Principles of Biology Exam 2

BIOL 1020 Auburn University

Plasma Membrane

phospholipid bilayer; surrounds cells and separates their contents from the external environment; selective barrier allows passage of materials and waste

Why is cell size limited?

to maintain a surface area to volume ratio

Why must cells maintain high surface area to volume ratio?

Metabolic requirements; to efficiently allow food and materials into the cell and waste products out of the cell.

How do cells maintain the surface area volume ratio?

By dividing

Prokaryotic Cell

lack a nucleus and have no membrane bound organelles

Eukaryotic Cells

have a nucleus and internal membrane bound organelles

Light Microscopes (LM)

ability to see most cells; visible light passes through a specimen and is bent by lenses to magnify the image

Magnification

the ratio of an object’s image size to its real size

resolution

the measure of the clarity of the image, or the minimum distance of two distinguishable points

contrast

visible differences in parts of the sample

Electron Microscopy (EM)

resolution of most sub cellular structure; 250,000x magnification, 500,000x resolution of the human eye

Fluorescence Microscopy

fluorescent dyes are used to identify cellular components

Scanning Electron Microscopes

look at the surface of a specimen giving a 3D image by focusing a beam of electrons onto the surface

Transmission Electron Microscopes

mainly used to study internal structure by focusing a beam of electrons through a specimen

Cell Fractionation

takes cells apart and separates the major organelles from one another

Explain how cell fractionation works.

Centrifuges fractionate cells into components and enables scientists to determine the functions of organelles, then biochemistry and cytology help correlate function to structure

Basic features of all cells

• plasma membrane

• semifluid substance called cytosol

• chromosomes

• ribosomes

Key characteristics of prokaryotic cells

• no nucleus

• DNA unbound in region called nucleoid

• no membrane bound organells

• cytoplasm bounded by plasma membrane

Key characteristics of eukaryotic cells

• DNA bounded in nucleus

• membrane bound organelles

• cytoplasm between plasma membrane and nucleus

• much larger than prokaryotic cells

Cytoplasm

everything outside the nucleus within the plasma membrane (cytosol and organelles)

Nucleoplasm

everything within the nuclear membrane

Nucleus

contains most of the cell’s genes and is usually the most conspicuous organelle

Nuclear Envelope

encloses the nucleus and separates it from the cytoplasm

Nuclear Pores

regulate entry and exit of molecules from the nucleus

Nuclear Lamina

composed of protein; maintains shape of nucleus

Chromosomes

organized DNA in discrete units; made of a single DNA molecule associated with proteins

Chromatin

DNA and proteins of chromosomes before they are condensed

Nucleolus

in the nucleus and is the site of all ribosomal RNA (rRNA) synthesis

Ribosomes

Protein synthesis; granular bodies with 3 RNA strands and about 75 associated proteins

• large and small subunits

• perform enzymatic activity for forming peptide bonds and translate genetic information into proteins

Bound Ribosomes

carry out protein synthesis on the outside of the endoplasmic recticulum or the nuclear envelope

Free Ribosomes

carry out protein synthesis in cytosol

What does a cell with a high rate of protein synthesis indicate?

A particularly large number of ribosomes and nucleoli (ex: pancreas cells)

What does the endomembrane system consist of?

• Nuclear envelope

• endoplasmic recticulum

• Golgi apparatus

• lysosomes

• vacuoles

• plasma membrane

Endoplasmic Recticulum

membrane network that winds through the cytoplasm; a lot of surface area; allows many important cell reactions to occur

ER Lumen

internal aqueous compartment in ER, separate from cytoplasm

Smooth ER

primary site of lipid synthesis, many detoxification reactions, etc.

Rough ER

attached ribosomes; insert proteins into the ER lumen as they are synthesized

Transport vesicles

small, membrane-bound sacs that transport proteins from the ER; bud off ER to fuse with other membranes to deliver contents

Golgi apparatus

a stack of flattened membrane sacs (cisternae) where proteins are further processed, modified, and sorted

• 3 areas: cis, medial, and trans

Cis face of Golgi body

near ER and receives vesicles; cisternal maturation model holds vesicles to consistently form new cis cisternae

Medial Region

where new cis cisternae are producers and older ones mature and move away from the ER; proteins are further modified and cisternae may become other products

Trans Face

nearest to plasma membrane; fully matured cisternae are broken into vesicles to take contents to proper destination

Vacuoles

large membrane-bound sacs that perform diverse roles; no internal structure; larger than vesicles

Central vacuole

typically a single, large sac in plant cells that can be 90% of cell volume; storage for water, food, salts, pigments, and metabolic waster

Tonoplast

membrane of plant vacuole

Food vacuoles

in most protozoa and some animal cells; usually bud off plasma membrane and fuse with lysosomes for digestion

Contractile vacuoles

used by many protozoa to remove excess water

Lysosomes

small membrane-bound spaces of digestive enzymes; degrade injested material or dead/damaged organelles

Can material digested by lysosomes be reused?

Yes, some material is sent to other parts of the cell

Where do cells get their energy?

usually obtained from the environment in the form of chemical energy (food) or light energy

Mitochondria

organelles where chemical energy is places in a more useful molecule; site of aerobic respiration

Chloroplasts

plastids where light energy is captured during photosynthesis

Formula for Aerobic Respiration

sugar + oxygen → carbon dioxide + water + energy(ATP)

Structure of mitochondria

• double membrane

• space between membrane=intermembrane space

• Inner membrane folded to create cristae and large surface area

• Inner membrane highly selective and host enzymes to conduct aerobic respiration

Mitochondial matrix

inside inner membrane; analogous to cytoplasm

Mitochondrial DNA

inherited from mothers in humans; divide separately from cell

Free Radicals

toxic; from mitochondria that leak electrons

Apoptosis

partially initiated by mitochondria; programmed cell death

Microbodies

small membrane bound organelles that carry out specific cellular functions (lysosomes, peroxisomes, glyoxysomes)

Peroxisomes

sites of many metabolic reactions that produce hydrogen peroxide (toxic to cell) which is then broken down to protect the cell

Where are peroxisomes found?

normally in all eukaryotes; abundant in liver cells (animals) and leaf cells (plants)

Glyoxysomes

in plant seeds; contains enzymes that convert fat to sugar; seedlings use as a source of energy until it can perform photosynthesis

Plastids

organelles of plants and algae that produce and store food; have their own DNA

Amyloplasts

starch storgage, amylose in roots and tuber

chromoplasts

for color, often in petals and fruits

Chloroplasts

green due to chlorophyll, main light harvesting pigment involved in photosynthesis

Photosynthesis Formula

Carbon dioxide + water + Light → Glucose + Oxygen

Chloroplast structure

• double membrane

• region within inner membrane is the stroma

• inner membrane is made of interconnected stacks of thylakoids stacked to make grana

• thylakoids enclose and aqueous region called the thylakoid lumen

Carotenoids

in chloroplasts; serve as accessory pigments for photosynthesis (makes leave red, orange, and brown in fall)

Explain Endosymbiont Theory

mitochondria and plastids evolved from prokaryotic cells that took residence in larger cells and became their energy converting organelles

Prove Endosymbiont Theory

Chloroplasts and mitochondria have separate DNA and ribosomes from the main cell, have two membranes, and reproduce and grow within the cell

Cytoskeleton

dense network of protein fibers that provide structural support specifically for animal cells; other functions: scaffolding for organelles, cell movement and division, transport within the cell

What are the 3 types of protein filaments that compose the cytoskeleton?

• microtubules

• microfilaments

• intermediate filaments

Microtubules

thickest, hollow, rod-shaped; made of alpha and beta tubulin; guide vesicles from ER to Golgi body to plasma membrane

Centrosome

located near nucleus, two centrioles in a perpendicular arrangement

Centrioles

9×3: 9 sets of 3 attached to microtubules to form a hollow cylinder; create the spindles for cell division

motor proteins

(kinesin or dyein) attach to organelle and microtubule (track to move on), use ATP to change shape and move

Motor Proteins are directional

kinesin moves towards the plus, dyein moves away from it

What are cilia and flagella made of?

microtubules

Cilia and Flagella

thin, flexible projections from cells; used in cell movement or to move things along the cell surface

Cilium

signal-recieving antenna for cell, signaling is crucial to brain function and embryonic development

Stalk of cilia and flagella

two inner microtubules surrounded by 9 attached pairs of microtubules

Microfilaments

solid filaments composed of 2 entwined chains of actin monomers; monomers can be added to lengthen or removed to shorten

What cell movement are microtubules responsible for

contractile movement (muscle contraction), forming cell extensions, “pinching in” during cell division

Intermediate filaments

slightly bigger than microfilaments; types of proteins differ by cell type and organism; reinforces cell shape and organelle position

glycocalyx

polysaccharides attached to proteins and lipids on the outer surface of the plasma membrane; cell communication and recognition, and structural reinforcement

What do animal cells have instead of cell walls?

they secrete varying amounts of compounds that can produce a glycocalyx and an extracellular matrix

Extracellular Matrix (ECM)

a gel of carbohydrates and fibrous proteins

Fibrous Collagen

main structural protein of ECM, very tough

Fibronectins

glycoproteins in ECM that often bind to collagen and integrins

Integrins

proteins in the plasma membrane that typically receive signals from the ECM

selective permeability

allows some substances to cross it more easily than others

Main function of membranes

• border

• border guarding

• surface for chemistry

Border

to separate aqueous environments so that differences can be maintained

Border guarding

regulating what gets in and out; helps establish appropriate environments in the cell even as the outside changes

Surface for chemistry

many enzymes are embedded in membranes to help control reactions

• getting reactants together

• getting catalysts and chain reactions together

What helps cells avoid equilibrium?

Embedded enzymes will have reactants on one side of the membrane and release products on the other side

Function of embedded proteins and glycoproteins

raising flags and sending/receiving messages for chemical recognition and signaling

Fluid Mosaic Model

the membrane is a mosaic of proteins bobbing in a fluid bilayer of phospholipids

Biological Membrane

lipid bilayers with associated proteins and glycoproteins