Ch. 3: Cell Structure and Function

Acid-fast bacteria

-cannot be identified by gram-stain

-very thin peptidoglycan layer

-glycolipids

-high amount of waxy lipids

-mycolic acid

Active transport

Energy-requiring process that moves material across a cell membrane against a concentration difference

Capsule

-outer membrane of prokaryotes (bacteria)

-highly organized (crosslinked and rigid)

-firmly attached to the cell wall

Chromatin

Substance found in eukaryotic chromosomes that consists of DNA tightly coiled around histones

Cilia

-contain microtubules

-much shorter than flagella

-large numbers on ciliated organisms

-helps protists move

-moves substances across surfaces in multicellular organisms

Concentration Gradient

A difference in the concentration of a substance across a distance.

Conjugation pili (sex)

-special type of fimbriae

-longerr than fimbriae but shorter than flagella

-bacteria typically have only one or two per cell

-transfer DNA from one cell to another (conjugation)

Cytoplasm

A jellylike fluid inside the cell in which the organelles are suspended

Diffusion

Molecules move down their electrochemical gradient through the phospholipid bilayer of the membrane

Endocytosis

process by which a cell takes material into the cell by infolding of the cell membrane

Endoplasmic reticulum

Rough

-covered with ribosomes

-site of synthesis for integral. Membrane proteins, exported proteins, and proteins destined for organelles

-glycosylation begins

Smooth

-no ribosomes

-involved in destroying toxins

-phospholipid synthesis

-steroid synthesis

Endospores

-unique structures produced by some bacteria

-defensive strategy against unfavorable conditions

-vegetative cells transform into endospores when multipe nutrients are limited

-resistant to extreme conditions such as heat, radiation, chemicals

Endotoxin

A toxic component of the outer membrane of certain gram-negative bacteria that is released only when the bacteria die.

Eukaryotic cells

-DNA as genetic material

-phospholipids in cell membrane

-very large

-animal cells - no cell wall

Plant cells - cell wall made of cellulose

Fungi - cell walls made of cellulose or chitin

-internal organelles (including the nucleus)

Exocytosis

Vesicles containing subtances are fused with cytoplasmic membrane, dumping their contentss to the outside

Facilitated diffusion

Molecules move down their electrochemical gradient through channels or carrier proteins

Fimbriae

-sticky, bristlelike projections

-used by bacteria to adhere to one another and to substances in the environment

-shorter than flagella

-serve an important function in biofilms

Flagella

-composed of filament, hook, and basal body

-rotation propels bacterium through environment

-rotation in reversible; can be counterclockwise. Or clockwise (runs and tumbles)

-bacteria move in response to stimuli (taxis)

Fluid mosaic model

Model which describes current understanding of membrane structure

Glycocalyx

-excreted from the cell and made of polysaccharides and/or proteins

-functions:

1. Attach to surfaces

2. Attach to other cells to form colonies

3. Evade phagocytosis

Golgi body

-receives proteins synthesized in the rough ER. From vesicles

-sugars added to proteins (glycosylation)

-proteins travel by vesicles to other organelles or to the cell membrane to be exported

Gram-negative cell wall

-Thin peptidoglycan

-outer membrane

-lipopolysaccharide (LPS)

-porins

-periplasmic space

Gram-positive cell wall

-thick peptidoglycan

-techoic acid

-lipotechoic acid

Hypertonic

when comparing two solutions, the solution with the greater concentration of solutes is said to be hypertonic

Hypotonic

when comparing two solutions, the solution with the lesser concentration of solutes is said to be hypotonic

Inclusions

-Chemical substances such as stored nutrients or cell products (energy rich materials)

-surrounded by thin membrane

Isotonic

when the concentration of two solutions is the same

Lipopolysaccharide (LPS)

Molecule that makes up the outer layer of the outer membrane of Gram-negative bacteria

Lysosome

-store and transfer chemicals within cells

-may store nutrients in cell

-contain catabolic enzymes

Mitochondria

-site of ATP synthesis by oxidative phosphorylation

-matrix is gel-like

-inner membrane and cristae contain proteins involved in ATP synthesis

Mycolic acid

A waxy lipid found in the cell walls of acid-fast bacteria.

N-acetyl glucosamine

NAG, molecule that holds a cell wall together

N-acetyl muramic acid

NAM, molecule that holds a cell wall together

Nuclear envelope

Double membrane which surrounds the nucleus

Nuclear pores

Allow exit of assembled ribosomes and mRNA

Nucleoid / Nuclear region

Location of genetic material in prokaryotes

Nucleolus

-Site of transfer RNA (tRNA)

-ribosomal RNA (rRNA) synthesis as well as ribosome assembly

Nucleus

Most prominant feature of eukaryotic cells, contains genetic material (DNA)

Organelles

Structures specialized to perform distinct processes within a cell

Osmosis

diffusion of water across a selectively permeable membrane

Outer spore coat

Protective coating on endospores consisting of dipicolinic acid and calcium, as well as a thick layer of peptidoglycan

Peptidoglycan

-polymer of polysaccharides and amino acids

-composed of alternating NAM and NAG

Periplasmic space

The space between the inner and outer cell membranes in Gram-negative bactera

Peroxisomes

-contain enzymes that degrade poisonous metabolic waste

-break down fatty acids for energy production

Phagocytosis

Solid substances are surrounded by pseudopods and brought into the cell.

Phospholipid bilayer

-the structure of cytoplasmic membranes is referred to as phospholipid bilayer

-composed of lipids and associated proteins:

-integral proteins

-peripheral proteins

Phototaxis

movement in response to light

Pili

-made of protein

-project through the cytoplasm, cell membrane, and cell wall into the environment

Plasmids

small circular DNA molecules that replicate separately from the bacterial chromosome

Prokaryotic cells

-DNA as genetic material

-phospholipids in cell membrane

-small cell size

-cell wall that contains peptidoglycan

-no internal organelles

-no nucleus

Ribosomes

-composed of two subunits

-"reads and decodes" RNA molecule

-protein (polypeptide) synthesis

Selectively permeable

a property of cell membranes that allows some substances to pass through, while others cannot

Slime layer

-a type of glycocalyx

-loosely attached to cell surface

-water-soluble

-sticky layer allows prokaryotes to attach to surfaces

Techoic acid

compound found only in gram positive bacteria

Vacuole / vesicle

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

How are eukaryotic cells different from prokaryotic cells?

-eukaryotic cells are significantly larger than prokaryotic cells

-eukaryotic cells have organelles (including nucleus) while prokaryotic cells do not

-prokaryotic cells have a cell wall containing peptidoglycan, while only some eukaryotic cells have cell walls containing cellulose or chitin

How are eukaryotic and prokaryotic cells similar?

-Both use DNA as genetic material

-both have phospholipids in cell membrane

What are the mechanisms that allow materials to be moved into and out of prokaryotic cells?

-Simple diffusion

-facilitated diffusion

-active transport

What are the mechanisms that allow materials to be moved into and out of Eukaryotic cells?

-simple diffusion

-facilitated diffusion

-active transport

-endocytosis

-phagocytosis