IB Biology Unit 1
facilitated diffusion
type of diffusion involving a membrane with specific carrier proteins that are capable of combining with the substance to aid its movment
diffusion
type of passive transport in a living system that involves a membrane
Paramecium
unicellular membrane of the kingdom known as Protista. Look at powerpoint on isa247 to see how this organism displays the functions of life.
electron microscope
use electrons passing through a dead specimen to form an image and provides us with the greatest magnifications and resolution
light microscopes
use light, passing through living or dead specimens to form an image
Davson-Danielli model
used previous lipid bilayer model, suggesting it was covered on both sides by a thin layer of globular protein
proteins (as related to phospholipid bilayer)
various types in membrane embedded in fluid matrix of phospholipid bilayer
Explain the role of protein pumps and ATP in active transport across membranes
Active transport is the passage of materials against a concentration gradient (from low to high) This process requires the use of protein pumps which use the energy from ATP to translocate the molecules against the gradient The hydrolysis of ATP causes a conformational change in the protein pump resulting in the forced movement of the substance Protein pumps are specific for a given molecule, allowing for movement to be regulate
Cell theory 3 main principles
All organisms are composed of one or more cells cells are the smallest units of life all cells come from pre-existing cells
Similarities between prokaryotic and eukaryotic cells
Both have a cell membrane Both contain ribosomes Both have DNA and cytoplasm
structure of phospholipids
Consist of a polar head (hydrophilic) made from glycerol and phosphate Consist of two non-polar fatty acid tails (hydrophobic)
lysosomes
Contain and transport enzymes. Site of hydrolysis / digestion / breakdown of macromolecules
Anaphase
Continued contraction of the spindle fibres cause the two sister chromatids to separate and move to the opposite poles of the cell Once the two chromatids in a single chromosome separate, each constitutes a chromosome in its own right
Overall characteristics of prokaryotic cells
DNA not enclosed within a membrane and forms one circular chromosome DNA is free; not attached to proteins they lack membrane bound organelles, ribosomes are complex structures within the plasma membrane, but have no exterior membrane cell wall is made up of peptidoglycan usually divide by binary fission small in size
Prophase
DNA supercoils, causing chromosomes to condense and become visible under a light microscope As DNA was replicated during interphase, the chromosomes are each comprised of two genetically identical sister chromatids joined at a centromere The centrosomes move to opposite poles of the cell and spindle fibres begin to form between them (in animals, each centrosome contains 2 centrioles) The nuclear membrane is broken down and disappears
Metaphase
Spindle fibres from the two centrosomes attach to the centromere of each chromosome Contraction of the microtubule spindle fibres cause the chromosomes to line up separately along the centre of the cell (equatorial plane)
Endocytosis
a form of active transport in which a cell transports molecules (such as proteins) into the cell by engulfing them in an energy-using process.
Exocytosis
a process in which an intracellular vesicle (membrane bounded sphere) moves to the plasma membrane and subsequent fusion of the vesicular membrane and plasma membrane ensues.
Rough endoplasmic reticulum
a site of protein synthesis
flagella
allow a cell to move
nuclear pore
allows communication between the nucleus and the rest of the cell
pili
hairlike growth on outside of cell wall used for attachment and joining bacterial cells in preparation for transfer of DNA
eukaryotic cell
has a nucleus and other organelles which are compartmentalized, in multicellular organisms
cholesterol
helps to regulate membrane fluidity and is important for membrane stability
Stargardt's disease
inherited disease caused by both parents passing on a gene to their offspring that codes for a defect in the processing of vitamin A. Leads to blindness research to threat this with stem cells is ongoing
passive transport
material moves from an area of high concentration to low concentration
nucleoid
non compartmentalized and contains a single, long, continuous, circular thread of DNA involved with cell control and reproduction
6 general functions of membrane proteins
sites for hormone binding enyzmatic action cell adhesion cell to cell communication channels for passive transport pumps for active transport
ribosomes
sites of protein synthesis
magnification equation
size of an image/ size of a specimen
ribosomes (eukaryotic)
small structures, free in cytoplasm or associated with the Endoplasmic reticulum
plasmids
small, circular, DNA molecules are not connected to the main bacterial chromosome replicate independently of DNA not required by cell under normal conditions
vacuoles
smaller than those found in plants, store water
hydrophylic
soluble and polar, phosphorylated alcohol side
chloropolast
specialized plastids containing the green pigment chlorophyll. Consist of grana within the colorless stroma. Sight for photosynthesis
hormone binding
specific shapes exposed to exterior that fit shape of specific hormones, attachment causes a change in shape of protein, message then relayed to interior of cell
golgi apparatus
stores, modifies, and packages proteins
Exception to rules of cells
striated muscle- one cell with multiple nuclei giant algae- cells are bigger than normal, has one nucleus, complex in form aseptate fungal hyphae- made by cloning, multiple nuclei, cytoplasm continuous along hyphae
prokaryotic cell features
the cell wall, the plasma membrane, flagella, pili, ribosomes, the nucleoid
Differentiation
the process during development whereby newly formed cells become more specialised and distinct from one another as they mature
Emergent Properties
the whole is greater than the sum of its parts: Multicellular organisms are capable of completing functions that individual cells could not undertake - this is due to the interaction between cells producing new functions
Stem Cell qualities
they can continuously divide and replicate They have the capacity to differentiate into specialised cell types
pluripotent stem cells
tissue specific stem cells can only produce new cells of certain tissue types
One therapeutic use of stem cells
Skin cells: Graft new skin cells to replace damaged cells in severe burn victims
7 functions of life
(MR H GREN) metabolism reproduction homeostasis growth excretion response nutrition
Evidence for cell theory
1. Microscopes Microscopes have increased man's ability to visualise tiny objects All living things when viewed under a microscope have been found to be made of cells and cell products 2. Experimental Evidence Cells removed from tissues can survive independently for short periods of time Nothing smaller than a cell has been found to be able to live independently Experiments by Francesco Redi and Louis Pasteur have demonstrated that cells cannot grow in sealed and sterile conditions
G1 Phase
A checkpoint stage before DNA replication during which the cell grows, duplicates organelles, synthesises proteins and produces ATP
G2 Phase
A checkpoint stage before division during which the copied DNA is checked for fidelity (mutations) and final metabolic reactions occur
Explain how mitosis produces two genetically identical nuclei
During interphase (the S phase) the DNA was replicated to produce two copies of genetic material These two identical DNA molecules are identified as sister chromatids and are held together by a single centromere During the events of mitosis, the sister chromatids are separated and drawn to opposite poles of the cell When the cell divides (cytokinesis), the two resulting nuclei will each contain one of each chromatid pair and thus be genetically identical
Cytokinesis
Final stage in which the cell divides the two resulting nuclei will each contain one of each chromatid pair and thus be genetically identical
State how growth, embryonic development, tissue repair and asexual reproduction involve mitosis
Growth: Multicellular organisms increase their size by increasing their number of cells through mitosis Asexual reproduction: Certain eukaryotic organisms may reproduce asexually by mitosis (e.g. vegetative reproduction) Tissue Repair: Damaged tissue can recover by replacing dead or damaged cells Embryonic development: A fertilised egg (zygote) will undergo mitosis and differentiation in order to develop into an embryo
smooth endoplasmic reticulum
Involved in the synthesis and transport of lipids and steroids, as well as metabolism of carbohydrates
Magnification Calculation Formula
Magnification = Size of image (with ruler) ÷ Actual size of object (according to scale bar)
Telophase
Once the two sets of identical chromosomes arrive at the poles, the spindle fibres dissolve and a new nuclear membrane reforms around each set of chromosomes The chromosomes decondense and are no longer visible under a light microscope
Structural Properties of Phospholipid bilayer
Phospholipids are held together in a bilayer by hydrophobic interactions (weak associations) Hydrophilic / hydrophobic layers restrict entry and exit of substances Phospholipids allow for membrane fluidity / flexibility (important for functionality) Phospholipids with short or unsaturated fatty acids are more fluid Phospholipids can move horizontally or occasionally laterally to increase fluidity Fluidity allows for the breaking / remaking of membranes (exocytosis / endocytosis)
Arrangement of phospholipids in membrane
Phospholipids spontaneously arrange in a bilayer Hydrophobic tail regions face inwards and are shielded from the surrounding polar fluid while the two hydrophilic head regions associate with the cytosolic and extracellular environments respectively
Two roles of extracellular components in plants vs animal cells
Plants: The cell wall in plants is made from cellulose secreted from the cell, which serves the following functions: Provides support and mechanical strength for the cell (maintains cell shape) Prevents excessive water uptake by maintaining a stable, turgid state Serves as a barrier against infection by pathogens Animals: The extracellular matrix (ECM) is made from glycoproteins secreted from the cell, which serve the following functions: Provides support and anchorage for cells Segregates tissues from one another Regulates intercellular communication by sequestering growth factors
Explain passive transport across membranes in terms of simple diffusion and facilitated diffusion
The plasma membrane is semi-permeable and selective in what can cross Substances that move along the concentration gradient (high to low) undergo passive transport and do not require the expenditure of energy (ATP)
Importance of SA to V for limiting cell size
The rate of metabolism of a cell is a function of its mass / volume The rate of material exchange in and out of a cell is a function of its surface area As the cell grows, volume increases faster than surface area (leading to a decreased SA:Vol ratio) If the metabolic rate is greater than the rate of exchange of vital materials and wastes, the cell will eventually die
S Phase
The stage during which DNA is replicated
Interphase
The stage in the development of the cell between two successive M phases This phase of the cell cycle is a continuum of 3 distinct stages (G1, S, G2), whereby the cell grows and matures (G1), copies its DNA (S) and prepares for division (G2)
Tumor
Tumor suppressor genes produce proteins which inhibit cell division Mutations to oncogenes result in uncontrolled cell division, resulting in the formation of a tumor Tumors can grow in size which causes damage local tissue; they may also spread to other parts of the body (malignant tumours)
centrioles
associated with nuclear division. composed of microtubules, found in centrosome, present in all eukaryotic cells, but absent from higher plant cells
enzyme
catalyse chemical reactions, grouped so sequence of metabolic reactions can occur
integral proteins
completely penetrate the lipid bilayer. They control the entry and removal of specific molecules from the cell
phospholipid
composed of a three carbon compound called glycerol, make up bilayer
glycoproteins
composed of carbohydrate chains attached to peripheral proteins. They play a role in recognition of like cells are involved in immune responses
starch granules
composed of carbohydrate stored in amyloplasts
plasma membrane
controls the movement of materials in and out of the cell, and it plays a role in binary fission of prok. cell
nucleolus
dense, solid structure involved in ribosome synthesis
Singer and Nicolson vs Davson Danielli Model
not all membranes are identical or symmetrical, as the first model implied membranes with different functions also have different composition and a different structure protein layer is not likely bc largely non-polar and would not interface with water as shown by cell studies
hydrophobic
not water soluble, nonpolar
cytoplasm
occupies complete interior
mitochondria
organelles that carry out respiration and have ATP information
merismatic tissue
plants contain these stem cells and farmers use them to create new plants
stem cells
populations of cells within organisms that retain their ability to divide and differentiate into various cell types
binary fission
process in which DNA is copied, the two daughter chromosomes become attached to different regions of plasma membrane and cell divides into two genetically identical daughter cells
oncogenes
produce proteins that promote growth and division
Symour J. Singer and Garth L. Nicolson
proposed that proteins are inserted into phospholipid layer and do not form a layer on the phospholipid bilayer surfaces
cell wall
protects and maintains the shape of the cell
active transport
proteins shuttle substance from one side to other by changing shape requires using energy in form of ATP
Emergent properties
results of cell production and differentiation process that depends on the interactions between all the different parts of a particular biological unit such as the cell
genes
segments of DNA on a chromosome, enable the production of all the different cells in an organism
chlorella
single-celled organism that has a chloroplast inside cell wall