Cells Unit Test

Cells that don't contain a nucleus are called ___________ cells.

prokaryotic

Receptors

Specialized proteins on the surface of the cell membrane called receptors receive information from outside of the cell (communication signals). Every receptor (type of protein) has a specific size and shape

Biotic

living Ex: Plants, animals, microorganism (bacteria), insects, dead rat

The _________ is located within the nucleus, and it makes ________ for the cell.

nucleolus, proteins

The _______ is a large, ____ structure that directs all of the cell's activities.

nucleus, oval

all organisms are composed of ___ or ____ cells.

one, more

Diffusion

Movement of molecules from an area of higher concentration to an area of lower concentration. Molecules move until they reach equilibrium (balance)

Osmosis

Movement of water from an area of high concentration to an area of low concentration (down the concentration gradient: no energy required)

Abiotic

Non-living Ex: Chair, sand, rocks

What do the daughter cells looks like at the end of mitosis in relation to the parent cell?

Once mitosis is complete the daughter cells look identical to the parent cell

What kinds of substances are able to cross through the cell membrane?

Only small substances are able to enter the cell without any help small substances -water -simple sugars (glucose) -Gases (02, C02 large substances (need help - facilitated diffusion) -Complex sugars -Starch -Salt

List the levels of cellular organization from smallest 🡪 largest

Organelle ---> cell ---> tissue ---> organ ---> organ system ---> organism

Why do plants need water?

They need water for photosynthesis- without it they cannot make glucose. They also need water to maintain the structure of the cells so they can support the stems and leaves.

How do guard cells and stomates work together to maintain homeostasis in plant cells?

To maintain homeostasis, plants must adjust their rates of transpiration in response to environmental conditions. The guard cells are also involved in maintaining homeostasis by regulation of water loss by the leaves. In case of extreme conditions like drought or high temperature, the guard cells tend to close the stomata (openings in leaves that help control gas exchange CO2 in O2 out) to minimize the water loss by the cell thereby maintaining homeostasis.

Describe the difference between unicellular and multicellular organisms.

Unicellular Organisms -Contain a single cell -carries out life functions without using organ systems -Earliest life forms -Have only organelles, not organs -Reproduce asexually -Can live in extreme environments -Examples: Amoeba, paramecium Multi-cellular -Contain multiple cells -Has organ systems that interact to carry out life functions carry out specific cell activities through a well-defined group of cells

Explain the difference between hypertonic, hypotonic, and isotonic solutions

Water movement (based on solute: solvent ratio) -If the solution (surrounding area) is HYPERTONIC (more solute than water) water moves out of the cell (cell shrinks) -If the solution (surrounding area) is HYPOTONIC (more water than solute) water moves into the cell (cell swells) -If the solution (surrounding area) is ISOTONIC (same solute and water) cell stays the same size

Why are there many ethical questions surrounding the use of embryonic stem cells?

"Those opposed to embryonic stem cell research argue that the potential benefits of such research do not justify the termination of a young human life. There is no question, they say, that even at the blastocyst stage a young human embryo is a form of human life... violation of the life, dignity, and rights of human beings...An assault against any human is an assault on humanity in general" (1). -Because it involves the destruction of human embryos, which some see as humans in an early stage of life. As a matter of religious faith and moral conviction, they believe that "human life begins at conception" and that an embryo is, therefore, a person.

Humans require organ systems to carry out life processes. Single-celled organisms do not have organ systems and yet they are able to carry out life processes. This is because (1) human organ systems lack the organelles found in single-celled organisms (2) a human cell is more efficient than the cell of a single-celled organism (3) it is not necessary for single-celled organisms to maintain homeostasis (4) organelles present in single-celled organisms act in a manner similar to organ systems

(4) organelles present in single-celled organisms act in a manner similar to organ systems

Identify a specific structure in a single-celled organism. State how that structure is involved in the survival of the organism.

- mitochondrion: site of respiration or releases energy -cell membrane: regulates what enters (or leaves) the cell

What are the 4 types of biomolecules in the body?

-Carbohydrates: provide the body with a source of energy and fuel, aid in the proper functioning of our brain, heart, nervous, digestive, and immune systems. The deficiency of carbohydrates in the diet causes fatigue and poor mental functioning. Categories of carbohydrates Monosaccharides: simplest sugar forms like glucose and fructose. Disaccharides: double sugars that are a combination of two monosaccharides. Polysaccharides: Polymers composed of several sugars -Lipids: provide energy storage. Structural cell membranes are composed of lipids that form a barrier and control the flow of material in and out of the cell. Lipids also help in mediating communication between cells and consist of fats and provide insulation -Proteins: provide structure and function within the body. are made of amino acids. each protein in the body has specific functions; some proteins provide structural support, help in body movement, and also a defense against germs and infections. Proteins can be antibodies, hormones, enzymes, and movement proteins -Nucleic acids: carry genetic information. DNA and RNA. They also help with the synthesis of proteins through the process of transportation and translation

What is the difference between chloroplasts and chlorophyll?

-Chlorophylls are part of the chloroplasts while chloroplasts are part of the plant cell -Chloroplasts are found in great concentrations in the plant's leaves. Chlorophylls are found inside the chloroplasts -Chlorophyll enables the green pigment in plants while chloroplasts are colored green because of the chlorophyll -Chloroplasts is where photosynthesis occurs and the chlorophyll absorbs the light energy from the sun used in photosynthesis

Enzymes

-Enzymes (found inside the cell) are specialized proteins that accelerate chemical reactions. (catalysts that lower activation energy. catalysts: a substance that helps a chemical reaction to proceed faster). -Enzymes are specific to only one chemical reaction (ex: amylase in our saliva helps begin breaking down our food) -Enzymes are very specific and only work with certain substrates that have a complementary shape to the enzyme -Temperature and pH levels affect the activity of enzymes -Enzymes denature (stop functioning) if they are not in their optimal conditions of temperature and pH level

Fermentation

-Lactic acid fermentation: when animals run out of oxygen, they build up lactic acid (C3H6O3: can cause muscles to cramp during exercise) as a byproduct (a secondary product derived from a production process) to help temporarily produce energy (ATP) -Alcoholic fermentation: When yeast runs out of oxygen, they release ethyl alcohol and carbon dioxide

Transpiration

-Transpiration is the evaporation of water from the leaves of a plant -As water evaporates through open stomates, the cell wall within the leaf begins to dry out

Cancer cells

-can cell can form a mass of cells called a tumor >Benign: non-cancerous, does not spread >Malignant: cancerous, can spread to invade/destroy surrounding healthy tissue -Metastasis: When cancer spreads from one part of the body to another

Uncontrolled mitosis

-cancer: uncontrollable cell growth -caner cells do not respond to signals that regulate cell growth (DNA is mutated. Mutation = change in DNA)

Why do receptors need to be of a specific shape and size?

-must be a certain shape because they receive information from outside the cell from specific molecules that match the shape of the receptor, if it were not the same shape the info would not transfer/not properly receive info -Chemical signals must have a complementary shape to bind to the receptors at the cell surface. Different receptors are specific for different molecules. -This is important because most signaling molecules are either too big or too charged to cross a cell's plasma membrane

What are the 5 major characteristics of life?

1. Are made of cells - Living things -Organisms that are constructed working things in the body, cells -Cells contain organelles -Plant and animal cells -Basic unit of life -Contains DNA to serve as genetic information 2. Grow and develop -change in size -gain complexity -Evolve/mature -Stages of life 3. Obtain and use energy -Plants get energy from the sun and use the process of photosynthesis -Metabolism -Break down food to produce energy -Different processes to obtain nutrients. ex: plants go through photosynthesis 4. Respond and adapt to their environment -hibernation -react to small stimuli -changes in response to environmental factors -evolution 5. Are able to reproduce -produce fertile offspring -continuing a species so it doesn't do extinct -produce offspring -can be asexual or sexual

Which set of functions is directly controlled by the cell membrane? 1) protein synthesis, respiration, digestion of food molecules 2) active transport, recognition of chemical messages, protection 3) enzyme production, elimination of large molecules, duplication of DNA codes 4) release of ATP molecules, regulation of cell reproduction, food production

2) active transport, recognition of chemical messages, protection

Which instrument was used in the 18th and 19th centuries and helped scientists develop the cell theory? 1) electron microscope 2) light microscope 3) microdissecting apparatus 4) ultracentrifuge

2) light microscope

Single-celled organisms carry out the activities needed to maintain homeostasis by using specialized internal 1) tissues 2) organelles 3) systems 4) organs

2) organelles

Which statement regarding the functioning of the cell membrane of all organisms is not correct? 1) The cell membrane forms a boundary that separates the cellular contents from the outside environment. 2) The cell membrane is capable of receiving and recognizing chemical signals. 3) The cell membrane forms a barrier that keeps all substances that might harm the cell from entering the cell. 4) The cell membrane controls the movement of molecules into and out of the cell.

3) The cell membrane forms a barrier that keeps all substances that might harm the cell from entering the cell.

What organelle releases energy for metabolic activity in cells? 1) chloroplast 2) ribosome 3) mitochondrion 4) vacuole

3) mitochondrion

What is the equation for photosynthesis?

6CO2 + 6H2O --(sun)--> C6H12O6 + 6O2 (reactant) (product) Carbon Dioxide + Water ---(sun)--> Glucose + Oxygen

Synthesis

A synthesis reaction occurs when two or more reactants combine to form a single product. This type of reaction is represented by the general equation: A + B → AB.

Examples of self-duplicating cellular structures are the A) mitochondria and chloroplasts B) mitochondria and cell walls C) cell walls and chloroplasts D) vacuoles and chloroplasts

A) mitochondria and chloroplasts

Which organism is considered an exception to the cell theory because it has a noncellular structure? A) alga B) bacterium C) virus D) moss

A) virus

Why is ATP important for all cells?

ATP is the main source of energy for most cellular processes. All organisms need energy. Life depends on the transfer of energy. ATP is an important source of energy for biological processes. Energy is transferred from molecules such as glucose to an intermediate energy source, ATP. This is true of eukaryotic and prokaryotic cells, although the ATP production mechanism differs across the two types. ATP powers a practically endless list of cellular processes. Without ATP, various metabolic activities in the human body cannot take place. Without ATP, cells wouldn't have their "energy currency" and would die. All living things are made of cells, and as their cells die, the organism dies.

What are the 2 kinds of respiration and how are they different?

Aerobic respiration -respiration that occurs when oxygen is present is called aerobic respiration there are three major steps in cellular respiration. together about 34-36 molecules of ATP are produced per molecule of glucose (enzymes are used in the process) Anaerobic respiration -cellular respiration that occurs when oxygen is not present is called anaerobic respiration (aka fermentation) -fermentation is the process that releases energy from glucose by producing small amounts of ATP without oxygen

How do plant cells differ in shape from animal cells?

Animal cells are mostly round and irregular and round in shape while plant cells have fixed, rectangular shapes.

Describe the difference between asexual and sexual reproduction

Asexual reproduction -Makes body cells in humans -Cells produced by cell division (daughter cells) are genetically identical to the parent cell Sexual reproduction -Makes sex cells in humans -Cells produced by fusing 2 parent cells -are different from parent cells

Which statement describes an exception to the cell theory? A) Plants and animals are made up of structural units known as cells. B) Mitochondria and chloroplasts contain genetic material and can replicate. C) All cells arise from preexisting cells. D) The cell is the basic functional unit of all living things.

B) Mitochondria and chloroplasts contain genetic material and can replicate.

Viruses are exceptions to the cell theory, but they have some characteristics of living things. What is one of these characteristics? A) They are made up of many specialized cells. B) They contain genetic material. C) They reproduce by mitosis. D) They contain chlorophyll.

B) They contain genetic material.

Microscopic examination of an animal cell reveals the presence of a plasma membrane but no cell wall. Which additional structures would normally be present within this cell? A) starch grains B) centrioles C) chloroplasts D) large vacuoles

B) centrioles

Which organelles outside the cell nucleus contain genetic material? A) lysosomes and cell walls B) chloroplasts and mitochondria C) endoplasmic reticula and cell membranes D) vacuoles and Golgi complex

B) chloroplasts and mitochondria

Which is the correct sequence of historical developments leading to our present knowledge of cells? A) electron microscope, cell theory, compound light microscope B) compound light microscope, cell theory, electron microscope C) cell theory, electron microscope, compound light microscope D) electron microscope, compound light microscope, cell theory

B) compound light microscope, cell theory, electron microscope

How is cellular respiration different from breathing?

Breathing involves inhale of oxygen from the atmosphere into the lungs and exhale of carbon dioxide from the lungs into the atmosphere ; whereas cellular respiration involves breakdown of glucose into carbon dioxide and water in living cells, releasing energy.

Hereditary information is stored inside the A) ribosomes, which have chromosomes that contain many genes B) ribosomes, which have genes that contain many chromosomes C) nucleus, which has chromosomes that contain many genes D) nucleus, which has genes that contain many chromosomes

C) nucleus, which has chromosomes that contain many genes

Certain poisons are toxic to organisms because they interfere with the function of enzymes in mitochondria. This results directly in the inability of the cell to A) store information B) build proteins C) release energy from nutrients D) dispose of metabolic wastes

C) release energy from nutrients

The function of a cell depends primarily on its A) life span B) color C) structure D) movement

C) structure

A liver cell can make enzymes that a heart cell can not make because liver cells A) digest large, complex molecules B) contain more DNA than heart cells C) use different genes than the heart cells use D) remove carbon dioxide from blood

C) use different genes than the heart cells use

What is the equation for cellular respiration?

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + ATP energy (reactants) (products) Oxygen + Glucose ---> Carbon Dioxide + Water + ATP (energy)

Explain how cancer can occur in cells

Cancer is uncontrollable cell growth. Cancer cells do not respond to signals that regulate cell growth. The DNA becomes mutated in these cells. Cancer can possibly occur with the presence of different Carcinogens, cancer causing substances. It is caused when there is damage or defect in mitosis.

What are the 3 basic principles of cell theory?

Cell Theory -all living things are composed of cells -cells are the basic units of structure/function (most basic unit of life) in living things -all cells arise from preexisting cells.

What is cell differentiation?

Cells are assigned their specific jobs whilst the embryo is developing. The process in which a cell changes from one cell type to another. Usually, the cell changes to a more specialized type.

What is cellular respiration?

Cellular respiration: (can be aerobic or anaerobic) the energy stored in food (glucose) is converted top ATP (energy currency used throughout the body) in the presence of oxygen -Occurs in the mitochondria of all living things (enzymes used in the process)

Identify an organelle in a plant cell that is the site of autotrophic nutrition.

Chloroplasts

What is the difference between a chromosome and a chromatid?

Chromosome A chromosome is a genetic material/consists of DNA wrapped around proteins in a highly organized manner. Chromatids A chromosome is made up of two strands that are identical to each other and these are called Chromatids. The two chromatids that make up a chromosome are called "sister chromatids". They are identical pieces of DNA held together by a centromere.

Why does cytokinesis need to occur right after mitosis?

Cytokinesis needs to occur at the right time and place so that each daughter cell has a complete diploid set of chromosomes, and so that the contents of the cell (cytoplasm and nuclei) are divided over two separate, identical daughter cells. Cytokinesis after mitosis completes cell division by slitting one cell into two and the result of mitosis without cytokinesis will be a cell with more than one nucleus.

To what would the phrase "is not a cell but has the ability to reproduce within a living cell" best describe? A) an alga B) a yeast C) a bacterium D) a virus

D) a virus

As a human red blood cell matures, it loses its nucleus. As a result of this loss, a mature red blood cell lacks the ability to A) take in material from the blood B) release hormones to the blood C) pass through artery walls D) carry out cell division

D) carry out cell division

Which cell organelle is composed of a series of channels throughout the cytoplasm that functions in the transport of molecules? A) lysosome B) chloroplast C) cell wall D) endoplasmic reticulum

D) endoplasmic reticulum

Which cell organelle is most directly involved with the bonding of amino acids? A) mitochondrion B) endoplasmic reticulum C) cell wall D) ribosome

D) ribosome

Explain the changes that occur when organisms have to go through anaerobic respiration/fermentation

During anaerobic cellular respiration, glucose is broken down without oxygen. The chemical reaction transfers glucose energy to the cell. In fermentation, instead of carbon dioxide and water, lactic acid (type of Fermentation in animals) is produced which can lead to painful muscle cramps.

What are the 2 kinds of stem cells and how are they different?

Embryonic Stem Cells: Come from human embryos and are capable of producing every cell type in the body (pluripotent: capable of giving rise to several different cell types). They also potentially have the scientific ability to cure many disease and injuries (Diabetes, Alzheimer's, Spinal Cord Injuries, etc). Adult Stem Cells: Come from body tissues (Ex: ski, blood, bones) and only regenerate the organ they come from (tissue-specific)

Why are enzymes important in the human body?

Enzymes speed up the process of normal chemical reactions in your body which would otherwise take much longer to happen. Enzymes are key for the body's homeostasis and are essential for digestion

What organelles are specific to either only plant cells or only animal cells?

Extra organelle in animal cell -Lysosome: contains enzymes that break down cell waste -Centrioles are paired barrel-shaped organelles located in the cytoplasm of animal cells near the nuclear envelope. Centrioles play a role in organizing microtubules that serve as the cell's skeletal system. Extra organelle in plant cell -Chloroplasts: Where photosynthesis occurs. Chloroplasts are plant cell organelles that convert light energy into relatively stable chemical energy via the photosynthetic process. Chlorophyll is the green pigment that is found in the chloroplasts of a plant cell that also makes the plant green -Cell wall: Gives structure and support to the plant cell

Describe the 3 parts of interphase

G1 phase (10 hrs): -The G1 phase is often referred to as the growth phase because this is the time in which a cell grows. During this phase, the cell synthesizes various enzymes and nutrients that are needed later on for DNA replication and cell division. S Phase (5-6 hrs): -Time of DNA synthesis (replication). In this way, the genetic material of a cell is doubled before it enters mitosis or meiosis, allowing there to be enough DNA to be split into daughter cells. G2 phase (3-4 hours): -Separates end of s phase from the onset of next M phase. This last stage is all about prepping the cell for mitosis or meiosis. During G2, the cell has to grow some more and produce any molecules it still needs to divide. It is a checkpoint to make sure mitosis can happen without any defects. At the end of interphase comes the mitotic phase, which is made up of mitosis and cytokinesis and leads to the formation of two daughter cells.

Where do gases move in and out of the leaves of a plant?

Gases move in and out of the leaves of a plant through pores called stomata

What does starch break up into after it is digested by enzymes?

Glucose

Guard cells

Guard cells are specialized cells surrounding the stomates that open/close them when necessary to reduce water loss (helps maintain homeostasis)

Explain the difference between passive and active transport

Passive transport requires no use of energy and high concentration to low concentration, while active transport does require energy goes from low concentration to high concentration Passive transport diffusion: the movement of molecules from an area of high concentration to low concentration (down the concentration gradient: no energy required) Active transport active transport: the movement of molecules from an area of low to high concentration (against the concentration gradient so ATP is required)

List the major organelles found in both animal and plant cells and explain their functions

Plant and animal cells are both eukaryotic cells, so they have several features in common, such as the presence of a... -Nucleus: "Brain of the cell" that contains DNA -Cytoplasm: Jelly-like fluid that holds all the organelles -Cell membrane: Barrier that holds the cell together and controls what goes in/out -Mitochondria: "Powerhouse of the cell" where respiration takes place to produce energy (ATP) -Ribosomes: Produces proteins -Golgi body: Packages proteins -Endoplasmic reticulum: Transports proteins (rough ER has ribosomes on it, smooth ER does not). Synthesis of digestive enzymes takes place in the internal space of the rough endoplasmic reticulum -Vacuole: Storage compartment

Why do you think the size of vacuoles are so different in plant and animal cells?

Plant vacuoles are larger than those of animal cells because plants need to be able to store more water for later if resources and water aren't available. Without enough water in the plant vacuoles, the plant will start to wilt.

Describe the differences between prokaryotes and eukaryotes

Prokaryotes -Simple organisms -Mostly unicellular -Do not have membrane-bound organelles -Prokaryotes lack mitochondria and instead produce their ATP on their cell surface membrane. Eukaryotes -Complex organisms -Multi-cellular -Have membrane-bound organelles

What are the 4 phases of mitosis and what major events occur during each phase?

Prophase -chromosomes become visible -nuclear membrane dissolves -spindle fibers form Metaphase -chromosomes line up in the middle of the cell -spindle fibers connect the centromeres to the poles Anaphase -Spindle fibers pull sister chromatids away to opposite poles of the cell Telophase -a new nuclear membrane forms around each set of chromosomes -chromosomes uncoil back into chromatin and spindle fibers -mitosis produced 2 nuclei membranes Splitting of the cell: Cytokinesis completes cell division by splitting one cell into two -animal cell: cell membrane draws inward and cytoplasm pinches in half -plant cell: cell plate forms between the two nuclei (gives rise to the cell wall)

Explain the process of how proteins are made and moved throughout the cells

Proteins are made by the ribosomes and transported by the endoplasmic reticulum

Facilitated diffusion

Proteins on the cell membrane help large substances enter the cell

According to bionomial nomenclature, how are organisms given a scientific name?

Scientists use a two-words naming system to give organisms their scientific names. The two Latin words are the genus (group) and species (specific type) of each organism

Where is the cell wall found and why does it have to be so strong?

The cell wall surrounds the cell membrane and provides a rigid structure. The cell wall has to be strong because it has to sustain high internal pressure and provide structure and support for the cell. It strengthens the cell and prevents water loss and over-expansion from water

Apoptosis

The death of cells which occurs as a normal and controlled part of an organism's growth or development. Programmed to die.

Active transport

The movement of molecules from an area of low to high concentration (against the concentration gradient so ATP is required)

What is the difference between a solute and a solvent

The solute is the substance that is being dissolved (usually the solid portion), while the solvent (usually the liquid) is the dissolving medium. Solutions can be formed with many different types and forms of solutes and solvents.

How does salt affect cells?

When cells are exposed to high levels of salt (sodium chloride) they lose water by osmosis and shrink. The cytoplasm condenses, the cell membrane shrinks, and the cell wall stays the same (Plant Cells). It is a hypertonic relationship.

What is the relationship between temperature, molecular motion, and diffusion?

When the temperature increases, energy increases, and therefore molecular motion goes at a faster rate, causing diffusion to quicken. Higher temperatures create more kinetic energy, causing the molecules to disperse and diffuse at a faster rate.

Explain the difference between photosynthesis and respiration

While photosynthesis requires carbon dioxide and releases oxygen, cellular respiration requires oxygen and releases carbon dioxide. It is the released oxygen that is used by us and most other organisms for cellular respiration

What is phtosynthesis?

a process used by plants (autotrophs) to convert light energy from the sun into chemical energy in the form of glucose (organic compound). The chloroplast is the site of photosynthesis (enzymes are used in the process). Plants use carbon dioxide and water, with energy from sunlight, to produce glucose, plus oxygen as a waste product.

which statement best compares a multicellular organism to a single-celled organism? a. A multicellular organism has organ systems that interact to carry out life functions, while a single-celled organism carries out life functions without using organs. b. A single-celled organism carries out fewer life functions than each cell of a multicellular organism. c. A multicellular organism always obtains energy through a process that is different from that used by a single-celled organism. d. The cell of a single-celled organism is always much larger than an individual cell of a multicellular organism.

a. A multicellular organism has organ systems that interact to carry out life functions, while a single-celled organism carries out life functions without using organs.

When most proteins, fats, and carbohydrates are digested completely, they are converted to end products that a. are soluble and can easily pass through cell membranes b. contain long chains of amino acids and fat acids c. contain atoms of carbon, hydrogen, oxygen, and nitrogen d. are a direct result of dehydration synthesis

a. are soluble and can easily pass through cell membranes

The development of the cell theory was directly related to the a. improvement of the microscope and microscopic techniques b. use of a five-kingdom classification system c. development of the gene-chromosome theory d. discovery of bacteria and viruses

a. improvement of the microscope and microscopic techniques

The energy needed for photosynthesis is trapped for the plant by?

chlorophyll

When cells begin to divide, the genetic materials within the nucleus _____ and _________, to form ___________.

coil, condenses, chromosomes

Passageways called the ___________ _________ carries ________ from part of the cell to another.

endoplasmic reticulum, proteins

Collections of sacs and tubes called _____ ______ distribute proteins and other materials throughout the cell.

golgi bodies

In a cell, information that controls the production of proteins must pass from the nucleus to the

ribosomes

Small, _____ structures called _________ break down food and recycle old cell parts.

round, lysosomes

Why is the cell membrane referred to as "semi-permeable"?

since only select things can pass though (exit and enter)

Which technique enabled scientists in the 1800s to identify cell organelles?

staining

Stomates

stomates are openings in leaves that help control gas exchange (CO2 in, O2 out)

Substrates

substrates (reactant) bind to the active site on an enzyme - they must have complementary shapes -The substrate (reactant) moves towards the enzyme's active site -The chemical reaction is triggered by the enzyme -The enzyme releases products