Cells as the basis of life Flashcards
What are cells?
The structural unit of living things. The basic functional unit of life.
What classifies a living thing?
Complex and have an organised structure.
Take energy from their surroundings and use it.
Have an internal composition that is chemically different from the external environment.
Respond to stimuli.
Reproduce themselves.
Grow and develop.
(The cell is the smallest unit that fits all these criteria).
What is the fluid mosaic model?
A model that proposes the cell membrane is a fluid mosaic composed of a phospholipid bilayer with protein molecules embedded.
What does the cell membrane do?
Separates the intracellular environment from the extracellular environment. It ensures the intracellular environment remain chemically different from the extracellular environment.
Regulates the passage of substances into and out of the cell.
Enables cells to recognise one another and certain ligands.
Enables the attachment of the cytoskeleton.
What is the main structural component of the cell membrane?
The phospholipid bilayer.
Describe the structure of a phospholipid.
A phospholipid has a hydrophilic (water-loving) head and two hydrophobic (water-fearing) tails.
Why is the cell membrane a fluid?
The phospholipids are constantly moving.
Why is the cell membrane a mosaic?
There are proteins embedded.
What are the two major types of cells?
Prokaryotic and eukaryotic cells.
Do prokaryotic cells have membrane-bound organelles?
No, prokaryotic cells lack membrane-bound organelles.
How is the DNA structured in prokaryotic cells?
It is typically a single, circular chromosome that floats freely in the cytoplasm.
Sometimes in rings called plasmids.
Where are chromosomes located in eukaryotic cells?
Enclosed within the nucleus.
What do prokaryotic and eukaryotic cells have in common?
Both have DNA, ribosomes, and a cell membrane.
What is a prokaryotic cell contained in?
A plasma membrane, usually surrounded by a cell wall. The cell wall often has short pili projecting from them and sometimes longer flagella.
What organisms are eukaryotic?
Protists, plants, animals and fungi.
Nucleus structure?
A double-membraned organelle that contains nuclear pores and the cell’s DNA.
Nucleus function?
Acts as the control center of the cell, storing genetic material and directing cellular activities.
Nucleolus function?
Produces ribosomes by synthesising ribosomal RNA (rRNA) and assembling ribosome subunits.
Mitochondrion structure?
Bean-shaped with a double membrane; the inner membrane is folded into cristae.
Mitochondrion function?
Generates ATP through cellular respiration, supplying energy for cellular processes.
Chloroplasts structure?
Double-membraned with internal stacks of thylakoids, containing chlorophyll.
Chloroplasts function?
Conducts photosynthesis, converting sunlight, water, and carbon dioxide into glucose and oxygen.
Golgi Body structure?
A stack of flattened, membrane-bound sacs.
Golgi Body function?
Modifies, sorts, and packages proteins and lipids for transport within vesicles to various destinations in or outside the cell.
Rough endoplasmic reticulum structure?
Network of membranes studded with ribosomes.
Rough endoplasmic reticulum function?
Synthesizes and processes proteins for secretion or for use in the cell membrane.
Smooth endoplasmic reticulum structure?
Network of membranes without ribosomes.
Smooth endoplasmic reticulum function?
Synthesizes lipids, detoxifies toxins, and stores calcium ions.
Ribosome structure?
Made of rRNA and proteins, found free-floating in the cytoplasm or attached to rough ER.
Ribosome function?
Synthesizes proteins by translating messenger RNA (mRNA).
Lysosome structure?
Membrane-bound vesicle filled with enzymes.
Lysosome function?
Breaks down waste materials, cellular debris, and damaged organelles.
Cytoskeleton structure?
A network of protein filaments (microfilaments, intermediate filaments, and microtubules).
Cytoskeleton function?
Provides structural support, enables cell movement, and aids in cell division and transport within the cell, gives cells their shape, holds organelles in place.
What is the main difference in vacuole structure between plant and animal cells?
Plant cells have a large central vacuole for turgor pressure, while animal cells have small or absent vacuoles.
Do fungal cells have a cell wall, and what is it made of?
Yes, fungal cells have a cell wall made of chitin, providing structure and protection.
What shapes are typical for plant, animal, and fungal cells?
Plant cells are usually rectangular, animal cells are often round, and fungal cells are often tubular or thread-like in structure.
Nucleolus structure?
A dense spherical structure within the nucleus, rich in RNA and proteins.
Vacuole (plants) structure?
A fluid filled space bound by a membrane.
Vacuole (plants) function?
Store organic compounds, inorganic molecules, metabolic wastes. Involved in growth of the cell, as it absorbs water.
What is phagocytosis?
When a cell engulfs a particle.
Vacuole (fungi) function?
Storage site, contain enzymes that breakdown compounds.
Endoplasmic reticulum function?
Transport of materials around the cell.
What is exocytosis?
Exocytosis is the process by which cells release large molecules, like proteins or waste, to the extracellular environment. A vesicle carries the material to the cell membrane, fuses with it, and then opens up to release the contents.
How is energy obtained?
From the environment in physical or chemical form.
What is an autotroph?
Self feeding.
What is a heterotroph?
Gain their chemical energy from another source.
What is photosynthesis?
Autotrophs, particularly plants, convert light energy from the sun into chemical energy stored in glucose.
Autotroph definition?
Organisms that can produce their own food using light energy or chemical energy from inorganic substances.
Heterotroph definition?
Organisms that cannot produce their own food and must obtain energy by consuming other organisms or organic matter.
Why is photosynthesis important to the earth?
It not only provides energy in the form of glucose for autotrophs but also produces oxygen, which is essential for the survival of most living organisms, including heterotrophs.
Why does the breakdown of glucose in the presence of oxygen release energy?
The amount of energy required to break the chemical bonds in the reactants (glucose and oxygen) is less than the energy released when the bonds in the products (carbon dioxide and water) are formed.
What is Adenosine Triphosphate?
A molecule that serves as the main energy carrier in cells. It provides energy for various biological processes.
How is ATP converted to ADP and inorganic phosphate (Pi)?
The bond between the third phosphate group and the rest of the ATP molecule is hydrolised (broken down with water) to form ADP + Pi. This reaction releases energy.
What is aerobic respiration?
The process by which both autotrophs and heterotrophs convert glucose into usable energy in the form of ATP, using oxygen.
What are the reactants in aerobic respiration?
Glucose and oxygen.
What are the products in aerobic respiration?
Carbon dioxide, water, and ATP.
How much ATP is produced in aerobic respiration?
Around 36-38 ATP molecules per glucose molecule.
Where does aerobic respiration occur in eukaryotes?
Cytoplasm and mitochondria.
What is fermentation (anaerobic respiration)?
An alternative energy-producing process that occurs without oxygen (anaerobic). This process generates energy less efficiently than aerobic respiration and is used by cells when oxygen is scarce.
How much ATP is produced in anaerobic respiration?
Only 2 ATP molecules per glucose molecule.
What are the products of anaerobic respiration (alcoholic fermentation) in plants and yeasts?
Ethanol (alcohol), carbon dioxide, and ATP.
What are the products of anaerobic respiration (lactic acid fermentation) in animals?
Lactic acid and ATP.
What are the main inputs of autotrophs?
Carbon dioxide (CO₂), water (H₂O), minerals and ions, and sunlight (for photoautotrophs).
What are the main outputs of autotrophs?
Oxygen (O₂) and glucose (C₆H₁₂O₆), with some recycling of nutrients.
What are the main inputs of heterotrophs?
Oxygen (O₂), organic molecules (food), water (H₂O), and minerals and ions.
What are the main outputs of heterotrophs?
Carbon dioxide (CO₂), water (H₂O), nitrogenous waste (e.g., urea), and other waste products.
What are inputs?
Inputs are the materials and substances that cells or organisms take in from their environment to carry out life processes.
What are outputs?
Outputs are the substances that cells or organisms release or excrete after processing inputs through metabolic activities.
What is the role of internal membranes in mitochondria?
Internal membranes, specifically cristae, increase surface area for the electron transport chain and ATP synthase, facilitating aerobic respiration.
What are metabolic pathways?
Series of biochemical reactions that convert substrates into products, involving multiple regulated steps.
What is the significance of specific enzymes in metabolic pathways?
Specific enzymes are required for each step, acting as catalysts to speed up reactions and ensure efficient metabolism.
How do environmental factors influence biochemical processes?
Factors like temperature, pH, and substrate concentration affect enzyme activity and can slow down or inhibit metabolic reactions, impacting cellular survival.
What is glycolysis?
A metabolic pathway that breaks down glucose to produce energy in cells.
Why does metabolism occur in steps?
Large steps produce unfavourable conditions - heat, acidity.
Small regulated steps release small quantities of energy that can be stored in ATP molecules.
Many regulated steps produce intermediate compounds that can be used as starting points for other reactions.
Each regulated step is catalysed by a specific enzyme.
How do thylakoid membranes in chloroplasts contribute to photosynthesis?
Thylakoid membranes house chlorophyll and other pigments for capturing light energy, crucial for the light-dependent reactions of photosynthesis.
What are the benefits of chemical use?
Medications: antibiotics, chemotherapy, pain relievers.
Agricultural chemicals: fertalisers, pesticides.
Food additives: preservatives, flavour enhancers.
What are the harmful effects of chemical use?
Toxic substances: heavy metals, pesticides.
Pollutants: air and water pollution, endocrine disruptors.
Drug abuse: recreational drugs, over the counter medications.
What is diffusion?
The movement of one substance from an area of high concentration to an area of low concentration.
Why is diffusion a passive process?
It does not require energy.
What is osmosis?
The diffusion of water molecules across a membrane from an area of low solute concentration to an area of high solute concentration.
What does osmatic pressure help maintain in animal and plant cells?
Animal cell’s shape.
Provides support in plant cells.
What might happen if the osmotic balance is not exactly right?
The cell may swell up and burst or shrivel (less severe in plant cells because of the cell wall).
What affects the molecules ability to traverse the plasma membrane?
Size
Charge
Lipid solubility.
What molecules is facilitated diffusion for?
Molecules that do not fit the criteria for diffusion through the membrane.
What is transport with the use of energy called?
Active transport.
When is active transport used?
When a molecule needs to move against the concentration gradient.
What does active transport require?
A carrier protein and energy.
What is facilitated diffusion?
The passive movement of larger or charged molecules through membrane proteins, moving down their concentration gradient.
What is active transport?
Moves molecules against their concentration gradient, requiring energy (usually ATP).
What is endocytosis?
The active process by which large molecules or particles are engulfed into the cell by forming vesicles.
What is exocytosis?
The active process by which cells expel large molecules or waste products by fusing vesicles with the membrane.
What is a concentration gradient?
The difference in the concentration of a substance across a membrane.
How does surface-area-to-volume (SA:V) ratio affect material exchange in cells?
A high SA:V ratio in small cells allows more efficient material exchange, while a low SA ratio in larger cells limits the rate of exchange.
What happens to exchange efficiency as a cell grows larger?
As a cell grows, the SA:V ratio decreases, reducing the efficiency of material exchange, which can limit cell size.
How does a steep concentration gradient affect diffusion across a membrane?
A steep concentration gradient increases the rate of diffusion, allowing materials to move across the membrane more quickly.
What effect does a shallow concentration gradient have on material exchange?
A shallow concentration gradient slows down the diffusion rate, leading to slower material exchange.
Why is active transport important in cells?
Active transport allows cells to move substances against their concentration gradient, using energy to maintain beneficial concentration differences.
Which types of molecules can easily pass through the cell membrane via simple diffusion?
Small, nonpolar molecules (like oxygen and carbon dioxide) can easily diffuse across the membrane because they are lipid-soluble.
How do large or polar molecules cross the cell membrane?
Large or polar molecules (e.g., glucose, ions) require transport proteins for facilitated diffusion or active transport to move across the membrane.
What are aquaporins?
A type of channel protein specifically for water molecules, allowing them to move rapidly across the cell membrane. Aquaporins facilitate osmosis.
What is the main function of transport proteins in the cell membrane?
Transport proteins facilitate the movement of molecules that cannot easily pass through the lipid bilayer, helping maintain cellular balance.
What do channel proteins do?
Channel proteins form pores in the membrane, allowing specific molecules or ions to pass through passively, without using energy.
What are aquaporins, and what is their role?
Aquaporins are a type of channel protein that specifically facilitates the rapid movement of water across the cell membrane.
How do carrier proteins function in facilitated diffusion?
Carrier proteins bind to a specific molecule, change shape, and transport it across the membrane down its concentration gradient without energy.
How do carrier proteins work in active transport?
In active transport, carrier proteins use energy (ATP) to move substances against their concentration gradient, as seen with the sodium-potassium pump.
What are channel proteins?
Provide a passage for specific molecules or ions through the membrane, allowing fast passive movement. Aquaporins are an example that transports water.
Why does DNA need to replicate before cell division?
There would be no genetic information in one of the cells if it didn’t replicate before.
What are male and female sex cells called?
Gametes.
What are cells containing homologous pairs of chromosomes called?
Diploid.
Why does the amount of DNA in a cell double before division?
The DNA doubles before division to ensure that each daughter cell receives a complete set of chromosomes, maintaining genetic integrity.
What is asexual reproduction?
A type of reproduction that involves a single parent and results in offspring that are genetically identical to the parent.
What are haploid cells?
Cells that contain half the number of chromosomes found in a typical body (somatic) cell. They have only one set of chromosomes, as opposed to diploid cells, which have two sets (one from each parent). Two haploid cells fertalise to make a diploid cell.
What are the phases of mitosis?
Interphase
Early prophase (prophase)
Late prophase (prometaphase)
Metaphase
Anaphase
Telophase
Cytokinesis
What is binary fission?
A form of asexual reproduction used by prokaryotic cells (such as bacteria) to produce two identical daughter cells, with the same number and type of chromosomes.
What is the process of binary fission?
DNA Replication: The circular DNA molecule replicates, producing two identical copies.
Cell Growth: The cell grows, increasing the distance between the two DNA copies.
Division: The cell membrane pinches inward, eventually splitting the cell into two genetically identical daughter cells, each with one copy of the original DNA.
What is mitosis?
Mitosis is the process by which eukaryotic cells divide to produce two identical daughter cells with the same genetic material as the parent cell, with the same number and type of chromosomes.
What is interphase?
The phase where the cell grows, duplicates its DNA, and prepares for cell division, setting the stage for mitosis or meiosis.
What happens in early prophase?
Chromosomes begin condensing, the mitotic spindle starts forming, and nuclear structures (like the nuclear membrane and nucleolus) begin to break down.
What happens in late prophase?
The nuclear membrane breaks down, the spindle fibers attach to chromosomes at their kinetochores, and chromosomes are fully condensed and ready for alignment.
What happens in metaphase?
Chromosomes line up in the middle of the cell, and spindle fibers attach to the centromere of each chromosome.
What happens in anaphase?
The sister chromatids of each chromosome are pulled apart to opposite poles of the cell by the spindle fibers.
What happens in telophase?
Chromatids reach opposite poles, and a new nuclear membrane forms around each set of chromosomes. The chromosomes begin to decondense.
What happens in cytokinesis?
The cell membrane pinches in, dividing the cytoplasm and forming two identical daughter cells.
What does sexual reproduction require?
Genetic information from two cells.
What is crossing over?
Where sections of non-sister chromatids might touch, break off, then rejoin. This exchanges genetic materials.
Where does crossing over occur?
Chiasma.
What is the source of genetic variation in asexual reproduction?
Mutation.
What are the sources of genetic variation in sexual reproduction?
Mutation
Crossing over
Independent assortment.
What is meiosis?
Meiosis is a two-part cell division process (meiosis I and meiosis II) that produces four genetically unique haploid cells from an original diploid cell.
What is the purpose of meiosis?
To reduce the chromosome number by half, creating haploid cells so that during fertilization, two haploid gametes can combine to restore the diploid number. This reduction ensures that the offspring have the correct chromosome number and prevents doubling with each generation.
What is crossing over and its purpose?
Homologous chromosomes exchange genetic material. This process creates new combinations of genes, leading to genetic variation among offspring.
What is random assortment and its purpose?
Homologous chromosomes align randomly along the metaphase plate. This randomness results in different combinations of maternal and paternal chromosomes in the gametes, increasing genetic diversity.
What is fertalisation?
The fusion of two haploid gametes, restoring the diploid number in the resulting zygote. This ensures that the zygote has two complete sets of chromosomes, one from each parent.
What is prophase I?
Chromosomes condense, and homologous chromosomes (one from each parent) pair up in a process called synapsis. Crossing over occurs, where homologous chromosomes exchange segments, creating genetic variation.
What is metaphase I?
Homologous chromosome pairs line up along the metaphase plate. Independent assortment adds genetic variation.
What is anaphase I?
Homologous chromosomes are pulled to opposite poles, separating the chromosome pairs.
What is telophase I and cytokinesis?
The cell divides, forming two haploid cells, each with one chromosome from each homologous pair.
What is prophase II?
Chromosomes condense, and spindle fibers reform in each haploid cell.
What is metaphase II?
Chromosomes line up along the metaphase plate in each haploid cell.
What is anaphase II?
Sister chromatids are pulled apart to opposite poles.
What is telophase II and cytokinesis?
Each cell divides, resulting in four genetically unique haploid cells, each with one set of chromosomes.
What are STEM cells?
Cells that have the capability to differentiate into any type of cell.
What is a differentiated cell?
A cell that has a specialised structure and function.
What happens at checkpoints in the cell cycle?
The activity is halted and the cell cycle does not proceed unless a specific signal is received.
What are the key triggers for a STEM cell to begin dividing during G1?
The size of the cell.
Signals received from the environment (growth factors) which trigger relay proteins.
When does the decision to divide or not occur?
At the end of G1 at checkpoint R.
What signal allow the cell to continue past checkpoint R?
The growth factor signal.
What are advantages to cell culturing?
Millions can be grown in a small space.
Hundreds of generations can be studied in a short span of time.
Mutations can be detected and the organism carrying them isolated.
Advancements in understanding of biochemistry.
Individual cell types can be grown to study their properties.
What are limitations of cell culturing?
The culture medium needs to have all the correct ingredients to promote cell growth.
Water availability, pH and temperature need to be maintained.
Sterile conditions are required, otherwise opportunistic organisms will grow instead of the desired cells.
