Unit 2: Cell Structure & Function

components of cell theory

all organisms are made up of cells; cells are the fundamental unit of life; cells come from preexisting cells

What does “fundamental unit of life” mean?

the cell is the simplest and smallest living entity

homeostasis

the active maintenance of stable internal conditions

How does the information of DNA direct a function within a cell?

it directs the formation of proteins (guides RNA synthesis which leads to protein synthesis)

Which molecule takes DNA information from the nucleus into the cytoplasm?

RNA

central dogma of biology

the flow of information in all cells: DNA to RNA to proteins

metabolism

all chemical reactions where cells transfer energy from one form to another and build/break down molecules

What molecule is the chemical form of energy for all organisms?

ATP (adenosine triphosphate)

anabolism

set of building reactions - require energy

catabolism

set of breaking reactions - release energy

unique shape of red blood cells

bioconcave shape - both sides curve inward (allows cells to be flexible to pass through narrow blood vessels and gives higher surface area to transport oxygen)

What is the result of a single amino acid change?

a change in its shape which then disrupts the function of the protein

What is the size difference between prokaryotes and eukaryotes?

eukaryotes are much larger in both diameter and volume

What is the cell wall of prokaryotes (eg. bacteria) made of?

peptidoglycan

What is the cell wall of plants made of?

cellulose

What is the cell wall of fungi made of?

chitin

What is the cell wall of algae made of?

cellulose, silicon, or calcium carbonate

endomembrane system

the interconnected membranes of the cell

Where can cell membranes be found in prokaryotes?

in photosynthetic bacteria (harness light energy)

What is the role of membranes inside the cytosol of the cell?

they allow separation of physical spaces so specific functions can occur within the spaces defined by the membranes

nucleus

houses chromosomes (hold and protect the cell’s genetic information)

nucleoid

where genetic material is located in a prokaryotic cell; not enclosed by a membrane

nuclear envelope

a cell membrane that encloses the nucleus; perforated by nuclear pores

nuclear pores

perforations in the nuclear envelope that allow proteins to pass in and mRNA to pass out

nucleolus

inside the nucleus; where ribosome assembly begins

cytoplasm

fluid portion of the cell that organelles float in; made of water, sugars, ions, and proteins; many cellular reactions occur in it

chromosomes

inside nucleus; made of tightly coiled DNA; store all of the organism’s genetic information (but only the needed genes in that specific cell type are switched on)

cell membranes

surround cells; made of a phospholipid bilayer; creates a selective barrier between the cell and its environment and embeds proteins in it

cell walls

only in plants, fungi, bacteria, and algae; provide structural support and protection for the cell

ribosomes

site of protein synthesis

How do vacuoles form?

by the fusion of multiple vesicles

difference of vacuoles between plants and animals

plants have a large central vacuole to store water; animals have many smaller vacuoles

vacuoles

store water, toxins, sugars, and ions

endoplasmic reticulum (ER)

produces proteins and lipids

rough ER

studded with ribosomes that produce transmembrane and organelle proteins

smooth ER

lacks ribosomes and is the site of lipid synthesis (fatty acids, phospholipids, steroid hormones)

Golgi apparatus

stacks of flattened membrane sacs (cisternae); further modifies proteins and lipids from the ER to make them usable for the cell, acts as a sorting station, site of glycosylation

cytoskeleton

internal scaffolding of proteins

glycosylation

covalently linking carbohydrates to lipids or proteins: takes place in the Golgi apparatus

lysosomes

generally only in animal cells; contain acidic enzymes that break down macromolecules and materials taken from outside the membrane through endocytosis

vesicles

transport substances from one organelle to another or to and from the cell membrane

How do vesicles form?

by pinching off, or “budding” from one membrane (ER) to the next (Golgi)

centriole

barrel shaped organelles from which microtubules grow; form spindle fibers (made of microtubules) that pull apart chromosomes during cell division

Which two energy processing organelles aren’t a part of the endomembrane system?

the mitochondria and chloroplasts

mitochondria

rod-shaped organelles with a double membrane (outer membrane and highly folded inner membrane); harness energy or organic molecules to produce ATP

mitochondrial matrix

the space enclosed by the inner membrane of the mitochondria

inter-membrane space

the area between the outer and inner membranes of the mitochondria

cellular respiration

a series of chemical reactions in which organic molecules are broken down and the energy stored in them is converted to ATP

How do the folds of the mitochondria relate to the process of cellular respiration?

the folds increase the surface area available for biochemical reactions that produce ATP, producing more ATP

chloroplasts

only in plant cells and green algae; have a double membrane and stacks of flattened sacs (thylakoids) grouped into stacks (grana) and liquid stroma; site of photosynthesis

photosynthesis

turning carbon dioxide, water, and light energy into oxygen and glucose

thylakoids

stacks of flattened sacs in the chloroplast; site of light-dependent reactions of photosynthesis

stroma

liquid in chloroplast that surrounds the thylakoids; site of light-independent reactions of photosynthesis

cilia and flagella

cellular appendages specialized for locomotion

function of the cytoskeleton

provides internal support for cells and helps determine cell shape

microtubules

hollow, structural rods that are assembled and disassembled when needed

microfilaments

extensively branch just beneath the cell membrane to reinforce the cell wall

function of microtubules and microfilaments

help with the process of cell division, cell shape, and cell movement

What are two cytoskeletal elements found in all eukaryotic cells?

microtubules and microfilaments

How do volume and surface area change as any object gets larger?

volume increases much more quickly than the surface area

diffusion

movement from high to low concentration

How does the rate of diffusion change as size increases?

rate of diffusion increases as size increases

osmosis

diffusion of water across a selectively permeable membrane

What adaptation do eukaryotic cells have to offset their smaller surface area to volume ratio?

highly folded internal membranes that increase the cell size and surface area to volume ratio

bulk flow

movement of fluid driven by pressure differences

amphipathic molecules

have both hydrophilic and hydrophobic regions

components of fluid mosaic model

phospholipids/cholesterol, proteins, and glycoproteins/glycolipids (and further structures)

further structures of the fluid mosaic model

cytoskeleton, cell wall, cilia, flagella

role of phospholipids in fluid mosaic model

makes up phospholipid bilayer: is uncharged so small, uncharged molecules can pass through

role of cholesterol in fluid mosaic model

gives the membrane rigidity (“islands”) and stability

role of proteins in fluid mosaic model

channels/gates: allow large, charged molecules to pass through but ATP has to be used; using ATP gives confirmation code to change protein shape

role of glycoproteins/glycolipids in fluid mosaic model

cellular flags: give identity to cell (when body doesn’t recognize cellular flags, it will attack itself - cancer, autoimmune diseases, blood types)

role of van der Waals forces in lipid interactions

weak intermolecular attractions are easily broken, so phospholipids move about with the tails interacting with each other so they can move laterally within the plane of the membrane (dynamic)

fluidity of cell membrane

more fluidity, less stability; ability of phospholipids to move laterally within the plane of the membrane

What factors increase the fluidity of a cell membrane?

shorter fatty acid tails, less van der Waals interactions, more unsaturated fatty acids, higher temperatures, cholesterol at low temperatures

transport proteins

move materials into and out of the cell

receptor proteins

allow the cell to receive signals from the environment

proteins in the mitochondrial and thylakoid membranes

pass electrons along the membrane to harness energy for use by the cell

anchor proteins

attach to other proteins and help maintain cell structure and shape

2 groups of membrane proteins

integral membrane and peripheral membrane proteins

integral membrane proteins

include transmembrane proteins that span the entire membrane

peripheral membrane proteins

are temporarily associated with either the internal or external side of the membrane

structure of transmembrane proteins

2 hydrophilic regions protruding from each face of the membrane and 1 hydrophobic region on the interior of the membrane

function of the hydrophobic region of a transmembrane protein

holds protein in the membrane and increases the stability of the protein within the membrane

function of the hydrophilic regions on external sides of transmembrane proteins

act as receptors

function of the hydrophobic region on the internal side of transmembrane proteins

interact with proteins in the cytoplasm to pass along the message

glycolipid

a carbohydrate covalently attached to a lipid; often function in cell recognition

glycoprotein

a carbohydrate covalently linked to a protein; often function in cell recognition

fluid mosaic model

molecules move laterally within the fluid lipid bilayer that is a mixture of various components

selectively permeable cell membrane

some molecules pass through freely, others have regulated movement, and others can’t pass through at all

What kind of molecules can easily cross the cell membrane?

nonpolar, uncharged, and small molecules (eg. oxygen, carbon dioxide, nitrogen, lipids, steroids)

What kind of molecules can’t easily cross the cell membrane?

polar, charged, and large molecules (eg. proteins and polysaccharides)

concentration gradient

difference in distribution of particles in solutions

dynamic equilibrium

molecules continue to move randomly in both directions once there are equal concentrations on both sides

passive transport

molecules moving across a membrane by diffusion because of differences in concentration between the inside and outside of a cell

simple diffusion

does not require cellular energy and only works from high to low concentrations

facilitated diffusion

diffusion across a cell membrane through a transport protein

two types of transport proteins used in facilitated diffusion

channel and carrier proteins

channel proteins

provide an opening between the inside and outside of the cell for certain molecules to pass through

carrier proteins

bind to and transport specific molecules across the cell membrane - 2 confirmations, 1 open to each side of the cell