unit 1 Flashcards
what does the cell theory state
- all living things are made up of cells
- cells are the smallest unit of life
- new cells come from pre-existing cells
What are the exceptions to the cell theory?
- Striated muscle - made up of muscle fibers that are enclosed inside a membrane (like a cell), but are larger than most cells and are multi nucleated
- Giant algae - gigantic in size (5-100mm), and complex in structure - consists of 3 anatomical parts
- Aseptate fungi - made of thread-like structures called hyphae that are not divided into sub-units containing a single nucleus, but many nuclei
What are the common features of cells?
- Every cell is surrounded by a membrane, which separates the cell contents from everything outside
- Cells contain genetic material which stores all the instructions needed for cell activity
- Many of these activities are chemical reactions, catalyzed by enzymes produced inside the cell
- Cells have their own energy release system that powers all of the cell’s activities
What are unicellular organisms?
organisms made up of one cell that carry out all 7 functions of life
What are the 7 functions of life? (MR H GREN)
- Metabolism - chemical reactions inside the cell
- Response - reacting to changes in the environment
- Homeostasis - maintaining & regulating internal cell conditions
- Growth - irreversible growth/change in size & shape
- Reproduction - producing offspring sexually or asexually
- Excretion - the removal of metabolic waste
- Nutrition - obtaining food to provide the energy and materials needed for growth
Why is a larger SA:Vol ratio better?
allows the cell to be more efficient. for every unit of volume that produces waste/heat and requires nutrients, there is more membrane to serve it
Why is SA:Volume ratio a limiting factor?
- as cells grow, SA:Vol ratio decreases.
- SA control rate of diffusion across cell membrane / rate of exchanging materials & heat
- volume control rate of: waste production, heat production and resource consumption
- as the cell grows, vol increases faster than SA
- as a result materials cannot be exchanged fast enough to remove waste and heat, nor provide the resources to be consumed
- the cell becomes unable to meet it’s needs, so it divides
- therefore, SA:Vol ratio limits the size of the cell
What are emergent properties?
- multicellular organisms have properties and functions that emerge from the interaction of the component parts of a complex structure.
the whole is greater than the sum of its parts.
(E.g. our lungs are made up of many cells, but the cells by themselves aren’t much use. it’s the many cells working together as a unit that allow the lungs to function)
What is differentiation?
the process where a cells become specialized by expressing some genes, but not others
What are stem cells?
cells that have the capacity to divide and to differentiate along different pathways
undifferentiated cells
What are the different types of stem cells?
- embryonic - used to replace damaged cells
- adult - such as bone marrow
- cord - obtained from the umbilical cord / placenta
therapeutic uses of stem cells for leukimia
Leukemia = Type of cancer in which abnormally large numbers of WBCs are produced in the bone marrow
- stem cells are removed from the bone marrow of patient / donor by using a large needle inserted into the pelvis
- high dose of chemo is given to kill all the cancer cells in the marrow = it loses its ability to produce blood cells
- after chemo treatment patient has a bone marrow transplant where the stem cells are transplanted back into the patient through a drip
What is the calculation for magnification?
Magnification = image size ÷ actual size
triangle = I
A M
What is magnification?
How much bigger the image is that the specimen
What is resolution?
The ability to clearly distinguish the individual parts of an object
Compare prokaryotic and eukaryotic cells
prokaryotes eukaryotes
- no nucleus - has nucleus
- 70s ribosomes - 80s ribosomes
- much simpler - more complex
both have DNA, ribosomes, plasma membrane & a cytoplasm
What is binary fission?
A type of simple cell division used by prokaryotic cells to reproduce & divide into 2 genetically identical daughter cells
Explain the process of binary fission
- DNA Replication: DNA copies it self
- DNA segregation: copies separate and each moves to an opposite pole.
- Cytokinesis: the cell membrane pinches in the middle to divide the cell into two identical daughter cells.
What organelles do prokaryotes have? (9)
- 70s ribosomes
- nucleoid containing DNA
- capsule
- cytoplasm
- plasma membrane
- plasmid
- pili
- flagella
- cell wall
What are pili?
Short, hair-like structures that help bacteria adhere to each other for the exchange of genetic material
What is the function plasmid?
Help bacteria adapt to unusual situations e.g antibiotic resistance
What is flagella?
Long, thin whip-like structure that helps bacteria move around
What is the nucleoid in a prokaryotic cell?
Region containing naked DNA which:
- stores the hereditary material (genetic information) that controls the cell and will be passed on to daughter cells.
- initiates binary fission.
What organelles do animal cells have? (10)
- nucleus
- mitochondria
- 80s ribosomes
- Golgi apparatus
- smooth endoplasmic reticulum
- rough endoplasmic reticulum
- lysosomes
- plasma membrane
- cytoplasm
- vesicle
What additional organelle do plant cells have?
- cell wall
- chloroplasts
- vacuoles
What is the structure & function of ribosomes?
· do not have an exterior membrane.
· consist of two subunits (rRNA+protein)
· found either:
- floating free in the cytoplasm or
- attached to the surface of the RER
- in mitochondria and chloroplast.
function = protein synthesis
What is the function of the smooth ER?
production of…
· Membrane phospholipids
· Sex hormones such as testosterone and estrogen
detoxification of drugs in the liver
What is the structure & function of the rough ER?
extensive network of tubules that extend almost everywhere in the cell
Has ribosomes on the surface
function = synthesizes proteins and transport them to be then excreted from the cell.
What is the structure & function of lysosomes?
membrane bound sacs containing hydrolytic (digestive) enzymes. break down old organelles and foreign matter for reuse.
What is the structure & function of the Golgi apparatus?
consists of flattened sacs called cresternae, which are stacked on top of one another.
function = collection, packaging, modification & distribution of materials synthesized in the cell.
What is the structure & function of mitochondria?
structure:
- have a double membrane
- inner membrane folded into cristae within a fluid filled matrix.
- cristae provide huge SA for chemical reactions
- contain own DNA and 70s ribosomes.
function = aerobic respiration & ATP production
What is the structure & function of the nucleus?
surrounded by a double membrane, in which there are pores (nuclear envelope)
function = contains chromosomes + control the cell
What is the function of the cell wall?
a rigid layer that supports, protects and provides shape to the cell
What is the function of the plasma membrane?
control transfer of substances in and out of the cell.
What is the function of the cytoplasm?
where chemical reactions take place
contains dissolved substances, enzymes and the cell organelles
What is the structure & function of chloroplasts?
structure:
- double membrane
- inner membrane forms flat discs filled with chlorophyll called thylakoids, in stacks called granum.
- these are surrounded by a fluid matrix called the stroma.
- contain own DNA and 70s ribosomes.
function = site of photosynthesis
explain the Davidson-Danielli model
- Developed in 1930s
- Bilayer of phospholipids with layers of protein on either side
- Electron micrographs showed two dark lines separated by a lighter band
- Proteins usually appear darker than phospholipids
explain the fluid mosaic model
- Singer and Nicolson (1966)
- Made of a phospholipid bilayer and proteins in a range of positions in the membrane (integral proteins are embedded in the bilayer; peripheral proteins are attached to the outer surface; glycoproteins have sugar units attached to the outer surface of the membrane)
What is a phospholipid?
- basic components of cell membrane
- amphipathic (part of the molecule is hydrophobic and part hydrophilic)
- a type of lipid made from 2 fatty acid chain ‘tails’ attached to a phosphate group ‘head.’
- the attraction between the hydrophobic tails in the center and between the hydrophilic heads and surrounding water makes them very stable
phospholipid head
- hydrophilic (loves water)
- made up of glycerol and phosphate
- faces the outside of the membrane of both sides
phospholipid tails
- hydrophobic (hates water)
- made up of 2 fatty acids
- faces the inside
what is cholesterol?
- a type of lipid molecule found in the cell membrane which is very hydrophobic
- restricts the movement of phospholipid molecules, thus reducing fluidity and permeability of the membrane to hydrophilic particles like Na and H ions
what is an integral protein?
- completely penetrate the phospholipid bilayer
- have both hydrophobic region (non-polar amino acids) and hydrophilic region (polar amino acids).
- act as pumps in active transport, channels in facilitated diffusion. - control the entry/exit of specific molecules into/out of the cell.
what is a peripheral protein?
- remain bound on the surface of the membrane or anchored to an integral protein.
- have hydrophilic regions (polar amino acids) only.
- play a role in recognition of cells; involved in immune response, cell to cell communication.
what is a glycoprotein?
proteins with carbohydrate chains attached
what is simple diffusion?
- the movement of particles from an area of high concentration to an area of low concentration.
- passive process
what is osmosis?
- the movement of water molecules, across a partially permeable membrane, from a region of high water concentration to a region of lower water concentration
- passive process
what is facilitated diffusion?
- high to low concentration
- protein channel needed because they are polar, so cannot pass through the non-polar middle of the membrane
- passive process
compare passive and active transport
passive transport =
- high to low, across a concentration gradient
- no energy is required
- no protein pump is required
- e.g. osmosis & diffusion
active transport =
- low to high, against a concentration gradient
- requires energy
- protein pump is required
- e.g. sodium-potassium pump
what is a channel protein?
- a protein that allows the transport of specific substances across a cell membrane
- high to low concentration
- involved in facilitated diffusion
compare simple and facilitated diffusion
similarities
- both go from high to low concentration (with the concentration gradient).
- no energy required (passive)
Differences:
- facilitated uses a selective transport protein, simple is directly through the phospholipid bilayer
- simple is slower than facilitated
- simple = transport of hydrophobic (non polar) molecules, facilitated = transport of hydrophilic (polar) molecules & charged proteins
what is the sodium-potassium pump?
- protein pump that requires energy in order to pump sodium and potassium ions against the concentration gradient.
- axon of a neuron
- 3 sodium out, 2 potassium in
what is endocytosis?
- the process by which macromolecules enter the cell.
- the fluidity of membranes allows materials to be taken into cells
- requires vesicles to move materials within cells.
- requires energy.
how does endocytosis work?
- It involves the pulling of the plasma membrane inwards (in-folding).
- A vesicle pinches off the plasma membrane.
- The vesicle enters the cytoplasm
- The vesicle carries its content anywhere in the cell.
what is exocytosis?
- the process by which macromolecules leave the cell.
- requires energy.
- the fluidity of membranes allows materials to be released out
- requires vesicles to move materials within cells.
- usually begins in the ribosomes of rough ER
how does exocytosis work? (protein transport)
- Proteins synthesized by the ER ribosomes are transported to the RER where they can be modified.
- Vesicles carrying the protein then bud off the RER
- Vesicles are transported to the Golgi apparatus to be further modified.
- The vesicles carrying the protein bud off the Golgi apparatus and carry the protein to the plasma membrane.
- The vesicles fuse with the membrane to expel the modified proteins outside the cell.
- The membrane then goes back to its original state.
Pasteur’s experiment
- Verified principle that cells can only come from pre-existing cells
Method:
· Two experiments were setup
· In both, Pasteur added nutrient broth to flasks and bent the necks of the flasks into S shapes
· Each flask was then heated to boil the broth so that all existing microbes were killed.
· After the broth had been sterilized, Pasteur broke off the swan necks from the flasks in Experiment 1, exposing the nutrient broth within them to air from above.
The flasks in Experiment 2 were left alone.
Results:
The broth in experiment 1 turned cloudy whilst the broth in experiment 2 remained clear. This indicates that microbe growth only occurred in experiment 1.
what is symbiosis?
two organisms living together
what is endosymbiosis?
- a larger cell takes in a smaller cell by endocytosis, so the smaller cell is inside a vesicle in the cytoplasm of the larger cell
- instead of being digested, smaller cell is kept alive to perform a function for the larger cell
- smaller cell divides as often as the larger cell so that one or more of them are inside vesicles in the new larger cells
endosymbiosis in relation to mitochondria & chloroplasts
· Mitochondria were once aerobic bacteria that were ingested by a larger anaerobic prokaryote to supply energy through aerobic respiration for the larger cell. The aerobic bacteria evolved overtime to become mitochondria.
· Chloroplasts were once photosynthetic bacteria that were ingested by a larger prokaryote to photosynthesis and provide organic matter to the larger cell. The photosynthetic bacteria evolved overtime to become chloroplasts.
evidence supporting the endosymbiotic theory for mitochondria & chloroplasts
- they have their own DNA (which is naked and circular)
- they have ribosomes that are similar to prokaryotes (70S)
- they have a double membrane and the inner membrane has proteins similar to prokaryotes
- they are roughly the same size as bacteria
what is the cell cycle?
- series of events that cells go through as they grow and divide
- interphase
- mitosis
- cytokinesis
what is interphase?
- a very active phase of the cell cycle with many processes occurring in the nucleus and cytoplasm.
- longest phase of cell cycle
what 3 phases make up interphase?
G1 = the cell grows larger + protein synthesis + number of mitochondria and chloroplasts increase.
S (synthesis) = DNA replication in the nucleus
G2 = cell grows and prepares for mitosis
what is mitosis?
- the division of the nucleus to form 2 genetically identical daughter nuclei.
- asexual reproduction
- prophase, metaphase, anaphase and telophase
what is supercoiling?
- occurs during S-phase and is when chromosomes condense
what happens during prophase?
- the spindle fibers start growing and start to extend from each pole to the equator.
- sister chromatids condense by supercoiling.
- sister chromatids thicken, shorten and become visible.
- the nuclear membrane starts breaking down
what happens during metaphase?
- the sister chromatids move to the equator and line up separately.
- the spindle fibers from each pole attach to each centromere on opposite sides.
- the spindle fibers are fully developed
what happens during anaphase?
- the spindle fibres contract to pull the sister chromatids apart splitting the centromeres.
- this splits the sister chromatids into chromosomes.
- each identical chromosome is pulled to opposite poles
what happens during telophase?
- the spindle fibres break down
- the chromosomes uncoil = no longer individually visible.
- the nuclear membrane reforms.
what happens during cytokinesis?
- division of the cytoplasm to form two cells
- occurs after mitosis
In plant cells:
- a new cell wall forms across the equator
- Plasma membrane is on both sides
- this divides the cell into two
In animal cells:
- the plasma membrane at the equator is pulled inwards until meets in the centre of the cell
- this divides the cell into two
what is the mitotic index?
Ratio between the number of cells in mitosis in a tissue and the total number of observed cells
mitotic index = no. of cells in mitosis / total no. of cells
used by doctors to predict how rapidly a tumor will grow and therefore what treatment is needed (high index indicates fast-growing tumor)
what are cyclins?
A group of proteins used to ensure:
- that tasks are performed at the correct time
- that the cell only moves on to the next stage of the cycle when appropriate
how do cyclins work?
- bind to enzymes called cyclin-dependent kinases.
- these kinases become active and attach phosphate groups to other proteins in the cell
- the attachment of phosphate triggers the other proteins to become active and carry out tasks specific to one of the phases of the cell cycle.
what are the 4 types of cyclins?
- Cyclin D - triggers cells to move from G0 to G1, and from G1 to S phase
- Cyclin E - prepares the cell for DNA replication in S phase
- Cyclin A - activates DNA replication inside the nucleus in S phase
- Cyclin B - promotes the assembly of the mitotic spindle and other tasks in the cytoplasm to prepare for mitosis.
what are tumors?
- the results of uncontrolled cell division
- can occur in any organ or tissue.
what is a primary tumor?
when cells adhere to each other and don’t invade nearby tissue.
are unlikely to cause any harm and are classified as benign
what is a secondary tumor?
when tumor cells become detached, move elsewhere in the body (metastasis) and develop into secondary tumour.
are very likely life-threatening and are classified as malignant, known as cancer.
what are carcinogens
agents that cause cancer
may include…
- mutagens: agents that cause gene mutations, which can cause cancer.
- some viruses
- high energy radiation such as X-rays and short-wave ultraviolet light.
what is the structure & function of vacuoles
membrane-bound storage organelle that are usually formed from the Golgi apparatus
- storage of materials (e.g. metabolic waste)
- enable cells to have a higher SA:V ratio
- in plants, they allow the uptake of water
what is the structure and function of centrioles
- associated with cell division
- composed of microtubules
- area in which they are found is called the centrosome
- present in all eukaryotic cells, but plant cells do not have centrioles
compare plant & animal cells
plants vs animal
- has cell wall - no cell wall
- has chloroplasts - doesn’t have
- carbs stored as starch - carbs stored as glycogen
