HUB2019F introduction to cells and tissues

cells are the ___ of all animals and plants?

building blocks

cells are formed from?

pre-existing cells

Each cell maintains _______ at the cellular level

homeostasis

what are cells?

fundamental unit of life

2 main classes of cells

prokaryotes and eukaryotes

eukaryotes

-nucleus
-membrane-bound organelles
-animals, plants, fungi

prokaryotes

-no nucleus
-no organelles
-bacteria

human body cells

-somatic
-sex

major parts of a cell

-plasma membrane
-cytoplasm
--cytosol
--organelles
-nucleus
--chromosomes
--genes

plasma membrane

outer membrane of cell that separates cell from surroundings

what does plasma membrane consist of?

phospholipid bilayer, cholesterol, proteins

what does plasma membrane contain?

integral proteins that span through the membrane and peripheral proteins - only partially embedded in one face of membrane

plasma membrane functions

-protection
-controls entry in and out of cell
-sensitivity to the environment
-structural support

Microvilli

tiny finger-like projections of the cell membrane containing microfilaments

microvilli function

increase surface area for absorption

Where are microvilli found?

-in areas where rapid diffusion takes place
-in kidney - reabsorption of molecules that are filtered out of the blood

Cilia

tiny hair-like structures of the surface of the cell containing microtubules

cilia function

-movement of fluid, mucous or cells over their surface
-move mucous to throat
-move fertilized egg to uterus

Nicotine negative effect

paralyses movement of cilia

Flagella

whiplike tails found in sperm to aid in movement

flagella function

propels sperm through its environment to oocyte

Cytoplasm

material between plasma membrane and nuclear membrane

what does cytoplasm contain

cytosol and organelles

Cytosol

-contains nutrients, ions, proteins, waste products as well as protein fibers
-site of many cellular reactions

organelles

structures suspended in cytosol that perform specific functions in the cell

The cytoskeleton consists of

microtubules, intermediate filaments, microfilaments

function of cytoskeleton

cells skeleton - framework of protein filaments that provide strength, flexibility and movement of cellular structures

Microfilaments

-smallest filaments
-composed of proteins actin and myosin

microfilaments function

-anchors and attaches the plasma membrane to the cytoplasm movement of cell
-or to change shape of the cell

intermediate filaments

-exceptionally strong filaments

intermediate filaments function

-support cell shape and fix organelles in place

Microtubules

-largest filaments comprised of tubulin

Microtubules function

-determine cell shape
-movement of organelles
-such as secretory vesicles and chromosomes cell division and cilia and flagella

Centrioles

paired cylindrical organelles near nucleus

each centriole is made of?

nine bundles of microtubules arranged in a ring

centrioles lie ___ to each other

at right angles

centrioles function

-during cell division form the spindle apparatus
-assist in movement of chromosomes during mitosis

centrosome

consists of 2 centrioles

Vacuoles

- Membrane-bound sacs for storage, digestion, waste removal and isolation of harmful material

ribosomes consist of

small and large subunits

Each ribosomal subunit is composed of

Multiple proteins and RNA

function of ribosomes

protein synthesis (mRNA is translated to protein on ribosomes = translation)

2 types of ribosomes

free and fixed

free ribosomes

produce proteins directly in the cytoplasm

fixed ribosomes

-attached to ER
-produce proteins destined for specific organelles, insertion into plasma membrane or export out of the cell

Endoplasmic Reticulum

network of intracellular membranes connected to the nuclear membrane

2 types of endoplasmic reticulum

rough and smooth

Smooth ER

-lacks ribosomes
-furthest from nucleus
-involved in synthesis of steroids, lipids and carbohydrates

Rough ER

-ribosomes attached
-connect to nuclear membrane and SER
-involved in protein synthesis

function of endoplasmic reticulum

folds and transports proteins to golgi apparatus

Proteasome

barrel-shaped structures contains protein digesting enzymes

proteasome function

-destroy unneeded, damaged or abnormal proteins
-cuts long proteins into small peptides - proteolysis

protein misfolding disorders

failure to destroy misfolded proteins

Golgi apparatus

consists of stacks of membranous discs - cis face and trans face

Golgi apparatus function

-modifies and packages proteins and lipids for export outside of the cell
-renews or modifies the plasma membrane
-packages proteins within vesicles for transport in the cell

lysosomes

contains digestive enzymes

Lysosomes function

to destroy damaged organelles or pathogens

primary lysosome

derived from golgi network

secondary lysosome

primary lysosome and substance to be digested

where are lysosomes numerous?

disease-fighting cells

Tay-Sachs disease

mutation in lysosomal enzyme, nerve cells funtion less efficiently - children experience seizures and muscle rigidity

Peroxisomes

small, spherical membrane-bound organelle

Peroxisomes function

contain oxidase enzymes that can oxidise organic substances - mostly long fatty acid chains

what can peroxisome enzymes do?

they can oxidise toxic substances such as alcohol - prominent in liver

what is a by-product of peroxisome oxidation?

H2O2

Catalase

regulates hydrogen peroxide by breaking it down into water and oxygen

mitochondria

double layered membrane

mitochondrial inner membrane forms folds called?

cristae

cristae inscrease surface area exposed to matrix which leads to

contain enzymes to make ATP

Mitochondria function

-energy production in a cell
-store calcium for cell signalling activities
-role in cell death (apoptosis)

erythrocyte mitochondria content

none

liver cells and muscle cells have how many mitochondria

hundreds and even thousands

more active cells ___

have more mitochondria

Nucleus

Control center of the cell

nucleus contains

DNA

nucleus structure

-nuclear envelope
-nucleoplasm ( chromatin, nucleolus)

nucleus function

-gene expression
-cell division
-information storage

nuclear envelope

double-layered membrane surrounding nucleus

nuclear envelop outer membrane

continuous with endoplasmic reticulum

nuclear pore complex

where 2 membranes fuse

nuclear pore

central opening of nuclear pore complex for nuclear traffic

Nucleolus

non-membrane bound structures

nucleolus composition

DNA, RNA and proteins

nucleolus function

to transcribe rRNA and synthesise ribosomal subunit proteins to produce ribosomes

chromatin

complex of DNA and protein

Nucleosome

section of DNA wrapped around a core of proteins

how does chromatin form chromosomes?

they condense during cell division

lipid droplets

spherical aggregates of lipid

lipid droplets function

energy storage

glycogen granules

aggregates of glycogen

glycogen granules function

energy storage

lipofuscin

brown pigment in cytoplasm

lipofuscin function

waste product

melanin

brown pigment in cytoplasm

melanin function

-skin and hair pigmentation
-present in nerve cells

histology

study of tissues

tissues

Groups of cells with a common structure and function.

4 basic tissue types

epithelial, connective, muscle, nervous

epithelial tissue

covers internal and external surfaces

epithelia

-covers external surfaces
-covers internal surfaces