SL Biology - Topic 1: Cell Biology

Some key concepts and examples from the Cell Biology topic

Functions of life

Metabolism

Reproduction

Sensitivity

Homeostasis

Growth

Response

Excretion

Nutrition

surface area to volume ratio

as organisms increase in size, their SA:V ratio decreases

differentiation

in complex multicellular organisms eukaryotic cells become specialized for specific functions as certain genes are expressed

stem cell

a cell which can divide an unlimited number of times and can differentiate into more specialized cells

totipotent

stems cells which can differentiate into any cell type, found in an embryo and the placenta

pluripotent

stems cells which can differentiate into some cell types, found in bone marrow

multipotent

stem cells which can only differentiate into closely related cell types, found in the umbilical cord

unipotent

stems cells which can only differentiate into their own lineage, found in adult organ tissues

magnification

image size/ actual size

endosymbiotic theory

to overcome a small surface area to volume ratio ancestral cells developed folds in their membrane, larger anaerobically respiring prokaryotes engulfed smaller aerobically respiring prokaryotes

Prokaryotic cell structure

small, simple cell structures that have no nucleus and reproduce by binary fission

Eukaryotic cell structure

larger, more complex cells with numerous membrane bound organelles reproducing by mitosis or meiosis

plasma membrane

a membrane controlling the exchange of materials in and out of the cell, formed from a phospholipid bilayer

nucleus

double membrane containing chromatins and the site of ribosome production

rough endoplasmic reticulum

continuous folds of the membrane called cisternae covered in ribosomes and the site of protein synthesis

Ribosomes

a complex of rRNA and proteins found in the cytoplasm which synthesize proteins

Mitochondrion

the site of aerobic respiration which are surrounded by a double membrane containing enzymes, producing ATP

Golgi apparatus

contains flattened membrane sacs which modifies proteins and lipids before packing them into vesicles

lysosome

a specialized form of vesicles containing hydrolytic enzymes used to break down waste and the immune system

chloroplast

contain membrane-bound compartments called thylakoids containing chlorophyll stacks to form grana.

phospholipids

the basic structure of the membrane formed by a hydrophilic phosphate head bonding to two hydrophobic fatty tails

simple diffusion

the net movement as a result of random motion of molecules down a concentration gradient

active transport

the movement of molecules and ions through a cell membrane against the concentration gradient using energy from respiration

endocytosis

the process by which plasma membrane engulfs materials forming a small sac called an endocytic vacuole.

exocytosis

the process by which materials are transported out of cells as substances are packed into secretory vesicles in the golgi apparatus, fuse with the surface cell membrane and are released.

mitosis

a regulated sequence of events that occur between once cell division and the next.

Interphase

the longest and most active phase during which a cell will increase in mass and size, synthesize proteins and begin replicating DNA

cyclin D

present first triggering a cell to move from G1 to S phase

cyclin E

highest concentration at the start of S phase preparing a cell for DNA replication

cyclin A

highest concentration in G2 phase activating the cell for mitosis and DNA replication

cyclin B

highest concentration at beginning of mitosis promoting the formation of the mitotic spindle

prophase

chromosomes condense and the two centronomes move towards opposite poles as spindle fibers begin to emerge and the nuclear envelope breaks down

metaphase

centronomes reach opposite poles as the chromosomes line up at the equator and spindle fibers reach and attach.

anaphase

sister chromatids separate and the spindle fibers begins to shorten pulling the chromosomes to opposite poles

telophase

chromosomes arrive at poles and decondense as a nuclear envelope reforms around each set and nucleoli form within each nucleus

mitotic index

number of cells with visible chromosomes/ total number of cells