MHS Module 2 - cell and its components p1

explain cell theory:

• cells are the building blocks of all mechanisms

• cells from the division of preexisting cells

• smallest units that perform all vital physiological functions

• cell maintains homeostasis at the cellular level

what is the plasma membrane:

• extracellular fluid (interstitial fluid): watery medium that surrounds a cell

• plasma membrane separates cytoplasm from the extracellular fluid

functions of the plasma membrane

physical isolation: barrier

regulation of exchange with the environment:

• ions and nutrients enter

• wastes eliminated and cellular products released

sensitivity to the environment: uses receptors to recognise and respond to specific molecules in the environment

structural support: anchors cell and tissues

what Is the plasma membrane made up of?:

lipids, proteins, carbohydrates

describe the membrane lipids:

phospholipid bilayer:

• hydrophilic heads - face outward on both sides, toward watery environments

• hydrophobic fatty-acid tails, inside membrane

• barrier to ions and water-soluble compounds

name and describe types of structural proteins membrane proteins consist of?

integral proteins: within the membrane

peripheral proteins: bound to inner or outer surface of the membrane

define anchoring proteins

attach the plasma membrane to other structures and stabilise its position

define recognition proteins:

recognise cells as normal/abnormal

define receptor proteins:

bind and respond to ligands (ions, hormones), triggering changes in the cells activity

define carrier proteins:

transport specific solutes through membrane, may require ATP as an energy depending on the ion being transported

define channel proteins:

regulate water flow and solutes passing through membrane

gated channels open or close to regulate passage of substances

explain membrane carbohydrates:

consist of proteoglycans, glycoproteins, and glycolipids:

• extend outside cell membrane

• form sticky sugar coat (glycocalyx)

function of glycocalyx:

lubrication and protection

anchoring and locomotion

specify in binding (function as receptors)

recognition (immune response)

explain the cytoplasm:

consists of all materials inside the cell outside of the nucleus

made up of cytosol (intracellular fluid):

• contains dissolved materials

• high protein and potassium levels

• low carbohydrate, lipid, amino acid and Na+ levels

what are the dissolved materials in the cytosol

nutrients, ions, proteins and waste products

name and explain the 2 types of organelles

nonmembraneous organelles:

• no membrane

• direct contact with cytosol

membraneous organelles:

• isolated from cytosol by a plasma membrane

what do nonmembraneous organelles include of:

cytoskeleton, centrioles, ribosomes, proteasome, microvilli, cilia and flagella

what do membraneous organelles consist of:

endoplasmic reticulum. Golgi apparatus, lysosomes, peroxisomes, and mitochondria

what are inclusions?

masses of insoluble materials;

• stored nutrients such as glycogen granules or lipid droplets

explain the cytoskeleton and its components

protein framework that provides shape and strength for the cell:

made up of:

• microfilaments

• intermediate filaments

• microtubules

define and name function of microfilament:

thin filaments composed of protein actin:

• provide mechanical strength

• interact with other proteins to adjust consistency of cytosol

• interact with thick myosin filaments for muscle

define and name function of intermediate filaments:

mid-sized between microfilaments and microtubules:

• durable

• strengthen the cell and maintain its shape

• stabilise position of organelles

• stabilise cell position

define and name function of microtubules:

large, hollow tubes of tubulin proteins:

• attach to centrosome

• strengthen cell and anchor organelles

• change cell shape

• move organelles within the cell with help of motor proteins

• form spindle apparatus to distribute chromosomes

• form centrioles and cilia of organelles

name the motor proteins that assist microtubules move organelles

kinesin and dynein

define microvilli + function:

finger-shaped projections of plasma membrane on their exposed surfaces:

• increase surface area for absorption

• attach to the cytoskeleton

describe centrioles:

lie perpendicular next to each other, made up of short microtubules

form spindle apparatus (for movement of chromosomes) during cell division

form basal bodies found at the base of some cellular extensions

centrosome surrounds a pair of cylindrical structures called centrioles

describe cilia, and name and define types of cilia:

long slender extensions of plasma membrane

move fluids across the cell membrane

primary cilium = nonmotile:

• found on a variety of cells

• detects environmental stimuli and coordinating activities

motile cilia cells:

• found on the lining of the respiratory and reproductive tracts

• anchored to a basal body

why are motile cilia cells important

beat rhythmically to move fluids or secretions across the cell surface

describe flagella:

• whiplike extension of the plasma membrane

• only found on sperm

describe ribosomes:

organelles that synthesise proteins

composed of small and large ribosomal subunits, contain rRNA

free ribosomes in cytoplasm manufacture proteins that enter cytosol directly

fixed ribosomes are attached to ER; manufacture proteins that enter ER for packaging

describe proteasome:

organelles that contain enzymes (proteases)

disassemble damaged proteins for recycling

describe endoplasmic reticulum + function

contains storage chambers known as cisternae

functions:

• synthesis of proteins, carbohydrates and lipids

• storage of synthesised molecules and materials

• transport of materials within the ER

• detoxification of drugs or toxins

describe the smooth endoplasmic reticulum: + function

no attached ribosomes

synthesizes:

• phospholipids and cholesterol (for membranes)

• steroid hormones (for reproductive system)

• glycerides (for storage in liver and fat cells)

• glycogen (for storage in muscle and liver cells)

describe the rough endoplasmic reticulum: + functions

surface covered with ribosomes

• active in protein and glycoprotein synthesis

• folds proteins into secondary and tertiary structures

• encloses products in transport vesicles for delivery to Golgi apparatus

describe the Golgi apparatus: + function

vesicles enter carrying proteins destined for export (exit)

• modifies and packages secretions such as hormones or enzymes, for release from cell

• adds or removes carbohydrates to or from proteins

• renews or modifies the plasma membrane

• packages special enzymes within vesicles (lysosomes) for use in the cytoplasm

define lysosome: + function

powerful enzyme-containing vesicles produced by Golgi apparatus

• destroy bacteria, break down molecules and recycle damaged organelles

describe the 2 types of lysosomes:

primary lysosomes:

• contain inactive enzymes

secondary lysosomes:

• formed when primary lysosomes fuse with damaged organelles and enzymes are activated

what do lysosomes do when cells are inactive

gradually breakdown proteins by recycling process:

• lysosome membranes become increasingly permeable, then disintegrating

• releases digestive enzymes

• enzyme rapidly destroys the cells proteins and organelles through autolysis (self-destruction)

• cellular materials are recycled

describe peroxisomes: + function

small enzyme containing vesicles, produced by the division of existing peroxisomes

mostly found in liver cells

• breaks down organic compounds such as fatty acid, producing free radical h2o2

• catalase (enzyme in peroxisomes) converts h2o2 to oxygen and water

describe the mitochondria

smooth outer membrane

inner membranes contains numerous folds called cristae; surrounding fluid contents (matrix)

take chemical energy from food (glucose) to produce the energy molecule ATP

name the 3 steps in mitochondrial energy production

glycolysis, citric acid cycle/Krebs cycle, electron transport chain

describe aerobic metabolism (cellular respiration)

• requires oxygen to break down food and produce ATP

• produces 95% of ATP needed to keep a cell alive

• glucose + oxygen + ADP —> CO2 + H2O + ATP

describe the nucleus: + function

largest organelle

control centre for cellular respirations

surrounded by a double membrane called the nuclear envelope

nuclear envelopes 2 layers separated by a narrow perinuclear space

how does the nucleus determine cell structure and functions?

controls:

• which proteins are synthesised

• under what circumstances

• amount synthesised

how does chemical communication occur between the nucleus and the cytoplasm

nuclear pores: regulates the transport of materials such as RNA, ions and small molecules. DNA cannot pass freely

explain the contents of the nucleus:

fluid portion called the nucleoplasm:

• contains nuclear matrix: network of filaments that provides structural support

nucleoli:

• are nuclear organelles

• synthesise rRNA and assemble ribosomal subunits

• made up of RNA, enzymes and proteins called histones

nucleosome:

• dna coiled around histones

• in non-dividing cells, the DNA is loosely coiled, forming a tangled network called chromatin

• in preparation for cell division, the coiling becomes tighter forming visible structures called chromosomes

explain the information storage in the nucleus

dna in nucleus stores the instructions for protein synthesis

• genetic code is the chemical language that translates instructions from DNA

• information is stored in the sequences of nitrogenous bases (A, T, C, G)

how is information read?

genetic code is a triplet code, because a sequence of 3 nitrogenous bases represents 1 amino acid

define gene

the sequence of nucleotides of a DNA strand that specifies the amino acids needed to produce a protein