CELL STRUCTURE (A2.2)

What does cell theory consist of?

• Cells are the basic structural unit of all living organisms

• All living organism are composed of cells (one or more)

• Cells are the smallest units of life

• Every cell is surrounded by a membrane

• Every cell contains geentic material needed for survival

• In cells, metabolic activity is controlled by enzymes

What is a microscope?

A scientific instrument used to magnify objects or images that are too small to be seen with unaided eye

How do you calculate magnification?

Image size / actual size

How do you calculate image size?

Magnification x actual size

How do you calculate actual size?

Image size / magnification

Discuss electron microscopy

• Beams of electrons pass through speciemen

• Electrons will be absorbed by the denser parts of the sample

• This is picked up by electron detector and used to form an image

• as electrons have shorter wavelengths then light, the image has a higher resolution

• THE IMAGES ARE IN BLACK AND WHITE

What does the microscopy technique freeze fracture microscopy entail?

• Freezing a sample and using a specialised tool to break the sample

• Pieces are used to observe using electron microscope to see internal structure

• Useful as it can visualise structures that are not visible like the internal plasma membrane

What does the microscopy technique cryogenic electron microscopy entail?

• Freezing to a cryogenic temp to fix the molecules and make them more firm or stable

• Freezing improves the resolution of the image formed and reduced damage that may occur form the electron beam

What does the microscopy technique immunofluorescence entail?

• Light microscopy, the fluorescent tag called a flurophene is attached to antibodies specific for antigens on the cell being viewed.

• When antibody binds to antigen, the structure is tagged with immunofluorescence

• Certain wavelengths of light is shone into tag, the tag will emit light of different wavelengths, This will appear as brightly coloured spots, allowing visual of location.

What does the microscopy technique fluorescent dyes entail?

• Light microscopy, dye will attach to certains structures.These areas appear as bright coloured sports and allow visualisation of the target molecule through specimen.

What is a prokaryotic cell?

A unicellular organism that does not contain membrane- bound organelles (free in the cytoplasm)

• Bacteria

• Archea

What are the parts of a prokaryotic cell?

• Cell wall

• Plasma membrane

• Cytoplasm

• Naked DNA in a loop

• 70s ribosomes

• Plasmid

• Capsule

• Flagellum

• Pili

What is the cell wall?

• The outside of the cell membrane

• Protects the cell against toxins and maintains shape of cell

What is the plasma membrane?

• Separates the cells interior from its external environment and controls enters or exits

What is the cytoplasm?

• Water- based jelly fluid that fills cell and suspends ions, organic molecules, DNA and ribosomes.

• Location for metabolic reactions

What is the naked DNA in a loop?

• It stores info needed for synthesising proteins

• Naked as it is not associated with histone proteins

• Found in nucleiod region

What are 70s ribosomes?

• Where translation of proteins synthesis occurs

• These ribosomes are smaller and lower mass than eukaryotic ribosomes

What is the plasmid?

• Small, circular pieces of DNA that can be transferred from one prokaryotic cell to another

• Known as horizontal gene transfer

What is the capsule?

• Outer layer of polysaccharides to protect the organism and allow it to adhere to surfaces

What is the flagellum?

• Responsible for the locomotion of the organism, spinning to propel the cell through its medium

What is the pili?

• Protein filaments on the cell wall that help in cell adhesion and in transferring of DNA between 2 cells

What is a eukaryotic cell?

• A multicellular organism; body of organism which consist of more than one cell

• Contains nucleus and membrane- bound organelles

• Bigger than prokaryotic cells

What is compartmentalisation?

• Has membrane bound organelles (mitochondria and chloroplasts)

• Allows for the interior of the organelles to have separate conditions to the cytoplasm of the cell

What are the advantages to compartmentalisation?

• Able to create higher concentrations of certain substances within organelles

• The ability to seperate toxins and potentially damaging substances from the rest of the cell

  • Lysomes allow for enzymes to be stored away form cell, so it wont break down the entire cell and fulfill a particular role.

• Control over the conditions inside organelles (pH) to maintain optimal conditions for the enzymes that function in those parts of the cell

What features overlap for both prokaryotic and eukaryotic cells?

• Plasma membrane

• Cytoplasm

What is the mitochondria?

• Double membrane- bound organelle that converts glucose into ATP during respiration

What are 80s ribosomes?

• Attached and free floating eukaryotic ribosomes and larger and have higher mass that prokaryotic ribosomes

What is a nucleus?

• DNA which is associated with histone proteins

• Organised into chromosomes

• Contains the nucleolus, which is involved in the production of ribosomes

• Double membrane which has pores through which certain molecules can pass including glucose, RNA and ions

What is the smooth endoplasmic reticulum?

• Produced and stores lipids including steroids

What is the rough endoplasmic reticulum?

• Has ribosomes attached to its surface which produce proteins that are usually destined for use outside the cell

What is the golgi apparatus?

• Processes and packages proteins, which are then released in the golgi vesicles

What is a vesicle?

• Small sac that transports and releases substances produced within the cells by fusing with the cell membrane

What is a vacuole?

• Helps maintain the osmotic balance of the cell

• Used to store substances and sometimes has hydrolytic functions like lysomes

What is the cytoskeleton?

• A system of protein fibres called microtubules and microfilaments

• Helps organelles to be in a place and maintains the structure and shape of the cell

What are the 8 life processes that a unicellular organisms will be capable of carrying out?

• Metabolism: chemical reactions that take place within the cells of an organism

• Response to stimuli: Reacting to changes in the external environments

• Homeostasis: the maintenance of constant internal conditions, despite external environments

• Movement

• Growth

• Reproduction

• Excretion

• Nutrition

What special cell structures do animal cells have?

• Centrioles: 2 cylindrical organelles that help establish and organise the microtubules

• Lysomes: membrane- bound bags of hydrolytic enzymes that break down and destroy biological molecules and old cellular organelles

• Vacuoles are smaller in animal cells than in plant cells

• Cilia: hair- like structures made of microtubules and are important for the movement of substances past the cell

What special cell structures do plant cells have?

• Cell wall made of polysaccharide called cellulose

  • It protects and resists osmotic pressure

• Chloroplasts: double membrane bound organelles that convert light energy into chemical energy in photosynthesis

• Larger vacuole to regulate osmotic pressures of the cell

What special cell structures do fungal cells have?

• Cell wall made of polysaccharide called chitin

• Large vacuoles to break down molecules in cell and are storage for small molecules like ions

• Centrioles: producing and organising the cytoskeleton and for cell division

  • Only present in the male gamete of some fungi

How do fungal cell reporduce?

• Reproduced through budding; number of scars indicate how many times the cell has divided

What does having an atypical cell structure in eukaryotes mean?

Do or dont contain abnormal numbers of cells structures and organelles

What atypical cell structures does the skeletal muscle have?

• Multi nucleated

• One cell has many nuclei due to the fact that muscles has formed by many smaller myocytes that are fused together

What atypical cell structures does the mature red blood cells have?

• Anucleate

• Do not contain a nucleus as cells will then have greater haemoglobin capacity and can transport more oxygen

What atypical cell structures does the sieve tube elements in the phloem of plants have?

• Anucleate

• Contain very little cytoplasms and few organelles

• Has low resistance for substances moving through a sieve tube element