unit 1 biology nat 5

What is the function of the nucleus in a cell?

Controls cell activities and contains chromosomes made of DNA.

What is the role of the cell membrane?

Controls the passage of substances into and out of the cell.

What is cytoplasm?

The site of chemical reactions within the cell.

What provides support to plant cells?

The cell wall, which is made of cellulose.

What is the function of vacuoles in cells?

Stores cell sap.

What do chloroplasts do?

Trap light energy for photosynthesis.

What is the site of aerobic respiration in cells?

Mitochondria.

Where does protein synthesis occur?

Ribosomes.

What are fungi?

A group of organisms that includes mushrooms, moulds, yeast, and toadstools.

What is a characteristic of yeast cells?

Yeast cells have a nucleus, cytoplasm, and cell wall but no chloroplasts.

How is bacterial DNA structured?

It is not contained in a nucleus and includes chromosomes and plasmids.

What materials make up the cell wall in different types of cells?

Cellulose in plant cells; different materials in fungal and bacterial cells.

What is a selectively permeable membrane?

A membrane that allows certain molecules to pass through but not others.

What is a concentration gradient?

A difference in concentration between two solutions.

What is passive transport?

Movement of molecules down a concentration gradient that does not require energy.

What are the two types of passive transport?

Diffusion and osmosis.

What is diffusion?

The movement of molecules from higher to lower concentration until evenly spread.

What happens to diffusion when concentrations are equal?

Diffusion stops, but molecules continue to move equally in both directions.

How can diffusion be observed?

By placing potassium permanganate into a beaker of water.

Why is diffusion important to living organisms?

It allows cells to gain useful substances and remove waste products.

What is osmosis?

The movement of water from a higher water concentration to a lower water concentration through a selectively permeable membrane.

How do cells gain or lose water?

Through the process of osmosis.

What determines the direction of water movement in osmosis?

The water concentration of the solution inside the cell compared to the water concentration of the solution outside the cell.

How is water concentration defined in a solution?

It is the proportion of a solution that is water.

How does osmosis relate to diffusion?

Osmosis is a special case of diffusion, specifically the diffusion of water.

What happens to red blood cells in a hypotonic solution?

They swell and may burst due to gaining water by osmosis.

What is the effect of a hypertonic solution on red blood cells?

They lose water by osmosis and shrink.

What is the outcome for red blood cells in an isotonic solution?

They experience no overall change in volume; no osmosis occurs.

What happens to plant cells in a hypotonic solution?

They become turgid as they gain water by osmosis, pushing against the cell wall.

What is the effect of a hypertonic solution on plant cells?

They lose water by osmosis, leading to plasmolysis where the cytoplasm shrinks away from the cell wall.

What is passive transport?

The movement of molecules across the cell membrane through specific transport proteins, occurring down a concentration gradient without the need for energy.

Give an example of passive transport in cells.

The uptake of glucose by liver cells via the transport protein GLUT4.

What occurs when plant cells are placed in a solution with equal water concentration to their cytoplasm?

They experience no overall change in volume; no osmosis occurs.

What happens to plant cells in a solution with a high water concentration compared to their contents?

They gain water by osmosis and swell, becoming turgid.

What is the role of the plant cell wall during osmosis?

It prevents plant cells from bursting when they become turgid.

What is the result of placing plant cells in a concentrated sugar solution?

They lose water by osmosis and become plasmolysed.

How does the selectively permeable membrane affect osmosis?

It allows water molecules to pass through more rapidly than solute molecules like sugar.

What is the concentration gradient in passive transport?

It is the difference in concentration of molecules across a membrane, from high to low concentration.

What is the significance of GLUT4 in glucose transport?

GLUT4 is a transport protein that facilitates the diffusion of glucose from the blood into liver cells.

What are the characteristics of a hypotonic solution for animal cells?

It has a lower concentration of solute and a higher concentration of water compared to the cell's contents.

What is the effect of a concentrated solution on animal cells?

They become hypertonic, leading to water loss and cell shrinkage.

What is the term for plant cells that are normal and turgid?

They are said to be in a hypotonic solution.

What happens to the cytoplasm of plant cells in a hypertonic solution?

The cytoplasm shrinks away from the cell wall.

What is the role of GLUT4 in glucose transport?

GLUT4 is a transport protein that facilitates the diffusion of glucose from the blood into the cytoplasm of liver cells.

What type of transport allows glucose to enter liver cells?

Passive transport allows glucose molecules to pass through the GLUT4 protein into the cell.

What is active transport?

Active transport is the movement of molecules across a cell membrane from an area of low concentration to an area of high concentration, requiring energy.

What energy source is used for active transport in cells?

Energy for active transport is provided by the breakdown of ATP inside the cell.

What is an example of active transport in nerve cells?

The sodium-potassium pump is an example of active transport found in the cell membrane of nerve cells.

What is the function of the sodium-potassium pump?

The sodium-potassium pump moves sodium out of the cells and potassium into the cells, aiding in the transmission of nerve impulses.

How much of your daily energy intake is used by sodium-potassium pumps in nerve cells?

Sodium-potassium pumps use around 20 percent of your daily energy intake.

What is the structure of DNA?

DNA is a double helix made of two strands of nucleotides twisted around each other.

Where is DNA stored in most animal, plant, and fungal cells?

DNA is stored in the nucleus, coiled up in thread-like structures called chromosomes.

What is the length of DNA in a human skin cell's nucleus?

The nucleus of a human skin cell contains about two meters of DNA.

What are the building blocks of DNA called?

The building blocks of DNA are called nucleotides.

What are the four types of DNA bases?

The four DNA bases are adenine (A), thymine (T), cytosine (C), and guanine (G).

How do DNA bases pair with each other?

Base A pairs with base T, and base G pairs with base C, forming complementary bonds.

What is a gene?

A gene is a sequence of bases on DNA that codes for a protein.

What determines the order of amino acids in a protein?

The sequence of bases in a DNA molecule determines the order of amino acids in a protein.

What are triplets in the context of DNA?

Triplets are groups of three bases in DNA that represent different amino acids.

What is the genetic code?

The genetic code is the set of rules by which the sequence of bases in DNA is translated into the order of amino acids in proteins.

What is the shape of DNA called?

The shape of DNA is called a double helix.

How are nucleotides linked together in DNA?

Nucleotides are linked together to form strands that twist around each other to create the double helix.

What holds the two strands of DNA together?

The two strands of DNA are held together by weak bonds between complementary pairs of bases.

What is the significance of the complementary base pairing in DNA?

Complementary base pairing ensures accurate replication and transcription of genetic information.

What is the role of messenger RNA (mRNA) in protein synthesis?

mRNA carries a copy of the DNA base sequence of a specific gene from the nucleus to the cytoplasm, where ribosomes use it to assemble amino acids into proteins.

Where is DNA stored in animal, plant, and fungal cells?

DNA is stored in the nucleus.

What structures are responsible for assembling proteins in the cytoplasm?

Ribosomes.

How long is a typical protein in terms of amino acids?

About 400 amino acids long.

How many different types of naturally occurring amino acids are there?

20 different types.

What determines the three-dimensional shape of a protein?

The sequence of amino acids in the chain.

Why is the three-dimensional shape of a protein important?

It determines the protein's function and its ability to interact with other molecules.

What are the four categories of protein functions?

Structural, Enzymes, Hormones, Antibodies.

What is the function of structural proteins?

They form supporting frameworks inside cells and body structures.

Give an example of a structural protein and its role.

Tubulin forms spindle fibers during mitosis.

What is the role of enzymes in biological reactions?

Enzymes catalyze biological reactions, speeding them up.

Provide an example of an enzyme and its function.

ATPase catalyzes the breakdown of ATP.

What is the function of hormones in the body?

Hormones communicate between different parts of the body and are transported in the blood to target cells.

Name a hormone and its function.

Insulin stimulates liver cells to take up glucose from the blood.

What role do antibodies play in the immune system?

Antibodies bind to specific bacteria and viruses to label them for destruction by other white blood cells.

What is the significance of enzymes in cellular reactions?

Enzymes speed up reactions at body temperature and remain unchanged, allowing them to be reused.

What are substrates in the context of enzyme function?

Substrates are the chemicals that enzymes act upon.

How do living cells increase the rate of chemical reactions without raising temperature?

By producing enzymes that provide a favorable environment for reacting molecules.

What happens if cellular reactions occur too slowly?

The cell may die, which can also harm the whole organism if it's multicellular.

What is the consequence of hydrogen peroxide buildup in liver cells?

It can poison the cell if not broken down quickly.

What is the relationship between protein structure and function?

The specific three-dimensional shape of a protein determines its function and interactions.

How do proteins interact with other molecules?

The shape of a protein determines what it can interact with, similar to how a key fits a lock.

What is the role of keratin in the body?

Keratin is a structural protein that makes up hair and nails.

What are the chemicals that enzymes act upon called?

Substrates.

What are the chemicals produced by the action of an enzyme called?

Products.

What enzyme do liver cells produce to break down hydrogen peroxide?

Catalase.

What is the process by which hydrogen peroxide is converted into water and oxygen called?

Catalysis.

What is the part of an enzyme that substrates attach to?

Active site.

What happens to a substrate during the degradation process catalyzed by an enzyme?

It is broken down into two products.

What is the term for the joining together of two substrates to form one product?

Synthesis.

Which enzyme catalyzes the synthesis of glucose-1-phosphate to form starch?

Phosphorylase.

What determines the optimum conditions for enzyme activity?

The conditions under which an enzyme is most active.

What is the optimum temperature for the enzyme activity of Thermus aquaticus?

Around 70°C.

How does temperature affect enzyme activity?

Enzyme activity increases with temperature to a maximum at the optimum temperature, then decreases at higher temperatures.

What happens to enzyme activity at low temperatures?

It is low due to reduced kinetic energy and fewer collisions between enzyme and substrate.

What occurs at the optimum temperature regarding enzyme activity?

The kinetic energy is ideal for the maximum number of collisions.