Cells are the basis of life Flashcards
Revision
Name four features cells have in common
plasma membrane, cytoplasm, DNA and ribosomes
Compare prokaryote and eukaryote cells
- Prokaryote cells are smaller and eukaryote cells are larger
- Pro have no membrane-bound organelles and Euk have membrane-bound organelles AND linear chromosomes
What is an example of a prokaryote and eukaryote cell?
Pro = Monera (bacteria)
Euk = plants, animals, fungi
Which cellular compound is found within both Prokaryote and eukaryote cells?
Ribosomes
What makes up the Golgi body and what is the function?
Phospholid bilayer and stack of membrane bound sacs
site of packaging and storing of chemicals to be secreted
What would you look for to determine if a cell is prokaryotic or eukaryotic?
The presence of membrane-based organelles. if present then the cell is eukaryotic. Pro do not have membrane-bound organelles.
What would you look for to determine if a cell is from a plant or an animal?
The presence of a cellulose cell wall. If present, the cell is from a plant. Animal cells do not have a cell wall.
How do prokaryotes differ from plant cells?
- Plant cells have a cellulose cell wall and prokaryotes cell walls are made of peptidoglycan.
- Plant chromosomes are linear and prokaryotic chromosomes are circular.
- Plant cells contain membrane-bound organelles and prokaryote cells do not.
In eukaryotes, photosynthesis occurs in the chloroplast. Describe the structure of chloroplast.
Chloroplast are large membrane-bound organelles that can be seen with a light microscope.
The outer membrane has a series of folded membranes that form stacks called grana.
The grana are green as they contain chlorophyll.
The grana are the site of the light dependent reactions.
The spaces between the grana are called stroma and are the site of the light independent reactions.
In eukaryotes, aerobic respiration occurs in the mitochondrion. Describe the structure of mitochondrion.
Mitochondria are large membrane-bound organelles found in the cytoplasm.
They can be seen with a light microscope if stained but structural detail cab only be seen with an electron microscope.
Some scientists think that mitochondrion and chloroplasts were once free-living prokaryotes. What structural evidence supports this idea?
Mitochondrion and chloroplast are similar in structure to some current free-living bacteria because some think large bacteria ingested whole smaller bacteria and this lead to the evolution of the eukaryotic cells.
A DOUBLE MEMBRANE surrounds BOTH mito and chloro!
Both contain DNA and RNA!
List 6 functions of of membranes in general.
- Control of substances moving into and out of cells
- Compartmentalisation of internal cellular spaces - organelles
- Intercellular communication
- Cell-to-cell recognition
- Site of many cellular reactions
- Electrical activity in excitable cells.
Membranes are selectively (semi) permeable. What does this mean?
Selectively permeable means that some molecules can pass through the membrane while others cannot. Example:
In animal cells, lipid-soluble materials, hydrocarbons, and oxygen are examples of molecules the cell allows to pass through.
Describe the fluid mosaic model of the cell membrane (structure and function)
The fluid mosaic model describes the structure of the plasma membrane as a mosaic of components —including phospholipids, cholesterol, proteins, and carbohydrates—that gives the membrane a fluid character. Plasma membranes range from 5 to 10 nm in thickness
What are two major compounds found in membranes?
Phospholipids and proteins.
List four factors that increase the rate of diffusion?
- Concentration gradient. The greater the differene in concentration, the greater the rate.
- Temperature. The higher the temperature, the greater the rate.
- Size of molecule. The smaller the molecules, the great the rate.
- State. Diffusion occurs faster through a gas than through a liquid.
What is meant by diffusion gradient?
Diffusion gradient is the difference in concentration of a substance from one to another. The greater the difference, the greater the diffusion gradient.
What is osmosis?
Osmosis is the passive movement of water molecules across a semi-permeable membrane from an area of low solute concentration to an area of high solute concentration.
It occurs to maintain equilibrium in cells and is a vital process for survival.
Explain why an animal cell placed in distilled water will burst but a plant cell placed in distilled water will not?
Water moves into cells by osmosis and the cell swells. A plant cells has a cell-wall and exerts a pressure that stops the plant from exploding. Animals cells do not have a cell wall so they explode.
What is diffusion?
Diffusion is the movement of particles from a region of high concentration to a region of low concentration until equilibrium is reached.
Compare the processes: diffusion, osmosis, active transport and vesicle mediated transport.
Diffusion and osmosis are passive and move molecules from high to low concentration without energy. Diffusion moves small molecules like oxygen. Osmosis moves water across a semi-permeable membrane.
Active transport requires energy (ATP) to move substances against the concentration gradient (low to high), such as ions in the sodium-potassium pump.
Vesicle-mediated transport (endocytosis and exocytosis) also uses energy to move large molecules via vesicles, like white blood cells engulfing bacteria or nerve cells releasing neurotransmitters.
Explain the movement of bulk materials
(endocytosis, phagocytosis, pinocytosis and exocytosis)
Endocytosis moves large molecules that cannot cross the cell membrane and requires the expenditure of energy.
Phagocytosis is the process where a SOLID particle is engulfed by the cell membrane.
Pinocytosis is the engulfing of FLUID substances by the cell membrane.
Exocytosis involves the RELEASE of a membrane -bound vesicle to the exterior of the cell
What are the four main groups of biomacromolecules?
Carbohydrates, proteins, lipids and nucleic acids.
What is meant by SA:V of a cell? And how is SA:V of a cell related to the size of a cell?
SA:V is the measure of the area of a cell surface compared with the volume of its contents.
Cells must have obtain requirements and remove wastes at a rate that allows the chemical reaction for life to occur.
The size of a cell will determine how fast diffusion occurs. If a cell is too large the rate of diffusion will be too slow to maintain supply and removal of wastes.
Why do cells tend to microscopic?
So they have a large SA:V ratio to allow for efficient moveetn of materials in and out of cell.
This includes nutrients such as glucose, oxygen and removal of wastes such as carbon dioxide.
What features do cells exhibit to increase their sa:v?
Cells that flatten themselves or have long extensions and irregular surfaces will have a greater SA:v
What is meant by the term organic molecule?
A complex containing molecule produced by living organism, They usually contain hydrogen and oxygen.
What is energy and why is it important to all living organisms?
Energy is the potential to work and this is the chemical reaction and the result of chemical reaction that occurs in cells. e.g energy is needed to do the work of synthesising new materials in cells and allwoing contraction in muscles.
Write a balance equation for photosynthesis.
List the factors that effect the rate of photosyntehsis.
- Amount of light
- frequency of light
- presence of chlorophyll
- presence of water
- presence of carbon dioxide
- temperature
Write a balanced chemical equation for aerobic respiration.
What is the immediate source of energy for a cell and how is this energy released?
The energy stored in the bonds of ATP is the immediate source of energy for cells.
What does the energy released from cellular respiration allow the cell to do?
The energy released allows the cell to grow, divide, repair, move, synthesis new molecules, active transport, signal and maintain cell structure.
In aerobic respiration the energy transfer from glucose to ATP is not 100% efficient. What other form of energy is produced?
Heat is released and lost to surroundings.
List the factors that affect the rate of cellular respiration.
- presence of oxygen
- presence of glucose.
- temperature.
What are the differences between aerobic respiration and anaerobic respiration?
Aerobic respiration has different reactants - oxygen is produced whereas in anaerobic respiration oxygen is not present.
The products produced are also different. In Aerobic respiration glucose is broken down to carbon dioxide in small molecules whereas in anaerobic respiration lactic acid/alcohol are produced in large molecules.
What are enzymes?
enzymes are proteins found in cells are are responsible for speeding up chemical reactions in organisms.
e.g when cells are breaking down glucose for energy, the molecule might take years to break down of its own accord, so to speed it up the breaking down of chemicals we have enzymes allowing glucose digestion to happen in a matter of seconds and a quick release of energy for cells to use.
Why are enzymes sometimes call organic catalysts?
Catalysts speed up the chemical reactions as do enzymes. Enzymes are organic as they are proteins that are produced by living organisms.
Why are enzymes so important to living organsims?
Without enzymes the chemical reactions occurring inside cells would occur too slowly to sustain life. Names of enzymes usually end in ‘ase’.
Enzyme are proteins.
What is the chemical structure of enzymes?
What is the lock and key model theory about hoe enzymes and subtrates interact to catalyse reactions?
What is the induced fit model? it elaborates on the lock and key model. The active site changes shape to accommodate the substrate and to bind.
In order to maintain life, cells require fundamental molecules. A energy source and a carbon source.
What is the difference between an autotroph and a heterotroph?
Autotroph are organisms able to produce their own food from their surroundings, using photosynthesis or chemosynthesis. e.g. plant using sunlight
Heterotrophs are not able to synthesis their own food so must rely on the consumption of other organisms for nutrition. e.g humans consume plants to obtain carbohydrates, proteins and nutrients.
Explain the effect of temperature on the rate of photosynthesis
Photosynthesis is controlled by enzymes, which are biological catalysts that speed up chemical reactions.
Temperature’s Role:
Low Temperatures: the rate of photosynthesis is limited because enzyme activity is slow. Enzymes require a certain level of kinetic energy (movement) to function effectively, and low temperatures reduce this movement.
Optimal Temperatures: As temperature increases, the rate of photosynthesis also increases because enzymes are more active and collide more frequently with their substrates (the molecules they act upon).
High Temperatures: if the temperature exceeds the enzyme’s optimal range, the enzymes begin to denature (lose their shape and function). This denaturation reduces the rate of photosynthesis, and at very high temperatures, the process can stop entirely.
explain the difference between a light and fluorescence and electron microscopy
Light microscopy is the passing of visible light through a sample. Staining methods can be used to enhance the appearance of cell structures.
Fluorescence detect fluoresence and phosphorescence
Electron uses a bean of electrons to illumiate objects and can see objects on a much smaller scale and provides more detail - so can see structures within cells which might be difficult to see under light microsope.
compare the structure and function of chloroplasts and mitochondria in plant cells
In plant cells, mitochondria and chloroplasts, while both involved in energy production, differ significantly: mitochondria generate ATP through cellular respiration, while chloroplasts are the sites of photosynthesis, converting light energy into chemical energy (sugars).
Controlled and independent and dependent variables
Controlled variables are the factors in an experiment that are kept constant throughout to ensure that the results are reliable and not influenced by other variables. By controlling these factors, you can isolate the effect of the independent variable on the dependent variable.
chlamydomonas reinhardtii and label it
explain abiotic factors and change
Abiotic factors are non-living components of an ecosystem that influence living organisms, including temperature, oxygen, pH, and sunlight, which are essential for life and can change significantly, impacting ecosystems and species.
