Biology Chapter on Cell Structures and Proteins

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Questions and Answers

Which structure is primarily involved in lipid synthesis and abundant in liver cells?

Nuclear envelope

Rough ER

Golgi apparatus

Smooth ER (correct)

Which type of bond is primarily responsible for maintaining the secondary structure of proteins?

Peptide bonds

Hydrogen bonds between amino acids (correct)

Disulfide bonds

Hydrophobic interactions

What is the role of double bonds in unsaturated fatty acids regarding membrane fluidity at low temperatures?

They increase cholesterol content in membranes

They shorten fatty acid tails, making membranes thinner

They form kinks preventing tight packing (correct)

They make unsaturated fatty acids more polar

What type of protein spans the phospholipid bilayer multiple times?

Transmembrane protein Signup and view all the answers

How do ions travel directly from one animal cell to an adjacent cell?

Through gap junctions Signup and view all the answers

What does the widespread presence of proton pumps across all domains of life suggest?

Proton gradients were used by the common ancestor of all life Signup and view all the answers

Which bonds stabilize the tertiary structure of proteins?

Hydrogen bonds between R groups Signup and view all the answers

What is a characteristic feature of integral proteins?

They can span the entire lipid bilayer Signup and view all the answers

What molecules pass through a cell membrane most easily?

Small and hydrophobic Signup and view all the answers

In a liver cell detoxifying alcohol, what happens to the hydrogen removed from these molecules?

It is transferred to oxygen molecules to generate hydrogen peroxide Signup and view all the answers

What is the advantage of light microscopy over electron microscopy?

Ability to view dynamic processes in living cells Signup and view all the answers

What will happen to red blood cells when transferred to seawater, which contains 0.45 M NaCl?

Water will leave the cells, causing them to shrivel Signup and view all the answers

Which organelle contains hydrolytic enzymes?

Lysosomes Signup and view all the answers

Which organelle is responsible for producing and modifying polysaccharides that will be secreted?

Golgi apparatus Signup and view all the answers

Proton pumps have evolved independently in cells from different domains due to what environmental change?

Increased acidity of oceans Signup and view all the answers

What is necessary for all cell membranes?

Proton pumps Signup and view all the answers

What is the primary function of polysaccharides attached to glycoproteins and glycolipids in animal cell membranes?

To mediate cell-to-cell recognition Signup and view all the answers

Which cellular structure contains the enzymes responsible for digesting a bacterium engulfed by a white blood cell through phagocytosis?

Lysosomes Signup and view all the answers

Where are cell surface integral membrane proteins synthesized in a paramecium?

By ribosomes bound in the rough ER Signup and view all the answers

Which type of molecules have large numbers of ribosomes present in their cells for production?

Proteins Signup and view all the answers

How does cholesterol affect the plasma membranes of some animals?

Enables the membrane to stay fluid at lower temperatures Signup and view all the answers

What allows water to pass quickly through cell membranes?

Water passing through aquaporins in the membrane Signup and view all the answers

In receptor-mediated endocytosis, where do receptor molecules end up after the process?

Integrated into the vesicle membrane Signup and view all the answers

Which type of organelle is primarily involved in the synthesis of oils, phospholipids, and steroids?

Smooth endoplasmic reticulum Signup and view all the answers

Which statement concerning bacteria and archaea cells is correct?

DNA is present in both archaea cells and bacteria cells Signup and view all the answers

What is the most likely explanation for the asymmetry of cell membranes?

The two sides of a cell membrane face different environments and carry out different functions Signup and view all the answers

A cell with a predominance of free ribosomes is most likely doing what?

Producing primarily cytoplasmic proteins Signup and view all the answers

What is the primary function of the smooth endoplasmic reticulum?

Lipid synthesis Signup and view all the answers

What type of organism could the described cell with enzymes, DNA, ribosomes, plasma membrane, and mitochondria be from?

Nearly any eukaryotic organism Signup and view all the answers

In lipid rafts, which property is increased due to the higher concentration of cholesterol molecules?

Rigor of the membrane Signup and view all the answers

What causes the partial negative charge in a water molecule?

Unequal sharing of electrons between oxygen and hydrogen Signup and view all the answers

Motor proteins interact with which structures to provide molecular motion in cells?

Cytoskeletal structures Signup and view all the answers

What is a major cause of size limits for certain types of cells?

Surface area needed for metabolic functions Signup and view all the answers

What is the effect of a higher concentration of cholesterol in lipid rafts?

Increased rigidity compared to the rest of the membrane Signup and view all the answers

Which of the following is NOT a component found in the described cell?

Cellulose fibers Signup and view all the answers

How do lipid rafts differ from the surrounding plasma membrane?

They have higher cholesterol concentration Signup and view all the answers

Study Notes

Cell Structures and Function

The Smooth Endoplasmic Reticulum (ER) is abundant in liver cells due to its role in detoxification processes.
Secondary structure of proteins is maintained primarily by hydrogen bonds between different peptide bonds.
Unsaturated fatty acids enhance membrane fluidity at lower temperatures because their double bonds create kinks that prevent tight packing of lipids.
Transmembrane proteins span the phospholipid bilayer, while integral proteins are embedded within.

Cellular Communication and Transport

Ions migrate between adjacent animal cells through Gap junctions, allowing direct cytoplasmic communication.
Evolutionary theory suggests that proton pumps were utilized by a common ancestor of bacteria, archaea, and eukarya, indicating their primordial significance.
Small and hydrophobic molecules cross cell membranes easily due to their solubility in the lipid bilayer.

Organelles and Enzyme Functions

Peroxisomes in liver cells detoxify by removing hydrogen from molecules and transferring it to oxygen, forming hydrogen peroxide.
Lysosomes contain hydrolytic enzymes crucial for digesting engulfed materials such as bacteria.
The Golgi apparatus produces and modifies polysaccharides for secretion, impacting cellular functions.

Membrane Dynamics

Light microscopy allows observation of living cells and dynamic processes, unlike electron microscopy which requires specimen preservation.
Red blood cells in seawater (0.45 M NaCl) will lose water, causing them to shrivel due to osmotic effects.
Cholesterol maintains membrane fluidity, particularly during temperature drops, allowing for flexibility in cellular processes.

Molecular and Protein Synthesis

Ribosomes are essential for protein production; high ribosome concentration indicates a specialization in protein synthesis.
Integral membrane proteins are synthesized by ribosomes on the Rough ER, while free ribosomes produce cytoplasmic proteins.
The presence of lipid rafts in membranes, rich in cholesterol, creates regions that are more rigid and potentially involved in signaling.

Water and Membrane Properties

Water crosses cell membranes rapidly via aquaporins, specialized channels facilitating this process.
Cell membranes exhibit asymmetry, as the two sides often serve different functions and face variable environments.

Cellular Size Limitations and Types

The size limits of cells are largely due to the need for a sufficient surface area to meet metabolic demands.
Cells that contain free ribosomes primarily produce proteins for cytoplasmic functions rather than secretion.

Bacteria and Archaea Characteristics

Both bacteria and archaea contain DNA; however, archaea differ by having unique cellular structures, with no membrane-enclosed organelles or nuclei.

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Description

This quiz focuses on important cellular structures, particularly those abundant in liver cells, and delves into the secondary structure of proteins. Test your understanding of the roles of rough and smooth endoplasmic reticulum, as well as the forces maintaining protein structure.