Biology - Chapter 2 Cell Structure and Function

organelle

an internal functional structure that is located within the cytosol of the cell

cytosol

the fluid portion of the cytoplasm that surrounds organelles within a cell

plasma membrane

a dynamic barrier that surrounds the cytosol of the cell

does a nucleus have a membrane

yes

does a endoplasmic reticulum have a membrane

yes

does a golgi body have a membrane

yes

does the transport/secretory vesicle have a membrane

yes

do mitochondrion have a membrane

yes

does a chloroplast have a membrane

yes

does a lysosome have a membrane

yes

does a peroxisome have a membrane

yes

does a vacuole have a membrane

yes

does a ribosome have a membrane

no

does a centriole have a membrane

no

primary function of a nucleus

protects and controls access to DNA; makes ribosome subunits

primary function of a endoplasmic reticulum

routes and modifies new polypeptide chains; synthesizes lipids

primary function of a golgi body

modifies new polypeptide chains; sorts and ships proteins and lipids

primary function of a transport/secretory vesicle

transports substances within a cell and/or releases them from the cell

primary function of a mitochondrion

generates ATP and other molecules

primary function of a chloroplast

produces sugars using light energy, carbon dioxide, and water

primary function of a lysosome

carries out intracellular digestion

primary function of a peroxisome

inactivates toxins

primary function of a vacuole

provides storage and contains waste; in plants maintains cell size and shape

primary function of a ribosome

assembles polypeptide chains that are used to form proteins

primary function of a centriole

makes microtubules for the cytoskeleton; involved in cell division

most of the DNA in eukaryotic cells is contained in the

nucleus

which 2 organelles (other than the nucleus) contain DNA

• chloroplasts

• mitochondria

importance of the nuclear envelope

• a double membrane made from 2 lipid bilayers

• the outer bilayers is connected to the endoplasmic reticulum (ER)

• embedded membrane proteins (eg. receptors and transporters) regulate the movement of molecules in and out of the nucleus

• water and gases move freely through the nuclear envelope

• other molecules require transportation mechanisms and pumps to cross the envelope

• the system protects DNA and controls RNA and protein production

• proteins attached to the inner surface of the nuclear envelope anchor DNA, keeping it organized

• these anchor proteins aid in the production of DNA during cell division

mitochondria

an organelle with 2 membranes; the site of most ATP synthesis during aerobic cellular respiration

theory of endosymbiosis

certain organelles in eukaryotic cells (eg, mitochondria and plastids) evolved from aerobic bacteria that took up permanent residence inside a host cell.

this is due to clues such as mitochondria resembling bacteria in size, form, and biochemistry, as well as having their own DNA which is similar to bacterial DNA, and dividing independently of the cell and having their own ribosomes

chromoplasts

an organelle that makes and stores pigment other than chlorophyll

function of amyloplasts

unpigmented plastids that store starch

cytoskeleton

a dynamic system of filaments that provides cell structure, helps with cell division, and enables the cell and inner organelles to move around

important roles played by microtubules

1. act as a dynamic scaffold for various cellular processes, assembling and disassembling as needed

2. play a key role in cell division, particularly in separating duplicated chromosomes during mitosis

3. help maintain cell shape, provide structural support, and are involved in the movement of organelles and vesicles within the cell

important roles played by microfilaments

1. primarily composed of actin, they help strengthen the cell and enable changes in its shape

2. assist in cell movement by forming at the edges and helping to drag or extend the cell in a certain direction

3. in muscle cells, microfilaments of actins and myosin interact to bring about muscle contraction

what types of cells have a cell wall

plant, protist, and fungal cells

primary wall

a cellulose coating that surrounds a plant cell

secondary wall

a coating that is added to a plant cell wall; it is more rigid and often thicker than the primary cell wall

what is the extracellular matrix (ECM)

a complex, non-living network of fibrous proteins and polysaccharides secreted by cells

the ECM plays a critical role in multicellular organisms by

• provides structural support

• tissue organization

• cell signalling

• adaptation to tissue type

• specialized ECM roles (ECM is collagen in bones; and it hardened by mineral deposits to provide rigidity)

cell junction

a structure that allows cells to interact with each other and the surrounding environment

the cell membrane is mostly made up of

phospholipids, which is composed of a glycerol molecule to which 2 fatty acids and a highly polar phosphate group are attached

the phosphate group (the polar head) is

hydrophilic (water loving)

the non polar tails (the 2 fatty acids) are

hydrophobic (water fearing)

amphipathic

molecules that have a hydrophilic and hydrophobic component

when added to water, phospholipids

form spheres called micelles

how are micelles formed?

the hydrophilic heads dissolve in the water and the hydrophobic tails mix with one another in the center of the sphere. this membrane can separate.

examples of micelles

vesicles and vacuoles

example of a phospholipid bilayer

cell membrane

phospholipid bilayer

a double layer of phospholipids creates a bilayer. the polar heads mix with water and the non polar tails create a middle layer through which polar molecules, such as water, cannot pass. ionic/charged materials are also blocked by the non polar tails.

how do water and ions move through the cell membranes?

they are allowed to move through channels in the membrane

specifically ‘allowed’ because cells have a large degree of control over passes through their membrane

fluid mosaic model

termed by singer and Nicolson as a description in 1972. the membrane and the proteins, lipids, and carbs it holds are all constantly moving

why is cholesterol important in animal cells?

• provides structure and support

• why animal cells don’t need a cell wall like plant cells

transport

specific compounds may be able to cross a membrane by way of a hydrophilic protein channel.

alternatively, shape shifting may allow some membrane proteins to shuttle molecules from one side of a membrane to the other

enzymatic activity

some membrane proteins, such as those associated with respiration and photosynthesis, are enzymes

triggering signals

membrane proteins binding to specific chemicals such as hormones triggers changes on the inner surface of the membrane, starting a cascade of events within the cell

attachment and recognition

proteins that are exposed to both the internal and external membrane surfaces act as attachment points for a range of cytoskeleton elements, as well as components involved in cell-cell recognition and bond to the ECM.

eg. surface proteins can recognize elements of disease-causing microbes that may try to invade cells, triggering an immune response