Cells as the Basis of Life
investigate different cellular structures.
prokaryotic and eukaryotic
Prokaryotic
Prokaryotic organisms do not have membrane bound organelles, i.e. they do not have a nucleus, mitochondria or chloroplasts. The prokaryotic genome is in a circular DNA/protein single chromosome called the nucleoid. Many prokaryotes have fimbriae which are short hair-like structures on the surface that help the prokaryote stick to other cells or to a substrate. Flagella are used by motile bacteria for movement to move either towards or away from stimuli.
Eukaryotic
A eukaryote has membrane organelles, e.g. nucleus, mitochondria. Eukaryotes include single-celled organisms, e.g. some protista and some fungi and multicellular organisms, e.g. plants, animals, some protists and some fungi.The endomembrane system of eukaryotic cells includes the cell membrane, the nuclear membrane, the endoplasmic reticulum, the Golgi apparatus, lysosomes and other vesicles and vacuoles found within the cell.
technologies that are used to determine a cell’s structure and function
Light microscope
Energy Source
The energy is generated by a light bulb.
Focus
Specimen
Preparation
Magnification
Resolution
Can live specimen be viewed?
Image: Colour /
Black & White
Condenser Lens - This lens system is located immediately under the stage and focuses the light on the specimen.
Place a drop of fluid in the centre of the slide.
Position sample on liquid, using tweezers.
At an angle, place one side of the cover slip against the slide contacting outer edge of the liquid drop.
Lower the cover slowly, avoiding air bubbles.
Remove excess water with the paper towel.
400-1000 times
Resolution in an ideal light microscope is limited to around 200 nm
yes
Colour
Electron microscope
Energy Source
Electron microscopy uses a beam of electrons as an energy source.
Focus
This beam is focused onto the sample using a magnetic lens.
Specimen
Preparation
Samples must be cut into very thin cross-sections. This is to allow electrons to pass right through the sample. After being fixed and dehydrated they are examined.
Magnification
Between 1 and 50 million times
Resolution
0.05 nm
Can live specimen be viewed?
no
Image: Colour /
Black & White
B and W
Prokaryotic and eukaryotic cell structures
comparing and contrasting different cell organelles and arrangements
Similarities
Golgi apparatus
Ribosomes
Cytoplasm
Differences
Nucleus
Chloroplasts
Mitochondria
Vacuole
Nucleolus
Endoplasmic reticulum
Lysosome
Functions of organelles:
Nucleus: The nucleus controls and regulates the activities of the cell.
Chloroplast: structure within the cells of plants and green algae that is the site of photosynthesis, the process by which light energy is converted to energy.
Mitochondria: Generates most of the chemical energy needed to power the cell's biochemical reactions.
Golgi apparatus: Helps process and package proteins.
Ribosomes: Site for protein synthesis in the cell.
Vacuole: Remove and stores waste and nutrients produced during autophagy (when part of the cell is broken down due to age or damage).
Cytoplasm: It provides a platform upon which other organelles can operate within the cell.
Endoplasmic reticulum: Its function is to produce proteins for the rest of the cell to function.
Lysosome: They break down excess or worn-out cell parts.
How materials can move into and out of cells
Diffusion and ossmosis
Diffusion
Passive movvement of a substance from an area of high solute concentration or low concentration.
Osmosis
Passive movemnet of water to an area of higher concentration
Cell membrane
Phospholipid
peripheral protein
Channel protein
Carrier protein
Cholesterol
Glycoprotein
Cholesterol functions to immobilise the outer surface of the membrane, reducing fluidity. It makes the membrane less permeable to very small water-soluble molecules that would otherwise freely cross. It functions to separate phospholipid tails and so prevent crystallisation of the membrane.
A channel protein, a type of transport protein, acts like a pore in the membrane that lets water molecules or small ions through quickly.
Phospholipids provide barriers in cellular membranes to protect the cell, and they make barriers for the organelles within those cells.
Peripheral proteins form temporary bonds with the cell membrane, allowing them to detach and reattach at specific times, with specific signals.
Carrier protein is a type of cell membrane protein involved in facilitated diffusion and active transport of substances out of or into the cell.
Glycoproteins are found on the surface of the lipid bilayer of cell membranes. Their hydrophilic nature allows them to function in the aqueous environment, where they act in cell-cell recognition and binding of other molecules.
Endocytosis and exocytosis
Endocytosis
Endocytosis is a general term describing a process by which cells absorb external material by engulfing it with the cell membrane. Endocytosis is usually subdivided into pinocytosis and phagocytosis.
Exocytosis
Exocytosis is the fusion of secretory vesicles with the plasma membrane and results in the discharge of vesicle content into the extracellular space and the incorporation of new proteins and lipids into the plasma membrane.
Ezymes
Whta are they?
Enzymes are proteins that help speed up metabolism, or the chemical reactions in our bodies. They build some substances and break others down. All living things have enzymes. Our bodies naturally produce enzymes. But enzymes are also in manufactured products and food
Made of
Enzymes are protein molecules which are made up of long chains of amino acids.
Activation energy
Enzymes provide an alternative pathway for a chemical reaction. They lower the activation energy, allowing reactants to reach the lower activation energy values more quickly and thereby increase the rate of reaction.
Models
Induced fit
The induced-fit model is a model for enzyme–substrate interaction to describe that the substrate is capable of inducing the proper alignment of the active site of the enzyme, causing the latter to subsequently perform its catalytic function.
Lock and key
Lock-and-key model is a model for enzyme-substrate interaction suggesting that the enzyme and the substrate possess specific complementary geometric shapes that fit exactly into one another.