Processes at cellular level Flashcards
What type of cell has the following characteristics?
- Small
- No membrane-bound organelles
- Relatively unstructured
- Not very organised internally
- A type of cell wall
Prokaryotic (bacterial) cells.
What type of cell has the following characteristics?
- Membrane-bound nucleus
- Larger than prokaryotic cells (are multi-cellular organisms)
- More complex than Prokaryotes
Eukaryotic cells
Define the term organelles
Specialised structures inside the cell that carry out various functions.
Cell wall function
A semi-rigid layer on the outside of the cell. It is composed of cellulose and it provides support for the cell.
Cytoplasm function
A jelly-like fluid. It is the site of many cellular reactions. It also acts as a medium for transport inside the cell.
Large central vacuole function
organelle can serve a variety of secretory, excretory and storage functions.
Nucleus function
The nucleus regulates all cell activity. It contains the genetic material (DNA) of the cell.
Chloroplast function
Absorb light energy to make glucose via photosynthesis. They contain the light-absorbing pigment chlorophyll.
Golgi body function
modify, sort and package proteins from the endoplasmic reticulum for storage and transport within and out of the cell.
Ribosomes function
site of protein synthesis. They can be free-floating within the cytoplasm or associated with the endoplasmic reticulum.
Endoplasmic Reticulum (ER): function
It creates a network of membranes throughout the entire cell. ER can be smooth (no ribosomes) or rough (ribosomes present).
Mitochondria function
The site where aerobic respiration is completed. Mitochondria have two membranes: an outer smooth membrane and an inner wrinkled membrane; inner foldings of the inner membrane are called cristae.
Cell membrane function
It separates the cytoplasm inside the cell from its surroundings, and regulates what enters and exits cell
Vacuole function
Membrane-bound compartments that can serve a variety of secretory, excretory and storage functions.
Lysosome function
Contains digestive enzymes to digest old organelles and parts of organelles.
Nucleolus function:
a non-membrane-bounded structure inside the nucleus. Its function is to transcribe DNA to ribosomal RNA (rRNA) and assemble it within the cell.
Name the structure with the following structures? (and complete the sentences)
- a phospholipid double bilayer ….
- Proteins move …..
- Various cell activities take place here and…
Cell membrane
- which is made of two layers: hydrophobic tails and hydrophilic heads
- freely in this fluid/flexing structure
- certain substances are allowed to move in and out of the cell membrane.
Name the three qualities of passive transport
- No energy (ATP) is required for substances to move across the membrane
- Substances move from high to low concentration
- Substances move with the concentration gradient
Define diffusion ( the three qualities)
- Passive transport
- Diffusion is the net movement of particles from an area of high concentration to a low concentration until the concentration is at equilibrium
- Substances are moving down the concentration gradient
Factors that affect the rate of diffusion:
(4)
- size of the molecules (small molecules move faster than larger molecules).
- temperature of the liquid or gas (warmer molecules move faster).
- state of matter that is being diffused (gas molecules move faster than those in liquids).
- concentration of chemicals (the greater the concentration gradient the faster the rate of diffusion down the gradient).
Comments on diffusion in cells (3)
Diffusion is much less efficient if ….
SMALL CELLS have a LARGER…..
- Diffusion is much less efficient if cells are larger- meaning a small surface area relative to their internal volume.
- SMALL CELLS have a LARGER
Surface Area : Volume
Define Facilitated diffusion in cells (5)
First hint: Facilitated or passive transport
- Passive transport
- Transportation of molecules that are too big to move across the cell membrane
- Requires transport proteins embedded in the membrane
- These proteins contain channels that the large molecules diffuse through
- Transport proteins are specific (carry only one type of molecule)
Define Osmosis
- Transportation of water molecules from high concentration to low concentration water concentration
- Transportation of water molecules towards the highest solute concentration
Define a hypertonic solution
Hypertonic: more solute than water molecules (solvent)
Define hypotonic solution
more water molecules (solvent) than solute
Define isotonic solution
equal amount of solute and water molecules (solvent)
If you put a cell inside a HYPERTONIC solution the water moves to….
the high solute/low water solution OUTSIDE the cell
If you put a cell inside a HYPOTONIC solution the water moves to….
the high solute/low water solution INSIDE the cell.
Within an isotonic solution, you have an equal amount of….
solute and water concentration inside and outside the cell
Within a hypertonic solution, the cell is losing water due to….
a high solute concentration outside the cell, this can lead to the cell shrinking
Within a hypotonic solution, the cell is gaining water due to….
a high concentration of solute inside the cell, this can lead to the cell bursting/cell rupture
Active transport definition (2)
- Substances require energy (ATP) to enter the cell
- Substances travel against the concentration gradient
ATP is Adenosine triphosphate. When you add water to it…..
energy ) is released and ADP is formed.
How does active transport work
(there is 4 points)
- ATP binds to a transport protein
- A molecule or ion being transported against gradient binds to the protein
- ATP is hydrolysed (reacts with water) and the energy released help the molecule/ion move across the membrane
- The molecule/ion is released and the protein is ready to transport again
Types of active transport (2)
- which one carries large particles and which one carries small particles.
- Membrane (carrier) proteins:
(smaller particles travel via carrier proteins) - Cytosis
(larger particles travel via cytosis)
Define ion pumps and give three examples
transmembrane proteins that use energy to move ions. Some common ion pumps are:
- Proton pumps (H+)
- Sodium-Potassium pumps
- Cotransport-Sodium-Glucose
Define endocytosis
Endocytosis is the infolding of the membrane to form vesicles/vacuoles that enter the cytoplasm.
Define the endocytosis term: Pinocytosis
the ingestion of surrounding fluid(s)
Define the endocytosis term: Phagocytosis
the ingestion of solid material
Define exocytosis
The vesicle fuses with the membrane and releases the content outside the cell.
What is plasmolysis
In the plant cells, the membrane pulling away from the cell wall
When does plasmolysis occur
happens when a cell shrinks inside its cell wall while the cell wall remains intact.
Enzyme function
Enzymes are the biological catalysts that provide an alternative pathway to lower activation energy.
Without enzymes metabolism….
would be very slow. Metabolism (metabolic reactions) refers to all chemical reactions occurring in a cell.
Anabolic reactions definition
is energy released or required
- Small molecules are assembled into large ones
- Energy is required
Catabolic Reactions
is energy released or required
- Large molecules are broken down into smaller ones
- Energy is released
Properties of enzymes (5)
- Enzymes are made of…
- They speed up…
- They are needed only in…
- They remain unchanged after…
- Each enzyme is specific….
- Enzymes are made of proteins
- They speed up chemical reactions inside the cytoplasm
- They are needed only in small amounts
- They remain unchanged after each reaction and can therefore be reused
- Each enzyme is specific for a substrate
What is the following model
- Substrate fits into the enzyme’s active site to form an enzyme-substrate complex
- The key (the substrate) that has a specific shape that allows it to fit into the lock (the enzyme)
Lock and key model
What is the following model
- Binding of the substrate to the enzyme alters the configuration of both the enzymes and the substrate, therefore a better fit
- Enzymes will fit the substrate with the correct functional groups are able to modify the active site of the enzyme
Induced fit model
How do enzymes work (using induced fit model)
the enzymes active site is flexible and can change shape to fit the substrate. Once the reaction takes place the end product is released and the enzyme returns to its previous shape.
What two theories must be taken into account when considering chemical reactions
- Particle theory
- Collision theory
Define particle theory
- Matter is made up of particles
- These particles are in constant motion
- Temperature affects the speed of particles
- With increase in temperature the speed of particles increases
Define collision theory
For successful chemical reaction to take place, the reactants must collide with sufficient force (energy) and at the correct orientation
Define activation energy
Minimum amount of energy required for chemical reaction to proceed
Factors affecting reaction rate (enzymes)
(4)
- Temperature
- pH
- Substrate concentration
- Enzyme inhibitors/toxins
Temperature and enzymes
- Enzymes have optimum temperature.
- Below this temperature they have less collision frequency.
- Above this temperature they denature
pH and enzymes
Enzymes also have an optimum pH. Outside of this range, the enzyme denatures.
Cofactor definition
a non-protein chemical that binds to enzymes to make the active site functional.
Competitive inhibitors
bind to the active site and stop the substrate from binding
Non-competitive inhibitors
bind outside the active site changing the enzyme’s shape so the substrate can’t bind
Inhibitors can act as poisons if….
they bind irreversibly
Enzyme structure
- what gives enzyme its specific shape
- What happens when enzyme denatures
- Hydrogen and disulphide bonds within the protein molecule give the protein its specific shape.
- When a protein denatures, the hydrogen and the disulphide bonds are broken.
How is hydrogen peroxide made? Why does it have to be removed? How is it removed? The chemical reaction…
- Hydrogen peroxide (H2O2) is a product of respiration and is made in all living cells.
- Hydrogen peroxide is harmful and must be removed as soon as it is produced in the cell.
- Cells make the enzyme catalase to remove hydrogen peroxide.
- 2H2O2 → 2H2O + O2
Respiration definition
- the process that occurs in the mitochondria of all living organisms, glucose is broken down to produce ATP
ATP is the energy molecule used by all organism to….
fuel chemical reactions within the cell.
Energy is needed by the organisms for….
- Active transport
- For chemical reactions in cells to produce molecules
- To carry out life processes
Where does respiration occur?
the cytoplasm (Glycolysis) and Mitochondria (Krebs cycle and electron transport chain.
Define Aerobic respiration
- Respiration in the presence of oxygen
- Oxygen is required to break down glucose into carbon dioxide and water. Energy is released in the form of ATP and heat
Aerobic respiration word equation
Glucose + oxygen → carbon dioxide + water + ATP + heat
Aerobic respiration symbol equation
C6H12O6 + 6O2 → 6CO2 + 6H2O + 36ATP + heat
Define Anaerobic respiration
- Respiration in the absence of oxygen
- Occurs in animals when there is shortage of oxygen
- Very little ATP is produced
Anaerobic word equation
Glucose → Lactic Acid + 2ATP
Name the order of the stages of aerobic respiration
Glycolysis, Transition/link stage, Kreb’s cycle, Electron Transport Chain.
Glycolysis (respiration)
occurs in the cytoplasm of the cells. Glucose is broken down into pyruvate; this stage does not require oxygen and produces 2 ATP molecules as well as hydrogen which move to the cristae.
Transition/Link stage (respiration)
pyruvate enters the matrix of the mitochondria; CO2 is removed, producing acetyl coenzyme A and more hydrogen which moves to the cristae.
Kreb’s Cycle (respiration)
occurs in the matrix. A series of reactions occur, producing CO2, and hydrogen and 2 ATP.
Meanwhile, the carriers molecules NADH and FADH2 have picked up hydrogens (and their electrons) taken from glucose during glycolysis and the krebs cycle and carry them to the electron transport chain (ETC)
Electron Transport Chain (respiration)
occurs on the cristae of the mitochondria. The hydrogens are passed along the electron transport chain, releasing energy which is captured as 34 ATP. Oxygen is required at this stage and water is produced. Each glucose molecule produces 36 ATP during aerobic respiration.
Anaerobic respiration
- if oxygen is absent….
(what phase will occur, how much ATP s produced, what happens…)
only glycolysis will occur, producing 2 ATP.
Very few organisms can obtain enough energy in the absence of oxygen.
If this occurs in muscle cells - lactic acid is produced, or in yeast (fermentation) ethanol and CO2 is produced.
Therefore, a build-up of toxic products
Where does Light dependent phase (LDP) of photosynthesis occur
in the lumen of the Thylakoid. (light reactions)
Light dependent phase (photosynthesis)
In the first phase the captured light splits water producing Oxygen and H+ ions (protons). Protons are transferred to the molecule NADPH. The protons move back through the membrane from the lumen to stroma and ADP is converted to ATP by ATP synthase enzyme
This phase happens in the thylakoid membranes of the grana
Where does Light Independent phase (photosynthesis) occur.
in the stroma of the chloroplast. (Calvin Cycle no light needed)
Light Independent phase
- ATP NADPH combine with RuBP (Ribulose bi-phosphate) Carbon Dioxide and are converted into G3P (2) by the enzyme RuBisCO.
- G3P (a 3 carbon sugar) is converted into glucose and also recycled back into the RuBP molecule.
Order of phases in Photosynthesis
- Light dependent phase
- Light independent phase
What is the order of stages in the cell cycle.
G1 phase, S phase, G2 Phase, Mitosis, and Cytokinesis
What happens in G1 phase of cell cycle
Growth phase where organelles duplicated (not chromosomes)
What happens in S phase of cell cycle
This is where DNA is replicated
What happens in G2 phase of cell cycle
Copied DNA is “spell” checked. More growth if needed, enzymes are made. Getting ready for dividing
What happens in Mitosis of cell cycle (simple)
Cell division (PMAT)
What happens in cytokinesis of cell cycle
cell splits into two cells
DNA Replication - occurs in a cell just before…
mitosis or meiosis. 1st step in cell cycle during interphase
What are the 5 steps of DNA replication
- The DNA molecule unwinds (topoisomerase) and ‘unzips’(helicase). Helicase breaks the hydrogen bonds linking the bases.
- Each opened up side of the DNA molecule acts as a pattern or template for assembling two new DNA strands.
- An enzyme (DNA polymerase) attaches new nucleotides to the unzipped DNA using the complementary base pairing (A pairs with T and G pairs with C).
- Two new DNA molecules are formed, each consisting of one old and one new strand.
- Finished strands are considered to be ‘semi-conservative’
Adenine pairs with…(DNA)
Thymine
Guanine pairs with…(DNA)
Cytosine
Mitosis definition
Cell division that occurs in all body cells and two new daughter cells are produced. Each new cell contains the same number of chromosomes that are present in the original cell, and are therefore identical to the parent cell.
What is the purpose of mitosis
to produce identical cells needed for growth, repair/replacement of cells and asexual reproduction.
What is the order of the phases of mitosis
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
Define Prophase
Chromosomes are already duplicated in S phase so 46 chromosomes
Define Anaphase
Duplicate chromosomes are pulled away from each other
Define Telophase
Two cells (actually two nucleus)
Define Metaphase
Chromosome line up in the middle of the cell
Define cytokinesis (mitosis)
Cytoplasm is split
DNA fits into the nucleus as it is…..
wrapped in packaging proteins called histones to form chromosomes.
Shade-adapted leaves are exposed to LOW intensity light, so….
leaf is thinner with a single layer of palisade cells
Sun-adapted leaves are exposed to HIGH intensity light so….
have thicker leaves with 2-3 palisade layers and can make glucose at a fast rate.
What is photosynthesis….
the process in which plants use sunlight to produce glucose for the plant.
Chloroplasts are….
large, oval organelles found in leaves, there are more in the palisade layer at top of leaf as there is more light here
Shade leaves tend to be….
larger and thinner (light only gets through a few layers and less energy to make less cells)
sun leaves are smaller and thicker as…
are longer and more palisade layers and sun penetrates leaf further.
Wax layers (of leaves)…..
prevent water loss as does having stomata on underside of leaf.
Palisade layer is near top of leaf to…
get more light.
Chlorophyll a:
This is the most abundant pigment in plants. Chlorophyll a absorbs light with wavelengths of (blue) and(red). It reflects green light strongly so it appears green to us.
Plants adapted to shade have the ability to use….
far-red light more effectively than plants adapted to full sunlight.
Shade plants grow broader…..
thinner leaves to catch more sunlight.
ONLY red and blue wavelengths of light are absorbed for…
photosynthesis, the rest is reflected, this is why leaves are green.
Photosynthesis equation (symbol):
6CO2 + 6H2O → C6H12O6 + 6O2.
What factors increase respiration rate?
- Increasing the OXYGEN concentration
- Having carbohydrates in your diet to break into glucose
- ENZYME at optimum temperature
- absence of Inhibitors
How does temperature affect the rate of respiration
As temperature increases the respiration rate will increase until the optimum temp. is reached.
how does the amount of oxygen available affect the rate of respiration
If there is more oxygen available then respiration rate will be higher because aerobic respiration will occur producing lots of ATP
How does cells demand for energy affect the rate of respiration
If there is higher demand for ATP,the respiration rate is higher.
How does the amount of glucose available affect the rate of respiration
The more glucose present, higher rate of respiration compared to less glucose availability.
Fermentation is an anaerobic process that….
passes electrons directly to the final electron acceptor
- Lactic acid is produced in mammals
Pyruvic Acid
pyruvic acid is when pyruvate dissociates in water to form a charged particle and a hydrogen ion.
Pyruvate….
is made from glucose in Glycolysis and is a reactant for Krebs cycle.
