Tour Of The Cell ch 6.

magnification

makes an object look bigger

resolution

how clear an object is

relationship btwn magnification and resolution

as magnification increases, resolution decreases

contrast

accentuation of differences in parts of the object

how can you see contrast easier

staining

microscope development has focused on improving magnification and resolution via...

- Beller glass

- quartz lenses used w uv light and camera

- electron microscopy

electron microscopy

uses electrons instead of light, the shorter wavelength of electrons gives greater resolution

galileo galilei + microscope

1600s: arranged 2 glass lenses to form primitive microscope

robert hooke + microscope

1665: viewed cells in mediterranean oak bark using microscope and called them "cellulae"

Antoni van Leeuwenhoek + microscope

viewed drops of water and called protists animalcules

schiden and shwaann

cell theory w microscope

abbe and zeiss + microscope

1900: first perfect microscope--> first to resolve many organelles including mitochondria and chloroplasts

- today's scopes are abt the same

why is oil immersion needed for 1000x microscope lenses?

oil has higher refraction index than air so gathers more light--> higher resolution

electron microscope

1930s: originally developed in germany

- used e- beam as opposed to light to view images, specimen coated with gold to conduct electricity

what was a disadvantage of the electron microscope

cells viewed are dead since it would have to be frozen to view under the electron microscope--> can't unfreeze specimen

2 types of modern microscopes

scanning e- microscope and transmission e- microscope

scanning e- microscope (SEM)

runs a beam of e- across the surface of a specimen; 3 dimensional images

transmission e- microscope

you see the inside of the specimen so you can study the internal parts

functions of cell membranes

-Keep damaging materials out of the cell

-Allow entry of materials needed by the cell

-sending/receiving chemical messages from other cells

importance of surface area to volume ratio in cells

if the ratio is too low, there is not enough cell membrane and the cell cannot carry on its normal metabolic functions efficiently enough to survive

the larger the cell, the _____ (lower/higher) the surface area:volume ratio

the larger the cell, the lower/higher the surface area: volume ratio

how do larger cells increase their surface area

they're elongated or folded

all cells have

plasma membrane, cytosol, chromosomes, ribosomes

cytosol

semi-fluid portion of the cytoplasm

what are chromosomes composed of?

DNA and protein

function of ribosomes

protein synthesis

do prokaryotic cells have a nucleus

no, dna is not bound by a membrane

Nucleoid

A non-membrane-bounded region in a prokaryotic cell where the DNA is concentrated.

structure of DNA in prokaryotic cells

short, circular and not associated with proteins

do prokaryotic cells have membrane bound organelles

no

importance of cytoplasm in prokaryotic cells

cytoplasm contains all structures needed for life

are prokaryotes unicellular or multicellular

unicellular

why do most prokaryotic cells have a cell wall

for shape and protection

what are the 2 domains of prokaryotes

Bacteria and Archaea

where is the DNA enclosed in eukaryotic cells

nucleus

Do eukaryotic cells have membrane bound organelles?

yes

organelles

internal membrane-bound compartments for specialized functions

Why is compartmentalization important?

breaks up work amongst organelles keeping things more organized; allows many reactions to proceed simultaneously in a very small space

_____ and _____ cells contain many of the same organelles

plant and animal

plasma membrane

A selectively-permeable phospholipid bilayer forming the boundary of the cells

functions of plasma membrane

- separates cell from outside

- regulates the flow of materials in and out of the cell

- allows interaction with other cells through receptors and signaling molecules

chromatin

loosely wound DNA and associated proteins inside nucleus

chromosomes

distinct unit of DNA and proteins

metaphase chromosome

dna tightly coiled around histone proteins

nuclear envelope

seperates nuclear material from cytoplasm

structure of nuclear envelope

2 lipid bilayers with small nuclear pores

function of nuclear envelope

- let water and small molecules pass through freely

- regulate movement of large molecules like protein+RNA

pore complexes

line the nuclear envelope; regulate information flow between the nucleus and cytoplasm

Where is the nucleolus found?

inside the nucleus

how many nucleolus are there in a cell

can be one or more per nucleus

what is the nucleolus made of

ribosomal RNA, proteins, ribosomes, and DNA

function of nucleolus

site of rRNA synthesis and assembly of ribosomal subunits

nucleoplasm

soluble (aqueous) part of the nucleus

ribosomes

small particles of rRNA and proteins involved in protein synthesis

how can any ribosome be used to synthesize any protein

The same ribosome can move from one mRNA to another, producing different proteins depending on the mRNA sequence it reads.

Ribosomes are like a factory machine.

mRNA is like the instruction manual.

tRNAs bring parts (amino acids).

The ribosome assembles the protein by reading the instructions.

where can ribosomes be found

cytoplasm and rough ER

are the ribosomes in the cytoplasm actually just free

no; they're attached to the cytoskeleton

endoplasmic reticulum

series of interconnected membrane enclosed tubes and sacs in the cytoplasm

how is the ER connected to the nucleus

one of the nuclear pores open up into the ER

what makes the rough er rough

ribosomes

how are proteins transported through er

Ribosomes attached to the RER synthesize proteins destined for:

- Secretion (export out of the cell)

- Insertion into the plasma membrane

- Use in lysosomes or organelles

As the protein is synthesized, it's threaded directly into the lumen (inside) of the RER through a pore in the RER membrane.

This is called co-translational translocation—the protein enters the RER while it's still being made.

Inside the RER, the protein begins folding into its 3D shape.

Some modifications (like adding sugar groups—glycosylation) may occur here.

The protein collects in pockets or cisternae of the RER.

These pockets bud off from the RER as transport vesicles, which are small membrane-bound sacs containing the protein.

The transport vesicles move to the Golgi apparatus, where they fuse with the Golgi's cis face (the receiving side).

which ER is responsible for synthesizing lipids

smooth er

functions of smooth er

Synthesizes lipids

Metabolizes carbohydrates

Detoxifies drugs and poisons

Stores calcium ions

why can the ER form membranes

cuz the smooth er can make lipids and the rough er can make proteins

golgi apparatus

A system of membranes that modifies and packages proteins for export by the cell

Dictyosomes

stacks of cisternae in the golgi apparatus

how are vesicles transported through the golgi

ER vesicles fuse with the cis side of the Golgi, adding their membrane to the Golgi and exporting their contents into the golgi sacs.

other vesicle buds off golgi on the trans side and leave, carrying away proteins, lipids, and other molecules

functions of golgi

- receives transport vesicles from ER

- sorts: separates proteins and lipids from the ER according to their destinations

- alters: modifies molecules and makes carbs through processes like glycosylation

- packages material into vesicles that are transported to other parts of the cell

glycosylation

adds or modifies carbohydrate (sugar) groups on proteins and lipids, turning them into glycoproteins or glycolipids.

lysosome

membranous vesicles containing digestive enzymes: breaks down proteins, fats, nucleic acids, and carbs

which type of cells are lysosomes usually found in?

animal cells

??? where are the enzymes found in lysosomes made

made by the ER

lysosome functions

phagocytosis and autophagy

Describe how lysosomes digest food particles or invading organisms

phagocytosis by a cell--> these particles enclosed in vesicles called food vacuoles--> lysosome fuses w contents of food vacuoles--> lysosome enzymes digest the food into smaller molecules that diffuse out of the lysosome and into the cytoplasm

autophagy

lysosomes break down damaged organelles

explain how autophagy works

a cell identifies the defective organelles and encloses them in 2 membranes with a peroxisome--> a lysosome fuses with the vesicle--> organelles are digested

after molecules are digested, can they be reused in cellular processes

yes

vacuole

a fluid-filled sac used for the storage of materials needed by a cell

how many membranes does a vacuole have

1

how many vacuoles do most cells have

1 or more

contractile vacuole

removes water from a cell; permanent

explain how contractile vacuoles work

purer water enters the cell through the cell membrane (osmosis)--> cell would keep taking up more water until it bursts if it didnt have a way to get rid of the water--> protists pump salts into the vacuole--> water enters the vacuoles cuz of osmosis--> when the reservoir is full, it contracts, squeezing water out through a pore in the membrane

how much of the cell does the centralized vacuole take up

around 75%

why's it important that the central vacuole forces organelles to be pushed against the plasma membrane

creates TURGOR PRESSURE

- Maintains cell rigidity and structure: The pressure keeps the plant cell firm and helps the plant stay upright. Without it, plants would wilt.

- Optimizes surface area for exchange: Pushing organelles toward the plasma membrane allows efficient exchange of nutrients, gases, and waste between the cell and its environment.

- Supports growth: The vacuole's pressure helps cells expand during growth without having to produce more cytoplasm.

functions of centralized vacuole

- involved in cell's water balance

- dump site for hazardous wastes, which cells often cannot excrete

- storage

importance of turgor pressure

In plant cells to gives rigidness to stand straight and do normal activities

are food vacuoles temporary

yes

hydrolytic vacuoles

basically lysosomes for plants

endomembrane system consists of

nuclear envelope, endoplasmic reticulum, golgi apparatus, lysosomes, vacuoles and the plasma membrane.

are peroxisomes involved in endomembrane system

no

Explain the endomembrane system of protein modification and transport.

Rough Endoplasmic Reticulum (RER) - Ribosomes on the RER make proteins, which enter the RER for folding and initial modification (like adding sugar chains).

Transport Vesicles - Carry proteins from the RER to the Golgi apparatus.

Golgi Apparatus - Further modifies, sorts, and packages proteins for their final destination.

Vesicles - Transport the modified proteins to the plasma membrane (for secretion), to lysosomes, or to other parts of the cell.

peroxisome

vesicles with enzymes to break form fatty acids (lipids), amino acids (proteins), and alcohol (toxin)

How does peroxidase neutralize hydrogen peroxide?

it does not produce oxygen gas just water

H2O2 + 2H --------->2H2O

function of mitochondria

provides energy for cells via cellular respiration

what part of the body is there an abundance of mitochondria

metabolically active cells like in muscle tissue

endosymbiotic theory

mitochondria and chloroplasts may have been dervied from bacteria that took up residence within eukaryotic cells 1 billion years ago

evidence for endosymbiotic theory

Mitochondria and chloroplasts possess their own DNA similar to prokaryotes

double membrane

reproduce by fission independent of cell

mobile within cell

structure of mitochondria

- outer membrane

-cristae- inner membrane that is folded

- inner membrane divides into: outer compartment and the matrix

where in the mitochondria do the metabolic functions happen

within the matrix fluid and along membrane cristae

what kind of organelles are plastids found in

photosynthetic organisms (plants and protists)