for growth and repair

Uncontrolled cell division can lead to...

Tumours

Cell division in bacteria is called...

Binary fission

Events during binary fission

Replication of DNA and plasmids, cytoplasm divides

Describe virus replication

Inject DNA/RNA into host, host makes more virus particles

Components of a cell surface membrane

Phospholipid bilayer, cholesterol, integral proteins, peripheral proteins, glycoproteins, glycolipids

Describe the fluid mosaic model

Describes how the molecules of the different substances that make up the membrane are arranged in a mosaic

Structure of a phosphlipid

Hydrophillic head made from glycerol and phosphate and hydrophobic fatty acid tail

Function of the phospholipid bilayer

Forms the basis of membranes in and around cells

Function of cholesterol

Restricts the movement of molecules whilst still allowing fluidity

Function of integral proteins

Enzymes and transporters

Function of peripheral proteins

Anchorage, cell recognition and receptors

Glycoproteins are...

Proteins with carbohydrate chain attached

Glycolipids are...

Carbohydrate with lipid chain attached

Define simple diffusion

Passive movement of particles down a concentration gradient from a high to low concentration

Molecules that move by simple diffusion

Small, non-polar molecules such as oxygen and carbon dioxide

Factors which affect diffusion

Temperature, surface area, concentration gradient, width of exchange surface

Define faciliated diffusion

Movement of particles down a concentration gradient from a high to low concentration involving a membrane protein

Molecules that move by facilitated diffusion

Large polar molecules such as glucose and ions

Define osmosis

Passive net movement of water from high water potential to low water potential through a selectively permeable membrane

Define active transport

Movement of particles against a concentration gradient involving a carrier protein and requiring ATP

Molecules that move by active transport

Sodium-potassium pump

Cell adaptations for rapid movement of molecules

Large surface area and large number of channel/carrier proteins (e.g. aquaporins)

Humoral response

Involves B cells which produce antibodies in response to a pathogen in the blood

Cell mediated response

Involves T cells which destroy infected body cells

Cell surface membrane proteins identify...

Pathogens, cells from other organisms of the same species, toxins and abnormal body cells

Antigen

A large 'foreign' molecule that stimulates an immune response

Antibody

A protein released by a B cell in response to a non-self antigen

Antigen-antibody complex

The complex formed when an antigen binds with a complementary antibody

Antigen variability

As a result of gene mutations, pathogens change the antigens on their surface

Phagocytosis

The process of a phagocyte engulfing a pathogen

Function of phagocyte

Non-specific white blood cells which engulf pathogens and destroy them

Function of lymphocyte

White blood cells which attack one type of pathogen only

Function of B-lymphocyte

Antibody-producing cells that recognise and target a particular antigen

Function of macrophage

A type of phagocyte which can become an antigen-presenting cell

Function of helper T cell (TH)

Regulator cells that release chemicals (cytokines) to activate specific B lymphocytes

Function of cytotoxic T cell (TC)

Destroy tumour cells and cells that are infected with viruses

Uses of monoclonal antibodies

Pregnancy tests, ELISA tests, magic bullet

Clonal selection hypothesis

B or T cell will bind with a particular antigen, stimulating large numbers of cells that are identical to itself and each other

Agglutination

When antibodies bind to more than one pathogen and cause them to form a clump

Plasma cell

A fully differentiated B-lymphocyte (white blood cell) which produces a single type of antibody.

Memory cell

A long-lived lymphocyte capable of producing antibodies to a particular antigen, long after the exposure that prompted its production

3 ways vaccines are made harmless

Killing or weakening the pathogen but antigens intact, using less harmful bacterial toxoids, using a microbial protein

Vaccination process

Inject harmless form of pathogen containing antigen,

Two differences between primary and secondary immune response

Secondary immune response makes more antibodies more quickly, before you get ill

Herd immunity

When the vaccination of a significant portion of a population provides some protection for individuals who have not developed immunity because the disease cannot spread as easily.

Active immunity

When a person produces their own antibodies as a result of exposure to the antigen of a pathogen

Examples of active immunity

Vaccination, exposure to disease

Passive immunity

When a person is given antibodies

Examples of passive immunity

Breastfeeding, antivenoms for snake bites

Three features of viruses

Capsid made of protein, 50 times smaller than bacteria, DNA/RNA in core

Antibiotics are ineffective against viruses because...

Viruses do not have a metabolism

Process of the ELISA test

PSA binds to antibodies, new antibody with enzyme attached binds to PSA, well washed to remove unbound antibodies, substrate added, colour change