biochemistry p2 Flashcards
Function of cell wall
A rigid but flexible structure made of cellulose. It acts as a pressure vessel, preventing over-expansion when water enters the cell. It is found in mainly plant cells, but can also be in fungi, algae and some bacteria
Function of cell membrane
The entire cell is covered by thus and it is mostly composed of phospholipids. It is ‘selectively permeable’ and controls the entry and exit of various chemical into and out of the cell.
Function of flagella
Tail-like projection that helps cells move
Cillia
slender protuberances that project from the cell body. (eukaryotic cells only) they can also aid in motion or serve as sensory organelles or clear debris like in the lungs.
Mitochondria
Provides energy by producing ATP through cellular respiration
Chloroplast
Captures light energy and so is involved in photosynthesis, making glucose (is only found in plant cells since animals injest glucose)
Cytoplasm
where most cellular activities occur, like glycolysis and cell division. It also is the space that contains the organelles.
Lysosomes
An organelle that breaks down ‘worn out’ organelles, viruses/bacteria and food particles. It does this with digestive enzymes in an acidic environment
Ribosomes
They make proteins out of amino acids
Centrioles
A structure essential for cell division and the organisation of the spindle fibres in mitosis. Found only in animal cells
Rough endoplasmic reticulum
Where many ribosomes are attached, thus it helps synthesize proteins
Smooth endoplasmic reticulum
A series of canals that carry materials throughout the cell and help synthesize lipids such as steroids
Vacuole
A membrane-surrounded, fluid-filled “storage space containing water, sugar, minerals or enzymes. Function will vary depending on cell type
Golgi bodies/apparatus
a structure that stores and packages proteins (such as enzymes) and lipids
Nucleus
The small control center of the cell that contains DNA. It also has small ‘pores’ on it that allows materials to enter and exit
Nucleolus
A spherical structure of the nucleus that makes ribosomal RNA (rRNA)
Chromosomes
Thread-like structures that contain genetic info
Intro to membrane transport
- the cell membrane is semi-permeable: some substances can move across the cell membrane while others can’t
Concentration gradient
a difference in concentration between one side of the membrane and the other
Passive transport
Processes that allow substances to move across the membrane without energy. They use the concentration gradient.
ex. difusion, osmosis and facilitated difiusion
Active transport
movement of molecules against a concentration gradient
- requires energy in ATP
- includes active transport (endocytosis and exocytosis)
Facilitated diffusion
Large, polar or charged molecules like glucose need to use this because theyre to big to fit between phosphate heads. They use protein channels which are suited to each molecule to get through.
Simple difusion
Small non-polar molecules like o2 that can slip between phisphate heads and go through large non-polar portion of the membrane.
- Rate of diffusion is affected by: Molecules size, polarity, charge (charged ions cannot diffuse), temperature and pressure (hot–> faster)
Transport proteins
Movement of particles from relatively low to high concentration using a protein carrier
Transport requiring vesicles
Membrane assisted
Endocytosis
Endocytosis is taking in large or polar macromolecules from outside the cell by engulfing them with their plasma membrane (membrane assisted)`
Pinocytosis
“cell drinking”
- the injestion of a liquid into a cell by the budding of small vesicles from the cell membrane
Phagocytosis
“cell eating”
- solid particles being taken in by membrane ex. amoeba feeding or an immune system engulfing bacteria to kill it
Osmosis
The movement of water from high to low concentration through a semi permeable membrane
- ex. cell in a hypotonic (low solute concentration) solution has water enter it so that solute concentration in the cell is equal to that outside
Receptor mediated endocytosis
Receptor proteins on a portion of the cell membrane bind with specific molecules outside the cell. The area containing the proteins us called coated pit, because its coated in a layer of protein.
Exocytosis
“reverse pinocytosis”, process where a cell directs the contents of its secretory vesicles out of the cell membrane. These membrane bound vessicles contain soluble proteins to be secreted to the extracellular environment as well as the membrane proteins and lipids that are sent to become components of the cell membrane
ex. releasing a neurotransmitter for cellular communication
Isotonic solution
- The ideal cell condition
- Concentration of water : solute is equal
- Water moves in and out of the cell at an equal rate - cell doesn’t expand or shrink
What are enzymes
- protein catalysts: they speed up chemical reactions without being consumed
- names often end in “ase”
Why are the necessary
- Reactant molecules must collide with enough force and with the correct geometric orientation for bond breaking to occur
-this happens in a random and uncontrolled manner in non-catalyzed environments (slow)
Where does the energy required for chemical reactions come from?
- most chemical reactions get their energy from heat, however, proteins are denatured at high temperatures, so living cells cannot rely on high levels of heat as a source of activation energy
(activation energy that must be overcome for a chemical reaction to occur) - The purpose on an enzyme in a cell is to allow the cell to carry out chemical reactions as quickly as possible without using too much energy
- enzymes do this by lowering the activation energy
Enzyme structure
- enzymes overcome the activation energy barrier by “holding’ chemical reactants in the correct orientation
- The Substrate is the reactant that an enzyme acts on
- it binds to a particular site on the enzyme called the active site. The active site is where catalysis occurs
- the substrate fits closely into active sites because enzymes cab adjust their shape slightly ti acommodate to the substrate
- This adjustment is referred to as “induced fit” and forms the enzyme-substrate-complex
Conditions that help enzymes work their best
enzyme-catalyzed reactions can be saturated
- the speed at which a catalyzed reaction proceeds cannot increase indefinitely by increasing the concentration of the substrate (all active sites get filled)
Every enzyme has an optimal temperature and pH that it works best at due to particle theory and denaturation
- Some enzymes require nonprotein cofactos such as inorganic substances (minerals: ex. Zn and Mn) or organic coenzymes (many Vitamins) before they can work properly
Things that inhibit enzymes
- inhibitors are chemicals that bind to specific enzymes
- this results in a change in the shape of the enzyme which shuts it down
- there are two main types of inhibitors: competitive and non-competitive
Competitive inhibition
- involves chemical compounds that bind to the active site of the enzyme and inhibit enzymatic reactions. the compounds compete with the true substrate for access to the active site (ex. penicillin)
- similar in shape to substrate
Non-competitive inhibition
- an inhibitor molecule binds to the enzyme at a site known as the allosteric site
- as a result the 3D structure of the enzyme is changed, which prevents the substrate from binding to the active site
- molecules that promote the action of enzymes can also bind to allosteric site- they’re called activators
Industrial uses of enzymes
the starch processing industry uses enzymatic hydrolysis –> hydrolyzes starch into maltose, then maltose to glucose
The dairy industry uses enzymes to create cheese
Cleaning industry uses enzymes to remove stains at lower temperatures and with less mechanical agitation
