IB Bio Unit 1

phospholipid bilayer

plasma membrane layers composed of phospholipid molecules arranged with polar heads facing the outside and nonpolar tails facing the inside.

cell membrane

double-layer of phospholipids that forms a boundary between a cell and the surrounding environment and controls the passage of materials into and out of a cell

fluid mosaic model

model that describes the arrangement and movement of the molecules that make up a cell membrane

semipermeable membrane

A membrane that allows some molecules to pass through but does not allow other molecules to pass through

diffusion

the process by which molecules move from an area of higher concentration to an area of lower concentration

facilitated diffusion

The spontaneous diffusion of molecules assisted by specific transmembrane integral proteins.

active transport

energy-requiring movement of molecules across a membrane from a region of lower concentration to a region of higher concentration

phospholipid

molecule that forms a double-layered cell membrane; consists of a glycerol, a phosphate group, and two fatty acids

passive transport

the passive movement of a substances across a cell membrane without the use of energy by the cell.

concentration gradient

difference in the concentration of a substance from one location to another

osmosis

diffusion of water molecules across a semipermeable membrane from an area of higher solute concentration to an area of lower solute concentration

isotonic

Solution that has an EQUAL concentration of dissolved particles compared with another solution across a semipermeable membrane. It has the same osmotic pressure.

Hypertonic

solution that has a higher concentration of dissolved particles compared with another solution. It has a higher osmotic pressure

hypotonic

solution that has a lower concentration of dissolved particles compared with another solution. It has a lower osmotic pressure.

endocytosis

uptake of liquids or large molecules into a cell by inward folding of the cell membrane

phagocytosis

"Cell eating", a type of endocytosis. Phagocytosis refers to the engulfing of larger, solid particles. Often the engulfed particle is another cell, like when a white blood cell, which is a part of the immune system, engulfs a bacterium to destroy it.

exocytosis

release of substances out a cell by the fusion of a vesicle with the membrane

prokaryotic

Describes a cell that does not have a nucleus or any other membrane-covered organelles.

eukaryotic

A cell characterized by the presence of a nucleus and other membrane-bound organelles.

organelles

A membrane-enclosed structure with a specialized function within a cell.

cytoplasm

jellylike substance inside cells that contains molecules and in some cells organelles.

nucleus

organelle composed of a double membrane that acts as the storehouse for most of a cell's DNA

endoplasmic reticulum

interconnected network of thin, folded membranes that produce, process,a nd distribute proteins...

ribosome

organelle that links amino acids together to form proteins...

golgi apparatus

stack of flat, membrane-enclosed spaces containing enzymes that process, sort, and deliver proteins...

rough endoplasmic reticulum

.parts of the endoplasmic reticulum to which ribosomes are attached on the cytoplasmic side..

vesicle

small organelle that contains and transports materials within the cytoplasm.

protein

polymer composed of amino acids linked by peptide bonds; folds into a particular structure depending on bonds between amino acids...

chloroplasts

organelle composed of numerous membranes that are used to convert solar energy into chemical energy; contains chlorophyll.

mitochondria

Plural for mitochondrion.. bean-shaped organelle that supplies energy to the cell and has its own ribosomes and DNA...

Exceptions to the cell theory?

Striated muscle fibres
Aseptate fungal hyphae
Giant Algae

Emergent properties

When the interactions of individual components produce new functions.
"the whole is greater than the sum of it's parts"

Differentiation

The expression of some genes and not others in a cell's genome. A process when newly formed cells become more specialised and distinct from one another as they mature.

Chromatin

nucleosomes (DNA wrapped around histone octameres) that are compacted into a fiber (chromatin) in order to organise loose DNA strands in the nucleus and make them more compact.

Totipotent

Can form any cell type including extra-embryonic (placental) tissue.
Can give rise to an entire organism.

Pluripotent

Can form most cell types, except extra-embryonic.
Cannot give rise to an entire organism.

Multipotent

Can differentiate into a number of closely related cells.
Ex. blood cells, skin cells and nerve cells.

What is the Cell Theory?

1. All organisms are composed of one or more cells
2. Cells are the smallest units of life
3. All cells come from pre-existing cells

What are the 7 functions of life?

1. Metabolism
2. Excretion
3. Homeostasis
4. Reproduction
5. Growth
6. Nutrition
7. Response

Ex. Paramecium and Chlorella

Decreasing order of size?

* Cells
* Organelles
* Bacteria
* Viruses
* Membranes
* Molecules

Equation for magnification?

magnification \= size of image/size of specimen

Nuclear pore

allows communication between the nucleus and the rest of the cell

centrioles

Cylindrical organelles associated with nuclear division. They are composed of microtubules. 2 of them make the centrosome.

centrosome

Organelle made up of a pair of centrioles. It organises the microtubules during cell division.

lysosomes

sacs bounded by a single membrane, they contain and transport degradative enzymes. They digest excess or worn out organelles, food particles, and engulfed viruses or bacteria. Lysosomes are like the stomach of the cell.

nuclear membrane

Also known as nuclear envelope. It is a double layered that separates the nucleoplasm and the cytoplasm.

cytosol

the fluid portion of the cytoplasm that is around the organelles.

chromosome

a highly coiled structure of many nucleosomes (or highly super coiled chromatin fibers)

extracellular matrix

ECM is a dynamic, physiologically active component of all living tissues. In addition to providing structural support for the cells embedded within a tissue, the extracellular matrix guides their division, growth, and development. In other words, the extracellular matrix largely determines how a tissue looks and functions.
It is made up of proteoglycans, water, minerals, and fibrous proteins (like collagen). A proteoglycan is composed of a protein core surrounded by long chains of starch-like molecules called glycosaminoglycans.

cell wall

The cell wall forms outside the plasma membrane initially as a thin primary cell wall. Thereafter, the primary cell wall (made of cellulose and hemicellulose) may thicken or a more durable secondary cell wall (cellulose and hemicellulose + lignin, an organic polymer that strengthens and hardens the cell wall) can form between the primary cell wall and plasma membrane.

pili

a protein-based, hair-like structure that extends from the bacterial cell. Some pili are used to attach to surfaces, but the special conjugation pilus is used specifically to attach to other cells and facilitate DNA transfer.

asexual reproduction

increasing the population of a particular organism --\> identical daughter cells/clones. For example: binary fission in bacteria.

flagella

Are long, thin, whip-like appendages attached to a bacterial cell that allow for bacterial movement (also known as motility)

integral membrane proteins

IMP is a type of membrane protein that is permanently attached to the biological membrane. All transmembrane proteins are IMPs, but not all IMPs are transmembrane proteins (ex. partially embedded proteins)

peripheral membrane proteins

are membrane proteins that adhere only temporarily to the biological membrane with which they are associated. These proteins attach to integral membrane proteins, or penetrate the peripheral (on edge/outer) regions of the lipid bilayer.

membrane protein functions

* sites for hormone-binding
* enzymatic action
* cell adhesion
* cell-to-cell communication
* channels for passive transport
* pumps for active transport

cell junctions

tight junctions (leak-proofs seals between cells), gap junctions (provide channels for transfer of water & ions between the cells), desmosome/adhesion junctions (hold adjacent cells together)

Sodium-potassium pump

A specialized type of transport protein found in the cell membranes. The NaK pump's job is to move 2 potassium ions into the cell while simultaneously moving 3 sodium ions out of the cell through the phosphorylation of ATP.

pinocytosis

"Cell drinking" the transport of fluid into a cell by means of infolding or invagination by the cell membrane so that a tiny vesicle or sac forms around each droplet, which is then taken into the interior of the cytoplasm..

Interphase

The resting phase between successive mitotic divisions of a cell. It is the stage of the cell cycle when a cell is preparing itself to duplicate. Sub-phases are G1, S, and G2

G1 - gap 1 phase

The cell is growing. At the beginning of G1, the cell is at it's smallest. It synthesises mRNA and proteins.

S phase

Synthesis phase, the part of the cell cycle in which DNA/chromosomes is replicated, occurring between G1 phase and G2 phase. Precise and accurate DNA replication is necessary to prevent genetic abnormalities which often lead to cell death or disease. Following replication, each chromosome now consists of two sister chromatids.

G2 - gap 2 phase

Cell growth and preparation for mitosis. Organelles increase in number, DNA begins to condense from chromatin to chromosomes and microtubules begin to form.

Cell cycle checkpoints

Cell cycle progression requires a sequence of processes, with later events dependent on the completion of earlier ones. This dependency ensures that each cell division accurately replicates the genome and transmits it to daughter cells.
Checkpoints control the cell's progress through the cell cycle, and ensure that key processes such as DNA replication and DNA damage repair are completed before the cell cycle is allowed to progress into the next stage. Checkpoints also ensure that both daughter cells receive the same number of chromosomes and that daughter cells are genetically identical to the parents.

Cyclins

are named such because they undergo a constant cycle of synthesis and degradation during cell division. When cyclins are synthesized, they act as an activating protein and bind to CDKs forming a cyclin-CDK complex. This complex then acts as a signal to the cell to pass to the next cell cycle phase. (this is because cyclins induce a conformational change that helps to expose the ATP binding cleft on the CDK enzyme, which allows them to perform phosphorylation). Eventually, the cyclin degrades, deactivating the CDK, thus signaling exit from a particular phase.
Examples: G1 cyclin and mitotic cyclins

centromere

In eukaryotes, a centromere is a region of DNA that is responsible for the movement of the replicated chromosomes into the two daughter cells during mitosis and meiosis. There is one centromere on each chromosome

prophase

1. Stage
The nuclear envelope disintegrates and the nucleolus disappears. The mitotic spindle forms, is completed by the end of prophase. The centromeres of each chromosome have a region called the kinetochore that attaches to the spindle. The centrosomes (the organelle with 2 centrioles) move to the opposite sides of the cell because the microtubules are elongating.

metaphase

2. Stage
Chromosomes move to the middle, "equator" of the cell, or the metaphase plate. The chromosomes' centromeres lie on this plate. the centrosomes are now at opposite poles and are preparing to move the chromosomes.

anaphase

3. Stage
The sister chromatids finally separate by rapidly moving towards each of their opposite poles. Each is now called a chromosome. The movement arises from the shortening of the microtubules. At the end, each pole of the cell has a complete, identical set of chromosomes and now only needs to divide.

telophase

4. Stage
The chromosomes are now at each their pole and a nuclear membrane starts to re-form around each set of chromosomes, which start to elongate back into chromatin. Nucleolus reappears and the spindle apparatus disappears. The cell is elongated and ready for cytokinesis.

cytokinesis

(in animal cells) Inward pinching of plasma membrane to form a cleavage furrow.
(in plant cells) A cell plate starts to form in the middle of the diving cell. It moves outwards from the central region.

mitosis

"Division of the nucleus", a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus, typical of ordinary tissue growth.

primary tumour

occurs at the original site of a cancer, i.e. where a cancer first started to grow. It may spread to become a secondary tumour somewhere else in the body. This is called metastasis.

secondary tumour

a metastasis: The spread of cancer cells from the place where they first formed to another part of the body. In metastasis, cancer cells break away from the original (primary) tumor, travel through the blood or lymph system, and form a new tumor in other organs or tissues of the body.

mitotic index

cells in mitosis/cells in total

oncogenes

A gene that is a mutated (changed) form of a gene involved in normal cell growth. Oncogenes may cause the growth of cancer cells. Mutations in genes that become oncogenes can be inherited or caused by being exposed to substances in the environment that cause cancer.

carcinogen

A carcinogen is any substance that has the potential to cause cancer in living tissues. A carcinogen causes a mutation that leads to cancer, which is obviously a harmful type of mutation. So, a carcinogen is a type of mutagen that specifically leads to cancer.

mutagen

A mutagen is something that causes a mutation in an organism's genetic code (DNA). Mutations can be neutral, beneficial, or harmful. Ex: cigarette smoke.