• The ability of a cell membrane to control which substances 

and how much of them enter or leave the cell 

• Allows the cell to maintain a difference between its internal 

environment and extracellular fluid 

• Supplies the cell with nutrients, removes wastes, and 

maintains volume and pH

diffuse freely across a lipid 

bilayer  

• Passive transport 

• Active transport 

• Endocytosis and exocytosis

Ions and large polar molecules require other mechanisms to 

cross the cell membrane 

__

__

__

• Requires no energy input 

• A passive transport protein allows a specific solute (such 

as glucose) to follow its concentration gradient across a 

membrane 

• A gated passive transporter changes shape when a 

specific molecule binds to it

• Requires energy input (usually ATP) 

• Moves a solute against its concentration gradient, to the 

concentrated side of the membrane 

• Active transporters move calcium ions across muscle cell 

membranes into the sarcoplasmic reticulum

• An active transport protein that moves two substances 

across a membrane at the same time 

• Example: The sodium-potassium pump moves Na

+

 out of 

the cell and K+

 into the cell 

By processes of ______ and ____, cells take in and 

expel particles that are too big for transport proteins, as well 

as substances in bulk

The fusion of a vesicle with the cell membrane, releasing 

its contents to the surroundings 

• The formation of a vesicle from cell membrane, enclosing 

materials near the cell surface and bringing them into the 

cell  

Specific molecules bind to surface receptors, which are 

then enclosed in an endocytic vesicle

Larger target particles such as microbes or cellular debris 

are engulfed by pseudopods which merge as a vesicle, 

which fuses with a lysosome in the cell 

A less selective  endocytic pathway that brings materials in 

bulk into the cell 

– the remains of 

ancient forests, a limited resource

such as oils, gases, or alcohols are made from organic 

matter that is not fossilized – a renewable resource

harvest energy directly from the environment, and 

obtain carbon from inorganic molecules

a process which uses the energy of sunlight to 

assemble carbohydrates from carbon dioxide and water

get energy and carbon by breaking 

down organic molecules assembled by other organisms

An organic molecule that selectively absorbs light of specific 

wavelengths

The most common photosynthetic pigment  

• Absorbs violet and red light (appears green)

absorb most wavelengths 

of visible light

• First stage of photosynthesis: in thylakoids 

• Light energy is transferred to ATP and NADPH 

• Water molecules are split, releasing O2

Second stage of photosynthesis: in stroma

• Energy in ATP and NADPH drives synthesis of glucose 

and other carbohydrates from CO2

 and water

An organelle that specializes in photosynthesis in plants 

and many protists

Folded membrane that make up thylakoids 

• Contains clusters of light-harvesting pigments that absorb 

photons of different energies and convert light energy into 

chemical energy (first stage of photosynthesis) 

• A semifluid matrix surrounded by the two outer 

membranes of the chloroplast 

• Sugars are built in the stroma (second stage of 

photosynthesis) 

Light-dependent reactions convert light energy to the energy 

of

Electrons are released from special pairs of chlorophyll a

molecules in

– the process by which light energy breaks down a 

water molecule into hydrogen and oxygen 

electron transfer chain 

(ETC)

electron transfer 

phosphorylation

a light-driven reaction that attaches a 

phosphate group to a molecule

electrons move from water to 

photosystem II, to photosystem I, to NADPH

The cyclic, light-independent reactions of the Calvin-Benson 

cycle

Enzyme-mediated reactions that build sugars in the 

stroma of chloroplasts

-Extraction of carbon atoms from inorganic sources 

(atmosphere) and incorporating them into an organic 

molecule 

-Builds glucose from CO2

-Uses bond energy of molecules formed in light-dependent 

reactions (ATP, NADPH)

• Small openings through the waxy cuticle covering epidermal 

surfaces of leaves and green stems 

• Allow CO2

 in and O2

 out 

• Close on dry days to minimize water loss 

The first cells on Earth were ________ that extracted 

energy and carbon from inorganic molecules in the environment, 

such as hydrogen sulfide and methane

 use photosynthesis to make food from CO2

 and 

water, releasing O2

 into the atmosphere

removes carbon dioxide from the atmosphere, 

and locks carbon atoms in organic compounds

 break down organic compounds for 

energy, and release CO2

 into the atmosphere

metabolic pathways (using oxygen) are used by 

most eukaryotic cells

metabolic pathways (which occur in the absence 

of oxygen) are used by prokaryotes and protists in anaerobic 

habitats

most of the aerobic respiration pathway 

takes place inside mitochondria  

make ATP during photosynthesis and use it to 

synthesize glucose and other carbohydrates 

• 1) Glycolysis

• 2) Acetyl-CoA formation and Krebs cycle 

• 3) Electron transfer phosphorylation (ATP formation) 

which converts one molecule of glucose into two molecules of 

pyruvate

the first stage of carbohydrate breakdown in both 

aerobic respiration and fermentation 

one molecule of glucose to two molecules 

of pyruvate, with a net energy yield of two ATP; two NADH 

also form

pyruvate, forming acetyl CoA and CO2

 (which diffuses out of the 

cell)  

acetyl–CoA 

formation and the Krebs cycle, occurs in the inner 

compartment (matrix) of mitochondria

• Occurs in mitochondria 

• Results in attachment of phosphate to ADP to form ATP

2

2

32

Typically, the breakdown of one glucose molecule yields 36 

ATP 

• Glycolysis: __ ATP 

• Acetyl CoA formation and Krebs cycle: __ATP 

• Electron transfer phosphorylation: __ ATP 

Pyruvate is  split into 

acetaldehyde and CO2 

• Acetaldehyde receives 

electrons and hydrogen from 

NADH, forming NAD+

 and 

ethanol

•Pyruvate receives 

electrons and hydrogen 

from NADH, forming 

NAD+

 and lactate

_____muscle fibers make ATP by aerobic respiration 

• Have many mitochondria 

• Myoglobin stores oxygen 

• Sustain prolonged activity

______muscle fibers make ATP by lactate fermentation 

• Have few mitochondria and no myoglobin 

• Sustain short bursts of activity

A structure that consists of DNA and associated proteins 

• Carries part or all of a cell’s genetic information

Each filament consists of a coil of DNA wrapped around “spools” of 

proteins called

Each DNA-histone spools is a ____, the smallest unit of 

chromosomal organization in eukaryotes

Human body cells have two of each type of chromosome –their 

chromosome number is

shows how many  

     chromosomes are in an  

     individual cell, and reveals  

     major structural abnormalities 

– pairs of 

chromosomes with the same length, shape, and centromere location

differ between females and males – 

human females have two X chromosomes (XX); human males have 

one X and one Y chromosome (XY) 

 found DNA (deoxyribonucleic acid) in 

nuclei, though it’s function was unknown  

A nucleic acid monomer consisting of a 

five-carbon sugar (deoxyribose), three 

phosphate groups, and one of four nitrogencontaining bases

: thymine and cytosine 

adenine and guanine

Two pyrimidines:

Two purines

 the energy- 

intensive process by which a cell 

copies its DNA

breaks 

hydrogen bonds 

between DNA strands

untwists the double 

helix 

joins free nucleotides 

into a new strand of 

DNA 

joins DNA 

segments on the 

discontinuous strand  

A short, single strand of DNA or RNA that is 

complementary to a targeted DNA sequence

Each new DNA molecule consist of one old strand and one new 

strand 

DNA synthesis proceeds 

only in the ___ direction

proofread DNA sequences during DNA 

replication and repair damaged DNA

a permanent change in the  

     DNA sequence 

Ionizing radiation (gamma rays, x-rays, most 

UV light)

Knocks electrons out of atoms 

• Breaks chromosomes into pieces  

    that get lost during DNA replication 

• Creates free radicals in tissues 

Forms pyrimidine dimers that  

     kink the DNA strand 

• Causes skin cancer

technologies produce an exact copy 

(clone) of an individual

uses SCNT to produce human embryos for 

research purposes

ribosome-inactivating protein 

(RIP)

– it inactivates the organelles 

which assemble amino acids into 

proteins

All of a cell’s RNA and protein products are encoded by DNA 

sequences called

Enzymes use the  

    nucleotide sequence of  

    a gene to synthesize a  

    complementary strand  

    of RNA

Main component of ribosomes, where polypeptide chains 

are built

The information carried by mRNA is decoded  into a 

sequence of amino acids, resulting in a polypeptide chain 

that folds into a protein 

A multistep process including transcription and translation, 

by which genetic information encoded by a gene is 

converted into a structural or functional part of a cell or 

body

Sequences that stay  

     in the RNA

A sequence of three mRNA nucleotides that codes for a specific 

amino acid

Consists of 64 mRNA 

codons (triplets) 

• Twenty kinds of amino 

acids are found in proteins 

• Some amino acids can be 

coded by more than one 

codon 

a 

start codon

complementary to an 

mRNA codon, and a 

binding site for the 

amino acid specified by 

that codon

• Initiation 

• Elongation 

• Termination

• A small ribosomal subunit binds to mRNA 

• The anticodon of initiator tRNA base-pairs with the start codon 

(AUG) of mRNA 

• A large ribosomal subunit joins the small ribosomal subunit

Initiator tRNA carries methionine, the first amino acid of the chain 

• The ribosome joins each amino acid to the polypeptide chain with a 

peptide bond __

Small-scale changes in the nucleotide sequence of a cell’s DNA 

that alter the genetic code

May result in a premature stop codon or a different amino acid 

in a protein product 

• Example: sickle-cell anemia 

Can cause the reading frame of mRNA codons to shift, changing 

the genetic message 

• Example: thalassemia 

Deletions  cause a ______, in which the reading frame of the 

mRNA codons shifts

transposable 

elements

Insertion mutations are often caused by the activity of _______, which are segments of DNA that can insert themselves 

anywhere in a chromosome 

The process by which cells become specialized 

• In multicelled organisms, most cells differentiate when they start 

expressing a unique subset of their genes 

• Which genes are expressed depends on the type of organism, its 

stage of development, and environmental conditions

consist of molecules and structures that can 

start, enhance, slow, or stop individual steps of gene 

expression

encode products that affect the expression of many 

other genes

is the process by which a complex body forms 

from local processes in an embryo 

Master genes that control 

differentiation of specific tissues 

and body parts in an embryo 

• Encode transcription factors with 

a homeodomain

A region of about 60 amino acids 

that can bind to a promoter or 

some other sequence in DNA

Researchers inactivate a gene by introducing a mutation into it, 

then compare the differences with normal individuals – and 

similar genes in humans

In cells of female mammals, either the maternal or paternal X 

chromosome is randomly condensed (Barr body) and is inactive 

The theory that X chromosome inactivation equalizes 

expression of X chromosome genes between the sexes

Three sets of master genes (A,B,C) encode products that initiate 

cascades of expression of other genes to accomplish intricate 

tasks such as flower formation

are single celled and do not have 

master genes

Any heritable changes in gene expression that are not due to 

changes in DNA sequence are said to be

A sequence of three stages (interphase, mitosis, and cytoplasmic 

division) through which a cell passes between one cell division 

and the next

 is a nuclear division mechanism that maintains the 

chromosome number 

, a single individual can reproduce by 

mitosis and cytoplasmic division

pairs of chromosomes having the 

same length, shape, and genes

Chromosomes condense 

• Microtubules form a bipolar spindle 

• Nuclear envelope breaks up 

• Microtubules attach to the chromosomes

A region near the nucleus that organizes spindle microtubules; 

usually includes two centrioles

• A dynamic network of microtubules that forms during nuclear 

division 

• Grows into the cytoplasm from opposite poles of the cell and 

attaches to duplicated chromosomes 

• Microtubules from opposite poles attach to different sister 

chromatids and separate them

A cleavage furrow partitions the cytoplasm 

• A band of actin filaments rings the cell midsection, 

contracts, and pinches the cytoplasm in two

A cell plate forms midway between the spindle poles; it 

partitions the cytoplasm when it reaches and connects to 

the parent cell wall 

The ends of  eukaryotic DNA strands consist of noncoding 

sequences called

a molecule that reverses telomere shortening that 

normally occurs after DNA replication

– a group of cells that lost control 

over how they grow and divide 

s any gene that helps transform a normal cell into a 

tumor cell

are molecules that stimulate a cell to divide and 

differentiate

 tumor 

suppressors

(such as ordinary skin moles) grow slowly, stay in 

one place, and are not cancerous

disrupt body tissues, both physically 

and metabolically

a nuclear division mechanism that 

halves the chromosome number

are regions in an organism’s DNA that encode 

information about heritable traits 

Sexual reproduction involves the fusion of reproductive cells 

(___) from two parents

in animal germ cells gives rise to eggs (female gametes) or 

sperm (male gametes)

is the process by which a chromosome and its 

homologous partner exchange heritable information in 

corresponding segments 

Diploid bodies with specialized structures that form spores 

(haploid cells) that give rise to gametophytes through 

mitosis

A multicelled haploid body inside which one or more 

gametes form

The fusion of two haploid gametes (sperm and egg) resulting in 

a diploid zygote

The particular set of alleles that an individual carries is the 

individual’s

An individual with two identical alleles of a gene is ____ for 

that gene

An individual with nonidentical alleles of a gene is ______ for 

that gene

A __ is the heterozygote offspring of a cross between two 

individuals that breed true for different forms of a trait

An individual’s genotype determines its ____, which refers to 

an individual’s observable traits

Diploid cells have pairs of genes on pairs of homologous 

chromosomes  

• The two genes of each pair separate during meiosis, and end up 

in different gametes

During meiosis, members of a pair of genes on homologous 

chromosomes get distributed into gametes independently of 

other gene pairs 

test for dominance relationships between 

alleles at two loci

genes are very close together; crossing over rarely occurs 

between them

Two nonidentical alleles of a gene are both fully expressed in 

heterozygotes, so neither is dominant or recessive 

• May occur in multiple allele systems 

Genes with three or 

     more alleles in a  

     population

One allele is not fully 

dominant over its partner 

• The heterozygote’s phenotype 

is somewhere between the two 

homozygotes, resulting in a 

1:2:1 phenotype ratio in F2

offspring 

Two or more gene products influence a trait 

• Typically, one gene product suppresses the effect of 

another

A _____ gene influences 

multiple traits