Module 1: Cells as the basis of life Flashcards
What does the cell theory state?
- Cells are the basic unit of life
- All life is made of cells
- All cells are made from pre-existing cells
- All cells maintain homeostasis (what is homeostasis?)
All cells have:
- a cell membrane
- cytoplasm:
- genetic material (usually DNA)
- genes:
- ribosomes:
- proteins
How do ribosomes and genetic material contribute to cells making proteins?
The genetic material (usually DNA) provides instructions for cellular activity. The genes send instructions to ribosomes where the ribosomes use the genes code to make the various proteins that are required for the organism to function .
What is the difference between prokaryotic and eukaryotic cells?
Eukaryotic cells contain membrane-bound organelles, such as the nucleus, while prokaryotic cells do not. These organelles have specialised roles go help the cells function.
Prokaryotes are small ( 0.1-5.0 amu) where as eukaryotic cells are large (10-100 amu)
Prokaryotes can be unicellular. Eukaryotes can be multi and uni.
Pro are less complex, Eu are more complex.
components of prokaryotic cells:
pro=no=no nucleus
- no membrane bound organelles
- dna found within the cytoplasm
- unicellular
- very small (0.1-5.0 um)
- less complex
- Large surface area
- Genetic material is stored in a singular DNA chromosome, which is contained in the nucleoid .
- This is attached to cell membrane by the origin of the chromosome.
- The cell membrane is surrounded by the cell wall.
- bacteria have a capsule outside the cell wall
- They can move around using the flagellum
- The pili also helps transfer DNA between organisms and for movement
- bacteria and archaea
what are the 6 kingdoms
bacteria and archaea (Prokaryotes)
Prostita, Funghi, Plantae and Animalia (Eukaryotes)
components of eukaryotic cells
Eu-=do have a nucleus
- Much larger and more complex than prokaryotes.
- They are unicellular and multicellular
- have membrane bound organelles.
- Divided into four kingdoms: prostita, funghi, plantae and animalia
- 10-100um
- developed from prokaryotic cells (endosymbiosis)
What is the theory of evolution of eukaryotic cells called
endosymbiosis
Plant cells
have cell walls to provide structure and support.
-Large vacuole
Plant cells have chloroplasts which are the site of photosynthesis.
-flagella only in gametes
animal cells
- no cell wall
- Small or no vacuole
- no chloroplasts
- flagella
Define organelle:
An organelle is a tiny cellular structure that performs specific functions within a cell.
Nucleus
plant and animal ?
holds DNA, coordinates growth,protein synthesis and reproduction
animal and plant
Mitochondria
plant and animal ?
produces the cells energy through respiration (power plant)
animal and plant
Chloroplasts:
plant and animal ?
plant
contain chlorophyll, which enables photosynthesis
Rough endoplasmic reticulum:
plant and animal ?
plant and animal
covered in ribosomes/ assists in transport of proteins after production
Smooth endoplasmic reticulum:
plant and animal ?
plant and animal function depends on cell: can produce lipids and steroid hormones
golgi body
plant and animal ?
plant and animal
stack of membrane bound vesicles that package proteins and molecules for transport
lysosomes
plant and animal ?
contains enzymes to aid digestion/ immune responses to destroy foreign bodies
plant and animal
Vacuole
plant and animal ?
stores nutrients and wastes
in plant cells collect water to provide rigidity
plant and animal
Cell wall:
plant and animal ?
plant cells
provides and maintains the shape of cells/ serves as protective barrier
Cell membrane:
plant and animal ?
plant and animal
protect the cell from its surroundings
ribosomes
plant and animal ?
make proteins- repairing damage or directing chemical processes
plant and animal
centriole:
plant and animal ?
plant and animal
help with cell division in animal cells
rare in plant cells
plastid
plant and animal ?
Synthesises and stores inorganic molecules
plant cells
flagellum
plant and animal ?
plant and animal
Helps with movement of substances across cell surfaces
What is a light microscope
A beam of light passes through the thin specimen on a slide. Produces images up to 1500X magnification (size) Maximum resolution of 200 nm (clarity)
how is a light microscope useful
Light microscopes are used to study living cells and for regular use when relatively low magnification and resolution is enough.
What is a Sem
Structures beyond the limit of resolution of the light microscope can be viewed. Sample to be viewed is labeled with fluorescent substances that will attach to the structures that the scientist wants to observe. The sample is illuminated with high-intensity light that causes the fluorescent substance to emit light.
how is a sem useful
It provides detailed images of the surfaces of cells (3D) and whole organisms that are not possible by TEM. It can also be used for particle counting and size determination, and for process control.
what is a tem
Uses an electron beam instead of light (photons) and gives a much greater magnification and resolution than light microscopes.
how is a tem useful
The transmission electron microscope is used to view thin specimens (tissue sections, molecules, etc) through which electrons can pass generating a projection image. (2d)
how can light microscopes observations be imporved?
digital image manipulation
tagging structures with fluorescent dyes
enhancing contrast using phase-contrast
Define permeability:
(a measure of the ability of a substance to pass through the membrane)
What affects permeability?
a) Size
b) electrical charge
c) lipid solubility
Small molecules and membrane:
Small molecules move across membranes fast.
Water-soluble (hydrophilic) molecules and membrane:
Water-soluble (hydrophilic) molecules have difficulty penetrating a membrane.
Lipid-soluble molecules and membrane:
Lipid-soluble molecules do not have trouble penetrating the membrane ; for example, urea and ethanol have high permeability.
Electrically charged molecule and membrane:
Electrically-charged molecules are not very soluble in lipids and therefore have low membrane permeability
Neutral molecules and membrane:
Neutral molecules (e.g. gases such as carbon dioxide and oxygen) have a high permeability.
Water molecules and mebrane:
Although water is a charged molecule, membranes are highly permeable to it. Water moves through special tiny hydrophilic pores in the membrane by the process of osmosis.
What do low permeability molecules need?
Molecules that have low permeability rely on carrier proteins to transport them across membrane in cells. This is known as active transport.
What is active transport?
the movement of ions or molecules across a cell membrane into a region of higher concentration, assisted by enzymes and requiring energy.
define endosymbiosis
a phenomenon whereby a single-celled organism resides within another cell as part of a mutually beneficial relationship
how do you calculate magnification?
The ocular lens is 10X magnification, so if the objective lens is 40X the total
magnification = 10*40 = 400X
what is passive transport?
Passive transport describes the movement of particles from an area where they are in high concentration to an area where they are in low concentration. It does not require energy
what are two examples of passive transport?
diffusion and osmosis
what is osmosis?
Osmosis is the movement of water across a semi-permeable membrane
what is diffussion?
is the movement of any molecules along a concentration gradient,
such as when a drop of food dye is placed water
what is the energy unit of all living organisms?
ATP Adenosine Triphosphate (ATP)
function of the cell membrane
cell membrane serves to protect the cell from undesirable external conditions and
controls the movement of substances into and out of the cell (including wastes). The cell membrane must also be flexible to allow the cell to contract and expand as the
cell’s contents change.
structure of the cell mebrane
The basicchemical unit is a “phospholipid” molecule; a lipid (fat) with phosphate groups attached. Each molecule has two distinct ends; one which is
attracted to water molecules (“hydrophilic”) and the other is repelled by water (“hydrophobic”).
which end is hydrophillic
“to like”
heads
which end is hydrophobic
‘hate/fear”
tails
phospholipid structure detailed
Two layers of phospholipids form each membrane. The molecules cling to each other, and line up with their hydrophilic ends outwards. The water-loving ends are attracted to the watery environment both inside
and outside the cell.The hydrophobic ends are repelled from the watery surroundings, and cling together inside the membrane itself.
what molecules are also embedded in the phospholipid bilayer?
mostly proteins- with carbohydrates attached
what functions do the molecules also embedded in the phospholipid bilayer have ?
“receptors” for messenger chemicals.
• identification markers, so your body knows its own cells from any
foreign invaders.
• to help chemicals get through the membrane.
why is it referred to as the fluid mosaic model?
a liquid structure and the different molecules embedded
within it are like the different shapes & colours in a “mosaic” tile
pattern.
what is simple diffussion?
simple diffusion refers to the process of movement of particles across a semipermeable membrane naturally.
factors that affect simple diffusion
・ Concentration (the greater the gradient, the faster the diffusion)
・ Temperature (the higher the temperature, the faster the diffusion)
・ Particle size (the smaller the particle size, the faster the diffusion)
what is faccilitated diffusion?
The protein channels in the cell membrane allow for the movement of particles. The process occurs when particles move down the concentration gradient.
Ø Transport proteins are more specific about what particles are transported
Ø Transport is more rapid than simple diffusion
Ø Transport proteins can become saturated as the concentration increases
what are channel proteins?
Channel proteins are found in membranes and are specific for substances. They do not bind with the molecules and open and close to allow specific molecules to be transported.
what are carrier proteins?
Carrier proteins bind the molecules being transported.
the importance of diffusion in everyday life:
1 In all living things, diffusion is used in transporting lipids waste products and other substances in and out of cells.
2. In a living cell, when oxygen is used up in respiration, the oxygen level is lowered.
The concentration of oxygen becomes lower than the surrounding (outside the cell) so oxygen will diffuse into the cell through the cell membrane.
3. When living cells produce carbon dioxide as a waste product, the surrounding concentration is lowered and so the carbon dioxide will diffuse out of the cell into the surroundings.
4. When cells in green leaves photosynthesis, they use up carbon dioxide and produce oxygen.
what is osmosis?
Movement of water into a cell occurs when there is a higher concentration of water molecules on the outside of the cell than inside the cell.
what decides how water is diffused in osmosis?
If it is dry outside the cell, water will diffuse out.
Water molecules will also diffuse into a cell if there is a high concentration of chemicals inside it compared to the outside.
If there is a greater concentration of solutes outside the cell, water will move out through the membrane.
what membrane does osmosis occur through?
How long will the water enter the cell for?
This process occurs through a semipermeable membrane. Cell membranes are permeable to water. Water will continue to enter the cell until the osmotic gradient is equal.
define isotonic solution
equal concentrations of solutes
will remain the same
define hypertonic solutions
have a higher concentration of solute
will shrink in size
define hypotonic solutions
have a lower concentration of solute
will grow in size
blood cells and osmosis
When red blood cells are in a hypertonic (higher concentration) solution, water flows out of the cell faster than it comes in. This results in crenation (shriveling) of the blood cell. On the other extreme, a red blood cell that is hypotonic (lower concentration outside the cell) will result in more water flowing into the cell than out. This results in swelling of the cell and potential hemolysis (bursting) of the cell. In an isotonic solution, the flow of water in and out of the cell is happening at the same rate.
what is crenation?
A process resulting from osmosis in which red blood cells, in a hypertonic solution, undergo shrinkage and acquire a notched or scalloped surface.
what is hemolysis?
bursting of the blood cell
what is endocytosis?
The cells take in materials in bulk by forming new vesicles from the cell membrane. Materials near the cell membrane are enclosed by the membrane, which then forms a vesicle. The vesicle transports the substance to its required location in the cell.
what is exocytosis?
The secretory vesicle membrane and cell membrane touch, some proteins alter the arrangement of the phospholipids. The membranes fuse, and the contents of the secretory vesicle are released from the cell/ The vesicle membrane becomes a permanent part of the cell membrane.
what does exocytosis secrete?
Exocytosis secretes protein, as well as cellular water and the breakdown of products from lysosomes.
size and cells:
Ø As the size increases, the surface area to volume ratio decreases.
Ø Smaller cells can exchange matter more efficiently.
How does the surface area to volume ratio affect a cell?
The surface area of the cell membrane affects the rate of exchange between the cell and its environment. Larger cells have greater metabolic needs, so need to exchange more materials.
how do cells create a larger surface area to volume ratio of a cell
Cell compartmentalisation allows organelles to have the right conditions and concentrations of enzymes and reactants. It reduces the amount of exchange that needs to occur across the membrane. It creates more space for membrane bound enzymes, which increases cell activity.
Cell membrane extensions occur in cells that are involved in absorbing nutrients or secreting wastes. By extending the membrane, it counteracts the surface area to volume problems these cells have.
A flattened shape will keep the volume constant, which allows for a larger surface area. It also reduces the distance that substances need to be transported to and from the membrane.
raw materials and surface area to volume ratio:
The greater the surface area the larger the amount of raw material that can enter at only one time.
BUT each unit of volume requires a specific amount of surface area to supply its metabolize with raw materials (all the way to the middle of the cell, the nucleus).
If a cell’s volume is too large the organelles in the center are too far away for diffusion of nutrients to effectively occur.
define autotroph:
Autotrophs (self-feeders) make their own organic compounds from inorganic compounds found in soil and atmosphere. This process is called carbon fixation. They are known as producers and include plants that carry out photosynthesis.
define heterotroph:
Heterotrophs (other-feeders) gain organic compounds by consuming other organisms. They are known as consumers and include animals and fungi.
cell requirements matter:
The elements found on Earth are found in all types of cells, both living and nonliving. These atoms are organised into larger compounds in living things.
inorganic compunds:
oxygen
water
nitrogen
carbon dioxide
inorganic coumpound: water
Water (H2O) is a solvent and transport medium. Chemical reactions in cells take place in a water-based fluid (cytosol).
inorganic coumpund: oxygen
Oxygen (O2) is needed for energy and is achieved through cellular respiration. Terrestrial organisms take it in by gas, and aquatic organisms take it in solution.
inorganic compound: carbon dioxide
Carbon dioxide (CO2) is the best source of carbon atoms for organic molecules. It is taken into plant leaves in gas, is converted into sugars and returns to the atmosphere (photosynthesis).
inorganic compound: nitrogen
Nitrogen (N) is part of amino acids that link to form protein molecules. Consumers get their Nitrogen from plants that are added to the soil from the N2(g) in the air.
examples of enzymes and vitamins built by minerals
Calcium (bones and teeth)
・ Sodium and Potassium (nervous system)
・ Magnesium (muscle function)
・ Iron (haemoglobin production)
e.g.’s of organic compounds:
lipids
carbohydrates
proteins
Nucleic acids
organic compounds: Nucleic acids
Nucleic acids carry genetic information. The two types are DNA and RNA, which are made of long chains of nucleotides, sugars and phosphates.
・ DNA carries information required to assemble proteins from amino acids
・ RNA helps with the manufacturing of proteins in the cells
organic compounds: lipids
Lipids are important in cell membranes. They are good for energy storage and help maintain structure of the membrane.
organic compounds: proteins
Proteins are composed of amino acids. They have many functions including enzymes, hormones, antibodies or carrier molecules (haemoglobin). Proteins are a part of the cell membrane.
organic compounds: carbohydrates
Carbohydrates are important for energy and structure of organisms. Glucose Sucrose Starch Cellulose
removal of wastes:
Autotrophs and heterotrophs have waste products from their metabolisms which are not useful which are known as excretion.
→ Carbon dioxide from cellular respiration
→ Nitrogenous wastes from the breakdown of proteins and nucleic acids
Passive involves osmosis and diffusion. Active is when toxins and ions are being removed against their concentration gradient (endocytosis and exocytosis).
photosynthesis worded equation
Carbon dioxide + water = glucose + Oxygen
what is photosynthesis?
When plants have light, water (H2O) and Carbon dioxide (CO2) and together make glucose (C6H12O6) produced in their green tissues, usually leaves. They trap the energy from the sun and convert it into chemical energy, which is stored in the bonds between the glucose molecules.
two main roles of photosynthesis:
Firstly it is the reaction which transforms radiant heat from the sun into chemical energy in organisms.
Autotrophs therefore begin food chains where energy is passed from one trophic level to the next trophic level.
Secondly photosynthesis releases gaseous oxygen and removes carbon dioxide from the atmosphere.
chloroplasts and photosynthesis:
They are the site of photosynthesis. This is where the light energy is converted into food (glucose) and Oxygen is released. The leaves, and sometimes stems, are green because of the chlorophyll pigment. Chlorophyll absorbs the light energy. In vascular plants. Chloroplasts are found in the mesophyll, which is at the upper surface of the leaf, meaning more sun exposure. This increases the rate of photosynthesis.
Inside each chloroplast are flattened membranes, called grana. The grana holds the thylakoids, where chlorophyll is made.
STAGE 1: LIGHT DEPENDANT REACTIONS
Chlorophyll captures solar energy and uses it to produce ATP. Water is then split into Hydrogen ions and Oxygen gas. These reactions take place in the grana, where chlorophyll is located.
Water = Hydrogen ions + Oxygen + ATP
Note: = light and chlorophyll
STAGE 2: LIGHT INDEPENDENT REACTIONS
They produce glucose, water and ADP. These reactions do not require solar energy. ATP from stage 1 provides the energy for stage 2. This energy allows Carbon dioxide and Hydrogen ions to form glucose and water. These reactions take place in the stroma.
Glucose + Water + ADP = Hydrogen ions + ATP + Carbon dioxide
what are the factors that affect photosynthesis?
Light intensity: when there is a little light, the light dependant reactions cannot occur
- Carbon dioxide concentration: when there is little Carbon dioxide, photosynthesis cannot occur
- Temperature: all reactions are catalysed by enzymes, and if temperatures become too extreme, the enzymes could denature and therefore photosynthesis could not take place
what is cellular respiration?
Cellular respiration is a chemical reaction that occurs in living cells. It uses glucose and oxygen to produce unstable energy, with Carbon dioxide as a waste.
what is ATP?
ATP is the immediate source of energy for cells. The unstable energy of ATP is contained in the phosphate bonds. The cycling of ATP and ADP means energy is always available.
The breakdown of glucose molecules results in three products:
・ Carbon dioxide
・ Water
・ Energy
how does cellular respiration work?
The first main stage is glycolysis. This is when the glucose molecules split into two parts and do not require oxygen.
The second main stage is aerobic respiration (Oxygen is present) or anaerobic respiration (if Oxygen is absent). In a living cell, anaerobic respiration occurs if there’s insufficient Oxygen, but aerobic happens all the time.
what is an enzyme?
Enzymes are known as catalysts of chemical reactions – they allow reactions to speed up and to take place with less energy. Many reactions would not take place without them .
· Enzymes are proteins that are rounded in shape.
· Enzymes are very important to cells because they help molecules to form, to breakdown, or to exchange parts
what is active site?
A chemical reaction takes place at the active site and the more complex molecule (substrate) is broken down into two simpler forms (products).
what is a substrate?
a more complex molecule
where does a chemical reaction take place (enzymes)?
This takes place either inside the cell (intracellular enzyme i.e. respiration and photosynthesis) or outside the cell (extracellular enzyme i.e. the digestive enzymes)
what occurs in an enzyme chemical reaction?
The substrates bind to the active site where a chemical reaction takes place. The two less complex molecules are metabolized into a more complex molecule to be used within our bodies. The substrates are the reactants of the chemical reaction.
lock and key:
Substrate and enzyme work like a lock and key.
first model
induced fit model:
But if the substrates don’t fit sometimes the enzyme can slightly alter its shape to accommodate the substrate. This is known as induced fit.
denature definition:
that is their shape is destroyed beyond repair and hence the substrate won’t bin
what is a cofactor?
Inorganic cofactors are generally inorganic ions, whereas coenzymes are small, non-protein molecules, often used to carry substances to and from reactions. Coenzymes are particularly important in terms of metabolic pathways.
cofactors activate some enzymes
effect of temperature on enzyme activity
as temperature increases, kinetic energy increases and there will be more collisions, which increases activity. However, above optimum temperature the enzyme denatures.
effect of PH on enzyme activity:
There are some enzymes that can work at very acidic or basic pH - but their activity will decrease as they get further away from their optimal pH. The pH affects the enzyme by causing changes to the bonds that give the enzyme its 3D tertiary structure.
These are bonds such as ionic, disulphide and hydrogen bonds. As the pH moves away from the optimal pH, either becoming more acidic (lower pH) or more basic (higher pH), the bonds start to become disrupted and the shape of the enzyme changes. The enzyme is denatured.
enzymes in the stomach optimum PH:
2
effect on concentration on enzyme activity:
Increasing substrate concentration also increases the rate of reaction to a certain point. Once all of the enzymes have bound, any substrate increase will have no effect on the rate of reaction, as the available enzymes will be saturated and working at their maximum rate.
Increasing Substrate Concentration increases the rate of reaction. This is because more substrate molecules will be colliding with enzyme molecules, so more products will be formed.
However, after a certain concentration, any increase will have no effect on the rate of reaction, since Substrate Concentration will no longer be the limiting factor. The enzymes will effectively become saturated, and will be working at their maximum possible rate.
kidney nephrons function
- Excretion – elimination of harmful and unwanted products of metabolism
- Osmoregulation – control of body water and salt levels
