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