cell structures and processes Flashcards
Cell membrane
forms boundary between internal environment and cytoplasm.
Functions are: recognition of other cells, transportation of material in and out of cell, provision of attachment sites for enzymes and hormones
fluid mosaic model
Double layer of lipids, lipid bilayer
ability to flow and change shape
Proteins embedded in layer
phospholipid
Phosphate group of head is hydrophilic
fatty acid tail is hydrophobic
Cholesterol in phospholipid bilayer
lipid in membrane
Helps maintain cell membrane stability at varying temps
transmembrane proteins
Proteins that extend across the entire membrane, past heads and tails
Function as transport proteins by, controlling entry and exit of substances, and act as passageways for specific substances
2 types: channel proteins, carrier proteins
channel protein
Passive transport/facilitated diffusion, don’t require energy
open and close in response to a stimuli
aquaporins
Channel protein
facilitates transport of water along concentration gradient
Carrier proteins
Binds to a specific molecule, changes shape and releases the substance on the other side
Uses energy
adhesion protein
Link cells together to maintain both 3D structure and normal functioning of tissues
receptor protein
Bind hormones and other substances that cause changes to the cell’s activities
Passive transport
movement of substances that don’t require energy
Move down concentration gradient
simple diffusion
Net movement of particles from region of high concentration to lower particle concentration
difference between concentrations is the concentration gradient
Occurs because of random kinetic movement of particles
Is a passive process
equilibrium
Particles are evenly spread out, therefore no concentration gradient
Diffusion across membrane
small uncharged molecules can pass through phospholipid bilayer
Facilitated diffusion
charged or large molecules don’t pass through phospholipid bilayer
2 proteins assist: carrier proteins and channel proteins
No energy required
osmosis
Diffusion of water across a selectively permeable membrane from an area of high water concentration to an area of low water concentration.
water moves passively past phospholipids
Isotonic
Same concentration of solute in cell and outside of cell.
no net change across membrane
Hypotonic
external solution contains less solute
Water diffuses into cell to balance H2O concentration
hypertonic
External has higher solute concentration
water diffuses from cell to outside
Osmosis in plants
plant contains large vacuole with solute
Turgid
hypotonic solution surrounds plant cell
Water diffuses firstly into cytosol, then into vacuole, vacuole swells, pushing cytoplasm and cell membrane against cell wall.
cell wall prevents bursting
When membrane stretched to max possibility, no more water can enter
plasmolysis
Water diffuses out, reducing volume of vacuole and causing cells to become limp or placid, plant will wilt.
if enough water lost, cell membrane pulls away from cell wall
Active transport (carrier proteins)
requires energy
Performed by proteins
can go against concentration gradient
Act as one way valve
Endocytosis
movement of solids or liquids into a cell from the environment via vesicle formation
Membrane changes shape by sending out projections that surround the prey, when projections meet, membrane fusion occurs
phagocytosis
Endocytosis of solids
pinocytosis
Endocytosis of liquids
recognition protein
Protein that acts as a marker on membranes
exocytosis
Process by which large molecules held in vesicles within the cell are transported to external environment
membrane-bound vesicle fuses to membrane and then releases its contents to exterior of the cell
Metabolism
sum of all biochemical processes occurring in an organism
Anabolic reactions
involve synthesis of complete molecules from simpler ones and usually require energy to form new chemical bonds
Catabolic reactions
involve breakdown of complex molecules into simpler ones and usually releases energy from breaking chemical bonds
Biochemical processes
chemical reactions in a cell occur in a series of regulated steps
Provides enough energy to maintain the processes of generating products from reactants
enzyme
Biological catalyst that speeds up biological reactions without undergoing any change itself
macromolecules
Lower activation energy required for a reaction to proceed
cellular metabolism
Sum of thousands of chemical reactions that occur constantly in each living cell
rate varies in organisms
Exergonic reactions
releases energy
When moleculer bonds are broken, energy is released
endergonic reactions
Energy is used
cells use energy released from catabolic reactions used for anabolic reactions
Activation energy
minimum amount of initial energy required to start a chemical reaction
Usually applied in heat energy
active site
Place on surface of an enzyme molecule where substrate molecules attach
substrate
A reactant on which an enzyme acts
enzyme-substrate-complex
Substrate must be of a compatible shape for binding to occur
Lock-and-key model
substrate must be of a compatible shape for binding to occur
Substrate fits active site of enzyme like lock-and-key
induced-fit model
Enzyme not shaped
bonds between enzyme and substrate slightly modify enzyme so that substrate can be accommodated by enzyme
Bonds within substrate molecule are stretched and bent by molecular interactions with amino acid groups that live active site, activation energy required drastically lowered
After product released, active site returns to OG shape
psychrophile
An orgasm that lives in extremely cold conditions
enzymes can operate at low temps
Thermophile
an organism that .ives in high temperature environments
Operates best at 95-105C
temperature and enzymes
As temps increases, molecules become more active and collide more often
temp too high and could denature enzyme
Lower temp means lower rate of enzyme activity, lower rate of reaction
pH on enzymes
Enzymes have optimal pH for reactions
active site shape can change due to pH, therefore denatures
Inhibitors
a substance that competes with substrate for an enzyme’s active site
Cofactor
small, inorganic substance that must be present in addition to an enzyme to catalyse a certain reaction
Coenzymes
non-protein organic substance that are required for enzyme activity
Relatively small compare to enzymes
ATP
Main energy carrying molecule used in metabolism
energy enters ecosystem through light energy
energy can be transferred between reactions
Nucleotide containing adenosine attached to a sugar group (ribose) and chain of 3 phosphate groups
when 3rd phosphate of chain breaks off it releases energy
Photosynthesis
biochemical process, in producers, that uses light energy and the raw materials carbon dioxide and water to synthesise organic compounds
ADP
When ATP has 2 phosphates left
energy has been released
Adenine Diphosphate
phosphorylation
When bond forms between an available phosphate group and ADP, producing ATP
Chloroplast
light captured by chlorophyll pigment found in chloroplast organelle
Has outer and inner membrane
stroma
Enclosed inner membrane
gel-like matrix rich in enzymes
Thylakoid membranes
suspended in stroma
Flat, sac-like structures called grana, granum singular
light dependent stage
when chlorophyll molecule in thylakoid membranes absorbs light energy, electron within become energised.
Energy used to split H2O in hydrogen ions (H) and oxygen gas (O2)
ATP molecules formed at this stage
Electron donated to NADP to form NADPH
light absorbed by three pigments: chlorophyll (green), Carctenoids (orange), and Xanthophylls (yellow)
Chlorophyll
absorbs red and blue light
Reflects green
light independent stage
occurs in stroma (fluid part) of the chloroplast
Glucose molecules created from CO2 and Hydrogen ions
Requires supply of CO2 and Hydrogen ions in NADPH and ATP
ATP made by dependent light stage provide chemical energy for conversion of carbon dioxide to glucose molecules
Reactions are anabolic, result in carbon being stored in glucose (carbon fixation)
During day (photosynthesis)
Chloroplasts convert newly formed glucose molecules to sucrose of starch
at night (light independent stage)
Cell converts starch to sucrose for export to other cells in leaves, stems and roots that lack chloroplasts
Cellular respiration
biochemical process
Occurs in cytosol and mitochondria
metabolises organic compounds, aerobically or anaerobically to release usable energy in form of ATP
Aerobic respiration
series of reactions in presence of O2, by which organisms obtain energy from organic molecules, via production of ATP
glycolysis, citric acid cycle (Krebs cycle) and electron chain transport
Glucose combines with oxygen to produce ATP
occurs in mitochondria
Process can proceed without O2, site for this reaction is cytoplasm
glycolysis
Takes place in cytosol
biochemical pathway made up of 10 reactions, each step controlled by enzyme
Initial reaction is glucose and final product from each molecule of glucose is 2 molecules of a compound called pyruvate
mitochondria
Produces large amounts of ATP
site of aerobic respiration
Inner and outer membrane and inner membrane space
cristae
Structure formed by heavily folded inner membrane of mitochondria
Embedded are enzymes called Adenosine Triphosphate (ATP) synthase
contains respiratory electron transfer chain proteins and transport proteins
Matrix
site for citric acid cycle
Space within inner membrane
Anaerobic respiration
takes place in cytosol in the absence of O2
Alcohol fermentation and lactic acid fermentation
alcohol fermentation
CO2 and ethanol
Products: glucose -> ethanol + CO2 + 2 ATP
ethanol is toxic therefore cell must revert to aerobic respiration other wise will be poisoned by ethanol
Lactic acid fermentation
end product of anaerobic respiration in animals
Lactic acid converted back to pyruvate allowing continued aerobic respiration
Glucose -> lactic acid + 2 ATP
Compensation point
when uptake of CO2 from photosynthesis is equal to output of CO2 from aerobic respiration
