Unit 2: The Cell

Flashcards based on Unit 2: The Cell lecture notes.

Where is the DNA located in a prokaryotic cell?

DNA is in the cytoplasm (no nucleus in prokaryotic cells).

What features are shared by both eukaryotic and prokaryotic cells?

Cell membrane, cytoplasm, ribosomes, DNA as genetic material

Which domain(s) of life contain members whose cells do not contain mitochondria?

The members of the domains Bacteria and Archaea do not contain mitochondria.

Describe the structure of the nuclear envelope. What is its function?

The nuclear envelope is a double membrane structure that protects the DNA contained within the nucleus.

What intracellular structure regulates the passage of molecules in and out of the nucleus?

The nuclear pores

What is chromatin?

DNA + proteins to keep it organized

What are chromosomes?

Condensed chromatin that is visible with a compound light microscope

Where is rRNA (ribosome component) manufactured in the nucleus?

The nucleolus

Cells that produce many proteins have many ribosomes, why?

Ribosomes are the site of protein synthesis (production) so protein producing cells require many ribosomes.

How many subunits compose a ribosome?

Two subunits. One small subunit and one large subunit.

Do ribosomes have a membrane?

No.

What is the function of the rough endoplasmic reticulum?

The rough endoplasmic reticulum is involved in production of proteins.

What kind of biomolecules does the rough endoplasmic reticulum produce?

The rough ER produces proteins (in cooperation with ribosomes).

If you identified a cell with large amounts of rough ER, what would be a logical conclusion about that cell?

A logical conclusion would be that the cell produces many protein molecules.

What granular organelle can be found attached to the rough ER?

Ribosomes

What are the functions of the smooth endoplasmic reticulum?

The smooth ER produces lipids and contains enzymes for detoxification.

What kind of biomolecules does the smooth ER produce?

The smooth ER produces lipids.

What are the functions of the Golgi apparatus?

The Golgi apparatus completes the synthesis of products produced in the endoplasmic reticulum (processes), stores the finished products in vesicles (sorts), and then sends those vesicles to their destination (ships).

Which organelle “ships” its products to Golgi apparatus?

The endoplasmic reticula (proteins from the rough ER and lipids from the smooth ER).

What kinds of enzymes are in a lysosome?

Hydrolytic enzymes that digest macromolecules.

Which organelle digests other damaged or defective organelles?

The lysosome.

Why do plant cells have a central vacuole?

Plant cells use their central vacuole to store pigments, waste products, and toxins. Turgor pressure is maintained as long as the central vacuole remains hypertonic to the soil.

What is the function of a contractile vacuole and why do many protists have one?

Contractile vacuoles act like bilge pumps to pump excess water out of a cell. Protists, which typically live in hypotonic environments, have a contractile vacuole to prevent them from bursting due to osmotic pressure.

What is the function of the mitochondria?

Production of ATP via aerobic respiration.

What is the second compartment called?

The matrix.

What is the benefit of mitochondrial cristae?

The cristae of the inner mitochondrial membrane increase the surface area of the membrane, which makes more room for electron transport chain components and ATP synthase complexes.

Do plant cells contain mitochondria?

Yes. Plant cell mitochondria produce ATP for cellular work, just like they do in animal cells.

What is the function of the chloroplast?

Production of sugars by fixing atmospheric carbon dioxide using the energy of light.

What are thylakoids and how are they important to photosynthesis?

Thylakoids are membranous sacs within the chloroplast that contain the light harvesting pigments (chlorophyll) and are the location of the light dependent reactions of photosynthesis.

Where is the stroma?

The stroma is the fluid that surrounds the thylakoids in a chloroplast.

What is the evidence that mitochondria and chloroplasts were once free- living organisms?

Both contain their own circular DNA. Both replicate independently from the nucleus of the cell. Both contain their own ribosomes that are like bacterial ribosomes. Both are double membrane organelles, and the inner membrane is like a bacterial membrane.

What cellular structure determines a cell’s shape?

The cytoskeleton.

What three kinds of fibers comprise the cytoskeleton of a cell?

Microfilaments, intermediate fibers, and microtubules.

What is the function of microfilaments?

Microfilaments maintain the cell’s shape, are involved in cell motility (pseudopodia), and play a role in cytokinesis.

What is the function of intermediate filaments?

Intermediate filaments provide tensile strength to the cell and anchor the nucleus in place.

What is the function of microtubules?

Microtubules resist cell compression, move organelles around within the cytoplasm, move chromosomes during cell division, and are components of both cilia and flagella.

What are some differences between cilia and flagella?

Cilia are short, hair-like fibers for motility and flagella are long, whip-like fibers for motility.

Short, hair-like extensions of the plasma membrane typically used in cell movement are called?

Cilia.

Describe the fluid mosaic model of the plasma membrane. What is fluid about membranes?

Membranes contain mostly phospholipids with many proteins embedded in the membrane. All membrane components are free to move around within the membrane, so it is fluid.

What is a mosaic?

Random distribution of phospholipids and proteins in a cell membrane create a mosaic effect.

What are 6 different types of membrane bound proteins?

Attachment, receptor, transport, junction, recognition, enzyme.

Why is the plasma membrane known as the gatekeeper of the cell?

The membrane is semipermeable and regulates entry and exit from the cell.

Which type of protein allows the movement of hydrophilic molecules across the plasma membrane?

Transport proteins (channel proteins)

Which type of protein delivers chemical messages to the cell across the plasma membrane?

Receptor proteins

Which type of protein serve as identification tags and cell-surface attachment sites?

Recognition proteins

Membranes that allow the passage of small molecules but block the passage of large molecules are called ___ permeable.

Semipermeable or selectively permeable

What is the function of cholesterol in the plasma membrane?

Cholesterol stabilizes the membrane’s phospholipids and helps control fluidity

How do membranes demonstrate the interconnection between all living organisms on Earth?

All cells have a cell membrane, and they all have very similar properties.

Which part of a phospholipid is hydrophilic?

The polar head group is hydrophilic.

What is diffusion?

Diffusion is the movement of molecules from greater concentration to lesser concentration until they reach equilibrium.

Is a concentration gradient necessary for diffusion to occur?

Yes.

The minimum requirement for diffusion to occur is that there must be ___ gradient.

A concentration gradient.

What is passive transport and why is it an important process for cells?

Passive transport is diffusion across the cell membrane with the concentration gradient, so the cell does not expend any energy.

What kinds of molecules can easily cross the plasma membrane by passive diffusion?

Small, uncharged molecules such as gasses.

What kind of molecules cannot easily cross the plasma membrane?

Large molecules and charged molecules (ions).

Which types of diffusion do not require energy expenditure by the cell?

Simple diffusion and passive transport.

Which types of diffusion require energy expenditure by the cell?

Active transport.

Osmosis is a special case of diffusion involving .

water.

What determines the direction of osmosis?

Tonicity, the concentration of dissolved solute, determines the direction of osmosis.

In what direction will water flow if the concentration of glucose inside a cell is 2% and the concentration of glucose outside the cell is 0.5%?

The inside is hypertonic to the outside, so water will flow into the cell.

Cholera is caused be a bacterium that releases a toxin that interacts with a plasma membrane __ protein.

channel

What term describes the movement of water between a cell and its surroundings?

Osmosis

If a cell contains 0.9% NaCl and the surrounding fluid contains 0.9% NaCl, what direction will water flow? Is the surrounding fluid isotonic, hypotonic or hypertonic to the cell?

If the concentration of NaCl is the same on both sides of the cell membrane, then water will flow in and out at the same rate (no net movement). The surrounding fluid is isotonic.

If a cell contains 0.9% NaCl and the surrounding fluid contains 9.0% NaCl, what direction will water flow? Is the surrounding fluid isotonic, hypotonic or hypertonic to the cell?

If the concentration of NaCl is greater outside than inside the cell, then water will flow out of the cell. The surrounding fluid is hypertonic.

If a cell contains 0.9% NaCl and the surrounding fluid contains 0.09% NaCl, what direction will water flow? Is the surrounding fluid isotonic, hypotonic or hypertonic to the cell?

If the concentration of NaCl is lower outside than inside the cell, then water will flow into the cell. The surrounding fluid is hypotonic.

Describe what happens to animal cells in isotonic, hypotonic, and hypertonic solutions.

Animal cell shape is maintained in isotonic solutions. Animal cells swell and burst in hypotonic solutions. Animal cells shrivel in hypertonic solutions.

In an isotonic solution, red blood cells appear .

normal

In a hypertonic solution, red blood cells appear _.

shriveled

In a hypotonic solution, red blood cells appear _.

swollen or all lysed

What is turgor pressure and why is it important to plants?

Turgor pressure is the hydraulic pressure that builds up inside plant cells and helps plants stand up against gravity.

Animal cells survive best in isotonic solutions and plant cells survive best in hypotonic solutions, why?

Animal cells lack cell walls to prevent dramatic shape changes; plant cells maintain high turgor pressure when the interior of the cell is hypertonic and the surrounding fluid is hypotonic, and they do not burst because of their cell wall.

The blood plasma of a man who drinks saltwater will become to his red blood cells, whereas the red blood cells will be to the blood plasma.

hypertonic; hypotonic

What is simple diffusion and how does it differ from facilitated diffusion?

Simple diffusion is the diffusion of small, uncharged molecules directly across the cell membrane. Facilitate diffusion is passive transport aided by transport proteins.

What molecule’s diffusion is facilitated by an aquaporin in the cell membrane?

Water

What is the difference between passive and active transport across the membrane?

Passive transport is diffusion from greater to lesser concentration. Active transport is diffusion from lesser to greater concentration, so the cell must expend energy.

Why does active transport require cells to input energy to move some molecules across the plasma membrane?

Active transport requires energy expenditure because molecules are moving in the opposite direction of natural movement (against the concentration gradient instead of with it).

How do endocytosis and exocytosis differ?

Endocytosis brings molecules into the cell and exocytosis releases molecules from within the cell.

What are three kinds of endocytosis and how do they differ?

Phagocytosis (large particles brought in at once). Receptor mediated (many small, specific molecules, brought in at once). Pinocytosis (many small molecules brought in at once).

Cells release hormones into the blood via .

Exocytosis.

When a white blood cell “eats” a bacterium, it does so via the process of .

Phagocytosis.

What kind of chemical reactions release energy? What cellular process releases energy?

Exergonic reactions release energy. Hydrolysis of ATP.

What kind of chemical reactions require energy input? What cellular process requires energy?

Endergonic reactions require energy input. Synthesis of ATP.

What is metabolism?

The sum of all chemical reactions in a cell is its metabolism

What molecule is often referred to as the energy currency of the cell?

ATP

What is phosphorylation?

Transfer of a high energy phosphate from ATP to a target molecule.

How is energy transferred using ATP?

Phosphorylation of the target is how energy is transferred using ATP.

What is the energy of activation of a chemical reaction?

The energy input required for a chemical reaction to proceed from reactants to products in the energy of activation.

How do enzymes lower EA?

Enzymes create a microenvironment at their active site that favors the reaction proceeding to products (which lowers the energy of activation required).

Are catalysts consumed in the chemical reaction they promote?

No

What is substrate?

The substrate is the molecule(s) that bind to an enzyme at its active site.

Where on an enzyme is the reaction catalyzed? (hint: substrate binds here)

The active site.

What is meant by induced fit?

The active site changes shape slightly to accommodate its substrate.

What is an enzyme cofactor?

Enzyme cofactors are required helper molecules that bind at the active site along with substrate.

Why do enzyme function best under optimal conditions?

Enzymes are proteins, and their optimal shape occurs under optimal conditions. The shape determines enzyme activity.

Why can’t most bacteria grow in a jar of pickles?

Pickles are made with vinegar, which is an acid. Most bacterial enzymes denature and do not function at the low pH of vinegar, therefore more bacteria cannot grow in a jar of pickles

Write the overall chemical reaction of cellular respiration.

C6H12O6 + 6O2 → 6CO2 + 6H2O + ATP

What makes oxygen a good molecule for cells to utilize in cellular respiration?

Oxygen is very electronegative and readily accepts electrons from donor molecules

What are oxidation and reduction reactions?

Oxidation-reduction reactions follow the path of electrons from molecule to molecule.

What is NAD+ and how is it important to cellular respiration?

NAD+ is a carrier of high energy electrons.

What happens during cellular respiration?

The carbons of glucose are oxidized, and the high energy electrons harvested are used to generate ATP.